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April 17

Jets in front of wings

All modern jetliners have jet engines that are placed well in front of the front edge of their wings. Why? —Preceding unsigned comment added by 71.70.143.134 (talk) 02:14, 17 April 2010 (UTC)

This is mostly speculation on my part, but I suspect weight distribution is at least part of the reason. Modern jetliners all use Tricycle gear arrangements, with the rear landing gear situated in the area of the wing. The center of gravity must be in front of the rear landing gear or bad things might happen, so pushing the fairly heavy engines, also mounted to the wings, as far forward as possible is presumably helpful. Also due to the shape of an airplane wing there is more strength near the leading edge, so pushing the engine nacelle forward makes sense. The engine nacelle itself should be attached at it's own center of gravity to keep it from torquing the wing, so if it is fairly long and attached near the front of the wing (where the wing is strongest) it's no surprise it might stick out. It probably also makes it easier to do maintenance on the engines. Winston365 (talk) 06:44, 17 April 2010 (UTC)

False premise. McDonnell Douglas MD-80 is a modern aircraft with rear mounted engines. Dragons flight (talk) 07:28, 17 April 2010 (UTC)

Sure, there are a bunch of airliners with rear mounted engines, although these days they are mostly for smaller aircraft (very common on business jets for example). These planes compensate by moving the wings farther towards the rear. Larg airliners these days put the nacelles on the wings though, which was implicit in the question asked. If you use engines mounted on the tail you can move the rear landing gear back as far as you need to to balance the aircraft, which also moves the wings towards the rear, but if you do decide to mount the engines on the wings that doesn't help as much, as moving the landing gear towards the rear of the aircraft would also move the engines back. Winston365 (talk) 07:45, 17 April 2010 (UTC)

Aircraft, and particularly high speed aircraft, are vulnerable to a potentially-destructive phenomenon called flutter. Aircraft designers aim to ensure the minimum speed for onset of flutter is well above the maximum speed of the aircraft. There are various modes of flutter and many of them can be avoided by ensuring the center of mass of the relevant part of the structure is ahead of the elastic axis of the part of the structure. For example, hinged control surfaces (ailerons, elevators and rudder) usually have lumps of lead (or depleted uranium!) attached to their forward edges to move the center of mass of the surface forward of where it would otherwise be. The more mass that is added means the higher is the flutter-onset speed.

Flutter of the wing can be avoided by ensuring the mass of the wing is well forward of the torsional axis of the wing. For this reason, aircraft designers place the engines well forward of the wing, on pylons. The further forward that the engines are located the higher will be the flutter-onset speed. This is just as true of turbo-props as jets. Note the location of the engines on the Vickers Viscount and P3 Orion. The further out along the wingspan that the engine is located, the more important it is to be located well ahead of the wing torsional axis. Some British aircraft had their engines buried in the wing root and the engines could be located near the trailing edge of the wing eg de Havilland Comet and the V bombers.

Similarly, high speed aircraft with fuel tanks on the wing tips must have the tanks protruding significantly forward of the leading edge of the wing. See the image at Learjet 25.

Another option is to have very stiff wings of relatively short span. That way, it is not critical that the engines be located forward of the wing. Concorde is an example of this third option. Dolphin (t) 08:30, 17 April 2010 (UTC)

The critical thing in any aircraft design is that the center of gravity be close to the center of pressure of the wing. (Generally, the 'center of pressure' is at the thickest part of the wing - a little way back from the front edge). If you imagine the lift from the wing pulling the plane upwards at the center of pressure - and gravity pulling it down at the center of gravity - you an easily imagine why you'd want those two points to be at the same place if you want the plane to be stable and to fly straight. So the entire issue of "balance" that everyone has been talking about relates to keeping those two points close together. Concord has triangular wings - the center of pressure is much further back than on a typical subsonic airliner - hence the engines need to be further back to keep a reasonable balance. SteveBaker (talk) 15:05, 17 April 2010 (UTC)

SteveBaker's comment is a popular one, but not entirely correct. On an airfoil of symmetric cross-section the center of pressure stays in a fixed location, usually around 25% of the chord, but on a cambered airfoil the center of pressure moves as the angle of attack changes. At high angles of attack (such as at low airspeed) the center of pressure is at its most forward position. But as the angle of attack reduces (such as when the airspeed increases) the center of pressure moves backwards, and may even lie behind the trailing edge of the wing! See Movement of center of pressure. It is impossible (and unnecessary) to always have the center of gravity close to the center of pressure because the center of pressure moves through significant distances during a flight.

To simplify the analysis of airfoils and aircraft stability, it is fortunate that there is a point that doesn't move and that helps determine the best position for the center of gravity. This point is called the aerodynamic center. For positive stability, the center of gravity should always lie within the specified range relative to the aerodynamic center.

However, back to the original question. The location of engines and wing-tip fuel tanks on the wings of aircraft is related to the avoidance of flutter, not ensuring the center of gravity of the aircraft is within the specified range. Dolphin (t) 02:49, 18 April 2010 (UTC)

Space elevator

Why does the center of mass of the space elevator have to at the Earth's geosynchronous orbit? I realize that it's to minimize tension forces acting on the elevator, but my confusion is the following: I understand that a particle in that orbit will be rotating at the same rate as the earth, but for an extended body such as the space elevator, I didn't think that was true. I thought treating the gravitational force as acting at the center of mass was only true for spherical or elliptical bodies. If I don't make sense let me know. 173.179.59.66 (talk) 07:25, 17 April 2010 (UTC)

The motion of any rigid body can be considered as a combination of the linear or orbital motion of the centre of mass (considering all forces as acting through the centre of mass), and the rotational motion about the centre of mass (considering the moments of forces about the centre of mass). It doesn't just apply to symmetrical bodies. At this scale. there might be a very small relativistic correction, and an adjustment because the centre of mass does not coincide with the centre of gravity, but the basic principle still applies and gives a reasonably accurate approximation. Dbfirs 08:26, 17 April 2010 (UTC)

Not correct. The force, and thus acceleration, on a non-spherical body is not the same as the force on a point mass at the body's center of mass. --99.237.234.104 (talk) 01:38, 19 April 2010 (UTC)

Centre of mass and centre of gravity mean exactly the same thing, don't they? --Tango (talk) 11:59, 17 April 2010 (UTC)

Normally, yes. But I think here the different (lower) gravity at the top of such a object means that the average centre of gravity is lower than the centre of mass. Our article, centre of mass, says "The center of mass is often called the center of gravity, but this is only true in a system where the gravitational forces are uniform.", I assume this is what it means. - Jarry1250 ^{[Humorous? Discuss.]} 12:19, 17 April 2010 (UTC)

Ah, yes. I suppose that makes sense. I'm not sure the concept of a centre of gravity is useful in that context, though. --Tango (talk) 14:01, 17 April 2010 (UTC)

Also note that there's another good reason to have a "station" at the geosynchronous height: so that space ships can dock there. At any other height any ships in orbit would zip past the station. Depending on the relative size of this station, it might be a substantial portion of the overall mass of the elevator. Also, at the geosynch height, it shouldn't exert any net force on the elevator shaft, which is a big plus. StuRat (talk) 13:40, 17 April 2010 (UTC)

The station (or something) needs to be above geosynchronous height in order to compensate for the cable below it. A large station would only have to be a tiny bit above, though. Once alternative suggestion is to have the cable continue a long way past geosynchronous height. A craft on a cable above that height would be accelerated upwards by centrifugal force (and yes, it does exist in the most natural frame of reference for this problem, which is one that co-rotates with the Earth). That gives you a very energy efficient way of reaching an Earth escape trajectory. --Tango (talk) 14:01, 17 April 2010 (UTC)

I understand the practical benefits of having the space elevator at a geosynchronous orbit, but my issues are more physics related. If external forces are applied on an object, then the object's center of mass will accelerate just as if all the mass were concentrated at that one point. Now, a small object (like a space shuttle) at a geosynchronous orbit will have the right combination of acceleration and orbital distance so that it's orbital period matches the rotational period of Earth. But if the space elevator's center of mass is at the same location, because its acceleration will be much bigger, then it seems to me that it won't be in a geosynchronous orbit. I would think that the center of mass ought to be higher than the geosynch orbit, but this doesn't seem to be the case, and I don't know why. 173.179.59.66 (talk) 18:12, 17 April 2010 (UTC)

Why would the acceleration be much bigger? The acceleration will be "g" (adjusted for height) whatever the mass, and whatever the size except for the correction for non-uniform gravity. Can anyone find a reference for the integration of gravitational attraction over a typical mass distribution of a space elevator? (I should be able to do this myself, but I'd probably get it wrong.) I would estimate that the centre of gravity will still be not far from the centre of mass, but the difference might be significant. Dbfirs 20:36, 17 April 2010 (UTC)

If you have a really heavy station at the top then the mass of the cable probably isn't very significant. --Tango (talk) 21:12, 17 April 2010 (UTC)

Yes, I agree that it will probably not be worth worrying about in that case. Dbfirs 21:33, 17 April 2010 (UTC)

... though I think that the torque produced by gravity (on a centre of gravity just below the centre of mass) should have the effect of keeping the elevator vertical, rather like a ship with the centre of gravity below the metacentre. (Do we have any experts on the dynamics of rolling ships who could check my theory?) Dbfirs 20:47, 18 April 2010 (UTC)

Yes, that would be true in uniform or variable gravity - just consider a pendulum. I think the force on the cable due to it being attached to the Earth would also keep it vertical and would probably be a bigger factor. --Tango (talk) 21:51, 18 April 2010 (UTC)

No! A pendulum is suspended from a fixed pivot well above its centre of mass. A "pendulum" suspended at its centre of mass will rotate at random or remain at rest in any orientation. Similarly, an object in any orbit is likely to turn at random unless it has some mechanism for keeping a fixed orientation. Does a space elevator have the cable attached to the Earth? Dbfirs 22:48, 18 April 2010 (UTC)

Ok, a pendulum is a bad example. It is still true, though. It is a result of tidal forces and is responsible for tidally locked moons often having their denser halves pointing towards the parent planet (an object with non-uniform density is roughly equivalent to a non-spherical one). Yes, the cable is attached to the Earth. I think the force is usually fairly small at that point, but it has been suggested that you could move the cable around to avoid space debris by having it attached to a moving platform, so the force can clearly by non-zero. --Tango (talk) 23:50, 18 April 2010 (UTC)

Yes, I think we are in agreement that gravitationally locked moons with a constant face to the centre of orbit are observable, but I suspect that the reason for the locking is non-uniform gravity, as well as non-uniform density, because they would tend to rotate about their centre of mass, not their centre of volume. (Tidal forces will have caused the slowing of rotation in the first place.) If the cable is attached to the Earth, then there is no problem anyway, except in designing incredibly strong tethers! The engineering problems seem vast (though not necessarily insurmountable). Dbfirs 08:26, 19 April 2010 (UTC)

Yes, it is due to non-uniform gravity. That is the cause of all tidal forces. --Tango (talk) 14:18, 19 April 2010 (UTC)

health/meth/sex/ed

(Removed question asking for medical advice) SteveBaker (talk) 14:55, 17 April 2010 (UTC)

Dude, I sympathize with your problems. Unfortunately we're not allowed to give medical advice like this on Wikipedia. I recommend you make an appointment to see your doctor. Axl ¤ [Talk] 11:14, 17 April 2010 (UTC)

(Removed medical advice) SteveBaker (talk) 14:53, 17 April 2010 (UTC)

Communicating dates to future civilizations

I'm sure someone must have thought about this before. Say we want to create a carefully protected archive of information related to our civilization so that even if most of the artifacts of our civilization are destroyed, future civilizations can still learn about our civilization and its history. Future discoverers of the archive will have to learn the language in which the archived materials are written. Numbers and formulas for chemical elements are quite easy to explain. But what about dates in historical records? How can we communicate to future civilizations which trip around the sun is year 2010 in our calendar? I guess we can keep some samples of carbon together with precisely measured radioactivity values and the measurement date, but that's probably not accurate enough to allow someone in the future to determine that year 2010 was 610432 earth-years ago. What better methods are available? —Preceding unsigned comment added by 98.114.98.221 (talk) 17:01, 17 April 2010 (UTC)

You could record the exact position of each planet. I don't know how often all 8 planets (aw, what the heck, toss in Pluto, too) repeat the exact same position, but it can't be very often. StuRat (talk) 17:17, 17 April 2010 (UTC)

The locations of stars would also help. The proper motion of stars is very slow, so by comparing our star charts with their own, they could tell roughly how much time had passed. They could then use the planets or something to narrow it down. --Tango (talk) 18:24, 17 April 2010 (UTC)

We could place stones in certain positions so that, when looking towards a certain direction over one of the stones, certain star constelations appear over the other stones. Then engrave in the stones which constelations appear in which dates. --Enric Naval (talk) 19:27, 17 April 2010 (UTC)

Does the Moon's orbit decay? If so, just record exactly how far from the Earth it is. Or, give our best estimate of the state of the Sun. There's a predictable progression of stellar composition from Hydrogen to the heavier elements as it runs out of fuel. Vranak (talk) 22:14, 17 April 2010 (UTC)

The Moon's orbit does decay (outward), but the change per year is tiny compared with the values you get with different methods of measuring it. StuRat (talk) 22:20, 17 April 2010 (UTC)

I think the moon's orbit decays inwards, so it is getting nearer earth, and it can be accurately measured by using the lazer reflectors left there by various moon missions. 78.147.241.153 (talk) 22:44, 17 April 2010 (UTC)

No, it decays outward. It can be measured accurately now, using the laser system, but a thousand years from now the Moon reflector will be buried in dust and the Earth station will be gone. An advanced civilization could set up a similar system, but the heights at both ends would be different from the current heights. StuRat (talk) 22:48, 17 April 2010 (UTC)

The Pioneer spacecraft carry information about the date and position from which they were sent as follows. There is a schematic drawing of the hydrogen atom and the 21 cm transition which defines a symbol for the unit of frequency that correpsonds to that 21 cm transiton. Then there is a drawing of pulsars with their frequencies showing where they are relative to Earth. If the Pioneer spacecraft are intercepted by some advanced civilization a million years later, they can not only tell from where it came from but also when it was launched using the spin down rates of the pulsars. Count Iblis (talk) 23:01, 17 April 2010 (UTC)

A fairly exact chronology of the Twelfth dynasty of Egypt was established based on clues left behind based on their references to astronomical events such as the heliacal rising of Sirius and to phases of the moon. See The Calendars of Ancient Egypt by Richard Anthony Parker. Gabbe (talk) 09:38, 18 April 2010 (UTC)

Head Hair

?Are there any disadvantages to not washing ones head hair for a long time (say 6 months)?--79.76.233.217 (talk) 17:17, 17 April 2010 (UTC)

Lice, ticks and fleas to name a few. --The High Fin Sperm Whale 17:24, 17 April 2010 (UTC)

You'll have to cite a source if you are claiming that these are prevented by head washing. I think they are prevented by avoiding such critters. Lice, in particular, aren't eliminated by normal head washing, otherwise there'd be no need for lice shampoo and those superfine lice combs, and the alerts in the elementary schools when, horrors, one of the kids is found to have head lice. Comet Tuttle (talk) 19:10, 17 April 2010 (UTC)

It tends to get greasy, smelly, and itchy. StuRat (talk) 17:29, 17 April 2010 (UTC)

Here's someone who conducted a similar experiment, though she also avoided showering and using deodorant. Google is failing me on my search for the person who I believe was a UK Member of Parliament who "outed" himself as not having washed his hair for the last decade, and claimed he had suffered no adverse effects, social or otherwise — anyone know who I'm referring to? Comet Tuttle (talk) 19:09, 17 April 2010 (UTC)

Didn't fail me... Matthew Parris - [1]. He does say he rinses it with water every day, but doesn't use shampoo. Ghmyrtle (talk) 19:18, 17 April 2010 (UTC)

Thank you! Comet Tuttle (talk) 22:22, 20 April 2010 (UTC)

I think the main disadvantage is a reduced social life. Some might be able to get away without it, depending on their kind of hair. I'm not one of them. Dauto (talk) 20:11, 17 April 2010 (UTC)

Exactly, it depends on the person. I've heard quite a few accounts of this sort of behaviour and it seems to work out for the best, although some people eventually do go back to washing. For middle-ground, just trying washing without shampoo, or just a minimal amount, and see how it works out for you. Vranak (talk) 22:09, 17 April 2010 (UTC)

If you thoroughly rinse and comb your hair under hot-as-you-can-bear running water, you will need noticeably less shampoo to get it clean, so I suppose it is possible that if you did this daily and lived in a reasonable clean environment you might get away without the shampoo altogether. DuncanHill (talk) 23:30, 17 April 2010 (UTC)

We have an article on that: Polish plait. There are people who went their entire lives without ever washing their hair. Ariel. (talk) 02:05, 18 April 2010 (UTC)

I didn't wash my hair for ages out of laziness... No one noticed it, yet at the same time they were horrified to find I hadn't done so. Now that I've started using shampoo again I find my hair does need washing at least once a week. We'll have a massive range of hair flora (like skin flora) that will happily live in our hair and will eat away at all the gunk from our scalp. Washing with shampoo will obliterate them and disrupt the once pristine ecosystem, I'm guessing that it takes time for the balance to return and so soon after washing your hair will be greasy etc. Similarly, I've never washed my face with soap and yet never get spots, meanwhile people who use clearasil all the time seem to always have spots (making them use more clearasil!). Why were you asking? 131.111.30.21 (talk) 11:38, 18 April 2010 (UTC)

Yeah, I go for months at a time without using shampoo as well. I'm not exactly obsessed with my hygiene, but no one's ever complained about my hair smelling. When I don't even rinse it for a week or two, though, it can start to smell. Luckily, that's only when I'm camping, or something, so everyone else is in the same boat. Buddy431 (talk) 17:54, 18 April 2010 (UTC)

Personal Obsevation: acquaintances of mine in the past who stopped washing their hair in order to grow long dreadlocks all asserted that after an initial several-week period of smell, grease and dandruff the scalp's "natural self-cleaning properties" kicked in and thereafter their hair became and remained clean, non-greasy and non-smelly (which indeed it was). 87.81.230.195 (talk) 19:19, 18 April 2010 (UTC)

I was under the impression that the correct (i.e. traditional - I know that you can go to a salon and have dreads done with backcombing and glue) way to grow dreads was 'grow longish, then wash as normal - but never brush/comb it again'. Folks do seem to believe that you have to be black for this to work - but apparently this is not the case. Black peoples' hair tends to dread up quicker, is all. --Kurt Shaped Box (talk) 22:10, 18 April 2010 (UTC)

Maybe the reason they have to use Clearasil all the time is because they get lots of spots and not the other way around? Nil Einne (talk) 15:03, 19 April 2010 (UTC)

Article needs help

Hey guys and gals. If any of yall have some spare time, the article on Robbie Mannheim needs some serious help from rational science-minded perspectives. My templates were removed without significant improvement. Finals week is approaching so I don't have the time right now to deal with edit war or doing significant fact checking. It's important to quickly remedy the article because currently it could be damaging WP's credibility. Cheers. -Craig Pemberton 22:42, 17 April 2010 (UTC)

Lol! Yes indeed! I think it's probably best to just delete that whole article and start again.. Send User:Anupam who's responsible for pretty much the whole article to Wikipedia:Reliable_sources. I don't think "Paranormal Experiences", "Strange Magazine", and "Good Spirits, Bad Spirits: How to Distinguish Between Them" count as reliable sources.. Unfortunately I think this requires someone a little more expert then me to tackle it. Vespine (talk) 23:11, 18 April 2010 (UTC)

I might at least put your templates back and start a thread on the talk page. Vespine (talk) 23:47, 18 April 2010 (UTC)

Dandelion-lettuce hybrid?

Earlier in the year I weeded something from my UK garden that had leaves like a dandelion, but was the shape of a lettuce as it had a large number of leaves. What could it have been? I may have scattered some salad-plant leaves there last year. 78.147.241.153 (talk) 22:48, 17 April 2010 (UTC)

It could not have been a dandelion-lettuce hybrid, because no exchange of genetic material occurred. However, lettuce and dandelions are both grouped in the tribe Cichorieae; it is possible there is a species sharing characteristics of both (for example, this). Intelligentsium 23:57, 17 April 2010 (UTC)

Which, though the file is named 'Babcockia', is apparently a species of Sonchus, or "hare lettuce". --ColinFine (talk) 20:45, 18 April 2010 (UTC)

It was really like a hedgehog of dandelion leaves. The dandelions I've seen are quite flat, but this thing was like half a sphere in shape, and also had bigger than usual leaves. It might be due to some old salad plant seeds I scattered there, but I do not know what exactly. 89.240.44.159 (talk) 12:31, 19 April 2010 (UTC)

Is there any realistic danger to Europe from Icelandic Volcanos?

Ok, so at the moment we just have an ash cloud. No big deal. Anything else I should be concerned about, and if so, how concerned? Inquisitive Fellow (talk) 23:09, 17 April 2010 (UTC)

Besides the ash cloud, no. However, the ash cloud is a big deal if you want to travel to or over Europe, as it clogs up airplane engines. And in about a week or two when the ash has circled the Earth we may see much brighter sunsets. --The High Fin Sperm Whale 23:21, 17 April 2010 (UTC)

The article states, "As of April 15, the eruption was not large enough to have an effect on global temperatures like that of Mount Pinatubo and other major past volcanic eruptions. However, previous eruptions of the volcano have lasted as long as a year, and the potential remains for a temporary global cooling effect." 124.157.234.136 (talk) 23:45, 17 April 2010 (UTC)

Depends what you mean by "danger". If it continues it could cause airlines to go bust. It could have a knock on effect on the economies of other countries, because they won't be able to get their goods and services to Europe. Concerts and sporting events are already being cancelled because the players can't get to the venues. Businesses are cancelling meetings and conferences. If and when the ash cloud falls to earth, it could damage people's health. [2] It just proves how interdependent we all are, and how dependent we are on the goodwill of Mother Earth. --TammyMoet (talk) 08:23, 18 April 2010 (UTC)

Without wishing to underestimate the personal inconvenience to people unable to travel this week, I think the overall economic impact will be minimal. UK airlines are estimated to be losing about £2m £200m per day, according to the BBC - but even if this continues for a whole year, it is far less than a tenth of 1% only 2.5% of the UK's GDP. And although airlines are losing money, ferry companies and rail operators are making money. Most goods travel by sea, road and rail, so the only products affected will be those that travel long distances with very short shelf-lives - and a shortage of Thai orchids in Tesco will hardly cause panic buying. As for business meetings, we have phones, video conferencing and net meetings - in my experience, most business travel is a non-essential luxury. Gandalf61 (talk) 09:16, 18 April 2010 (UTC)

On the surface Gandalf you're right. However, cancelling a conference where 600 delegates are attending from across the world costs the organisers money: they will still have to pay for the venue, catering... if you're stranded the other side of the world who's going to do your job? That could bring a business to its knees, especially the smaller ones. Take the F1 circus: 6 jumbo jets to get the freight stuff across the world, plus people, plus spectators... it's not just the commercial airlines here, it's the freight stuff. We could run out of fruit and veg within a week apparently! This article summarises this. The figure they give for airline losses is greater than Gandalf's by 100 times. [3] As you can see from any supermarket shelf, many of the green veg are flown in from Africa or even South America. This will have an effect on their economies as well as our plates in the UK. --TammyMoet (talk) 10:07, 18 April 2010 (UTC)

Hmmm, typically the attendees of a conference will have paid for attending a few months in advance. If the organizers can see the problem happening a few days in advance, they could make last minute arrangements with the catering companies etc. and then be better off. They could then perhaps use the saved money to partially compensate the people who cannot attend. Count Iblis (talk) 13:50, 18 April 2010 (UTC)

Usually there are cancellation clauses in the contract which mean if you cancel less than a set period of time beforehand (could be 48 hours or 7 days) you still have to pay the full fee. Usually the hire fee has to be paid to the venue on booking, which is months if not years in advance, so in order to do what you suggest, you would first have to sue the venue to get even a partial refund. You can cancel the event, but the expenditure is still in place. And what if the flight ban gets lifted and people make the journey, only to find the event has been cancelled and they haven't informed you? (if you're travelling for over 24 hours this is a real possibility) I've organised events for many years, and cancelling is a real nightmare. --TammyMoet (talk) 14:06, 18 April 2010 (UTC)

I see, so you won't want to cancel a conference but perhaps scale it back as best as you can? I've only visted conferences and my experience is that the catering is often poor (under normal circumstances). There isn't enough food for the whole day; after a few days more and more people will eat extra meals in restaurants. So, it seems to me that conference organizers are not spending enough on catering. Count Iblis (talk) 14:26, 18 April 2010 (UTC)

It's poor but very expensive. You are not just paying for the bad food, you are paying for all the people who serve it, for them to put it all away, for them to rent the trucks they need to bring it in and out, assemble tables, etc. Even very minimal food is very expensive, as anyone who has planned a wedding reception knows, much less a full conference with hundreds of people. And since this is an "act of god" (that is, not anybody's fault), it screws up a lot of cancellation policies, insurance policies, etc. Anyway it's beside the point here—aircraft costs are just the tip of the iceberg, because they have an entire sector of the economy depending on their functioning. Shipping of all sorts is mangled by lack of flights; the ability of people to move around is a key aspect of global commerce even today; and there are huge opportunity costs and cancelled service costs which hurts everyone involved. --Mr.98 (talk) 14:38, 18 April 2010 (UTC)

Let's examine some of these exaggerated claims. Cancellation of conferences and sporting events - a headache for organisers, but no net economic impact very small net economic impact on a national or global scale, as refunds put money back into people's pockets, which they then spend elsewhere. "We could run out of fruit and veg within a week apparently!" - complete nonsense. The UK imports 90% of its fruit and 60% of its vegetables - but only very perishable luxury items are flown in. No-one is going to pay for potatoes or pasta to be air-lifted, are they ? I am sure we can survive without aspargus and fresh pineapple chunks if we have to. "The ability of people to move around is a key aspect of global commerce" - well, yes, but people can still travel by road, rail and sea. And most business travel is simply an excuse to be wined and dined at someone else's expense - I think many companies would actually be more profitable if their staff spent less time on corporate jollies. Gandalf61 (talk) 16:06, 18 April 2010 (UTC)

Why would you assume cancellations have no economic impact? Consider that the companies who you've booked in advance, even in an ideal situation where they've not put out expenses ahead of time that cannot be returned (like food purchases), are now stuck with a weekend worth of labor that they either have to pay for, or there are laborers who thought they'd be getting paid but are now not. In all cases, with insufficient cancellation time, somebody will be out some cost or opportunity cost. There are all sorts of NPR stories about people who ship to Europe from out of Europe being totally screwed, losing entire perishable shipments, etc. All of these things cost significant amounts of money. They are investments that have now gone bad and are probably not covered by insurance. A week's notice is not enough for things to be cancelled or redirected without some economic loss. --Mr.98 (talk) 17:02, 18 April 2010 (UTC)

I'm sure the people who are directly impacted by this are quite heavily inconvenienced (financially, or otherwise) but the impact on the economy of, say, the UK would be negligible. Most air travel is for business and most business air travel isn't necessary for business, in as far as business contributes to the overall economy. Zain Ebrahim (talk) 12:03, 19 April 2010 (UTC)

Small? Sure. Neglible, perhaps if this ends soon, but if it really goes on to some extent for months I doubt it. (As a point of reference, I wouldn't consider say 1% of a countries GDP neglible.) Also I'm unsure about your last claim. I tried a quick search but couldn't find any results but I strongly suspect most air travel is for pleasure (or similar) not business. Note that the money a business spends on the travel and associated costs (hotels etc) may make a neglible difference to the economy but it adds up. E.g. if all hotels and airlines shut down because no one uses them do you really think that will be no impact? This is clearly an impossible scenario but it does highlight the point that these things (i.e. tourism) are part of the economy and it's unlikely they won't be affected. As I said below, perhaps the business will be better off if they don't spend that money on the travel, but that means a positive impact, not no impact. Ultimately a scenario where there's no net impact is unlikely to me. Nil Einne (talk) 13:53, 19 April 2010 (UTC)

Well whatever anyone says, I'm still annoyed as I said in an earlier discussion that my packet from Germany has almost definitely been delayed because of the disruption. (Although I admit it's not going to make an economic impact although having paid a fair amount for the shipping because of Deustche Post/DHL's flatrate (i.e. not by weight) shipping costs I'm rather peeved.)

More to the point, plenty of people planning to go to Europe have likely cancelled their holidays. If they have travel insurance policies, they may or may not get most of their money back. But even if they do, it doesn't mean there's no impact because the insurance companies may still lose money and the people themselves may decide to travel elsewhere rather then travel to Europe, which means all the money they would have spent in Europe would go elsewhere, given the details I've mentioned (e.g. insurance), it's clear that 'no net impact' is not accurate but in addition, telling the European businesses and governments who've lost money because it went elsewhere, say Asia or the US, it's okay because there's no net impact is not going to go down well.

Back to my earlier point, there are plenty of European sellers of goods who will find people won't be buying stuff. Similar to the earlier case, these people may buy their goods from elsewhere, e.g. Asia or perhaps they'll buy them locally where the good costs more. This will be good for the other sellers of goods but arguing it makes no difference because there's no net impact seems odd, for example if they buy them locally this would probably mean they spent more (otherwise they would have always bought them locally).

In the converse example, sellers of goods elsewhere, like on eBay or DealExtreme are likely to find European buyers reduced; some may just delay their orders, others may turn to local dealers. Again if they're local there's a good chance these items will cost more which while good for the local dealers and perhaps local economy, clearly means 'no net impact' is rather inaccurate. Even if they simply delay their orders isn't going to mean no net impact. Money the sellers could have received and spent on other things is now not going to be received. It stays around in the buyers bank which again may be good for the European banks and therefore economy but as I've already said, there's clear not no net impact.

In terms of travel, yes there are other ways to travel, but the people who choose to travel by air much have had a reason, if that reason is speed then the loss of that option is not going to have no impact. Note that even if people travel less, and even if they good for the company, that ignores the impact their non-travel has on other people who would have benefited from their travel. More to the point, less travel doesn't mean positive impact if you have to pay more for the travel that does take place, e.g. because it costs more (flying is generally expensive but it's not always more expensive then other options) or because the person is away for longer.

P.S. It seems obvious to me that the Thai orchid growers will lose out if people don't buy their orchids. Or if people have already bought their orchids but they can't de delivered, there's a fair chance things will change for Tesco because they can't sell the orchids they purchased but which couldn't be delivered (and they've also wasted the money they spent on orchids, if they get it back from insurance or whatever, again someone loses out). Even if you presume the people still spend all the money they would have spend at Tesco at Tesco which is a big if, they'll be buying more other goods which may be beneficial for these sellers of other goods but is not a case of no impact.

To summarise, no net impact is overly simplistic or just wrong when there are plenty of lost opportunity costs (I think that's the economics term) and the money is going to substanially different places including different countries then it would have otherwise. Yes, some will gain, some will lose but for many countries the effect is likely to be negative and even from a global perspective it's not likely to be no net impact. Perhaps people will realise they're relying too much on air travel and may change as a result which may have a net positive effect but that's a big if.

As with others, I've wondered if this could be severe enough to push an airline over the edge, this hasn't happened yet but I've seen some suggestion it could last several weeks (although the latest news is flights may resume soon albeit things will remain relatively disrupted for weeks and of course people may still be concerned about what will happen so may change their plans). If all this does push an airline over the edge, I don't think anyone is going to go out and tell the people who lose their jobs if this happens not to worry because there was no net impact.

P.P.S. [4] is an example of some of what I'm talking about. All very small scale, but no net impact is clearly overly simplistic and even then very likely wrong.

Incidentally I don't live in Europe as may be obvious, and the only inconvience I'me likely to suffer is very, very minor (my comment on the package was primarily intended to be facetious similarly to the last time I mentioned it). I don't know anyone that well who's much worse off then me (although as NZ is a agricultural exporter, it could have some impact here). So I have no personal reason to really care that much. However I do have a history of disliking statements that IMHO are overly simplistic, miss the point or are just plain wrong. Talking about things in the abstact is fine, and often beneficial but as I've emphasised it's worth remembering there are plenty of people who have far more reason to care, and you can bet many will be much more annoyed then me at any such statements.

P.P.P.S. Just for further clarification, I'm not saying this is going to destroy the economy of many countries or bring down the world, indeed as I said in another comment, as it stands, the impact may be small.

Nil Einne (talk) 23:48, 18 April 2010 (UTC)

Should have done this some time ago, but some references partially supporting Gandalf's point partially supporting my point supporting Gandalf's point about the small impact on food (although no one challenged that) [5] [6] [7]. I'm obviously biased, but these generally seem to support my POV. If this doesn't continue for much longer, the impact may be neglible, but potentially/probably not none for a many places nor for the global impact, however if it continues for long enough it definitely could have a small impact. Perhaps it's a matter of semantics, to me, saying there's no net impact means zero overall impact and is a quite different thing from saying there's neglible impact (which means there is potentially some impact but it's a as one of the sources says a blip on the radar), I obviously have no idea if that was what was intended. Nil Einne (talk) 14:51, 19 April 2010 (UTC)

As you seem to be very upset about the phrase "no net economic impact" - which I only used once - I have amended it to clarify what I meant. Gandalf61 (talk) 16:27, 19 April 2010 (UTC)

My last comment before I leave this discussion for good, in that case, although I do feel your comment only really considered one side and may missed some key points, I agree with the more generally point that some people are perhaps somewhat exaggerating the long terms effects of the disruption as things stand at the moment and the overall effect is likely to be small (however may still have some pretty big effects on some people and not just those trying to travel). As I mentioned, I do feel some statements can harm the discussion and have no qualms about pointing this out as I did in this case, even if the statement is only an aside (although it did seem to me to be the core of the argument, even if that wasn't your intention). As may be obvious, I also agree with a number of the other comments, e.g. Mr.98's. Edit: Er sorry was rereading the thread and realised I forgot one more point, I saw this in my earlier research and it's even in our article. AFAIK, the US$200 million/day figure is for all airlines. For the UK, I've seen £20m million/day for BA [8]. This perhaps isn't surprising as I'm sure Gandalf and most would recognise, the UK airlines themselves aren't 2.5% of the UK's GDP. Nil Einne (talk) 16:49, 19 April 2010 (UTC)

If you cancel a conference you have to refund everyone that paid to attend it (whether they would actually be able to make it or not). --Tango (talk) 14:41, 18 April 2010 (UTC)

Incidentally, I am not sure why everyone thinks that conference funds are totally refundable. Many of them will already be spent and non-refundable (you cannot just cancel a huge booking at a hotel and get everything back). When I have been at conferences that were partially cancelled by weather (half of it was called off), I got nothing back. I was told that they might put on the conference again in a few months and then my previous conference ticket would be honored. That would have required twice the amount spent on travel and lodging, though (because my hotel wouldn't refund my costs, of course, because they don't care about the conference). Yes, if you cancel something weeks in advance you can sometimes (but not always) get the money refunded. But in many cases you cannot because you have signed contract of some sort that prohibit this. At least in the US. --Mr.98 (talk) 17:02, 18 April 2010 (UTC)

Back when I was involved in running conferences (or, strictly speaking, conventions) we usually took out insurance against events outside our control causing the event's cancellation. (For those I was involved in, accommodation and conference facilities were mostly provided by the same venue.) Whether or not a natural event like this would be included or excluded (as, say, an "Act of God") would depend on the terms of the particular insurance policy. 87.81.230.195 (talk) 19:12, 18 April 2010 (UTC)

I wouldn´t say the volcanic ash cloud clogs airplane engines. I got the impression that no one wanted to take chances. However, the Dutch airline KLM carried out a test flight Saturday night and detected no problems from the volcanic ash. As far as I know, they flew through the cloud.--Quest09 (talk) 17:18, 18 April 2010 (UTC)

There were two rather well-known incidents in the 1980s where Boeing 747s lost all four engines while flying through an ash cloud. Both times, the pilots were able to restart enough engines to land safely, but nobody wants to take the risk again. --Carnildo (talk) 01:34, 20 April 2010 (UTC)

April 18

Vegetarianism and Diabetes

Is there any medical reason a diabetic should not be a vegetarian? A nutritionist told an acquaintance of mine that it's basically impossible for a diabetic to be healthy and satisfied on a vegetarian diet, but I've also heard of a vegetarian diet being recommended to control diabetes. (Please note, I am NOT asking for medical advice here. I'm not diabetic, and I'm a vegetarian for ethical reasons and wouldn't return to eating animal flesh even if I thought my health would benefit by it in some way. This is more of a "settling a bet" kind of question, even though I haven't actually made a bet.) 71.104.119.240 (talk) 02:02, 18 April 2010 (UTC)

Diabetics basically can not properly handle carbohydrates. So it's better for them to get most of their calories from protein instead. This is very very hard to do on a vegetarian (even more so a vegan) diet. The current recommendation is not to cut out carbs totally, but rather to limit them. But anecdotally diabetics who cut carbs almost totally out of their diet do very well. Ariel. (talk) 02:10, 18 April 2010 (UTC)

What Ariel said was unsubstantiated, dangerous and possibly deadly bullshit. Diabetic diets include prescribed amounts of carbohydrate for every meal. Please check with such reliable sources as the American Diabetes Association rather than random persons posting nonsense on the internet. See [9] for instance. Edison (talk) 03:21, 18 April 2010 (UTC)

I said that: "The current recommendation is not to cut out carbs totally, but rather to limit them.". But deadly? Seriously? And despite what the American Diabetes Association says, not everyone agrees, and here is a study that says so. This is not a settled issue though. Ariel. (talk) 04:09, 18 April 2010 (UTC)

discussion about the ethics of vegetarianism

I wasn't aware that there are ethical reasons to be a vegetarian. Dauto (talk) 02:51, 18 April 2010 (UTC) Dauto, Thats a moveable feast. See Vegetarianism and religion. AFAIK ref the OP there is no problem at all with Diabetes and being vegetarian. --BozMo talk 07:34, 18 April 2010 (UTC) I don't know what you mean by moveable feast. Sure, some religions promote vegeterianism, while some other relegions specifically call for non-vegeterian dishes for specific porposes. Fish and lamb come to mind. Some of them forbid specific kinds of meat such as pork or beef without calling for outright vegeterianism. The overall picture is that relegions are all over the place. My question wasn't about relegion though, it was about ethics which is a different thing. Dauto (talk) 14:08, 18 April 2010 (UTC) There is a big difference between religion and ethics (they are related concepts, certainly, but not equivalent). --Tango (talk) 14:45, 18 April 2010 (UTC) Most vegetarians are vegetarian for ethical reasons. They don't think it is ethical to kill animals for food or they don't think it is ethical to treat animals in the way some animals bred for food are treated so don't eat any meat in order to not support the industry or they practise a religion that says it is unethical to eat meat. --Tango (talk) 14:45, 18 April 2010 (UTC) Does that mean that most vegetarians see the meat eaters as a bunch of ethicless people? I rather doubt that. Dauto (talk) 15:56, 18 April 2010 (UTC) Just because it hasn't appeared yet: Ethics of eating meat. Dauto, it would be unfair to call someone who has a different set of ethical principles to oneself "ethicless". 129.234.53.144 (talk) 17:33, 18 April 2010 (UTC) In general it's probably not "ethicless" so much as "ethically challenged". Most vegetarians-for-ethical-reasons in the western world, even militant ones, recognize that there is a large culture and history of meat-eating, so they are likely to believe meat-eaters to be morally ignorant, rather than morally depraved. Most ethics-based pro-vegetarianism campaigns focus on "conscience building" and promoting awareness, rather than moral condemnation. ("You can be a better person" rather than "You are an horrible, evil person.") All this is highly dependent on the vegetarian, though. I've met quite a few who for whom it is a completely personal choice, and who really don't care what others do. -- 174.24.208.192 (talk) 17:48, 18 April 2010 (UTC) Have to agree with 71.104 below, I'm not saying people have to agree with the ethical reasons and I perhaps shouldn't be surprised about a debate about the ethical reasons on the RD even if it's OT, but I'm rather surprised people are seriously unaware plenty of people have ethical reasons (even many of the religious ones have reasons based in ethics even if many religious don't agree with such reasoning) Nil Einne (talk) 10:40, 19 April 2010 (UTC)

25 years ago my first husband became Type 1 Diabetic. He had to inject insulin as well as alter his diet. Being the cook in the family, I well remember this diet! Only 2 portions of red meat a week: change to wholemeal/whole grain products for everything refined (bread, rice, pasta). Plenty of veg. Potatoes with skin on only. No added sugar: very little fat. Been trying to find a reference for this diet, but as it was so long ago I think it's not available. Current NHS advice is that there is no special diet but just to eat healthily: however, the GI or GL diets are well received among the diabetic community. [10] So, is being vegetarian compatible with managing diabetes? It looks like it - providing you still remember to eat healthily! Eating cheese and chips every day is never a good idea (unfortunately). --TammyMoet (talk) 08:13, 18 April 2010 (UTC)

This study (by a vegetarian advocacy group) claims to show vegetarian diets can be quite useful for diabetics. The people in this study were eating a very carefully planned diet though, no chips and cheese I'm sure. Qrsdogg (talk) 13:14, 18 April 2010 (UTC)

Much thanks to those of you who took the time to consider and compose thoughtful responses to the question I asked. As for those of you who felt the need to take the discussion off-topic with what I suspect on the basis of personal experience has more to do with criticism of my moral choices than any actual curiosity about the ethics of vegetarianism (including one individual who felt the need to send a message to me personally) - I only mentioned my ethical stance in order to clarify that I was in no way asking for medical advice by posing this question, as I had no intention of changing my habits no matter what the answer was. Whatever my own private opinions may be, there was nothing judgmental or proselytising about the question I posed; I didn't come here to engage in debate, and I have no interest in doing so. If you must know, though I seriously doubt there's anyone hanging around the Wikipedia reference desk who isn't familiar with the concept that some people don't eat animal flesh for reasons of conscience, Tango and 174.24.208.192 had it about right. 71.104.119.240 (talk) 10:32, 19 April 2010 (UTC)

Sunrise and sunset

In the southern hemisphere (l live in Australia) the day of earliest sunrise is about two weeks before the summer solstice, and the day of latest sunset is about two weeks after the summer solstice. The day of latest sunrise is about eight days after the winter solstice, and the day of earliest sunset is about eight days before the winter solstice. Is it the same in the northern hemisphere, or the opposite? If there is a difference, why? Dolphin (t) 06:04, 18 April 2010 (UTC)

The solar time article, specifically the section on apparent solar time gets at the reasons for this. Around the summer solstice in the Southern hemisphere, each apparent solar day is longer than average, both because because of the tilt of the Earth's axis and because the Earth is near perihelion, which pushes the sunrises and sunsets forward each day. In the winter the apparent solar days are also longer than average because of the tilt of the axis, but tempered by the fact that the Earth is near aphelion so the effect is smaller. In the northern hemisphere the equivalent effect would be that the earliest sunrise would probably be about 8 days before the solstice and and the latest about 2 weeks after the winter solstice (I don't know for sure that the numbers are exactly the same, but I assume so). See also equation of time. Rckrone (talk) 07:29, 18 April 2010 (UTC)

You can ansewer the first part of this yourself here. The World Clock – Time Zones--Aspro (talk) 07:38, 18 April 2010 (UTC)

To add something to what I said before, the degree of this effect is going to depend on your latitude. At latitudes closer to the equator where the length of daylight fluctuates less, the shift in the apparent solar day compared to the official time will dominate more in terms of determining earliest/latest sunrise/sunset, while at farther latitudes the larger fluctuation in length of daylight will put those earliest/latest days closer to the solstices. So those 8 days and 2 weeks numbers would apply only to the northern latitude equivalent to yours. Rckrone (talk) 07:56, 18 April 2010 (UTC)

Yes, it is the same in the northern hemisphere (our earliest sunset is mid-December and our latest sunrise is early January). I puzzled over this apparent asymmetry for about forty years (not continuously!), until I realised that the effect is caused simply by the shift in the time at which the sun is at its highest (local noon), so it is not an asymmetry at all (at least not in the way I had thouhgt). The BBC gives a concise explanation. The effect changes over centuries, but has been this way round since the year 1246. Dbfirs 08:19, 18 April 2010 (UTC)

OP, if you are correct that "earliest sunset is about eight days before the winter solstice," then NO it is not the same throughout the north. Where I live, the earliest sunset occurs on December 5th-ish. By the way, if we used sundials rather than clocks, earliest sunrise/latest sunset would occur on or about the date of the summer solstice, and vice-versa for the winter date. But we use clocks based on the artificial "mean sun," which always goes exactly the same speed; this leads to the discrepency between clock-noon/midnight and true-noon/midnight, which in turn makes the earliest/latest (clock-time) "horizon crosses" dates vary from the solstice dates. 63.17.77.124 (talk) 02:29, 20 April 2010 (UTC)

My thanks to everyone who contributed to this thread. All contributions have been very useful. I am now much wiser on the matter than I was a week ago. I will summarise the situation as follows:

• Regardless of the hemisphere, the earliest events (earliest sunrise and earliest sunset) occur earlier than the solstice. (Earliest sunrise occurs earlier than the summer solstice; and earliest sunset occurs earlier than the winter solstice.)
• Regardless of the hemisphere, the latest events occur later than the solstice. (Latest sunrise occurs later than the winter solstice; and latest sunset occurs later than the summer solstice.) Dolphin (t) 02:57, 20 April 2010 (UTC)

A neat summary! If I understand the Equation of time correctly, this pattern is just coincidental because the graph crosses the axis around the time of the solstices (zeros on Christmas day and June 13th), and the effect at the December solstice should be greater than the effect at the June solstice (does this correspond to observations in both hemispheres?). This will change in a few centuries. Dbfirs 12:45, 22 April 2010 (UTC)

Concentration of urine

In which part of nephron actual concentration of urine is determined? —Preceding unsigned comment added by Aditya Handargule (talk • contribs) 07:34, 18 April 2010 (UTC)

I don't understand the question, please clarify. StuRat (talk) 13:59, 18 April 2010 (UTC)

Perhaps the questioner can find answers in the articles Nephron, Kidney (Kidney#Osmolality regulation, perhaps?) or Renal physiology -- 174.24.208.192 (talk) 17:26, 18 April 2010 (UTC)

Short answer: collecting ducts alteripse (talk) 18:57, 18 April 2010 (UTC)

enzyme activity

an increase in enzyme activity in a cell is mechanistically due to trascription. this mechanism can be domenstrated by: a)measuring total enzyme acticity in the cell free extract. b)ELISA. c)nothern blot d)western blot. —Preceding unsigned comment added by Pradyumn chauhan (talk • contribs) 10:00, 18 April 2010 (UTC)

We won't do your homework for you. The real point of multiple choice homework questions like this is not to "get the answer", but to make you look up, read about, and understand the concepts involved in the question. I suggest you start with transcription (genetics) and also check out some or all of mRNA, enzyme, ELISA, northern blotting and western blotting. If you have problems understanding any of these pages come back here and we will be glad to help. 131.111.185.69 (talk) 10:58, 18 April 2010 (UTC)

Proposed emergency ash reducing: "Rapid glacier removal operation" off the top of volcano on Iceland.

Goal: Substantially cut down on the international healthcare expenses, in the years to come, stemming from the currently ongoing eruption.

Perhaps a little over-dramatized (but not too much!), one might say that:

The Volcanic ash in the air, is basically microscopically tiny pieces of razor sharp broken glass that is swirling around, all over Europe.

(Hence, neither you nor the Wildlife of the northern hemisphere (which cannot stay indoors keeping the doors shut on bad days), would like to have too much, or any at all, of this in your lungs!).

The ammount of emitted volcanic ash is first and foremost determined by the Volcanic Explosivity Index (VEI) of the volcano in question. (The VEI ranges from "gentle" (VEI=0) to "mega-colossal" (VEI=8)).

The ongoing eruption of the volcano: "Eyjafjallajökull" on Iceland, is currently rated as having a VEI between 0 and 1. (i.e. the ammount of volcanic ash should not be too bad).
But the ash-problem is dramatically exasperated by the meltwater from the Glacier that rests on top of the volcano, because the meltwater flows down into the volcano where it then explosively evaporates. ;-(

Q1: Therefore I wonder, why are not the combined military forces of Iceland, Europe, Russia and North America, trying to mitigate the ash-problem by employing Directed-energy weapons and microwave Masers (so that the glacier could be melted away as if it was ice inside a Microwave oven).
(Some of the pictures in the news seems to show that because of wind in the area, then visibility is good enough! i.e. the target glacier is not covered by smoke that would block enery rays).

Q2: If the above, for some reason, is out of the question then why are they not employing Napalm to do the job?
Even though one, of course, would loose the "surgical precision" of cutting away the ice with the above mentioned "rayguns". Yet, there surely must be more than one heroic and competent icelander that would be willing to walk up there and skillfully place the Napalm by hand! (Of course one would have to be really confident that the result of ones action would be an overall reduction of the waterflow down into the volcano!).

Of course, within a couple of weeks then the volcano itself will have melted a hole in the glacier, but much of that meltwater will have gone down and exploded in the volcano. A few weeks or days of unnecessary intense ash exhaustion ammounts to a big difference!

One might argue that the above mentioned operations would be horribly expensive -- and they would have to act really fast, which will make it even more expensive -- but compared to the saved worldwide expences for healthcare in the years to come, then the cost of a "Rapid glacier removal operation" would be truly negligeble.
--89.9.57.218 (talk) 14:28, 18 April 2010 (UTC)

This may cause bigger problems:

Hooper warned that the eruption may be only a taste of the future if climate change causes ice sheets to melt further. As the last ice age ended, volcanic activity in Iceland increased 30-fold because of reduced pressure on the earth’s mantle.

“Since the 19th century the ice caps in Iceland have been shrinking yet further,” said Hooper. “This will lead to additional magma generation, so we should expect more frequent voluminous eruptions in the future.” Count Iblis (talk) 14:34, 18 April 2010 (UTC) |}

One off-question reply (above) collapsed!
Please remember the How to answer a question guideline at the top of this page! which says: "Keep your answer within the scope of the question as stated.". (The reference desk is not a chat-room). (Well, not quite anyway!).
--89.9.5.27 (talk) 15:04, 18 April 2010 (UTC)

The ash is very high in the atmosphere (that is why it can move so far), we are at the bottom of the atmosphere. While it will eventually fall to earth (and is already doing so in places), the medical concerns are fairly minimal (the only medical advice I saw when ash was falling in Scotland was for asthma sufferers to make sure they had their inhalers with them when going outside, they weren't even advising them to stay indoors). I haven't seen any estimates of the medical cost, but I expect them to be small. The economic cost of suspending all air travel will probably be greater, anyway. Melting the glaciers could cause additional problems that would be worse (increased sea levels, increased eruptions, decreased albedo resulting in greater global warming, etc.). --Tango (talk) 14:51, 18 April 2010 (UTC)

(ec) I think the proposal falls under the category of Geoengineering - using large-scale, technological actions to control earth processes. Two problems emerge: first, it is not clear that any action we can take (including your ice-melting suggestion) would actually mitigate or even impact the danger due to volcanic eruption or ash. Our understanding of the complex interplays between these geophysical phenomena is limited, to say the least. We might even make the situation worse. The second problem is that such actions are very expensive, and it is hard to justify very expensive programs, especially if the results will be uncertain. One issue is that the scale is huge - we would need to expend considerable resources to match the quantity of energy that a volcano can unleash - and those resources might be better used to mitigate the problem in other ways. Nimur (talk) 14:57, 18 April 2010 (UTC)

Hmm...

1. There is no doubt about the fact that water flowing into a volcano will cause dramatic explosions! And thus cause substantially increased ammounts of volcanic ash!
2. The melting of just one small glacier will not be more than a «drop in the ocean» and will have far smaller consequences than all the ash avoided

--89.9.5.27 (talk) 15:16, 18 April 2010 (UTC)

Do you have any idea of the scale of things here? The energy to do what you suggest is enormous. We don't have a directed energy weapon that could melt even a minuscule amount of that ice. And napalm would not do a thing - all the heat goes up, almost none would melt the ice. You would probably need a volcano to melt that much ice :) Ariel. (talk) 15:27, 18 April 2010 (UTC)

That crazy idea doesn't have an icecube in hell chance of working. Dauto (talk) 15:29, 18 April 2010 (UTC)

I ran some numbers, assuming about 300x500x500 meters of ice, you would need 1.501x10^16 joules of energy. Look at Orders_of_magnitude_(energy)#1015 to see how much energy that is - it's about 10 megatons of TNT, i.e. an atom bomb - actually several of them. And even that would not be enough, since most of the energy would be wasted, and sent up into space. Ariel. (talk) 15:38, 18 April 2010 (UTC)

Ah, yes! These are the kind of enlightening replies that I (the OP) was hoping for. Thank you all!
Hmm.. If napalm will not work because most of its heat energy would go upwards...
...Then how about Thermite?
Of course one might need a "few hundred pounds" of it, but one might be able to use it to burn a channel in the glacier, which would divert at least large ammounts of water away from flowing into the volcano. --89.9.5.27 (talk) 15:45, 18 April 2010 (UTC)

A few hundred? While thermite would probably do a good job, and iceland actually produces lots of aluminium, a quick calculation shows that termite can melt about 11 times it's mass in water ice. So 300 pounds of thermite can melt about 36 gallons of water. I don't think that's going to help much. The scale of planetary events is stupendous. Humans don't come close to controlling those quantities of energy. Ariel. (talk)

I have no doubt that if we had solid evidence that melting a glacier would be worth the effort, we could marshal the technology and the resources to do what the OP has suggested (perhaps the most effective technologies would not be napalm or ray-guns, but we could analyze and design an effective method). I disagree with some of the assertions that humans are incapable of controlling that much energy. For perspective, look at what humans are already are capable of. We regularly move mountains; we make the rain start or stop; we control the weather; we generate earthquakes (and control for the natural ones); we split continents in half (actually, we've done this more than once!); we have moved the ocean; we have changed the topology of canyons and filled them up; we have chemically modified our atmosphere many times in many ways; and we harness more energy than a volcano every single day. But all of these things are difficult; they are expensive, they require a huge degree of cooperation, and many times, they have unintended consequences - sometimes the side-effects outlive the original purpose with catastrophic results. The above seemingly-miraculous feats of technology have historically been justifiable, despite the resources necessary. So - while the nay-sayers here are bringing up some valid numbers - and it is totally accurate to say that it would require a huge quantity of prohibitively expensive resources - it all boils down to this. If we decided, with a confidence level beyond a reasonable doubt, that we could make this volcano situation better by melting ice (or any other sort of action), we would take that action, despite its resource-cost. But as of right now, our understanding of the situation is that its effects are actually too small to warrant the sort of massive engineering and economic burden of addressing the situation at the source. It is more efficient to divert aircraft pathways - it is more efficient to accept and plan for (or neglect) any potential global health or climate hazards. All things considered, and even though this volcanic eruption is huge in scale, it is a metaphorical "drop in the bucket" in terms of global resource allocation. It is more effective for us to focus on small expenditures of energy - like dredging the East River to allow super-post-Panamax ships to dock on the East Coast, saving millions of gallons of petroleum that would otherwise be needed to drive freight from a more distant port. So, a tiny project like dredging a river can have trillions of dollars of economic significance; while "de-volcano-izing Iceland" would be extremely expensive with very little direct return (a mere $200 million per day, petty change by comparison). Ultimately, teams of politicians make decisions about which resource expenditures are "cost-effective" - hopefully guided by scientific and engineering analysis. But I think it's unfair to the OP to categorically tell him/her that his idea is "impossible." It's certainly possible - it's just not efficient. Nimur (talk) 16:51, 18 April 2010 (UTC)

A bit of lateral thinking to reduce the resources required: On the equator each square meter receives about 400 watts of the sun's energy per square meter. At the latitudes of Iceland, it might be possible to speed up the melting by reducing this glacier's albedo. This could be done with such things as tons and tons of lamp black or even tons and tones of grey dust. The only problem remaining is where to get enough at such sort notice and how would you cover twenty square miles of glacier with it... Oh! But wait !!!--Aspro (talk) 16:58, 18 April 2010 (UTC)

Perhaps most interesting is that in this era of presumed energy shortage, it is still not cost-effective to harness the immense quantity of freely available geothermal energy that is currently being wasted "melting ice" instead of powering our automobiles and internet data centers. Iceland is ahead of the game, but imagine if they developed the technology to capture and export the volcanic energy, instead of letting it go to waste. I don't know what a volcano-energy-harvester would look like, but I have a sneaking suspicion it would look a lot like this: thousands of tons of very expensive steel structure, tubes, pipes, pumps, and chemical reactors. But why would we waste our efforts harnessing easily-available energy that rose to the surface under its own power, when there is so much energy available many miles below the ocean floor, thousands of miles away from where it is needed? Nimur (talk) 17:04, 18 April 2010 (UTC)

The big problem with harvesting energy from a volcano is that it is too concentrated: you'll have trouble keeping the harvesting equipment intact. --Carnildo (talk) 01:41, 20 April 2010 (UTC)

If shrinking of glaciers increases volcanic activity, then that should be proof that global warming increases volcanic and seismic activity! But the problem with your idea is that the current eruption could also trigger a second eruption at Katla which sits underneath a larger glacier and would produce even more ash. ~AH1^(TCU) 01:03, 22 April 2010 (UTC)

Asexual reproduction

What is the real difference between fragmentation and budding? Is strobilation a form of budding? Or should it be considered a form of larval amplification? Propagule formation is or is not a type of asexual reproduction?

Thanks in advance.--82.55.196.145 (talk) 15:56, 18 April 2010 (UTC)

I think fragmentation happens to the organism, while budding is done by the organism. To me strobilation does not seem to be a form of budding, because the bud is specially made for the purpose, but strobilation is pieces of the entire animal. But all that is just guessing. Ariel. (talk) 17:08, 18 April 2010 (UTC)

... and propagule can be either sexual or asexual, depending on the part used. Dbfirs 20:14, 18 April 2010 (UTC)

Ok, thanks; I imagined the difference was the one suggested by Ariel, but I read that bulbils of Allium are produced through a fragmentation event! Ephyrae are made for the specific porpouse of strobilation and they are not pieces of the animal, but real individuals. I'm a little bit confused.--87.3.123.226 (talk) 11:04, 19 April 2010 (UTC)

iodized salt

how do they add the iodine to salt . do they mix it with powdered iodine or soak it in a liquid iodine solution —Preceding unsigned comment added by Jonny12350 (talk • contribs) 16:05, 18 April 2010 (UTC)

The NY times reference link in our iodised salt article says they spray two ounces of potassium iodate on each ton of salt ... in the Third World. Haven't found yet the process used in the industrialized countries. Comet Tuttle (talk) 16:17, 18 April 2010 (UTC)

Here it is: This page from the "Salt Institute" says, "Modern salt plants routinely spray potassium iodide or potassium iodate onto the salt while it moves along a conveyor belt before it is packaged. In lower-tech operations, iodine is sometimes added as a dry ingredient and physically mixed with the salt." Apparently the US FDA doesn't permit the use of potassium iodate for this purpose, though it's the most common additive globally; so in the US they have to add a couple of additives because otherwise, "Without a stabilizer, potassium iodide is oxidized to iodine and lost by volatilization from the product." Comet Tuttle (talk) 16:30, 18 April 2010 (UTC)

The bit about potassium iodate made me wonder why it's not permitted by the FDA, and this page has some more info if anyone else is curious. That page also has some complaints on the accuracy of the wikipedia article on potassium iodate. Ariel. (talk) 16:52, 18 April 2010 (UTC)

Another discussion of various methods. --jpgordon^{::==( o )} 17:55, 18 April 2010 (UTC)

Wikipedia is the encyclopedia anyone can edit...why didn't they fix what was wrong (or even add a question to the talkpage, so it would get fixed) instead of just complaining off-site? They have two complaints: a cite-needed statement about FDA approval (now removed, because they link an FDA letter to the contrary) and a dosage chart...from WHO which they claim is a bogus-pills vendor? Anyway, back to your regularly-scheduled discussion. DMacks (talk) 03:44, 19 April 2010 (UTC)

Saltwater ecosystems

I am trying to find information on saltwater ecosystems, mainly what animals live in saltwater and what their diets are. Can someone help me out? Thanks, Eagles 24/7 (C) 17:28, 18 April 2010 (UTC)

It helps to know that the ocean is the most common natural salt-water environment - so you can search for life forms that live in the ocean. Invariably, these will be saltwater ecosystems (though some organisms live in both salt- and fresh-water, or brackish environments). Take a look at the "lifeforms" section of our marine biology article to get started; there are hundreds of links within that section alone. There are too many animals in such environments to make a general statement about their diet - each organism fulfills a different ecological niche - but if you can narrow down a little, we can help you find information about specific organisms. For example, baleen whales are marine animals that mostly eat krill. Nimur (talk) 17:51, 18 April 2010 (UTC)

Which, of the millions of species which live in saltwater, are you interested in ? StuRat (talk) 17:52, 18 April 2010 (UTC)

@Nimur: Thanks, I'll go check that out. @StuRat: I'm not really sure which ones I'm looking for, but I'll figure it out. Thanks, Eagles 24/7 (C) 18:02, 18 April 2010 (UTC)

Historical Alternatives to Ballistic Pendulums

Hello. Were there any historical alternatives to ballistic pendulums when finding bullet speed (perhaps shooting a bullet in a tank of water, which would be safer)? Thanks in advance. --Mayfare (talk) 17:29, 18 April 2010 (UTC)

SPARK SHADOWGRAPHS have been in use for a while.[11]. There are also ballistic boxes but I don't know how good they are for working out velocity.[12]--Aspro (talk) 17:56, 18 April 2010 (UTC)

You can perform chemical analysis on the charge to estimate total released energy, but the purpose of such testing is to account for "non-ideal" characteristics. Take a look at ballistics - particularly internal ballistics (although all the various categories are relevant). Some firearm muzzle velocity can be measured with RADAR - especially if the projectile is large (though it can also be applied to smaller munitions). Here's a RADAR to measure ballistics for large artillery. Nimur (talk) 17:55, 18 April 2010 (UTC)

You can measure the speed directly using a high speed camera too. SteveBaker (talk) 21:05, 18 April 2010 (UTC)

ocean currents

why do most of the warm ocean currents flow along east coast while cold currents flow through west coast? —Preceding unsigned comment added by 117.200.67.69 (talk) 17:35, 18 April 2010 (UTC)

Which coasts do you mean ? The US ? StuRat (talk) 17:45, 18 April 2010 (UTC)

The relevant article is boundary current. These processes result from the Coriolis effect. There are some exceptions to the general rule the OP has identified, because geography is complex and ocean currents are affected by many interacting parameters. Nimur (talk) 17:57, 18 April 2010 (UTC)

Coriolis by itself doesn't do it. The main reason is that the ocean's movement is 'forced' by the prevailing winds which are from east to west at the tropics (trade winds) and from west to east at temperate latitudes (westerlies). Dauto (talk) 18:39, 18 April 2010 (UTC)

True, but Coriolis is responsible for the lateral components of both trade winds and westerlies. Dbfirs 20:08, 18 April 2010 (UTC)

See Gulf Stream, Labrador Current and California Current for details on specific currents around the US. ~AH1^(TCU) 00:59, 22 April 2010 (UTC)

bond formation of SiO

what type of bonds involve in SiO(Silicon mono oxide).If they are different to CO (Carbon Mono Oxide ) plz give explaination.--True path finder (talk) 19:57, 18 April 2010 (UTC)

I would expect they are the same as carbon monoxide (CO): One O⁺ with a triple bond to a C^-. --The High Fin Sperm Whale 21:11, 18 April 2010 (UTC)

The silicon monoxide article would be a good place to find this information. Not every property or bonding pattern from carbon structures is identical. DMacks (talk) 14:09, 19 April 2010 (UTC)

single crystal chalk (kitchen chemistry woohoo!)

My friend wants to know if powdered chalk can reconstituted into more solid chunks of chalk. (It's magnesium carbonate.) It's basically for more convenient handling as gymnasium weights, rather than any sort of blackboard-writing. My current plan is to dissolve the chalk in boiling vinegar, and then slowly distill it over a long period (an hour?). Will this work? John Riemann Soong (talk) 21:31, 18 April 2010 (UTC)

Do you mean chalk, gypsum or magnesium carbonate? The stuff you write on blackboards with, despite the common name, is gypsum. Neither gypsum or chalk is magnesium carbonate. Chalk is calcium carbonate and gypsum is calcium sulfate dihydrate. I'm not sure any of them will dissolve in vinegar. They will react with it and become some other compound, so distillation wouldn't get it back. To get it to form a large crystal you probably have to heat it up a lot until it melts (probably without exposing it to oxygen, or anything else it might react with, in the process) and then cool it slowly. (The melting point of chalk is 825°C, so not easy to reach.) --Tango (talk) 22:04, 18 April 2010 (UTC)

{ec}You will decompose it to magnesium acetate, and carbon dioxide will escape. You may be able to crystalise that salt however and then carve it into a weight, as it will not be very hard. However don't expect it to be too strong either! It is likely to be brittle. You will need a lot of vinegar to do this. Tens of liters. Melting it will not be a kitchen capability. It is easier to melt lead or solder in the kitchen if you want to make weights. Graeme Bartlett (talk) 22:07, 18 April 2010 (UTC)

The "chalk" I usually see in gyms and billiard-halls is more of a compressed chunk of powder rather than a single crystal. A single crystal would probably be hard, have a clean geometric shape, and be translucent/transparent rather than an amorphous powdery opaque blob. DMacks (talk) 22:16, 18 April 2010 (UTC)

Well I meant gymnasium chalk MgCO3. AFAIK I would get magnesium bicarbonate if I dissolve at a low pH, which is water soluble. I also expect boiling water to help me dissolve the rest. Completely protonating magnesium carbonate to carbonic acid + magnesium acetate is likely to be difficult, naturally. John Riemann Soong (talk) 00:40, 19 April 2010 (UTC)

magnesium bicarbonate is not very stable and you really need to have a high pressure of carbondioxide to counter the decomposition. Heat would help the decomposition by boiling off carbon dioxide, and you are more likely to get a crust forming than a single crystal. Graeme Bartlett (talk) 09:08, 19 April 2010 (UTC)

If all you need is weights, why not just mix it with a small amount of glue? And why chalk for weights anyway? I can think of lots of other materials that might be better. Ariel. (talk) 09:15, 19 April 2010 (UTC)

Completely protonating magnesium carbonate to carbonic acid + magnesium acetate is not difficult at all (this will happen when you dissolve it), and will result in a lot of CO2 being released. This works for any carbonate or bicarbonate salt.24.150.18.30 (talk) 01:21, 20 April 2010 (UTC)

Is there any way to trigger weak polymerisation? John Riemann Soong (talk) 20:54, 20 April 2010 (UTC)

April 19

Rain will clear the skies of ash, but can we artificially fill up the water by nuclear power?

1. Many submarines and some large ships use nuclear reactors for propulsion, and for all of their energy needs.
   If one of them were to anchor up off the coast of Iceland and, running its nuclear reactor on "full steam" (pun intended), used all the heat energy available, then how much sea water could theoretically be evaporated per 24 hours?
2. Nuclear power plants often use seawater for cooling.
   If one of the power plants on the coast of Europe were to be solely employed to evaporate water, then how well would it do per 24 hours?

All I have heard about rain-making, earlier, is the Cloud seeding, but at least that part of the job is allready well and surely taken care of by the volcano Eyjafjallajökull on Iceland. Now, if only we could get some millions of Cubic metre of extra water up in the skies, to soak the volcanic ash...
--Seren-dipper (talk) 00:16, 19 April 2010 (UTC)

It would be insignificant. Even if you could get together a gigawatt of electricity generation to devote to evaporating water (and that corresponds to several nuclear power plants) it would only be equivalent to the energy from the sun on about 4 square kilometres of ocean (can someone check my arithmetic?). The sun is so much more powerful than anything we can create that there is really no point us trying to help it along. --Tango (talk) 00:26, 19 April 2010 (UTC)

That's correct. it would be completely insignificant. Besides, lack of humidity in the air is not the limiting factor that prevents rain. Atmospheric lift is the main controlling factor. BTW cloud seeding doesn't work either. Dauto (talk) 01:27, 19 April 2010 (UTC)

I question the accuracy of the last statement. Yes the state of research is rather poor, it's difficult to prove what would have happened if you hadn't seeded and and many of those who use or promote it don't have good evidence it works (and personally I expect it doesn't work as well as many of them may like) however

Cloud seeding has been shown to be effective in altering cloud structure and size and in converting supercooled liquid water to ice particles. The amount of precipitation due to seeding is difficult to quantify. Cloud seeding may also suppress precipitation.[citation needed]

Overall, there is general expectation that winter cloud seeding over mountains will produce snow, expressed by professional organizations.[1][2][3][4] There is statistical evidence for seasonal precipitation increases of about 10% with winter seeding.[5] The World Meteorological Organization has indicated that cloud seeding produces positive results in many cases but is dependent on many factors such as specificity of clouds, wind speed and direction, and terrain.

These don't exactly suggest it doesn't work (which I take to mean there's strong evidence it hardly ever or even never works). Also:

A 2003 study[23] by the United States National Academy of Sciences urges a national research program to clear up remaining questions about weather modification's efficacy and practice.

Which while not saying it works, hardly suggests the NAS thinks it's a clear cut case with strong evidence it never works.

As I mentioned there are plenty of people, particularly developing countries who use cloud seeding and while I would agree many of them don't appear to have undertaken research or otherwise have good evidence they're doing anything useful, some of this does take place in developed, democractic countries where there's perhaps lesser ability for completely useless programmes to be undertaken and usually some requirement for evidence for such programmes. (None of this means they're immune to carrying out nearly useless programmes with little evidence to support the benefit.) E.g.

In Australia, CSIRO’s activities in Tasmania in the 1960s were successful[citation needed]. Seeding over the Hydro-Electricity Commission catchment area on the Central Plateau achieved rainfall increases as high as 30% in autumn. The Tasmanian experiments were so successful that the Commission has regularly undertaken seeding ever since in mountainous parts of the State.

While uncited, it's easy to find evidence this programme continues in Australia [13]. Some of the latest research I could find [14] (PRs [15] [16])

The Chinese do do their own research although a lot of it isn't published in peer reviewed scientific journals (or at least recognised ones) unfortunately so many would feel it's next to useless, but e.g. [17] [18] [19]

Note that even if the effect is small that many would feel it's not cost effective, or it simply changes the place or time of rainfall, or is otherwise useless for many of the purposes it's advocated and used for, this doesn't mean it doesn't work per se.

Recently of course, various geo-engineering suggestions to reduce global warming, including cloud seeding are being consider, albeit not generally to produce or reduce precipitation, e.g. [20]

Nil Einne (talk) 09:17, 19 April 2010 (UTC)

I certainly don't see how it could help. When you look at those impressive photos of the volcano (this one, in particular) the white stuff coming out of the top is steam (well, water vapor) - the dark stuff is the ash. As you can see, there is already a lot more steam than ash - and the steam isn't winning! SteveBaker (talk) 01:51, 19 April 2010 (UTC)

Surely all the ash is way above the height that generates rainfall. —Preceding unsigned comment added by 86.4.186.107 (talk) 05:48, 19 April 2010 (UTC)

Some, but not all. StuRat (talk) 14:30, 19 April 2010 (UTC)

use for nuclear waste

What articles cover using the heat generated by nuclear waste to boil water after the nuclear waste is processed by "freezing" it into ceramic or glass marbles to fill up a tank through which water is passed? 71.100.1.71 (talk) 03:45, 19 April 2010 (UTC)

I don't think there is an article. The heat given of by wast is thought of as 'low grade' heat. In economic terms, the capital investment for the plant, machinery and maintenance, that would be need to utilize this low grade heat for something, would be more than the cost of using other energy sources. In other words, with current technology, it is not worth the effort.--Aspro (talk) 08:17, 19 April 2010 (UTC)

The OP correctly spelled "waste". Cuddlyable3 (talk) 08:51, 19 April 2010 (UTC)

This article: Nuclear reprocessing. Instead of using the heat directly, the parts of the waste that still contain usable energy are separated from the ashes, and then reused. The article should also give you links to reactors that are able to burn uranium down to basically nothing, with almost no leftover (radioactive) waste at all. The article should also talk about the pros and cons of doing so. Ariel. (talk) 09:12, 19 April 2010 (UTC)

Not down to "nothing", but rather down to stable (non-radioactive) elements and isotopes. StuRat (talk) 14:17, 19 April 2010 (UTC)

Err, you still end up with fission products, which are very nasty and radioactive. You just don't end up with as much waste as you do if you don't do reprocessing (you use up the transuranics and actinides). You still have nasty waste, though. Just less of it. It still takes hundreds of years to decay (and the fact that the half-life is shorter than the transuranics is an indication that it is a higher level of waste). --Mr.98 (talk) 14:29, 19 April 2010 (UTC)

I believe that there was some thought of using radioactive isotopes as a direct source of home heating, early on, before the dangers of radioactivity became apparent. Now, we'd also have to be concerned about terrorists getting hold of the devices and releasing the radioactive material in a city as part of a "dirty bomb".

One application where it might make more sense is in long-term human space flights, where using conventional fuel for heating is out of the question. Perhaps, once a fuel rod is "used up" in the normal electricity generating reactor, it could be retained as a heat source. StuRat (talk) 14:22, 19 April 2010 (UTC)

Radioisotope thermoelectric generator does something like this. There are rather specific criteria for which isotopes are good candidates for this. I'm doubtful that the random slew of fission products you get in high-level waste would have appropriate characteristics. --Mr.98 (talk) 14:29, 19 April 2010 (UTC)

For deep space exploration Stirling engines show more promise than RTGs due to their higher efficiency. NASA have had prototypes, running faultlessly, for a couple of years at a time. Mono isotopes would again be the best option for the heat source due to shielding considerations (with perhaps additional heat supplied by a focused solar collector). Exhausted fuel rods would require lots more shielding, which is what one tries to avoid in space craft. If the Moon is used as a staging post, then a 'minimum mass' reactor may be practical using Luna sourced material for the shield. Mass Estimates of Very Small Reactor Cores Fueled by Uranium-235, U-233 and Cm-245 These reactors should also have very long operating lives. --Aspro (talk) 17:39, 19 April 2010 (UTC)

ISS framework overbuilt?

I see that the backbone of the International Space Station weighs 147 tons on earth. Given the weightless environment of orbit, what need is there for such strength?Bobstuart (talk) 03:55, 19 April 2010 (UTC)

Spacecraft weigh a lot for a variety of reasons. The ISS is manned, so it must be pressurized - therefore, it must be built to withstand the pressure gradient between its interior and the vacuum outside. Also, the modules must be structurally supported, so there is a need for some quantity of material to connect the pieces. Finally, keep in mind that the space station components must be built on the ground (in "1-G") and survive a very vigorous shaking during launch (possibly subject to serious vibrations and accelerations). The structure has to withstand all of these conditions. In any case, I think you might underestimate just how much materials actually weigh (rather, how much mass they have). All told, 150 tons is not a whole lot of material; you might try to compare the mass of a similar-sized office-building on Earth. I've seen estimates for the mass of a house averaging out to about one to two tons per square-foot of occupied area (of course, the mass isn't uniformly distributed, with more mass in the walls than on empty floor); so the ISS weighs about as much as a small corner of your kitchen! Considering its habitable volume, it's actually pretty light. You might also want to try comparing it to an aircraft. A top-of-the-line single seat F-35 has a takeoff weight of about 30 tons - again, the ISS is pretty darned light, considering that it houses around six people "comfortably" - living areas, bathroom, work areas, laboratory, and exercise facility! Nimur (talk) 05:18, 19 April 2010 (UTC)

First, it's vanishingly unlikely that it is overbuilt: given the cost of lofting mass into orbit, you can be reasonably sure that the rocket scientists pared the weight to the bone. Somewhat per Nimur's answer, you're perhaps confusing weightless with massless. As & when the ISS' position is moved, the structural components need to get all of the mass to move in lockstep; weight is not very relevant. Mass is, and needs a structure sufficient to enable all components to accelerate and then decelerate without coming to pieces. --Tagishsimon (talk) 10:20, 19 April 2010 (UTC)

That's the key here - the impact force when (for example) a 16 tonne remote controlled resupply vessel or a 78 tonne shuttle docks with the ISS is dependent on the mass - not the weight (Force = Mass x Acceleration) - and the mass is the same whether in free-fall or on earth. Also, the ISS needs to be boosted up to a higher orbit a couple of times a year - either using the engines of a docked spacecraft - or using the limited capability provided by a couple of rocket motors on the Zvezda module. So the ISS needs a certain amount of structural strength to avoid breaking up under that (rather gentle) acceleration too. But it is also true that the plans for the space station were scaled back after initial design and the construction of some of the parts were complete before that decision was made (8 modules of the 23 that the ISS was originally designed for were cancelled) - so there may be some over-design inherent in that process. SteveBaker (talk) 13:28, 19 April 2010 (UTC)

This brings up an interesting Q: Could it be built lighter if they used a series of widely distributed, tiny, continuous booster rockets for station-keeping ? Think of flames the size of lighters. Or, this might be a good application for ion engines, which are more efficient, but have very low thrust. Docking might need to be more gentle, too, perhaps using an automated system. The only flaw I see is if the station is occasionally "knocked out of position", say by contact with a cloud of space gas or the exhaust plume from a passing rocket. StuRat (talk) 14:02, 19 April 2010 (UTC)

No. Distributing the propulsion over many small rockets would degrade performance. Two problems are: inert mass and specific impulse, probably the most important metrics for "efficiency" of a rocket engine. Smaller engines have a higher inert mass fraction - you need proportionally more tube, pipe, valve, fuel tank, and so forth, per unit of energy extracted. And smaller engines, because of size constraints, generally must use designs with poorer specific impulse, meaning "worse mileage per gallon" (specific impulse is a more accurate description). You would significantly decrease the propulsion system effectiveness per unit mass if you split it up that way. What you might gain is high-frequency maneuverability - see reaction control system for one use of "tiny boosters." As far as ion engines, there are current technological limitations and practical issues with the total impulse - so while they have great specific impulse ("fuel efficiency"), they've got very little total power (no good land-vehicle analogy exists, but think of a super-efficient engine which is constrained to only operate at a couple miles per hour - great for some applications, but terrible for moving a large vehicle). Nimur (talk) 15:34, 19 April 2010 (UTC)

That's "terrible for rapidly accelerating a large vehicle", but great for slowly moving it (or keeping it from moving, in this case), in the absence of any friction. Do you understand that I propose using the ion engines continuously, for station keeping (not just for brief periods as conventional engines are used) ? Thus, if they are used for 1000 times the duration, then 1000 times less thrust is fine. Ideally the orbit would be kept completely constant in this way, as opposed to being allowed to decay, then corrected. This would have other advantages, due to not having to deal with a variable orbital height, speed, and period. StuRat (talk) 16:54, 19 April 2010 (UTC)

Right. But it doesn't matter if they're used continuously or non-continuously. The total amount of impulse is the limit - $F\Delta t$. Measures of specific impulse (and total impulse) are already normalized so that it is easy to compare different types of burns, including fast powerful burns and slow, steady, low-intensity burns. Ion engines have higher specific impulse but less total impulse than we can pack into a chemical rocket. Perhaps technology improvements will change the maximum total impulse, as it is an engineering limit, and not a physical limit. Consequently, for a given mass budget, a chemical rocket is more capable of delivering the impulse (and therefore, for the ISS as a whole vehicle, the required delta v) necessary to station-keep. Nimur (talk) 17:01, 19 April 2010 (UTC)

Here's a good read, StuRat: Smart 1#Spacecraft design. As you can see, the Hall effect thruster was very efficient in terms of energy extracted per mass of propellant. But the total quantity of energy extracted, was actually abysmally small. Because the spacecraft was tiny (300 kg or so), this small quantity of energy was sufficient to reach 3700 m/s delta V, mostly for lunar injection; but to maintain a stable orbit to make this possible, they had to fly circles around the planet. Really, the magic was in precise mathematical analysis to optimize the gravity assist from the moon with as little energy expenditure as possible. I doubt this technology would be remotely feasible for station-keeping against gas drag. But what do I know... Nimur (talk) 17:12, 19 April 2010 (UTC)

Are you counting the reduction in the weight of the frame, which distributed, lower thrust ion engines would allow ? StuRat (talk) 17:10, 19 April 2010 (UTC)

Does anybody have some numbers? Frame weight vs other bits? Maximum accelerations? Certainly, those could be reduced by shock absorbers for the docking process and by using ion drive or smaller rockets, which might well save more structural weight than they cost in fuel. I agree that the frame might see its highest loads during the trip to space, but perhaps it is not needed in space. Very few lightweight modern vehicles use a separate frame. Aircraft have been largely monocoques since the 30s.

One of the funniest pictures I ever saw was of an (Atlas?) rocket in a museum. The pressure to the upper fuel tank had failed, and it had buckled under the weight of the payload. The ISS's occupied modules are pressure vessels, intrinsically strong and rigid. They could have been reinforced with aramid windings if any more structure was needed, and gained a lot of protection from space junk or meteorites.

Small sub-frames would suffice for mounting solar panels, radiators, etc. If those components are over-built soly to survive launching, they could be re-designed to reduce inertia loads by having packing material discarded after delivery. All connections could be designed with the minimum rigidity needed, to help localize any impact damage. —Preceding unsigned comment added by Bobstuart (talk • contribs) 08:06, 20 April 2010 (UTC)

I'm skeptical of the argument that the heavy frame is needed for the trip into space, as the components are brought up a few at a time, and can be well packed to protect them from g-forces. StuRat (talk) 13:37, 20 April 2010 (UTC)

sperm for Iceland

Seriously, for those not in the know. Icelanders want diversity in there population due to many inherited genetic flaws. Is there somewhere I can get more information on this and find possibly a contact through which I can donate my sperm? 71.100.1.71 (talk) 03:56, 19 April 2010 (UTC)

Maybe they prefer some who can spell "their"?--Lgriot (talk) 07:39, 19 April 2010 (UTC)

What? It's about the population of there, thus "there population".—Tamfang (talk) 03:40, 20 April 2010 (UTC)

_{no, Tamfang , it is that population, to rhyme with tw**}

Here is a link to the Iceland Directorate of Health, which could provide some leads. Ghmyrtle (talk) 08:10, 19 April 2010 (UTC)

Joke responses

You must clearly specify whether your donation will be in U.S. or Imperial gallons which are 3.785 or 4.546 liters respectively. Cuddlyable3 (talk) 09:13, 19 April 2010 (UTC)

Are you trying to be BB? The OP didn't suggest anything about donating gallons of material. Maybe the intend to donate in litres? Or more likely in samples which I suspect (somewhat supported by Sperm donation) is the normal way sperm banks take donations. (The samples then being divided into seperate vials, the number depending on sample volume and practice of the sperm bank.) Or they're flexible and would donate in whatever units the Icelandic authorities want? Nil Einne (talk) 10:23, 19 April 2010 (UTC)

Iceland enjoyed massive injections of Anglo-American sperm during the Second World War. DuncanHill (talk) 10:41, 19 April 2010 (UTC)

"Enjoyed" you say? I'd like to see a reference to back up that claim.--Rallette (talk) 12:06, 19 April 2010 (UTC)

how do you cite the wistful look on an old lady's face as she recalls the young men who used to pop round for a helping of puffin? DuncanHill (talk) 12:13, 19 April 2010 (UTC)

Indeed. The things that lie concealed behind the formulaic "personal communication with author".--Rallette (talk) 12:20, 19 April 2010 (UTC)

Realistically, it seems that most IVF in Iceland is contracted out to other Nordic countries. Cryos International, out of Denmark, has a network of clinics and physicians. Because of the nature of this topic, they require you to register and log in in order to contact clinics; they are not looking for people who are just joking around about sperm donation. Nimur (talk) 17:22, 19 April 2010 (UTC)

being really happy ==> more brain damage?

What prevents dopamine neurotoxicity from being a problem in "naturally happy" people? For example, the intense rushes induced by naturally-produced beta-endorphins and runner's high? John Riemann Soong (talk) 04:08, 19 April 2010 (UTC)

My understanding is that dopamine neurotoxicity requires concentrations massively higher than could be achieved naturally -- it requires drugs, in other words. Also endorphins, which are related to opium, having a considerably stronger effect of suppressing the pain/suffering system than of activating the dopamine-dependent reward system. Looie496 (talk) 06:02, 19 April 2010 (UTC)

Yes, but it's possible to be really high while on an endorphin rush, to the extent that I will attest to its greater potency over alcohol or even methamphetamine. Which makes me wonder about the neurotoxicity of "natural" endorphin rushes (in general, not asking for medical advice). I know that if you combine physical exertion with a socially intense situation (like a party) the rush can be mind-blowing. John Riemann Soong (talk) 06:19, 19 April 2010 (UTC)

In addition to the levels being lower for a "natural high", the duration is also shorter. Unlike a 24-hour artificial high, a natural high probably only last a few hours, at most, and certainly not during sleep, giving the body time to reset/repair. StuRat (talk) 13:48, 19 April 2010 (UTC)

There are different kinds of "naturally happy" people. Some people go "happy" and benign after a stroke kills off some of their brain (and some do the opposite). I would not assume a naturally happy person has higher dopamine. --BozMo talk 09:29, 19 April 2010 (UTC)

Happiness is not a very precisely defined term. There is however evidence that people with extroverted personalities, who tend to be more sensitive to reward than average, generally have higher levels of brain dopamine function. I am not aware of evidence for any kind of natural motivational state giving rise to toxic levels of any brain chemical, with the exception that there is evidence for brain damage produced by stress-induced cortisol. Looie496 (talk) 22:36, 19 April 2010 (UTC)

Arterial injuries

Before I ask I should say that this is not a request for medical advice. I am not asking what one should do in the situation described, merely what medical opinion holds the prospects to be. I should also say that trying to picture this is not for the squeamish, but here goes. The article on blood squirt says that in the case of carotid arteries, "a completely severed artery will spurt blood for about 30 seconds and the blood isn't going to spurt much higher than the human head. If the artery is just nicked, on the other hand, the blood will spurt longer but will be coming out under pressure and spraying much further." If a person suffers an injury such that blood is squirting out of them under pressure like this, is there any hope for them? The mere thirty seconds until enough blood is lost that it no longer spurts suggests not to me, in the case of full severance, but I'm interested in the second scenario described in that quote. I suppose what I'm asking is whether blood can possibly clot under such high-pressure conditions, or whether applying pressure to a wound like that could possibly stem the flow. I suspect that in an operating theatre something could be done but I struggle to imagine how any victim of an injury to a major artery outside of such a favourable setting could do anything to save themselves. Am I right? Thanks in advance. — Trilobite 05:06, 19 April 2010 (UTC)

No severed major artery can clot fast enough to prevent death by exsanguination, but exsanguination can often be prevented by pressure on the wound in all major peripheral arteries, including the lower aorta. The carotids and upper aorta are a special case because the blood supply to half the brain would be immediately terminated even if pressure is applied to stop the bleeding. alteripse (talk) 10:54, 19 April 2010 (UTC)

Well, not quite -- depending on the patency of the vertebral arteries and the communicating arteries in the circle of Willis, even the complete loss of flow through a single carotid artery may not (and should not) fully interrupt the blood supply of a complete hemisphere. I know of cases where patients have both carotid arteries fully occluded (by atherosclerotic plaques) but who suffer no conspicuous symptoms — their brains are completely supplied with blood through the vertebral arteries. TenOfAllTrades(talk) 17:19, 19 April 2010 (UTC)

Perhaps, but collateral circulation is more likely benefit a gradually developing occlusion rather than a sudden complete one-sided interruption. While I would not be surprised if there have been occasional survivors I suspect those who do not suffer massive damage or death are in a small minority. alteripse (talk) 19:05, 19 April 2010 (UTC)

Oh, I agree that a slowly-developing occlusion will tend to lead to adaptation (and enlargement) of other vessels — but I would hesitate to jump to the conclusion that acute closure of a single carotid will lead to complete cessation of blood flow in one hemisphere. Part of the problem is that injuries which rapidly and completely occlude one otherwise-healthy carotid artery are quite rare; it's difficult to know exactly what would happen to a healthy individual in that situation. I do know that surgical ligation of the common carotid is indicated from time to time, but I'm having difficulty finding papers on recent cases. This paper suggests that roughly half of surgical ligations are accompanied by neurological symptoms or death, but it only deals with cases up to the early 1950s. TenOfAllTrades(talk) 21:53, 19 April 2010 (UTC)

To Alteripse & TenOfAllTrades: carotid endarterectomy involves cross-clamping the carotid artery. Axl ¤ [Talk] 07:39, 20 April 2010 (UTC)

can combine theory

DEAR SIR, GOOD DAY TO YOU.I WANT TO KNOW ABOUT SUPER STRING THEORY CAN COMBINE DNA STRUCTURE? NUCLEAR FUSION CAN COMBINE QUANTUM THEORY? PLEASE REPLY ME.THANK YOU. KOKOGYI,BURMA —Preceding unsigned comment added by 203.81.72.200 (talk) 05:53, 19 April 2010 (UTC)

First, please don't type in all caps; it is unpleasant to read. Anyway, what do you mean by "combine"? Someguy1221 (talk) 06:08, 19 April 2010 (UTC)

There can be very few connections between DNA structure and super-string theory. They are not at all the same sort of string!

Quantum mechanics does have some bearing on Nuclear fusion, but it is not essential for the basic theory.

Read our articles (linked above) for more information. I suppose that quantum theory could include nuclear fusion in its predictions, and super-strings are supposed to explain the whole universe, but they haven't got very far! Dbfirs 11:57, 19 April 2010 (UTC)

See the second comment on this blog posting Count Iblis (talk) 20:55, 19 April 2010 (UTC)

Test for swelling in knee joint

I vaguely remember a clever test for swelling in the knee, which involved the patient sitting with legs extended and the practitioner stroking the knee joint to empty it of fluid and then stroking it once more, in order for it to "fill up" again, if any swelling is indeed present.

I've tried Googling for it, but so far without joy. Can anyone point me in the right direction?

And no, this is not a request for medical advice, I'm not planning on using any information gained for diagnosis etc just assuaging curiosity. --Dweller (talk) 10:04, 19 April 2010 (UTC)

Milking the knee. Axl ¤ [Talk] 20:39, 19 April 2010 (UTC)

Thanks! --Dweller (talk) 10:19, 20 April 2010 (UTC)

Air Conditioning

is it true that split air conditioners are not capable of taking fresh air i.e. whether it recirculates the same air? if so the oxygen content will decrease in the room. 203.199.205.25 (talk) 10:21, 19 April 2010 (UTC)

This is not normally a problem when there are windows and doors to provide some air circulation, but in an overcrowded or sealed building there might be a build-up of carbon dioxide and a lack of oxygen even when the air conditioner is blowing cold air. Most countries have regulations about air changes per hour in buildings. Photosynthesising plants can help to restore the balance, but opening a window is usually more effective. Dbfirs 12:21, 19 April 2010 (UTC)

Well, think about it for a moment. It's not really any different from being in a room without any air conditioning. The oxygen depletion in such cases is hardly serious! SteveBaker (talk) 13:09, 19 April 2010 (UTC)

Circadian rhythm abnormalities in non-humans?

I recently discovered that I have delayed sleep phase syndrome, i.e. that my mind and body are biologically programmed to be most alert in the evenings and late at night and to crave sleep in the morning. I find myself wondering if natural circadian rhythm abnormalities have been observed in any other species. Does it ever happen that a member of a generally nocturnal species simply can't sleep during the day and can't stay alert at night? Or do diurnal non-human animals ever have a condition like mine? I know that species-atypical behavior is in most cases likely to get an animal in the wild killed, but has this ever been observed of animals in captivity (as the animal's natural behavior, not the result of any kind of human manipulation)? 71.104.119.240 (talk) 10:42, 19 April 2010 (UTC)

Think. You seem to be asking if a member of another species went to a doctor and complained of symptoms indicating that its sleep/activity cycle was out of synch with its peers. Or are you asking whether veterinarians ever make a diagnosis of delayed sleep phase in pets or farm or zoo animals? Or whether ethologists watching wild animals have ever diagnosed one as having an abnormal sleep cycle? Or whether the circadian rhythm pattern of a whole species fails to match some external standard derived from other species? alteripse (talk) 10:48, 19 April 2010 (UTC)

A large part of why human sleep patterns get messed up is that they can, without deadly consequences. This is also true of some other animals, like house cats. While they are naturally nocturnal, they can adjust their schedule, just like we can. Most animals, on the other hand, would stay in their nest/den during normal sleep time, whether they were actually asleep, or not, and go out to hunt for food when it's time for that. If they didn't get any sleep during the last sleep period, they would likely be sleepy enough when the next sleep period hits. Thus, unlike with humans, it's self-correcting. StuRat (talk) 13:34, 19 April 2010 (UTC)

There are lots of genetic mutations known to induce circadian rhythm abnormalities. The most extensive knowledge is for fruit flies, but there are also rhythm-altering mutations known for mice, rats, and maybe hamsters. In most studies the mutations are artificially induced, for example by subjecting fruit flies to X rays. Such mutations are bound to occur naturally to some degree, but assessing circadian rhythms is quite laborious, so there isn't very much information about their prevalence. (A caveat, though, is that the literature on circadian rhythms is vast and there may be work out there that I'm not aware of.) Looie496 (talk) 22:29, 19 April 2010 (UTC)

I wasn't aware that my question was that complex. How my question could be construed to be about anything other than human observation of abnormal patterns in an individual member of a species, I can't fathom. I'm not an idiot; I know animals don't go to the doctor and I wouldn't consider the biological patterns common to most members of a species somehow aberrant just because some other species has a different pattern. (The fact that I know the words "nocturnal" and "diurnal" perhaps ought to suggest that I'm familiar with the concept that different species often exhibit different patterns, no?) I don't care if there's any kind of formal diagnosis; I'm simply wondering if there has ever been an observation of an animal, in the wild or captivity, that had a persistent abnormal sleep cycle comparable to a human circadian rhythm sleep disorder. Looie496 gave the kind of answer I was looking for - thank you. 71.104.119.240 (talk) 03:38, 20 April 2010 (UTC)

Considering that the only way to verify that an animal is actually suffering from DSPS (the same way to verify a human is actually suffering from it) is to undergo treatment; you might ask about reports on animal studies of the various forms of treatment. Short of that, as someone else eluded to, there is no way to tell if an animal has DSPS or is simply lazy. --144.191.148.3 (talk) 17:57, 20 April 2010 (UTC)

I wasnt intending to insult you. Rather than accusing you of something silly, I was attempting to remind you that such a "sleep disorder" has a social and a subjective component that cannot exist in animals. The closest you could get would be some experimental situation where if you messed up the circadian rhythm of an expermental animal in a way that mimicked the objective features of the human sleep disorder, you might describe it as having the disorder, but even this model would have about the same relation to the human disorder as diagnosing depression in rodents. I stand by my suggestion that if you think about the components of human sleep phase disorder you will yourself recognize that it's not a question likely to have a meaningful answer. alteripse (talk) 19:14, 20 April 2010 (UTC)

Thank you, alteripse. I do understand where you're coming from, I appreciate your taking the time to respond to my question, and I'm sorry I was so touchy. I do see what you mean - that's why I used the word "abnormalities" instead of "disorder" in my question. I'm asking more about physiology than consequences. I recognize that the practical consequences will be different for humans and animals. I'm less concerned about whether the animals get to sleep or not than the observation of their circadian rhythms. Regardless of social consequences, biological systems that work in pretty much the same way can break down in pretty much the same way. A friend of mine has had hip trouble and so did one of my dogs. Another dog I know takes medication for anxiety, as do I. I presumably have some sort of abnormality of the suprachiasmic nucleus of the hypothalamus or a related structure; I wonder if any similar abnormality has been detected in members of another species on the basis of core temperature readings, unusual patterns of eating, sleeping, and/or alertness, etc. It may be an unusual question, and it's very possible that, for the reasons Looie mentioned among others, few if any scientists have taken an interest in naturally abnormal circadian rhythms among non-humans (or received a grant to research it) - but I still believe it's a legitimate question. 71.104.119.240 (talk) 20:13, 20 April 2010 (UTC)

Close. It's Suprachiasmatic nucleus --Aspro (talk) 21:59, 20 April 2010 (UTC)

Greenwich meridian.

Why does not the 0 deg meridian(WGS-84) pass through the Greenwich meridian?Or otherwise why is not the 0 deg meridian in WGS-84 chosen to pass through the Greenwich meridian? —Preceding unsigned comment added by 116.90.224.116 (talk) 11:14, 19 April 2010 (UTC)

You will find it explained here.--Rallette (talk) 11:54, 19 April 2010 (UTC)

Basically, an accidental difference, and since the choice is arbitrary, and the difference is only five and a half seconds of arc, it has not been necessary to standardize. Also, because of drifting tectonic plates, exact longitudes are impossible over decades or centuries. Dbfirs 12:09, 19 April 2010 (UTC)

How much ash to stop a car?

If the amount of volcanic ash kept increasing, which would be the first to stop operating - humans or cars? Thanks 89.240.44.159 (talk) 12:26, 19 April 2010 (UTC)

There are plenty of cases where people have driven cars through ash plumes - wrecking their engines in the process - yet living to tell the tale. People might well have problems breathing in dense ash - but we don't have to - we stay indoors or breathe filtered air or wear masks or whatever. Car engines can't do that. It's a bit complicated though - if the ash is fairly coarse, it clogs the air filter and the engine stops running without serious damage. If the ash is very fine (which it evidently is in the case of the current icelandic volcano) then it can bypass the filter and instead do serious damage to pistons, piston rings and cylinder liners that would probably allow the engine to continue to run - but make it burn oil and have poor compression. The ash can also work its' way into lubricated moving parts and cause rapid wear to bearings and such like. This USGS document is worth reading. "Change oil, oil filters, and air filters frequently (every 50 to 100 miles in heavy dust, i.e., less than 50 feet visibility; every 500 to 1,000 miles in light dust)." SteveBaker (talk) 13:06, 19 April 2010 (UTC)

Also note that people who must go outside in smoke/ash will take action to protect themselves, like wearing a wet rag over their mouth to act as a filter. StuRat (talk) 13:28, 19 April 2010 (UTC)

Wet rags may be better than nothing in an emergency, but this would be an opportunity to use some up of those N95 respirators which got stock-piled against the deadly swine flue epidemic (remember that?) . Recommended dust masks for protection from volcanic ash--Aspro (talk) 13:47, 19 April 2010 (UTC)

Those don't work on kids and only last from a few hours to about a day. StuRat (talk) 14:43, 19 April 2010 (UTC)

Electric cars would do quite well, as would a human wearing MOPP gear. As noted above, it is greatly going to depend on the density and size of the ash particles in question. 65.121.141.34 (talk) 20:03, 19 April 2010 (UTC)

Assuming unprotected unmodified cars and outdoors people. As the dust increases, would the cars or the human be the first to stop moving? 92.27.146.2 (talk) 23:32, 19 April 2010 (UTC)

Unless your car is a convertible, I would suspect the car would die first if it is only large ash particles, and the person would go first if they are very small, as the car itself would provide some protection from larger particles but much less against small particles. This is conjecture, and may greatly vary on what type of car you are driving, how fast you are driving it, how good your air filter is etc. Googlemeister (talk) 16:29, 20 April 2010 (UTC)

Billiard ball and slipping

I'm trying to do a question that revolves around striking a billiard ball horizontally with a cue, at a height above the centre of mass. I won't give the question, but can I have some hints on how to approach this? Physics isn't my forte. I think I want to resolve the impulse into a tangential component to find the angular velocity - but then what do I need to do to find the linear velocity? Thanks :-) 131.111.248.99 (talk) 12:57, 19 April 2010 (UTC)

If the cue strikes the ball at its center height, the ball translates across the surface of the billiard table but it doesn't rotate. If the cue strikes the ball slightly above the center, the ball rotates as well as translates. If the point of impact is exactly right, the rate of rotation will equal the linear velocity divided by the radius of the ball so that the ball will roll across the surface of the billiard table without any sliding relative to the surface. Dolphin (t) 13:10, 19 April 2010 (UTC)

I'm no physicist either. Under what circumstances would there be no rotation but also no friction? ←Baseball Bugs ^{What's up, Doc?} carrots→ 07:39, 20 April 2010 (UTC)

Friction with the table felt will make it roll, rather than slide, if you strike the ball anywhere near that point. StuRat (talk) 13:25, 19 April 2010 (UTC)

The objective of the question is to determine the circumstances in which there is no sliding friction between the ball and the felt. Dolphin (t) 13:28, 19 April 2010 (UTC)

How do you know that ? The question isn't even listed. StuRat (talk) 14:37, 19 April 2010 (UTC)

That question is also in my physics textbook. It seems to be a universal question to accompany the chapter on angular motion, angular acceleration, polar moment of inertia etc. A billiard ball can contact the surface of a billiard table with any combination of linear velocity and angular velocity. If the ball is translating without rotating, friction quickly gives the ball an angular acceleration so that it rolls without sliding, but some energy has been lost to the friction. Conversely, the ball can be rotating without translating, but friction quickly provides traction, the ball accelerates across the surface, but some energy has been lost to the friction. There is a critical case of particular interest, and that is the case where angular velocity is equal to linear velocity divided by the radius of the ball. In this situation there is no sliding so no friction and energy is not lost (in the short term.) Dolphin (t) 07:45, 20 April 2010 (UTC)

Unfortunately, finding that point is part of the question. :-) I'm not sure how to set up my equations to begin with. 131.111.248.99 (talk) 13:12, 19 April 2010 (UTC)

The linear momentum of the ball will be the impulse provided by the cue. The angular momentum will be force x (distance above center of ball) x time. Force and time are the same in both equations. Linear momentum is mass times linear velocity; and angular momentum is polar moment of inertia times angular velocity. If you set angular velocity equal to linear velocity divided by radius, it should be possible to solve for (distance above center of ball). Dolphin (t) 13:22, 19 April 2010 (UTC)

I just don't see how this general premise can be correct. There is always going to be some degree of friction between the ball and the felt, no matter where you hit it or how it's rotating. If you have a felt surface of sufficient size, the ball is eventually going to stop, no matter where or how hard you hit it. ←Baseball Bugs ^{What's up, Doc?} carrots→ 07:51, 20 April 2010 (UTC)

That's true, but we are talking here about the initial motion of the ball (first few milliseconds), and the position of strike to transfer maximum momentum to the ball. If the ball rolls without slipping, then the friction force is very much lower and can safely be ignored when considering the initial motion. (Unless someone has spread treacle on the table) Dbfirs 20:02, 20 April 2010 (UTC)

help with the seasons

I dont get it, how the earth is tilted and hence the seasons.I can only understand it if the earth moves on its axis i.e =0 degrees on the equinox and tilts back 23.5 degrees in winter and tilts forward 23.5 degrees in summer. I feel that I dont understand the diagrams that are usually given as it makes it look like the sun is moving.

I assume that the earth and the sun are in the same plane, so how is the sun moving.

Can you show me an experiment to do which will show me clearly the shadows? —Preceding unsigned comment added by 89.241.1.51 (talk) 14:39, 19 April 2010 (UTC)

The sun is not moving, but the earth is. Don't assume that they are both in the same place. Dauto (talk) 14:55, 19 April 2010 (UTC)

The OP said "same plane", not same place. Dismas|^(talk) 14:56, 19 April 2010 (UTC)

Both the Earth and the sun are moving. For simplicity, it is common to consider the sun somewhat stationary, at least relative to the motion of the planets - but we shouldn't be planting heliocentric theory into the OP's mind. Nimur (talk) 15:43, 19 April 2010 (UTC)

Does the diagram in Seasons#Astronomical help? You may have the misconception that the axis always points toward (or away from) the sun as the earth moves in its orbit. This is incorrect; as you can see in the diagram, the axis always points in the same absolute direction; as a result, the north pole sometimes points toward the sun, and sometimes away from it. -- Coneslayer (talk) 15:00, 19 April 2010 (UTC)

Okay, some words and then some sort of experiment. There are a three things going on with the earth worth mentioning. First. it rotates around its own axis (i.e. spins) once every 24 hours. That gives us days & nights, and has nothing to do with seasons. Second, it orbits the sun every 365 days or so ... think about a fixed sun, and a planet revolving around it - perhaps in terms as simple as a couple of balls on your floor. Now it so happens that the axis of the earth about which it spins every 24 hours is 23.5° off vertical, relative to the plane of motion of the earth (or the floor, in our simple analogy). What is more, the axis always points the same way irrespective of the motion of the earth around the sun (and in our example, whether it is on this side of the centre ball, or that side, the axis still point at that wall over there. So. Start with the earth in a position in which its rotational axis is pointing vaguely towards the sun. And then consider the position six months later, when the earth has travelled half way around the sun. Now, think about which part of the earth is nearest the sun in each of these two cases. In the first case, it will be a line around the top half of the earth (remember, the earth is still spinning). In the second case, a line around the bottom half of the earth.

Now, the experiment. Get a ball, mark the north & south pole on it, and set it up so they are about 23.5° off vertical. Instead of the sun, have a felt tip pen sited horizontally at about the middle of the ball. Get the axis of the earth vaguely pointing in the direction of the sun ... bring the earth to the felt tip pen, and spin it around its axis. Then move the axis so that it is pointing away from the sun. ... bring the earth to the felt tip pen, and spin it again around its axis. You should end up with a distinct pair of lines, hopefully approximating the tropics of cancer & capricorn. And the point is, half of the time it is the northern hemisphere which gets more sun than the southern; and half the time it is the other way around. And that drives the seasons. Hope that helped somewhat. --Tagishsimon (talk) 16:01, 19 April 2010 (UTC)

You don't really need an experiment...but a few minutes spent playing around with a ball and a flashlight will hopefully make this clear to you (put the flashlight over the other side of the room from the ball and do it with the room lights turned off). Ask yourself this: Why is it that in any 24 hour period, we have more hours of daylight in summer and less in winter? Why is it that there are months of continuous daylight and months of continuous night at the north and south poles? SteveBaker (talk) 18:41, 19 April 2010 (UTC)

(from OP) Got it! thx Tagi —Preceding unsigned comment added by 89.241.1.51 (talk) 21:48, 19 April 2010 (UTC)

Do royalty masturbate?

Well, do they? —Preceding unsigned comment added by 188.221.55.165 (talk) 18:28, 19 April 2010 (UTC)

They're not such a homogeneous group that a simple yes or no would suffice, even did we have access to that sort of private information. However they're humans, and so on balance, they're as likely to do so as any of us. --Tagishsimon (talk) 18:34, 19 April 2010 (UTC)

Firstly - how on earth do you think anyone would be able to answer that authoritatively? Secondly: Yes, of course. SteveBaker (talk) 18:41, 19 April 2010 (UTC)

With sources, of course, which Religious_views_on_masturbation#Orthodox_and_Conservative_Judaism lacks - but does make the claim that Egyptian pharaohs masturbated into rivers ceremonially. Pharaohs were royalty, right? Vimescarrot (talk) 18:44, 19 April 2010 (UTC)

Yes. You can safely assume that almost everyone masturbates or has masturbated at some point. 82.43.89.71 (talk) 20:59, 19 April 2010 (UTC)

With the possible exception of Edward Scissorhands. ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:02, 20 April 2010 (UTC)

I suspect that if this kind of question actually interests you either need to masturbate more or masturbate less. Or better yet, you should get yourself a girlfriend, and then the last thing you will care about is other people's sex lives... --Ludwigs2 21:21, 19 April 2010 (UTC)

There are plenty of serious, academic studies about both sex and masturbation, and while I suspect that Mr. 188 probably isn't the next Alfred Kinsey, it's a valid area of inquiry. Buddy431 (talk) 21:39, 19 April 2010 (UTC)

Why not post this question here? Note that you can only do that after answering the previous question, as that's the rule for posting in that thread. Count Iblis (talk) 22:55, 19 April 2010 (UTC)

Do we dare ask why you want to know? 71.104.119.240 (talk) 03:27, 20 April 2010 (UTC)

Why wouldn't they? Vranak (talk) 06:09, 20 April 2010 (UTC)

Some might ungraciously say that all the royal family were a bunch of masterbators--79.76.130.158 (talk) 14:13, 20 April 2010 (UTC)

Of course, they don't do it exclusively, as that would interfere with them (in)breeding a new generation of royal pains. StuRat (talk) 22:22, 19 April 2010 (UTC)

Plants

I know a conker stores energy for the new plant when it first grows, before it takes root and develops leaves etc. What is the energy stored as; fat, protein, something else? Also, when the plant has fully taken root and used all the energy from the conker, would the conker be hollow? 82.43.89.71 (talk) 20:58, 19 April 2010 (UTC)

Yes, the energy is stored as; fat, protein, and something else. Wikipedia - as always - has an article about seeds. Yes, once the 'conker' (or other seed) has fully sprouted, the empty husk is left behind.--Aspro (talk) 21:17, 19 April 2010 (UTC)

Thanks. I was also wondering, would the conker actually decrease in weight as it's energy is being used, or is it more like an electric battery in that it stays the same weight when discharged? 82.43.89.71 (talk) 22:46, 19 April 2010 (UTC)

Yeah it would get lighter. Just as when humans eat food, some of the materials are used directly to build new cells in the growing plant, and the materials that gets broken down for energy end up as mostly water and carbon dioxide with some other types of waste that are also gotten rid of. Rckrone (talk) 23:10, 19 April 2010 (UTC)

Volcano - worst case scenario

File:Pompeii the last day 1.jpg

Don't I count?

How long could the volcano keep disrupting air travel if it was say, at the 90th percentile for length of time of eruption? 78.146.55.24 (talk) 22:42, 19 April 2010 (UTC)

The current disruption is unprecedented (at least in Europe), so I guess it is already well past the 90th percentile. --Tango (talk) 22:51, 19 April 2010 (UTC)

Well, wait a minute, I'm going to assert that at least one eruption in Europe has been more disruptive. Comet Tuttle (talk) 23:19, 19 April 2010 (UTC)

Actually on Island itself there have been far larger eruptions, like the eruption of Laki. Count Iblis (talk) 23:25, 19 April 2010 (UTC)

Iblisspeak to English conversion: "Island" = "Iceland". :-) StuRat (talk) 23:40, 19 April 2010 (UTC)

A pedant writes..... "Island" = what the people of Iceland call Iceland. DuncanHill (talk) 12:02, 20 April 2010 (UTC)

We're not talking about big volcanic eruptions. We're talking about big disruption to air travel caused by volcanic eruptions. The size of the eruption is just one factor that affects the amount of disruption caused. This level is disruption is unprecedented, despite the eruption itself being fairly standard. --Tango (talk) 00:15, 20 April 2010 (UTC)

Have you forgotten we are all super-pedantic? You said "disruption", not "air travel disruption". Hmph. Comet Tuttle (talk) 22:23, 20 April 2010 (UTC)

Well, the Vesuvius eruption in question downed all commercial air traffic for more than a millenium ;-). --Stephan Schulz (talk) 09:41, 20 April 2010 (UTC)

Well, Laki did shut down commercial boat traffic: "The summer of 1783 was the hottest on record[citation needed] and a rare high pressure zone over Iceland caused the winds to blow to the south-east. The poisonous cloud drifted to Bergen in Norway, then spread to Prague in the Province of Bohemia by 17 June, Berlin by 18 June, Paris by 20 June, Le Havre by 22 June, and to Great Britain by 23 June. The fog was so thick that boats stayed in port, unable to navigate, and the sun was described as "blood coloured".[6]" Count Iblis (talk) 14:51, 20 April 2010 (UTC)

OK, at the 90th percentile for Icelandic volcanos? 92.27.146.2 (talk) 23:29, 19 April 2010 (UTC)

Cockatoos and music

Has anyone advanced a theory yet as to why it is that some Cockatoos seem to have a deep appreciation of human music and even have their own particular favourite songs or genres of music? I wouldn't have thought that it was a new thing but it seems to be something that science has only just recently noticed. —Preceding unsigned comment added by 95.148.107.232 (talk) 22:49, 19 April 2010 (UTC)

Music (or birdsong, to be specific) is quite important to birds, since they use it as a method of communication, to impress mates, etc. I guess human music is close enough to qualify. That's probably why we also appreciate the songs of birds, more than, say, the sound of a laughing hyena. StuRat (talk) 23:14, 19 April 2010 (UTC)

I think we should also consider the possibility that early human ancestors evolved to pay close attention to bird song. Maybe hearing their warning cries helped us avoid dangerous predators - maybe knowing their location helped us find eggs to eat...that kind of thing. That being the case, it's very possible that our musical sense is our appreciation of their music. It wouldn't then be surprising if the birds didn't completely hate our mimicry of their songs. I have no clue whether this is true (and it would be hard to prove) - but it's a possibility. SteveBaker (talk) 01:11, 20 April 2010 (UTC)

The scientist who's been working with Snowball believes that it (the bird's desire to dance/bob his head/jump around to the music) may have something to do with a link between areas of the brain responsible for hearing and motor movement. Both humans and parrots are apparently 'vocal mimics' when it comes to learning to communicate using sound - and this creates some sort of neural pathway between the two parts that elicits a response to a musical beat in both people and parrots as an unintended consequence. Or something along those lines. I'm probably oversimplifying. --Kurt Shaped Box (talk) 01:26, 20 April 2010 (UTC)

April 20

ISI flight path during landing

Hey, I live in Japan and I'm interested in trying to spot one of the shuttles on their last flights, preferably before landing, and I have a couple questions. The landing trajectories (images) on the NASA site only generally show North America, is the flight path deviated from its regular orbit before it passes over North America? I guess this is the same question then: Does the shuttle enter the atmosphere over or near North America, or earlier? The shuttle sometimes orbits close to Japan, and I'm hoping that it might fly overhead on preparation for landing. Thanks! P.S. I'm relatively certain that Discovery wont be anywhere near Japan this time around, so I'm mainly trying to figure out how I might check for further missions. 219.102.220.42 (talk) 01:30, 20 April 2010 (UTC)

The website heavens-above tracks a bunch of satellites including ISS and the space shuttle missions, you can see the shuttle's current "path" in orbit by clicking the mission and then clicking on "orbit". It also predicts into the future but i'm not sure how reliably the STS missions can be predicted ahead. But sign up, it's free, and put in your lat and long and see what it comes up with. It's probably your best bet, unless NASA has something even more detailed online. Vespine (talk) 05:29, 20 April 2010 (UTC)

Those flightpaths are likely to be untrue as of this morning - there is a lot of cloud over Florida and they are looking at a later return to Earth - or a diversion to Edwards AFB in California. SteveBaker (talk) 13:11, 20 April 2010 (UTC)

You will not be able to see what I think you hope to see from Japan. It is possible that the Shuttle will overfly Japan during deorbit (today it passed several hundred miles east of Japan), but it will still be well above the atmosphere when it flies over. If the lighting conditions are right you may be able to see it during this time but it will look no different than any other Shuttle sighting, meaning it will look like a star rapidly crossing the sky. The trajectories for future missions are likely not published since they are difficult to predict far into the future.
This page has entry event information (including geographic coordinates) for today's Discovery landing, the landing was at KSC on orbit 238 (the third table). The deorbit burn occurred over the southern Indian Ocean, and lowered perigee so the Shuttle's orbit intersected the atmosphere at the proper time. This is the first deviation from the normal orbit, but doesn't change the ground track very much. Entry Interface (when the Shuttle crosses 400,000 feet altitude) occurred over the northern Pacific Ocean, this is the general area where the atmosphere becomes significant and one could consider 'entry' to begin. After this the ground track will deviate as the Shuttle navigates to the landing site. anonymous6494 22:03, 20 April 2010 (UTC)

knee posture?

What do you call the way the knee bends in the other direction in humans. Normally, the knee should bend forward when standing like a softer >. But in this case, the knee is depressed when standing so the profile of the leg is more like a < but not that extreme. I'm not seeking medical advice, just curious on what the symptom is called. --121.54.2.188 (talk) 01:48, 20 April 2010 (UTC)

Hyperextension of the knee. StuRat (talk) 02:03, 20 April 2010 (UTC)

Or "wonky knees" to use the medical term. DuncanHill (talk) 02:09, 20 April 2010 (UTC)

In my place, they call the knees "like that of a chicken".--121.54.2.188 (talk) 02:19, 20 April 2010 (UTC)

Which is a little weird, since chickens' knees bend the same way as ours do. 64.235.97.146 (talk) 16:56, 20 April 2010 (UTC)

See Hypermobility. -- Wavelength (talk) 02:10, 20 April 2010 (UTC)

Those who are knock-kneed may appear to have inward-bending knees also. George Reeves was somewhat knock-kneed, which I suppose was due to being cramped in that little rocket ship from Krypton while his bones were still soft. ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:10, 20 April 2010 (UTC)

Yup it looks like those pictures but it is inward rather than sideward.--121.54.2.188 (talk) 02:19, 20 April 2010 (UTC)

word for a taxonomy guide

Many years ago I met someone who had written a book on how to identify bat species, in the form "If your bat has this feature, turn to page 23; otherwise turn to page 19." What is the word for such a key?  —Tamfang (talk) 02:32, 20 April 2010 (UTC)

Single-access key. Intelligentsium 02:41, 20 April 2010 (UTC)

meditation

may i please know the most incredible power of 'meditation'? How long will it take for one doing regular meditation to achieve it? —Preceding unsigned comment added by 125.21.50.214 (talk) 04:51, 20 April 2010 (UTC)

Have you had a read of our article on Meditation? Maybe Nirvana might help a little too. My opinion is that meditation is an extremely subjective experience and as such you probably won't get very well defined answers for a question like this. Vespine (talk) 05:17, 20 April 2010 (UTC)

From the purely scientific point of view, meditation is nothing more than a state of intense focus, calm, and relaxation. This may enhance (or be enhanced by) physiological effects, such as a change in respiration and heart rate, and even neurochemical changes. This has been studied scientifically: for example, Physiological Effects of Transcendental Meditation (1970). Here's a perhaps more accessible article, "Meditation on Demand" from Scientific American. These results indicate that physiological changes occur almost instantly during the meditation period. If you're seeking philosophical or alternative viewpoints about meditation, you might find the humanities desk helpful to point you toward those sorts of resources. Nimur (talk) 06:50, 20 April 2010 (UTC)

See the article about Phala. Cuddlyable3 (talk) 07:51, 20 April 2010 (UTC)

I wonder how someone can be both intense and relaxed. ←Baseball Bugs ^{What's up, Doc?} carrots→ 07:57, 20 April 2010 (UTC)

pain receptors of preys

More often, a prey experiences excruciating pain while being hunted. Is that like their pain receptors are less sensitive (responsive) than ours? Because the 'hunting' occurs for quiet a long period down the evolution, i doubt if they are evolved in a way that they experience less pain than the others(nonetheless, it dies) - anandh, chennai —Preceding unsigned comment added by 125.21.50.214 (talk) 06:41, 20 April 2010 (UTC)

See the article Pain. Pain is an important part of animal life, vital to healthy survival.Cuddlyable3 (talk) 07:49, 20 April 2010 (UTC)

It's an unfortunate fact that the pain of being ripped to shreds by a predator is something that evolution can't remove. When an animal dies, it's genes cannot subsequently be passed to the next generation - so animals that (by some random evolutionary change) get a painless death have no evolutionary advantage whatever compared to those that die in the most painful way imaginable. In fact, the opposite might even be true. In a family of animals with similar genetics, if one animal screams horribly as it's ripped to shreds by a predator, the other animals in the group might be alerted to the presence of the predator - or might be much more careful to avoid that predator when they realize how nasty this experience might be. Groups of animals with a gene for extra pain at death might well out-perform other groups with a gene for less pain at death. Evolution is not a kind process. On the plus side, there might be an advantage to predators to be able to kill painlessly in order to avoid too much of a ruckus - and animals that use poison or who (like lions) grab their prey by the throat may be doing that to keep the prey quiet while they die. SteveBaker (talk) 13:10, 20 April 2010 (UTC)

One reason why the predators might want to kill the prey quietly is so that other animals (of their species or another) which would steal their kill don't find it right away. StuRat (talk) 13:23, 20 April 2010 (UTC)

I would like to strongly caution the OP against anthropomorphizing the non-human animals. "Experiences excruciating pain" is an entirely human notion. Birds and mammals most likely can feel pain (as they exhibit both the behavior patterns consistent with it and neuro-chemical pathways that may account for it), but we cannot possibly know how they perceive it, or if they can grade it on a scale from one to ten. Other vertebrates may feel pain, but it is not certain. Cephalopods may or may not feel pain. There have been some work on the possibility that lobsters can feel pain, but I'm not sure if there is anything conclusive on that. A crayfish seems largely unphased by losing a leg, a human... significantly less so. Arthropods can certainly be trained using aversive stimuli, but it is not certain if any of those stimuli may be described as pain. Saying "an insect feels excruciating pain" is the same as to say "an insect has an immortal soul"; it is a personal belief, and does not belong in the scientific discussion until it is thoroughly tested. Does a single-cell organism with negative photo-taxis feel pain when exposed to light? Does your computer feel pain when it fails to boot? Its monotone beep certainly sounds like it's experiencing an excruciating pain... --Dr Dima (talk) 18:33, 20 April 2010 (UTC)

So, do you feel more comfortable to proceed on the assumption that non-human organisms don't feel pain until it's proven otherwise, or the assumption that they might feel pain until it's proven that they don't? Indeed, given that I can't know for certain that other humans perceive pain as I know I do, should I assume that you don't feel pain until you prove to me otherwise? A version of the Precautionary principle may be found attractive in such circumstances. Perhaps I should own up to a religious bias relating to such questions: we Wiccans regard ourselves as a part of nature, rather than divine appointees to a hegemony over it. (No personal spin on this intended, Dr Dima, but I think this is a profoundly important area of personal ethics.) 87.81.230.195 (talk) 01:34, 21 April 2010 (UTC)

We have a (rather poor) article Pain in animals. It seems that most vertebrates can probably feel pain as we interpret it, but things are less certain for other phyla. In the UK, octopuses are regarded as "Honorary Vertabrates", meaning, for example, that anesthesia must be used when cutting them open. Buddy431 (talk) 19:59, 20 April 2010 (UTC)

Evolution, intelligent design, and irreducible complexity.

I'm not sure whether I'm wrong or right... can someone please affirm or correct me? The way I see it (and I've never been taught otherwise, I go to a Christian school, so feel free to refute me) is that inter-species evolution through natural selection doesn't make sense, because for new body parts to grow like a wing (for a crude example) loads more DNA information is required, and I don't see where that information would come from. Also, even if this was possible, Darwin states that the components of the wing would grow gradually, so until it was a fully working wing, it seems to me that it would just be a pointless deadweight, which would give the owner of the wing a disadvantage, therefore natural selection would remove it. Anyway, I'm just trying to gain a better understanding of the subject. Sullyj4 (talk) 07:38, 20 April 2010 (UTC)

Check the Wikipedia article Evolution of birds. Cuddlyable3 (talk) 07:45, 20 April 2010 (UTC)

Scientists are not suggesting that a completely new species appears suddenly (although that silly suggestion is often used by creationists in an attempt to ridicule and discredit the notion of evolution by natural selection.) The immediate ancestors were not creatures without wings - they were birds, perhaps with smaller wings and lighter body weight. At least one of those ancestor birds developed a very minor genetic modification, perhaps a slightly longer wing, that meant it was better equipped to survive and reproduce, and so gradually that genetic modification became part of the evolution of a species of modern bird. This species of modern bird might have taken 100,000 years to evolve from its ancestor species which is now extinct. The majority of animal and plant species that have ever lived are now extinct. I strongly recommend the book River Out of Eden by Richard Dawkins. Dolphin (t) 07:56, 20 April 2010 (UTC)

Please don't recommend Darwin's Rotteweiler as reading material. How about Carl Zimmer? —innotata 23:39, 20 April 2010 (UTC)

Why not? Dawkins is an excellent writer, he really knows his stuff, and his popular science texts are very accessible. In addition to River out of Eden, the new The Greatest Show on Earth: The Evidence for Evolution has also been reviewed quite favourably. --Stephan Schulz (talk) 00:03, 21 April 2010 (UTC)

The problem with Dawkins isn't his science, which is fine, it's his anger, which bleeds through every word he writes. It'd be fine if he kept to the facts of evolution. But he doesn't. He seethes with such bitterness that it is distracting to the point of making him lose his point to the proper audience. He does a better job of making people who already hate religion hate it more, and does a lousy job of providing a means for the religious to fit the truth of evolution into their worldview. --Jayron32 00:57, 21 April 2010 (UTC)

Neither am I suggesting that's what they suggest. What I mean is, what about before those 'birds, perhaps with smaller wings and lighter body weight.'? the wings must have come into the equation some time. Sullyj4 (talk) 08:47, 20 April 2010 (UTC)

The fossil record tells us a little about some of the creatures, now extinct, that have lived on Earth in past ages. Scientists don't know exactly how one species evolved into another because no-one was around at the time. It is serious scientific business to gather what evidence can be found, suggest plausible mechanisms that can account for what is observed, and allow other scientists to review the suggested explanation. (Scientific scepticism is both valued and important in the international scientific community.) So when scientists suggest how birds evolved from the ancestors it is an attempted explanation, not doctrine or dogma. Scientists don't actually know, but they are willing to make suggestions and allow other scientists to agree or disagree. Dolphin (t) 12:37, 20 April 2010 (UTC)

Where creationists get painted into a corner on this is their insistence that the earth is only 6,000 years old, which obviously isn't enough time for species creation to occur. Their usual complaint about evolutionists is that it requires huge amounts of time. That's the impasse, or one of them. ←Baseball Bugs ^{What's up, Doc?} carrots→ 08:03, 20 April 2010 (UTC)

Correction: young earth creationists Sullyj4 (talk) 08:47, 20 April 2010 (UTC)

And even those who might agree with the age of the earth still can't comprehend how species can evolve into other species. But that's because they can't really conceive of the endless trial-and-error that mother nature can make over billions of years. We barely comprehend a century or a millennium. Even a million years, a short time on the geoligic scale, is beyond our comprehension. One way to get a handle on it, though, would be to estimate the number of generations of a species that could occur in, say, a million years. That makes it a little more real. ←Baseball Bugs ^{What's up, Doc?} carrots→ 08:07, 20 April 2010 (UTC)

13.75 ±0.17 billion years is the currently estimated age of the universe yeah? Don't quote me on this, but I think someone might have done a probability equation and figured that it would take longer than this age for life to begin. Sullyj4 (talk) 08:47, 20 April 2010 (UTC)

There are many such equations put out by creationists. The problem is that they are all deeply flawed, in that they make unsupported assumptions about the first replicators, and in that they assume processes that are not random at all are random. We don't know how likely it is for live to evolve under the right circumstances. --Stephan Schulz (talk) 10:23, 20 April 2010 (UTC)

I don't find the creationist's estimates of the probability REMOTELY tenable. Let's look at what we have here: The basic building blocks for a self-replicating molecule are everywhere. We've done dozens and dozens of different experiments based around the chemistry, thermal conditions, radiation, etc of a dozens of possible "early earth" environments - all of them produce an abundance of complex organic molecules within a matter of days. From the far distant icy moons of Saturn and Jupiter, we detect organic molecules - we find them even in the horrible conditions on Venus and Mars - and in the interstellar gas clouds. So there is zero shortage of basic materials. The materials are chemically inclined for form long chains - they do it spontaneously. The question of how the "abiogenesis event" came about is then purely a matter of the odds of a randomly assembled string happening to be self-replicating. This is, without doubt, a rare event. But we know that almost every one of the 10¹² stars in our galaxy has a bunch of planets and moons. Let's say there are 10 places in each solar system where life could maybe form. There are 10¹¹ galaxies - so there are at least 10²³ places where life could have formed in our 'observable' universe - the entire universe is AT LEAST 10²⁶ times bigger (in diameter) - which is 10⁷⁸ times bigger in terms of volume - and hence probable number of galaxies! The anthropic principle says that the intelligent beings wondering how this happened have to be on whatever moon or planet it actually formed on - so it's not a coincidence that it happened to be on Earth. OK - well, how many chances were there for it to happen here on earth? If these chemical reactions were happening in the oceans (not necessarily the best current theory - but let's run with it to get a feel for the numbers) - then we might suppose that each drop of water might produce maybe a thousand new, random chain of amino acids every microsecond...that's probably a huge underestimate - but again, we can afford to be generous. How many drops of water are there in the world oceans? There are 360 million square kilometers of ocean with an average depth of 3.8km - so we're talking about a thousand million cubic kilometers of water (10⁹ km³) which is 10¹⁸ cubic meters. If a "drop" is 1mm x 1mm x 1mm then there are 10²⁷ drops of water. The oceans have been around for 4.4 billion years - which is about 10¹⁷ seconds. At one chemical reaction per drop of ocean per second per planet/moon in the entire universe, there have been 10¹⁵⁴ chances for a self replicating molecule to have formed at random. If we assume that some variation of our modern genetic code were required for that to happen, with A, G and T to choose from, 10¹⁵⁴ is something like 3³⁰⁰ - so the chances are good that every possible string of letters up to 300 characters long will likely have shown up completely at random. So is 300 base-pairs enough to make a self-replicating molecule? I think that's a definite "maybe". Researchers are still working on this part of the theory - but it's certainly not some kind of crazy long-shot that the abiogenesis event was sheer random luck. Once we have just one self-replicating molecule in the entire universe, evolution guarantees that we have life. SteveBaker (talk) 21:24, 20 April 2010 (UTC)

To gain a better understanding of the mainstream science position on such matters, I suggest you read our articles on irreducible complexity, evolution of the eye, evolution of flagella and entropy and life. But ultimately your conclusions will depend on your initial assumptions. If you start from the premise that the Biblical account of the creation of life is literally true, then there is no need for a mechanism such as evolution to explain the complexity of life on Earth as we see it now, so Occam's razor says it is an unnecessary encumberance. If you start from the premise that it should be possible to explain the complexity of life (and, indeed, other phenomena) without supernatural forces, then the modern theory of evolution is the only game in town. This is not because scientists have not considered alternatives - see the history of evolutionary thought; it is because it is the only scientific explanation that has stood up to rigorous examination. Gandalf61 (talk) 08:22, 20 April 2010 (UTC)

The "information" argument is bogus. Any random process is a source of information in the sense of information theory. Creationists and IDers redefine (using a very loose sense of "define") it to mean something very different (though I've yet to see an operational definition of, say, "specified complexity"), and then make unsupported claims about it. --Stephan Schulz (talk) 10:16, 20 April 2010 (UTC)

Wings are modified forelimbs, so the change required isn't too great; you just have to add some feathers (or webbing for bats) and some flight muscles. The feathers are also useful for keeping warm, so they can evolve without being effective for flight. Once you have wings, but no flight muscles, you can glide. Gliding is very useful in itself, so the feathers can evolve into wings without flight muscles being ready. The flight muscles (and lighter bones, etc.) can then evolve gradually making better and better gliders until eventually they are actually flying. It is often difficult to work out what the gradual steps were in any particular bit of evolution, but that doesn't mean they don't exist. We have worked out the steps for a very large number of features of modern species and there is every reason to believe will we eventually work out the steps for those features that are still a mystery to us. --Tango (talk) 11:55, 20 April 2010 (UTC)

• I'm not sure whether I'm wrong or right... can someone please affirm or correct me? - Well, science says you are wrong. There is zero doubt about that much!
• ...I've never been taught otherwise, I go to a Christian school, - That's a horrifying thing. It's one thing to teach evolution alongside creationism - and to let people make up their own minds, or at least understand the mainstream view - but to simply not teach it at all is terrible.
• that inter-species evolution through natural selection doesn't make sense, - The problem is that creationists typically claim that evolutionists say "Well one day there was a Dinosaur - then 'poof!' we have a genetic mutation and now there is a bird." - but that's absolutely NOT what evolution says. It's a very, VERY gradual process for such a complex change to come about.
• because for new body parts to grow like a wing (for a crude example) loads more DNA information is required, and I don't see where that information would come from. - It's like you took a bucket with 1000 six-sided dice in it. You shake up the bucket and dump it out - what are the odds of getting 1000 sixes? Just about zero! If you kept dumping out that bucket, it would probably take longer than the life of the universe to get 1000 sixes. However, if you're allowed to dump out the bucket, and keep all of the dice that show up with 6's - shaking up the ones that are left over and trying again - then after the first try you get about 160 sixes, you shake up the remaining 840 dice, do it again and you get 140 sixes, then 116 with 700 left - and so on. After about 35 rolls of the dice - you have all sixes. That's how evolution works. Each tiny change produced by a change in just a few base-pairs in the DNA molecule or just a couple of genes picked up from one parent versus the other make a tiny improvement to the animal or plant. With each generation, the population of animals adapts minutely towards a better fit to it's environment. After thousands or tens of thousands of generation, you get the animal you see today.
• Also, even if this was possible, Darwin states that the components of the wing would grow gradually, so until it was a fully working wing, - Yes, but don't make the creationist mistake of then saying "What use is half a wing?" - because that's not what happens. Some species of dinosaur evolved slightly fluffy scales - those fluffy scales were good for keeping the dinosaur warm - the fluffy scales gradually changed into 'feathers' - not feathers good for flying - but fluffy feathers like a small chick might have. Then some variation of this dinosaur maybe found benefit to being able to climb trees to find food - some variation of that found it useful to be able to jump from one tree to the next - having longer feathers on the forelimbs made possible to glide a bit from one tree to the next - then holding those forelimbs out more horizontally made it able to jump further - then having stronger muscles, then longer feathers, then the ability to flap, then lighter bones, then...all the things you need to have something we'd call a "bird". Each stage of the way involved one more six being rolled on that bucket of 'genetic dice' - each beneficial 'six' was kept by the process of 'survival of the fittest' - each failed '1' roll resulted in a dead dinosaur that couldn't make it to that next tree - had to climb down and got eaten by a predator on the forest floor. Over a LOT of generations, dinosaurs change by a thousand intermediate species into something we'd call a "bird".
• it seems to me that it would just be a pointless deadweight, which would give the owner of the wing a disadvantage, therefore natural selection would remove it. - And that doubtless happened with some feature or other. Maybe some of the dinosaur-descendants evolved fluffy feathers on their back legs, that (for some reason of flight stability or whatever) turned out to be worse rather than better - and that species of dinosaur died out without leaving any descendents.

drop the hypothetical, four-winged dinosaurs actually existed! http://scienceblogs.com/notrocketscience/2008/10/microraptor_the_dinosaur_that_flew_like_a_biplane.php 83.134.175.147 (talk) 17:09, 20 April 2010 (UTC)

• Anyway, I'm just trying to gain a better understanding of the subject. - That's a good thing! Curiosity is a good trait! Use your brain - don't take everything you're told as true unless you can understand why. Your teachers are essentially telling you: "Birds appeared by magic." - that's not much of an explanation. Life would be very difficult if every difficult question were answered that way. "Why didn't you do your homework last night?"..."Magic!"..."Why did your car stop running? Did it run out of gas?"..."Nope - it was magic."..."How come there are birds?"..."Magic!". We can't run the world like that. When we have a good explanation for something, we should use that explanation - and there are few scientific principles as solid, clear, coherent, well-endowed-with-evidence as evolution.

SteveBaker (talk) 12:58, 20 April 2010 (UTC)

(Edit Conflict) To try to address a couple of Sullyj4's concerns as briefly as I can:

Organisms often wind up with surplus/duplicate DNA through such mechanisms as the duplication of single genes or entire Genome duplication: the latter has happened at least 4 times in our own (distant) genetic history and is very common in plants - most of our domestic serial crops are polyploidal hybrids of wild originals.

The resulting 'spare' copies of those genes can then be subject to mutations (thus creating new 'information') without affecting the organism by the loss of their original function, and those mutated genes can occasionally result in beneficial new characteristics, perhaps in a slightly different niche or environment than that which suited their carriers' ancestors better. (Most won't, and may well be disadvantageous, so organisms with them will generally not survive and pass on those disadvantageous genes - this is how "Evolution by Natural Selection" works: all the real 'duds' die and the few 'improvements' thrive better than the 'unimproved', either overall or in new niches, and are said to have been "selected".

While organs like wings or eyes are evolving in a species gradually over many, many generations, there is never a stage where (for the majority of the species) they are non-functioning encumbrances: if they were then - in line with the above and with your original supposition - their owners would survive less well and the genes for those versions would not be passed on. Every (rare) 'modification' that is retained (by successful reproduction) is in some way an 'improvement', while the (numerous) 'disimprovements' are not retained. This is not as obvious as it might be because we naturally tend to focus on the (few) successful mutations/improvements who went on to breed rather than the (many) unsuccessful ones that, at best, bred less often, and more often than not never even survived as far as hatching/birth.

It's tempting to look at the current version of an organ and think that a less-fully evolved version would have been 'useless' or at least inferior, but this is erroneous. At the time that version evolved by selection it was an improvement over what had gone before (or it wouldn't have been selected for and wouldn't have persisted) and was 'the best so far' (for that particular species). Consider birds' wings: originally they were (we think on the basis of what evidence we have, which is considerable) functioning arms, which had feathers for insulation and display; in some species (of what were then small dinosaurs) the feathers and also the bones and muscles of the arms and body (which were also being selected for or against by the environment), grew large enough to help (by aerodynamics) their owners to jump further, then glide (perhaps from trees) and finally fly, by which time the arms were wings and those dinosaurs were additionally what we call birds. Several 'lines' of those early birds developed for millions of years, but in the long run only one line, the Neornithes, survived (and diversified) to the present.

It's important to remember a few things.

First, the evolution of an organ or organism has no 'future target', it's only ever driven by adaptations to the current environment.

Second, it can (usually) only build on what is already there by a series of (generally minor) modifications that are then selected for and retained. The notion of "Irreducable Complexity" argues that there must have been some stages where 'the improvements were too radical/the organ is too complex' to have come about by this "tiny footsteps" process, but it's an argument invalidly proceeding backwards from a hoped-for conclusion (this couldn't have happened through E by NS so God did it) and no example has yet been identified where an evolutionary explanation has not been found (though IC proponents sometimes pretend it hasn't), though some have taken a few years to work out.

Third, the fossil record is, and always will be, very incomplete because fossilisation is a rare event requiring special conditions and there are large swathes of geography and time where the conditions were wrong or whose rocks have subsequently been destroyed by erosion. Consequently there is, and always will be, disagreements about how various fossil species are related to each other and to living ones, and new discoveries can cause revisions to established ideas. These however are fine details, which do not affect our understanding of Evolution (which is also supported by various other sciences, such as Genetics) as a whole, and certainly don't "disprove" it.

Sorry this wasn't as brief as I'd intended, but this is a large and complex subject that has taken many thousands of scientists over a century to bring to our current state of understanding, so it's hard to properly answer questions about it briefly. It's also fascinating, so I'd encourage you to continue pursuing it. 87.81.230.195 (talk) 13:00, 20 April 2010 (UTC)

"Evolution is cleverer than you are." Imagine Reason (talk) 13:13, 20 April 2010 (UTC)

....and I've never been taught otherwise, I go to a Christian school

Isn't there an inspection system for schools to see if the curriculum satisfies some minimal standards? Count Iblis (talk) 14:46, 20 April 2010 (UTC)

Many, if not most, changes, do not work. It is "back to the drawing board" time and time again, as concerns evolution, concerning most changes in organisms. Organisms have a behavioral dimension in addition to a physical dimension, especially concerning the higher order of biological entities. This can complicate our envisioning of the process of evolution. For instance, the rudiments of a "wing," at its moment of inception, can serve a different purpose entirely, than the purpose it may eventually serve. Bear in mind that evolution only has to provide some small advantage to one individual member of a species as concerns survival and reproduction, which is to say that evolution has no long-term plan whatsoever. The term evolution can be thought of as only retroactively applied. When looking back over a long period of time, it can be said that "evolution" has taken place. But each incremental change can be small indeed. Bus stop (talk) 15:00, 20 April 2010 (UTC)

One problem with the way the original poster has apparently been taught is that the conclusions he presents about evolution are not based on evidence, but inductive reasoning. See Problem of induction. We all know that the evolution over the millenia of the wing and of the eye were improbable — but we have the evidence of the fossil record that they did evolve; so here we are. Comet Tuttle (talk) 18:50, 20 April 2010 (UTC)

One question our OP might like to put to his/her "intelligent design" teachers is this: "Please explain the Recurrent laryngeal nerve in the giraffe." This is the most crazy piece of "intelligent design" you could imagine - it can really only be adequately explained by evolutionary theory. SteveBaker (talk) 21:36, 20 April 2010 (UTC)

I did a Google search for the heading of this section ("Evolution, intelligent design, and irreducible complexity."), and I found the following page.

• Irreducible Complexity is Evidence for Intelligent Design. -- Wavelength (talk) 22:02, 20 April 2010 (UTC)

I don't have much to add to the already excellent answers here, but I'd like to point out that there are organisms alive right now that possess what could be considered "half formed wings". See Flying squirrel and Gliding possum. On their own these do not constitute proof of evolution, and who knows if these animals will eventually adapt to have more fully formed wings, but I wanted to point out that a "missing link" between wing and no-wing doesn't have to be a "Dead weight" like the question-asker assumed. APL (talk) 01:37, 21 April 2010 (UTC)

Is volcanic ash worse for aircraft than other dust and sand?

I can remember several occasions in the UK when there was a liberal sprinkling of sand on cars etc, which was said to come from the Sahara[21]. Aircraft were not grounded or as far as I know diverted at that time. Now all aircraft are grounded, and there is hardly any reside on cars, maybe a very light dusting. Why should volcanic dust result in planes being grounded but desert dust not do so? -- Q Chris (talk) 07:56, 20 April 2010 (UTC)

Read the linked article and you'll see some of the problems peculiar to volcanic ash. ←Baseball Bugs ^{What's up, Doc?} carrots→ 08:00, 20 April 2010 (UTC)

... and these are particularly harmful volcanic particles because of rapid cooling of the magma in the ice-filled caldera. Dbfirs 08:54, 20 April 2010 (UTC)

Hmm. It depends on a lot of things, including critically the size and shape of the particles and melting points. Sand gives similar problems with forming glass in the back turbine blades of jet engines but it tends to happen at low altitude over the desert (there were warrantee issues with the Saudis on this 20 years ago). But the dynamics of the passage of particles in air between surfaces is reasonably complex: at some lengthscales they pass through the engine without getting near a surface (I think there is a Stokes number on that balance), at others they nearly touch and can bounce off an air layer if the shape is round enough (including if they are molten), at others they conventionally bounced without getting molten enough to stick at other regimes again they will stick only to already deposited particles (then they form "dendrites" I think they are called, a bit like soot webs). All in all it is difficult being sure whether or not a volcanic cloud is safe, which is the biggest problem, often the risks are small. --BozMo talk 09:18, 20 April 2010 (UTC)

Incidentally reading through the links it might be worth clarifying that jet engines are hot because the thermodynamic efficiency is greater at higher temperatures, (we don't explain it well). Clever people have designed jet engines so that at max output the gas temperature (which gives the efficency) flowing through the engine is significantly higher (hundreds of degrees) than the melting point of the solid turbine blades between which they are flowing in the engine. The turbine blades are kept cool by a slow bleed of cooler air out of perforations on the blade (which give it a tiny cool air jacket). I have an RB211 turbine blade lying around somewhere, I will try to dig it out to put up a photo. The problem is that the volcanic particles melt in the gas flow but then set when they hit the surfaces of the blades which are cooler. At worse they hit at the stagnation point at the front of one of the early sets of turbines and block the perforations which let the cooler air out. You can then get the front set of turbine blades over heating and melting which is not good. But this is seriously hard to model with confidence. --BozMo talk 09:32, 20 April 2010 (UTC)

Since we know that volcanic ash clouds can shut down jet engines (because it's happened on previous occasions), and since - due to the difficulties of researching such scenarios - we don't know nearly enough about what exact conditions will result in damage, we have to err on the side of caution.

Those conditions will include things like extent, density and altitude. The current ash plume is very widespread, and high up, at normal cruising altitudes; the Saharan sand may have been less extensive (and so more avoidable), at different (lower?) densities, and different altitudes (some manifestly lower since it reached ground level). 87.81.230.195 (talk) 11:01, 20 April 2010 (UTC)

The tricky part of this is that even if the ingestion of volcanic ash doesn't cause the engine to fail catastrophically - it may cause horrible amounts of wear and bearing damage. The cost of this kind of incident could be very high even if passengers and crew are never aware of a problem during the flight. I'll mention the USGS advice I found yesterday about driving cars in volcanic ash situations - they recommend an oil change and a change of oil and air filters every 50 to 100 miles driven! Now translate that advice to a two million dollar jet engine! It wouldn't take much cumulative damage to the engines to make flying in such conditions unprofitable. SteveBaker (talk) 12:30, 20 April 2010 (UTC)

Russian EMP weapon used in Smolensk?

Various articles on the internet e.g. Kavkazcentre.com claim that Russia used EMP to down Polish plane near Smolensk. Could this be at all possible? And if so would it leave traces on the plane's instruments and/or the black boxes? This is my first try with Wikipedia and am not certain whether I am doing this right.220.253.193.132 (talk) 09:58, 20 April 2010 (UTC)

It would be too much of a risk for a government to do, as such a device would be readily detected. Space and Remote Sensing Sciences (ISR-2) .Its probably just another conspiracy theory. Much work has gone into protecting aircraft electronics from ordinary interference but damage from a Electromagnetic pulse would be apparent from the extent and nature of the fried and damaged components. Even capacitors would show puncture marks in their dielectric material due to the over voltage (OK, perhaps not in the mica's but in many of the common varieties).--Aspro (talk) 10:24, 20 April 2010 (UTC)

I don't think it's very likely, but the remote sensing you refer to only monitors nuclear EMPS—EMPs released by nuclear reactions (as a result of a nuclear bomb). A non-nuclear EMP device would probably not be detectable from space. --Mr.98 (talk) 14:56, 20 April 2010 (UTC)

? What are you gonging on about? Some 'two watt' animal tracking collars are quite successfully monitored by satellite (it's straight up). Filters can easily cope with the high noise to signal ratio picked up by EMP receivers. It ain't a weapon if it can't can't even reach into space. I've received five watt transmissions from the shuttle. --Aspro (talk) 00:30, 21 April 2010 (UTC)

It would be obvious from the 'black box' flight recorder - which is guaranteed to have been examined carefully. At the very least, the recording would have stopped abruptly long before the plane crashed - but there would be plenty of other signs of this having happened. This can't possibly have happened without the collusion of the authorities who examined the black box. The capabilities of EMP devices are greatly over-stated. We can be very sure this didn't happen as described - it's just another ridiculous conspiracy theory. SteveBaker (talk) 12:20, 20 April 2010 (UTC)

It would also fail to explain how the Russians convinced the pilot to attempt landing in thick fog after he was told by the control tower to divert to Moscow or Minsk. —Preceding unsigned comment added by 76.195.161.25 (talk) 13:09, 20 April 2010 (UTC)

Keep in mind that conspiracy theorists will throw out any sane explanations and focus on things that cannot be proven. Even when the theories are proven completely wrong, they will attempt to make those theories "fact" by spamming them all over the internet. -- kainaw™ 14:35, 20 April 2010 (UTC)

If my wife dies, how much time would I have to extract her eggs with which to produce children in-vitro?

I swear, if I find and marry the love of my life just to have her die before we have any children, even THAT will not stop us from having children!

So how long after her death would her eggs still be usable? How long can her eggs last in some kind of cryogenic freezer until they're ready to be fertilized through in-vitro methods?

Also, how much would it cost in the US? Which country would I have to fly to in order to find the same treatment for a far lower cost? --Let Us Update Wikipedia: Dusty Articles 10:27, 20 April 2010 (UTC)

You can get rough idea about what's involved here. Oocyte cryopreservation, & In vitro fertilisation.This article mentions that the eggs are harvested from 'live' donors because hormone treatment is given in the run up of the operation, to release the mature eggs. Ethics committees might/will also feel they just have to get involved for a donation from a dead donor. So you might have to persuade your wife to die in somewhere like China and to have the hormone treatment and egg retrieval done first. --Aspro (talk) 10:44, 20 April 2010 (UTC)

I think if you have the wife's consent, then many countries would allow it. Since it is apparently impossible (or, at least, very difficult) to get ova from a dead woman, you would have to do it in advance "just in case" and you can get the wife to sign something consenting to them being used after her death. --Tango (talk) 12:01, 20 April 2010 (UTC)

I agree - if you have your wife's consent - do it while she's still healthy. If you don't have her consent then you shouldn't do it at all - and in any case, you'd probably find it very hard to find a reputable medical facility who would do it after her death. SteveBaker (talk) 12:15, 20 April 2010 (UTC)

Indeed. In the absence of fertility treatment, only one or two ova mature in each menstrual cycle (see oogenesis), and we don't (AFAIK) have the ability to bring immature ova to maturity outside of the human body, so harvesting ova from your dead hypothetical wife is very unlikely to be successful. Gandalf61 (talk) 13:01, 20 April 2010 (UTC)

The fact that it's very unlikely to be successful and therefore no one is going to try may make this a moot point but I'm not convinced ethically you wouldn't be able to convince a facility to try if it were possible. Why would they treat this so much different then Posthumous sperm retrieval which while not allowed in some places (like France), is allowed in others like the UK (with written consent) and the US (where there's no law so it's up to the facility, I don't know how they handle it but it's unlikely any would do it without consent but some may use e.g. something like the Israeli system of implied consent where they allow it if you can present enough evidence to convince them your partner would have wanted it)? (I presume most people know this, it's a common theme on TV.)

Edit: Actually enough people seem to think there's enough chance it may be possible in the future that there are refs discussing the ethics ref 1, ref 2 (brief mention at the end about the need for a surrogate and how that could affect the ethics), ref 3 (brief mention of it as a future possibility), ref 4 (says 'In addition to the research potential of donated human ovarian tissues, actual clinical utility for assisted reproduction may be close to being possible'), ref 5 (mentions it as the next logical step), ref 6, & ref 7 (not sure if it has anything relevant, couldn't read the full text)

Nil Einne (talk) 16:47, 20 April 2010 (UTC)

deleted youtube vids

is there a site where i can watch deleted youtube vids the vid i wanna watch is

http://www.youtube.com/watch?v=ZzIfeo1L04Q&feature=related —Preceding unsigned comment added by Jonny12350 (talk • contribs) 13:44, 20 April 2010 (UTC)

I tried http://www.youtube.com/v/ZzIfeo1L04Q it didn't work, but I did see the title and initial photo. The old websites that let you watch deleted videos essentially created the same URL, back when youtube didn't delete videos right away. It doesn't work anymore. Ariel. (talk) 18:37, 20 April 2010 (UTC)

In this case, it says it was removed by the user who uploaded it. Apparently ax9426 (http://74.125.153.132/search?q=cache:9cMaio82KY8J:www.youtube.com/watch%3Fv%3D3j1BEss6MRc+%22chemical+spill+in+downtown+st+louis%22+ax9426&cd=1&hl=en&ct=clnk&gl=nz&client=firefox-a). You could try contacting them Nil Einne (talk) 21:40, 20 April 2010 (UTC)

is there a way to find who the user was that uploaded it? —Preceding unsigned comment added by Jonny12350 (talk • contribs) 22:59, 20 April 2010 (UTC)

Silver nitrate

What is the formula of Silver (I) nitrate (V)? Is it Ag (NO3) or smth. else? Thanks. —Preceding unsigned comment added by Atacamadesert12 (talk • contribs) 15:24, 20 April 2010 (UTC)

Yes: the silver ion has a charge of +1, and the nitrate a charge of -1, so the ratio of the two is one to one. Typically, this would be written AgNO₃. Buddy432 (talk) 15:46, 20 April 2010 (UTC)

As you might have anticipated, we have an article on silver nitrate.

Ben (talk) 16:36, 20 April 2010 (UTC)

eggs

why is it that a egg is stronger on its long side than the short side —Preceding unsigned comment added by 41.18.200.49 (talk) 18:12, 20 April 2010 (UTC)

The reason is that on the long side, the pressure is spread out over a larger area, so a specific place takes less pressure. On the short side, the pressure is applied on a small area, so it cracks more easily. Hope this helps, --The High Fin Sperm Whale 18:36, 20 April 2010 (UTC)

The pointier side is more of an arch, which is a strong structure for the reasons THFSW mentioned. --Sean 18:41, 20 April 2010 (UTC)

That explanation aint right. In fact, the pointier end will expose a smaller area leading to higher pressure. That's the oposite of what THFSW said. Dauto (talk) 19:55, 20 April 2010 (UTC)

The question aint right either (unless I am misunderstanding?) Dbfirs 20:08, 20 April 2010 (UTC)

I'm with Dbfirs here. Eggs seem pretty strong end-to-end but are easy to crush/crack sideways. DMacks (talk) 20:10, 20 April 2010 (UTC)

Eggshell is like concrete - it's very strong in compression but very weak in shear. When you push on the pointy end of the egg, the force vector may be resolved into two components - one parallel to the shell surface (which is a compression force) and one at right angles (which is a shear force). Assuming you aren't stabbing the egg with a pin (which is equally easy everywhere) but rather with a more distributed, blunt force, most of the force at the pointy end of the egg ends up being parallel to the surface and very little is at right angles. When you hit the side of the egg, the reverse is the case. Hence the egg is stronger where the curvature is sharper (ie end-to-end) than it is side-to-side where the curvature is less. The principle of the arch is somewhat similar - and it works because stone and concrete and other common building materials share the same good-in-compression characteristics of eggshell. SteveBaker (talk) 20:21, 20 April 2010 (UTC)

Thanks for that. I've always found the "spreads the pressure over a greater area" to be nonsense, but never thought about asking it. Certainly clears that up! Vimescarrot (talk) 21:58, 20 April 2010 (UTC)

--87.114.87.107 (talk) 23:13, 20 April 2010 (UTC)

Is it cold in here, or is it just me?

What is the relation of core body temperature to thermal sensation/thermal comfort? For example, could a difference in core body temperature explain why one person feels uncomfortably chilly while the person sitting right next to him (dressed the same) thinks the temperature is lovely? I'm not talking about extremes of heat or cold (either ambient or endogenous), but humans within the normal range of core body temperatures in an environment in the room-temperature range (20-25 degrees Celsius, 68-77 degrees Fahrenheit). 71.104.119.240 (talk) 20:28, 20 April 2010 (UTC)

Yes, body temperature effects how one feels the surrounding temperature. A sick person with fever will feel cold. Hunger, hormonal levels, medications, anemia, etc. will also have effect. Personally, when I ride a car with other people, opening the windows is often an issue between fellow passengers. --88.242.252.205 (talk) 22:20, 20 April 2010 (UTC)

It is more likely to be correlated to the fitness of their vascular system. Having cold showers at public school ensures that vasoconstriction becomes very adapt at avoiding heat loss. Some medical conditions such as ME have been found to have an mild elevated base temperature – but I'm presuming you mean: otherwise healthy people. A poor diet preventing the liver from utilising the body's fat reserves can also cause a person to feel cold. Also, drugs like chlorpromazine, which the Nazi's experimented with in their concentration camps, in the hope that it could save their pilots dying from exposer when they parachuted down into the cold North Sea. This drug makes people appear, not to notice the cold. They don't scream out, with the pain of becoming hypothermic.--Aspro (talk) 22:36, 20 April 2010 (UTC)

I think even tiny changes in core body temp, like a tenth of a degree, are enough to make you feel either hot or cold. StuRat (talk) 22:38, 20 April 2010 (UTC)

Yes, a very good point. Yet deviations greater than that don't seem to register in some situations. Feeling cold because one is four fifths the way up K2 'verses' feeling the cold because one is suffering from what ever King David suffered from. Quote: Kings 1:2 King David was now very old, and no matter how many blankets covered him, he could not keep warm. Kings 1:2 So his servants said to him, "Let them seek a young virgin for my lord the king, and let her attend the king and become his nurse; and let her lie in your bosom, that my lord the king may keep warm." [22]

I hate to hitch a ride on this person's question, but could lack/excess of sleep also cause one to feel hot or cold? I find that oftentimes if I fail to get more than a couple hours sleep, I feel cold the majority of the following day in what would normally be a comfortable room temperature. Ks0stm ^(T•C•G) 22:45, 20 April 2010 (UTC)

I second your suggestion, Ka0stm. being domestically solitary and currently unemployed, I tend to abuse my diurnal rhythms, and not infrequently notice periods of subjective temperature swings that have no obvious environmental cause. 87.81.230.195 (talk) 01:14, 21 April 2010 (UTC)

I'd think that acclimatisation would be the main factor to look at as 'thermal comfort' is somewhat subjective. If you've ever been on holiday somewhere hotter that where you live you'll know that it feels cold when you get back home, but your core body temperature will be the same, it's your perception of the temperature that has changed. I'd be interested to see some studies though, I know that I as a recovering alcoholic felt very cold when i first gave up booze (the liver generates heat while processing alcohol in case anybody doesn't know) so I can see that a tiny increase/decrease in core body temp can make a huge difference. —Preceding unsigned comment added by 87.114.87.107 (talk) 23:12, 20 April 2010 (UTC) edit.. i forgot my tildes

Alcohol may be metabolised as fuel but it is also a vacodilator. In other words, warm blood flows to the skin, giving the delusion of warmth. This is why a stiff brandy from a St. Bernard to warm one cockles on the mountain pass can prove fatal.--Aspro (talk) 23:31, 20 April 2010 (UTC)

of the following, which informs the innate sense of rhythm

is it: 1. One's breathing pattern (breaths per minute) 2. One's pulse (heartbeats per minute) 3. One's gait (steps per minute while walking etc) Specifically, which of these would be likely to "match up" with someone singing a song with a set tempo. I am inclined towards #3, because I see people moving back and forth rhythmically to keep their rhythm (pianists, saxophonists, etc), and also it is my impression that marches are played in a tempo informed by a brisk marching gait. However the other possibilities (or something else) seem just as likely to me. Thank you. —Preceding unsigned comment added by 84.153.182.163 (talk) 20:51, 20 April 2010 (UTC)

Causes for human genitalia variation range?

From both real life experience and watching lots and lots of adult films, I can conclude that the structure of the penis is pretty darn consistent from man to man. Sure, some are longer than others, perhaps some are thicker, but there's none of the variation seen in female genitalia - specifically the labia majora and labia minora - the latter of which comes in all sorts of shapes, sizes, and lengths. Another indicator of the wide range of configurations is that it is possible for women to undergo plastic surgery to adjust the appearance of their labia to suit personal preference, cultural norms, etc. In terms of human development, what are the differences between the genders that create relatively standardized male genitalia and such wide variation in that of females? Is it hormonal? 61.189.63.145 (talk) 22:09, 20 April 2010 (UTC)

Just wagering a guess, but the structure of the penis is probably rather uniform because of the evolutionary purposes it has. It has two specific purposes: urination and penetration of the vagina. If it came in "a variety of shapes and sizes", I'm guessing it would lose efficiency at preforming one or both of these tasks. (For example, a micropenis would have a much harder time penetrating a female than would an average sized penis.) Ks0stm ^(T•C•G) 22:51, 20 April 2010 (UTC)

April 21

tongue map

hey everyone. In biology class I've got to find a tongue taste map for the lab investigation in taste we are doing. the professor says not to use wiki, so I need an accurate tongue map from a reliable source. Any idea where I can find one? <3 ~Liviya —Preceding unsigned comment added by 76.235.111.187 (talk) 00:45, 21 April 2010 (UTC)

Did you try typing "tongue map" into google images? --Jayron32 00:48, 21 April 2010 (UTC)

Have you tried a printed encyclopedia? APL (talk) 00:56, 21 April 2010 (UTC)

It may be of interest that recent articles in the popular scientific media (sorry, can't immediately find a linkable reference, but New Scientist is a likely source) have asserted that the hallowed 'map' of highly differentiated taste areas on the tongue was based on a very old and flawed study that has now been discredited. Apparently the 'buds' for the various tastes are only weakly concentrated in different areas, and these concentration areas vary between individuals. You might want to follow up this line (don't just take my unsupported word for it) and surprise (or possibly gratify) your professor. 87.81.230.195 (talk) 01:05, 21 April 2010 (UTC)

Oh! Good point. If you look at the Tongue map article, you'll see that the "research" section of the article has two cites (footnotes) that link to articles explaining that tongue maps have been discredited. (The Nature article is a pay article, I'd try the Scenta article.)

With a little google searching I was also able to fine this article. APL (talk) 01:24, 21 April 2010 (UTC)

toba bottleneck

I was wondering if any thought has been given to the loss of technology during the toba eruption and bottleneck. IE. construction of the pyramids, astrology, etc.  ???? —Preceding unsigned comment added by 68.34.218.91 (talk) 01:45, 21 April 2010 (UTC)

cleaning up chemical spills

i notice in this vid

http://www.youtube.com/watch?v=f5M3rUqaEYs

he spills concentrated acid and powdered sodium hydroxide. how exactly is this cleaned up?