Wikipedia:Reference desk/Archives/Science/2009 May 3

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May 3

virus evolution

Why do viruses have the potential to kill people? What is the evolutionary advantage in killing one's host? russ (talk) 00:31, 3 May 2009 (UTC)

They can usually find another host. Think of always-fatal viruses like rabies. Edison (talk) 00:38, 3 May 2009 (UTC)

Its the time from infection to kill the host that is the primary evolutionary issue. If you are a virus and kill your host before you can replicate then you are not very evolutionary fit. If you can replicate and transfer your daughter virons to another host then it makes little difference to your fitness whether the host later dies as a consequence of your infection. Rockpocket 00:52, 3 May 2009 (UTC)

I disagree. If the virus kills the host species, then this will put an evolutionary pressure on the host species to develop a resistance. Thus, you will either end up with an extinct host species or one which has a resistance to the virus, neither of which is good for the virus. A virus which isn't particularly harmful, such as the one that causes plantar warts, or one which is actually helpful in some way, should thus do better in the long run. StuRat (talk) 16:08, 4 May 2009 (UTC)

Then you don't understand evolution very well, because it doesn't occur with forethought of "the long run". Since the same virus will not typically infect the same host twice, it has no effect whatsoever on the virus' replicative fitness whether that host dies or not post-transmission. Selection doesn't occur with a view of what might happen down the line. If it did, we wouldn't have any extinct species, as they would all have evolved to avoid the unforseen. Rockpocket 19:32, 4 May 2009 (UTC)

Rapidly fatal viral infections are almost always zoonoses, i.e. transmission of a virus that's adapted to a primary host into another host to which it's not as thoroughly-adapted. The characteristics of a virus may take a long time to adapt to a new host. A good example is HIV, which evolved from SIV after transmission to humans about 100 years ago. The source appears to have been chimpanzees in central Africa. Many primate species in Africa have highly-adapted strains of SIV that do not appear to cause illness even though they replicate to high levels. I realize that this question was probably raised because of the current influenza hoopla, and it's important to remember that this virus probably entered the human population only a few months ago - it has not had much time to adapt to us as hosts. There are viruses that are well-adapted to humans, like TTV, GBV-C, and HCV, and they don't usually kill the host (and if they eventually do as in the case of HCV, it usually takes decades). --Scray (talk) 01:36, 3 May 2009 (UTC)

There are a few exceptions where the lethality goes along with the mode of transmission. One example is Ebola, which transmits itself by causing victims to spew blood all over the place. Another is rabies, which transmits itself by causing animals to bite other animals (requiring serious damage to the nervous system). Looie496 (talk) 01:53, 3 May 2009 (UTC)

There is no human-to-human spread of rabies - as a human infection it's exclusively a zoonosis, so the question of human adaptation is moot. Ebola is a very unsuccessful human virus (not endemic as far as we know) and we know nothing of its transmission in its natural host(s). --Scray (talk) 02:05, 3 May 2009 (UTC)

Well, there has undoubtedly been some human-to-human spread, as when tissues from a rabid human were transplanted to others, who then died. And I expect that at least one rabid human spread it to another by biting or otherwise. Edison (talk) 04:03, 3 May 2009 (UTC)

Point well-taken - I worded that too strongly; nevertheless, human-to-human transmission of rabies is rare, and does not contribute to rabies virus evolution. --Scray (talk) 14:58, 3 May 2009 (UTC)

(EC) Given the current HIV pandemic I would say that HIV seems to be well adapted as a Human Virus. I also think it a little misguided to call the current swine flu a zoonosis. It is a new strain of flu that contains some genetic material that is believed to have come from swine flu virus and from bird virus as well, but it also contain genetic material believed to have originated from human flu virus so it can be considered only partially zoonosis-like and as far as we know pigs might even be completely immune to that virus. We don't know. Dauto (talk) 02:00, 3 May 2009 (UTC)

"Well adapted" compared to what? The severity of HIV disease does little or nothing to enhance its spread, and I would argue that if left unchecked HIV would eventually become milder - as it is in its natural host. We'll have to wait for genetic analyses of influenza A/H1N1 2009, but I won't be surprised if a strain very similar to this one is recovered from pigs found in/near La Gloria, Veracruz, Mexico. --Scray (talk) 02:08, 3 May 2009 (UTC)

Yes, Aids could become milder over time. It could also become more severe. It can go either way. It all depends on which way will enhance its fitness. Dauto (talk) 02:26, 3 May 2009 (UTC)

(EC)In light of my answer above one might wonder why viruses cause such severe disease every time they jump from other animals to humans. The fallacy here is that the premise is unproven - would we know that a virus has made the jump if it has not caused disease? Outbreaks of disease get noticed; in contrast, very rarely have scientists done systematic searches for viruses that are not causing disease. One example of such a search revealed evidence of Simian foamy virus transmission from primates to humans (PMID 15043960), without evident disease. It seems reasonable to surmise that this is not an isolated phenomenon. --Scray (talk) 02:03, 3 May 2009 (UTC)

(EC) Over time a viral diseases (or any other infectious diseases for that matter) can evolve to be less dangerous as mentioned above, but the oposite is also possible. Dauto (talk) 02:16, 3 May 2009 (UTC)

Thanks, I had not thought of it in that way. I guess as humans we too are not so concerned about destroying the environment in which we live. Many people are unable, or unwilling to acknowledge our destructive input into our host environment so I guess the way we live our lives is much the same as that of a virus. Not that I would equate the amazing things that people have done with the simple 'life' of a virus russ (talk) 00:13, 5 May 2009 (UTC)

Being virulent is a disadvantage unless a virus is spread by a vector. If the virus is too virulent then the person infected will be unable to move and will die quickly. This will reduce the number of people that they can infect and limit the spread of the virus, Ebola is an example of this, it can kill 50% of the people it infects but outbreaks are generally small. The virulence of Myxomatosis in Britain was high at first but then fell because it was killing too many rabbits. It created a selective pressure on the virus to become less virulent. Influenza is not generally that virulent which means that infected people are still fairly active and can therefore pass on the virus to lots of other people. As Scray pointed out zoonoses get around this for example by an insect transferring the virus between people. Yellow fever can kill as many as 85% of the people it infects and is transmitted by mosquitos. —Preceding unsigned comment added by Smartse (talk • contribs) 20:35, 4 May 2009

No one has mentioned the common cold, which is a good example of a virus which does the sufferer no real harm, and is spread before they even notice any symptoms. Mahahahaneapneap (talk) 23:02, 9 May 2009 (UTC)

Broken leg on a horse = death sentence?

A friend told me that if a horse breaks a leg, people usually put it to death. Is this true? ScienceApe (talk) 02:36, 3 May 2009 (UTC)

It's sad but true. Most end up that way. Nowadays it is becoming a little more come to atempt surgery but that is not always successfull. Dauto (talk) 02:57, 3 May 2009 (UTC)

Horses legs are rediculously fragile. Stand on your hands and feet. Put a Volkswagen on your back. That's about what its like being a horse all day. Their leg bones are fantastically thin and, if they break a leg, it will never heal properly. The horse will likely live the rest of its life miserable pain, and it may not even be able to walk well enough to properly feed and water itself. Horses have other issues, they quite truly have to stand on their feet all the time; if they rest on their torso for extended time they are so heavy that they can literally suffocate from their own weight. So while you can heal up from a broken leg by sitting or lying in bed, a horse cannot. There are slings which can support a horse for short periods of time, but even they aren't terribly practical or healthy for the horse given the amount of time it would take to properly heal a broken leg. As mentioned, there have been some advancements in veterinary medicine where more horses are able to survive a broken leg than in the past, but the prognosis is still pretty grim most of the time. --Jayron32.talk.contribs 03:30, 3 May 2009 (UTC)

One famouse case was Ruffian (horse). She was an American filly who broke her leg in a match race, and had to be put down. The story was told in the 2007 Ruffian (film). BrainyBabe (talk) 03:39, 3 May 2009 (UTC)

One counter-example is Mariah's Storm, the inspiration for the film Dreamer. She broke a leg, but was treated rather than put down. After her leg healed, she returned to racing and won several stakes races. -- KathrynLybarger (talk) 04:48, 3 May 2009 (UTC)

On the other hand, in 2006 and 2007 Barbaro underwent months of treatment but could not be saved. --Anonymous, 05:52 UTC, May 3, 2009.

This is just semi-informed speculation, but I think a major factor is how the bone breaks. If it's a clean fracture, it has a much better chance of healing. Sadly, as Jayron notes, horse leg bones are fragile given the amount of stress they bear, and racing horses especially tend to shatter their forelegs. This kind of injury will be much more difficult to heal. And as noted here and in the linked articles, the pain factor and inability of horses to "understand" the medical process often mean that the kinder course is to make a swift end of things. Franamax (talk) 10:01, 3 May 2009 (UTC)

Is the same true for all horses or just the ones that have been bred for racing? I was under the impression that thoroughbreds are specifically selected to have long, thin legs (which more easily shatter) and oversize chests (which put more strain on the legs) in the name of faster running. If a standard nag somehow broke its leg, would its chances be as slim (financial considerations notwithstanding)? Matt Deres (talk) 16:16, 3 May 2009 (UTC)

That's a great question. At the other extreme (from race horses) might be Icelandic horses, which have strong, short legs, and develop slowly (often not ridden until age 4). The most important predictor of recovery might be if there's a breed that can survive lying down for weeks. --Scray (talk) 16:22, 3 May 2009 (UTC)

I suspect that such horses could be saved, but it's just not worth it financially, due to the cost of the treatment and the length of time when it can't earn any money. For example, if the bone is shattered, all the fragments could be removed and a replacement bone (perhaps titanium or surgical steel) could be used. However, the cost of making such a replacement bone and the surgery would likely exceed the value of the horse. StuRat (talk) 16:00, 4 May 2009 (UTC)

The problem isn't so much money lost as it's the fact that horses aren't designed to be immobile for long periods of time. They cannot lay down for long, so any horse recovering from a broken leg has to be in a sling, and must put more weight on the three unbroken legs, which often leads to those legs and feet developing problems. That's what got Barbaro, it wasn't the broken leg, it was laminitis in the other legs that forced them to put him down. In Ruffian's case, she wouldn't stop trying to use the broken leg, and put too much weight on it, thus negating the surgery, etc. Calmer horses often survive broken legs (as long as they aren't too complex) much easier than racehorses, which are high strung. It's actually amazing that horses don't break their legs more often, actually. Ealdgyth - Talk 22:52, 4 May 2009 (UTC)

Just to give an idea of quite how thin horses' legs are, and how amazingly strong... I have a Welsh Cob mare – far more heavily built than a racehorse. I can hold the thinnest part of her leg in one hand, with my fingers almost meeting on the other side. That's thicker than my own wrist, but not as thick as the thinnest part of my shin. She probably weighs something like 450 kilograms (990 lb); plus 100 kg of saddle and me on top. Even if she does no more than walk, each leg has to take all that weight at some point – she can also pull loads, run, jump and buck. Imagine the force of half a ton of active horse being transmitted through your own shin bone – then imagine trying to carry that much weight with a broken leg, without the option of crutches. Richard New Forest (talk) 09:23, 5 May 2009 (UTC)

To add: Barbaro's broken leg was actually almost healed, they even were taking him out for short walks on the grass. As Ealdgyth said, it was the consequences of abnormal pressure on his other three feet that got him. They were treating him for laminitis in his other back hoof for several months and he was making progress with basically both hind legs in supportive casts, but then it hit both his front feet and at that point he literally didn't have a good foot left to stand on. Those who have pointed out that some horses with broken legs have been healed, that is also true. Another example of a horse saved was [{Raffles (horse)], and that was a good 50 years ago. In the case of [{Eight Belles]], she broke both front pasterns while still running on them. So not only both front legs gone, but probably totally shattered bones. She didn't stand a chance. Horses have a better chance breaking a hind leg than a front leg, as the front carries more weight. Barbaro had multiple fractures in his hind leg (the X-Ray is online somewhere) and the basic surgery was successful. It was the rehab that they still haven't mastered. But at the end of the day, it usually is cost that usually decides the issue. What's even more amazing than Richard's Cob putting up with him (noogies at Richard) is watching [{Eventing]] and Show jumping. There, the horses don't just run, they jump and you can tell from slow-action photography that they usually land first on ONE leg for a split second before the other. The equine leg is a remarkable mechanism! Montanabw^(talk) 22:47, 5 May 2009 (UTC)

Wikipedium

What is Category:Chemical elements doing here? And how come only some of the other desks have categories? (Aren't there enough to go around?) Clarityfiend (talk) 04:25, 3 May 2009 (UTC)

All better [1]. As for the other cats and the other desks, I don't know. Dragons flight (talk) 04:29, 3 May 2009 (UTC)

Just to clarify (heh) when you want to show a category name, you need to use the leading colon, as in [[:Category:Chemical elements]]. If you don't do that, the page gets actually put into the category and it just doesn't show up where you thought you put it - and you can tend to miss it, I've done that 100 times or so. :) To fix it, you just search the wikitext for "[[Category" and put in the leading colon, just like Df did. Franamax (talk) 09:35, 3 May 2009 (UTC)

Man, WP oughta have a bone-head filter for things like that (same for embedding images themselves vs link to their page). DMacks (talk) 22:10, 3 May 2009 (UTC)

But then I wouldn't get credit for the extra 100 edits fixing my own bone-head mistakes. Not to mention image and template mistransclusions. :) Franamax (talk) 12:59, 5 May 2009 (UTC)

What happened to this gentleman?

I recently asked if anybody could help me identify the gentleman in this video (WARNING: the video shows a man dying):

http://www.youtube.com/watch?v=jHhX4roeEco&feature=related

Captain Disdain and Ganeshk kindly identified him for me as M. N. Vijayan and Captain Disdain noted that he did, in fact, die of a heart attack. [2]

I am very interested to understand what might have happened from a medical point of view. I am wondering whether he died there and then, or whether he just collapsed and died later. Can people die so very suddenly of a heart attack (alive one second, dead the next) or would it take a few minutes for death to actually occur? Perhaps somebody has details of exactly what happened in this case.

One more thing, the gentleman's eyes rolled back in his head? Why does this happen? The "default" position of the eyes would seem to be with the pupils facing forwards. Is that the case and, if so, why do they roll back like that?

Any help with the above would be very appreciated. BlankyFranky (talk) 09:33, 3 May 2009 (UTC)

A lot of this depends on what you mean by death (which has some discussion). For example, although I don't have a medical background nor do I know much about the details of his case, my guess is that if a portable defibrillator was available and used and this guy was later taken to hospital, he may have survived. Defibrillation can commonly save many people who would have otherwise died of a heart attack, and usually the sooner the more likely one is to survive, one of the reasons automated external defibrillators are becoming common (my local library has one according to advertisments). There are of course other areas where the person would likely have been considered dead in the past but where they can now be saved. Conversely, we are able to keep the body alive, when the brain is basically dead. Nil Einne (talk) 10:49, 3 May 2009 (UTC)

I fully agree with Nil Einne. The most common cause of sudden death is ventricular tachycardia, which generally occurs due to ischemic myocardium at the edge of a prior infarct. The triggers for ventricular tachycardia in such situations are not clear.

Regarding eye position, we did have a related discussion here recently, though that dealt with eyelid position rather than rotation of the globe (in a quick look I don't see any WP content on neutral position of the globe - that's an opportunity). It's important to note that one cannot tell that someone is dead simply by facial expression, so the rapidity with which someone dies cannot be surmised by video. --Scray (talk) 14:12, 3 May 2009 (UTC)

A heart attack will never cause instantaneous death -- medically, death is defined as a complete cessation of brain electrical activity, and that always takes several minutes at minimum. A heart attack or stroke can, however, cause unconsciousness within a few seconds. And of course there are many types of trauma that can cause instantaneous death. Looie496 (talk) 15:41, 3 May 2009 (UTC)

Gyroscopic couple

What is the difference between active and reactive gyroscopic couple???What are their directions absolutely???What are their significances?? —Preceding unsigned comment added by 121.246.174.130 (talk) 13:02, 3 May 2009 (UTC)

sounds like homework questions. You might look up gyroscope to start, then come back if you have further questions. —Preceding unsigned comment added by 79.75.105.45 (talk) 00:42, 5 May 2009 (UTC)

Best shape of a blade to cut through a homogenous medium?

I'm thinking of making a home-made tool somewhat like a shovel to cut through the soil under the grass turf of a lawn so that several long narrow strips of turf can be removed to create a vegetable-bed. The simplest design would have a horizontal straight blade that is positioned at 90 degrees to the direction of movement of the tool. But is it worth making this blade pointed rather than sraight - would it cut through the soil any more easily? I can see how the end of a knife would be easier to stab into something if it was pointed rather than flat, as the force would be concentrated into a small contact area. But once the leading edge of the blade is fully in something, then the cross-sectional area of the blade is constant, so it should not make any difference if the blade is pointed or straight. On the other hand, the fronts of fast planes like the Concorde are always pointed, although they do pass through an elastic medium, and I expect soil is not very elastic, although the ends of trowels are always pointed too. On the other hand, again, the fronts of modern submarines are rounded rather than pointed. Is there any reason why a straight blade would not be as good as an equally sharp pointed one of the same cross-sectional area? I'd also like to hear of any easy quick method to remove turf from the soil (burning?) apart from using a mechanical turf cutter, which are too expensive. 89.242.97.56 (talk) 13:20, 3 May 2009 (UTC)

A spade would probably work pretty well. I don't think a point would be much better than a straight blade for the reason you give - it will only help at the beginning of a cut, once it is all the way in it is no better than a straight blade. You could just use a narrow spade and get the same benefit, more consistently. I expect a trowel is pointed to allow precision, rather than to make it easier to cut with. --Tango (talk) 13:47, 3 May 2009 (UTC)

Thanks, although the problem with a spade is that it requires a lot of force strength and energy, and the user rapidly gets too tired to continue. 89.242.97.56 (talk) 14:10, 3 May 2009 (UTC)

Yeah - but as Tango pointed out - your sloping/pointed blade will be no better. Although it would be easier to get started with a pointed blade - the total distance you have to push it through will be greater - so that will exactly cancel out. What you need to do to make the task easier is to find some way to employ leverage (or gearing) to provide some kind of mechanical advantage. SteveBaker (talk) 14:19, 3 May 2009 (UTC)

Thanks, but if that is the case why is the front part of Concorde and similar planes pointed rather than blunt? 89.242.97.56 (talk) 14:24, 3 May 2009 (UTC)

A plane doesn't cut the air, it pushes it out of the way, that makes a big difference. Aerodynamics depends on far more than just cross sectional area, pushing a spade through soil doesn't really. Your best option, I think, is just to use a really sharp spade. (Although, that doesn't seem quite right - a sharper blade is simply one that is more pointed, just in a different direction, I guess the fact that your are working on a much smaller scale makes a difference because sharp knives certainly cut better than blunt ones.) --Tango (talk) 14:32, 3 May 2009 (UTC)

A pointed blade (in the manner you seem to describe) will have more drag than a straight one; more of the linear edge of the tool will be in contact with the soil. So, it might penetrate easily, but will quickly bog you down. I've stripped sod more often than I'd care to remember and the best tool I've used is a flat spade, but the more important thing was to try to use the nature of the sod itself to maintain cohesion. If you punch out the outline of where you need the sod removed (with the spade) and then get an edge up to work with, sod will typically roll up quite nicely if you gently manipulate it, using a spade or hand tool to help the uncooperative bits. Matt Deres (talk) 14:45, 3 May 2009 (UTC)

There certainly are sod cutters that are not ride-upon gasoline engine devices, and I'd bet you can *buy* one for not much more than you'd spend making such a beast. At least as a reference point, stop by your local a-to-z rental center or equivalent shoppe, and *look* at what they've got available.

Anecdote: A small, lightweight, female friend of ours was "always" (or so it seemed) turning another part of her backyard into yet another garden plot, and used such a device -- imagine something like an old single-bottom plow, with two handles for stability, etc -- without any difficulty. --DaHorsesMouth (talk) 20:50, 3 May 2009 (UTC)

The analogy with aircraft design is not a good one. The 'drag' due to air resistance increases as the square of the speed - so at high speeds, drag completely dominates. At the speed a spade moves through soil, 'drag' is not an issue - the work goes into mechanically separating the soil and cutting through roots. If you imagine it takes some amount of effort to cut through one square inch of dirt/roots per second - then the shape of the blade doesn't matter at all - the same total number of square inches have to be cut for the same rate of forward progress regardless of the shape of the blade. SteveBaker (talk) 00:03, 4 May 2009 (UTC)

What you've said implies that a blunt blade would be just as good as a sharp one because the cross-sectional area is the same, which seems counter intuitive. 89.243.185.122 (talk) 09:29, 4 May 2009 (UTC)

No - because you are moving the tool in a direction at right angles to the edge in that case. With a sloping - versus square blade - you are passing through an amount of soil that doesn't vary depending on the slope of the blade. In the vertical direction, the sharp edge is moving the soil vertically - at right angles to the direction the blade is travelling. (This is really hard to explain without doodling on a white-board!) SteveBaker (talk) 13:28, 4 May 2009 (UTC)

Thank you for all replies so far. I'd appreciate any suggestions on how to make such a tool in practice, in the easiest way, perhaps by adapting ready-made things. I can do basic things like hacksawing, bending thin sheet metal in a vice, drilling holes, filing. I would like to add one, two, or four wheels (or maybe something like a sledge might do?) so that the blade stays at a constant depth, so that in use you can put all your strength into pushing or pulling it, rather than having to finesse steering it up and down. A simple shovel would be more tiring as repeatedly stabbing the soil with it would use up a lot of energy - I've tried it. I want to make the blade between 15cm and 30cm across, and cut the turf in narrow strips. I need an L-shaped or U-shaped blade so that there is a blade to cut the turf vertically also. The biggest problem is avoiding getting too tired from the hard physical work to continue. 89.243.185.122 (talk) 09:46, 4 May 2009 (UTC)

You're asking for advice for making the tool - but ignoring the advice telling you that a straight spade is just as good (if not better)? SteveBaker (talk) 13:28, 4 May 2009 (UTC)

No, your assumption is wrong. But its more than just the blade. 78.146.76.224 (talk) 19:36, 4 May 2009 (UTC)

You might find this image search for sod cutter to be helpful. --Sean 11:51, 4 May 2009 (UTC)

Tsunami hit US?

It is reported that a tsunami may have hit the US northeast coast about 2,300 years ago.. Could it happen again? See http://news.bbc.co.uk/2/low/science/nature/8028949.stm
GlowWorm —Preceding unsigned comment added by 98.21.109.223 (talk) 17:35, 3 May 2009 (UTC)

The BBC did a programme on the possibility of a tsunami triggered by a landslide in the Canary Islands [3] --TammyMoet (talk) 18:04, 3 May 2009 (UTC)

Anything which has happened in the past, geologically speaking, will happen again. The question is when. 2,300 years is a blink of an eye on a geological time scale, but it could just as easily take 10,000 years before another such occurance happens. If it does, historians would call that sort of event "very rare" and geologists would call that sort of event "very common". --Jayron32.talk.contribs 19:26, 3 May 2009 (UTC)

There's a set of pretty substantial faults running along the island chain of the Caribbean. They aren't very active, but a major eathquake there, comparable in size to the one that created the Asian tsunami, would probably create a substantial tsunami on the U. S. east coast. Looie496 (talk) 21:41, 3 May 2009 (UTC)

The Canary Island issue is discussed in the Volcano section of the La Palma article. Dominica seems to be the island discussed as a possibility in the Carribean.[4] Rmhermen (talk) 15:10, 4 May 2009 (UTC)

Note that the West coast of the US is also hit by tsunamis, such as when chunks of the Hawaiian Islands fall off in massive landslides every few thousand years. StuRat (talk) 15:52, 4 May 2009 (UTC)

There are lots of things that could cause a major tsunami on the west coast, including large fault zones less than a hundred miles offshore, or a major quake in the Aleutians. The city of Eureka in northern California has been hit by moderate tsunamis several times in the 20th century. Places like that have an active tsunami alert system. Looie496 (talk) 16:02, 4 May 2009 (UTC)

Pigs in Egypt

Why do they want to kill all pigs in Egypt? And why do they have pigs at all in Egypt? Both seem useless to me.--Mr.K. (talk) 18:07, 3 May 2009 (UTC)

I don't know why they want to kill them. Originally they said it was to prevent swine flu, but that makes no sense because swine flu is spread human to human, not pig to human (if it was spread pig to human, there wouldn't be any risk of a pandemic). They then changed their minds and said it was for general public health reasons, which makes no sense either. As for why they have them - for the same reason anywhere else does, for food. Not all Egyptians are Muslim. --Tango (talk) 18:47, 3 May 2009 (UTC)

The "why" of it is either that they aren't listening to what the scientists are saying - or (like the Chinese government) they are deliberately taking unnecessary action in order to appear more "in control" - making it very clear that they are not ignoring the problem. Sadly, this just makes them seem stupid...but that's life. Naming this disease "Swine Flu" was a horrible, horrible mistake - it really has nothing whatever to do with pigs. Those who know this are frantically back-pedalling and trying to get everyone to call it "H1N1". SteveBaker (talk) 19:04, 3 May 2009 (UTC)

I think this is an unfair over-simplification for a couple of reasons. For one, "the scientists" are not speaking with one voice, and I've seen some pretty stupid quotes coming from scientists who should know better. Second, it may well have a lot to do with pigs (at some point), at least that's what a UN team apparently thinks as it's headed to La Gloria, Mexico to see if they can find "Pig Zero". So, "they" (Egyptian leadership) have made what seems to be an unfortunate and ill-informed decision, but the message coming from "the scientists" is pretty confusing. --Scray (talk) 19:54, 3 May 2009 (UTC)

Its origins certainly have something to do with pigs, but the pigs have played their part now. It's all about humans from now on. --Tango (talk) 22:39, 3 May 2009 (UTC)

I don't think I said anything to the contrary, and certainly did not intend to. --Scray (talk) 01:33, 4 May 2009 (UTC)

Perhaps it is a way of oppressing the non-Muslim minority, by taking away the livelihood of the farmers. Many countries in the middle east oppress those residents who do not observe the established religion. Edison (talk) 19:16, 3 May 2009 (UTC)

If so, it would be entirely out of character for Egypt to do so. Egypt has a history of decent relationship with it Coptic minority, and the government, while not exactly a Western-style democracy, isn't exactly Saudi Arabia or Iran either. Its a secular government, and there has not been any change in the government recently to indicate that they would all of a sudden decide to make life uncomfortable for 10 million of its citizens, just cuz it felt like it. Consider this a clear case of Hanlon's razor. Never ascribe to malice what could more easily be explained by stupidity. In this case, I think the Egyptian authorities are more likely to be stupid than mean... --Jayron32.talk.contribs 19:23, 3 May 2009 (UTC)

There have been few "rasher" decisions than this one" SpinningSpark 20:28, 3 May 2009 (UTC)

I was planning on making the same pun, but don't worry, I won't hog the credit. StuRat (talk) 15:46, 4 May 2009 (UTC)

I found this article very informative. It describes the grotesque living conditions of the pig farmers and their animals, and includes this bit, which might be the key to explaining the government's move:

In 2008, President Hosni Mubarak ordered all animal rearing, particularly pigs and chickens, to be moved out of populated areas for hygienic reasons. The order was never implemented, however, and authorities say the current crisis is a perfect opportunity.

--Sean 12:10, 4 May 2009 (UTC)

Yes, this is what I suspected, that the authorities wanted to get rid of pigs anyway, but were worried about the public backlash. If the public currently associates the pigs with flu, rightly or wrongly, then the authorities may be able to accomplish their goal with minimal repercussions. StuRat (talk) 15:46, 4 May 2009 (UTC)

Also note that it only adversely affected persons not practicing the established religion, however "secular" a country is with an "official" religion:"According to the constitution of Egypt, any new legislation must at least implicitly agree with Islamic law" "..Copts complain of being minimally represented in law enforcement, state security and public office, and of being discriminated against in the workforce on the basis of their religion." It is "..necessary for non-Abrahamic religious communities to either commit perjury or be denied Egyptian identification cards."(from Egypt) . Edison (talk) 03:16, 5 May 2009 (UTC)

What is the Weight of the Earth in Pounds?

I CANNOT BELIEVE that I could not find the answer to this on the Internet (and, yes, I did search the archves).

Now, when answering this question, I DO NOT want to know the mass of the Earth, as mass and weight are different.

Also, I KNOW that technically, the Earth's weight is zero or something because of the fact that weight is determined by the amount of gravitational force on something and that there is none, or it is the gravitational force of the sun or something. All I want to know is if, purely hypothetically speaking, if we were to duplicate the earth and put it on a scale that is on the Earth, and, therefore, would determine the Earth's weight based on the gravitational force of the Earth, what it would say (in pounds).

I also don't care to hear a long-whinded explanation, as I found when browsing the Internet, I just want a number (which I know would have to be an approximation), followed by "lbs." or whatever and would greatly prefer a source (even if it is a Wikipedia article itself).

Try http://www.google.com/search?q=mass%20of%20the%20earth%20in%20pounds --Tango (talk) 18:43, 3 May 2009 (UTC)

Oh, and you do want the mass. Pounds is a measure of mass. Pounds-force is just the weight of one pound on the surface of the Earth. --Tango (talk) 18:44, 3 May 2009 (UTC)

Asking for the weight of the earth is a little meaningless - saying "weight" when you really mean "mass" is a generally acceptable mistake for those who don't really understand the distinction - but you're clearly not making that mistake. The term 'weight' specifically means the force exerted by a certain mass under a certain gravitational field. You have to know both the mass AND the gravitational field strength in order to give an answer for 'weight'. By convention, unless you say "What is the weight of X on the surface of mars?" or something, we assume you mean "What is the weight of X on earth's surface?". So what you're asking is: "What is the weight of the earth on the earth's surface?" - which is pretty darned meaningless! So - you get to find the mass - and you'll have to be happy with that. However, for comparative purposes (eg "How heavy is the earth compared to a mack truck?"), knowing the mass is plenty good enough. Our article earth says the mass is 5.9736 × 10²⁴ kg - which is 1.31695337 x 10²⁵lb (note: lb - pounds, not lbf - pounds-force). An object with that mass, placed on the surface of the earth would be pulled by the earth with a force of 1.31695337 x 10²⁵lbf. However, if you placed this object onto your bathroom scales - the scales would read twice that because the object itself would have the same gravitational field as the earth...well something like that. The problem is that gravitation depends on distance - so if the object were the same size as the earth. it's center of gravity would be much further away...you could imagine all of the mass of the earth compressed into a tiny dot - but then it's a black hole and we really don't want to go there. SteveBaker (talk) 19:00, 3 May 2009 (UTC)

No, SteveBaker. The scale wouldn't read double. Think about it again. Dauto (talk) 05:24, 4 May 2009 (UTC)

Hmmm - well, the force exerted between our two earths is proportional to the product of their two masses - which is a gargantuan amount! But the acceleration is the force divided by the mass - so each earth is accelerating towards the other at a routine 9.8ms^-2. What is our bathroom spring-scale really measuring? One definition of weight is the force exerted by gravity - so I guess what the scales are reading is proportional to the product of the mass of the earth and the mass of the object it's weighing - so I guess you're right. No doubling. But weight is also defined as m.g - where 'g' is the local acceleration due to gravity. But in this case, the acceleration is twice what it was (because earth1 and earth2 are both accelerating at 1g towards a point midway between them. Relative to earth1 - and the bathroom scales sitting on the surface, earth2 is accelerating downwards at 19.6ms^-2 - so has the 'weight' doubled? I think this depends on which definition of weight you choose! Generally, when you weigh a 'normal' sized object, the acceleration of the earth towards the object is negligable - but not so in this case. Meh - as I said originally - this is a rather meaningless question. The term 'weight' really only has meaning for small object at the surface of the earth. SteveBaker (talk) 13:06, 4 May 2009 (UTC)

Why would there be any difference between an Earth on a bathroom scale and an apple on a bathroom scale? The only difference is their mass, so at what mass would the weight suddenly double? It makes no sense for an Earth on a bathroom scale to be any different to anything else on a bathroom scale. --Tango (talk) 14:45, 4 May 2009 (UTC)

Actually, as Edison points out below, there is another difference - size. The centre of mass of the 2nd Earth would be further away from the surface of the 1st Earth than the centre of mass of the apple - that reduces the weight measured by the bathroom scales. Whether you take that into account or not, you certainly don't get double. (We had a similar discussion here not long ago about a force metre held horizontally with two masses pulling it via pulleys - it's the same principle.) --Tango (talk) 17:46, 4 May 2009 (UTC)

What? Pounds-force is a measure of mass? I don't think that's right... --Tango (talk) 22:37, 3 May 2009 (UTC)

Oopsie! Thanks...I've fixed it. SteveBaker (talk) 23:38, 3 May 2009 (UTC)

(EC)The weight of an object depends on the gravity pulling on it. Weight equals mass times gravitational acceleration. A simplistic solution would be (5.97 × 10²⁴ kg) x (9.78 m/s²) = 5.83 x 10²⁵ Newtons, which equals 1.31 x 10²⁵ pounds, or 13,100,000,000,000,000,000,000,000 pounds. This answer assumes that the Earth#2 which is being weighed is a point mass resting on the scale, which somehow does not get pushed far down inside Earth#1. A better answer would take into account that the part of Earth#2 farther away from Earth#1 would not be as strongly attracted. This would reduce the weight appreciably. The force (weight) would be the gravitational constant, 6.67259 x 10^-11m³/s²kg, times the mass of the Earth, times the mass of the duplicate Earth, divided by the square of the distance between them, which could be taken as twice the radius of the Earth, 6.4 x 10⁶meters. So we have (6.67259 x 10^-11) x (5.97 × 10²⁴)² /(2 x (6.4 x 10⁶)² = 1.45 x 10²⁵ Newtons, which equals 3.26 x 10²⁴ pounds. Again, in reality, the two planets would smash together into a hot messy blob. No guarantees on the math. Edison (talk) 19:11, 3 May 2009 (UTC)

That's funny. you say you don't want a 'long-whinded explanation' but than you ask people to give you the weight using 'lbs' as unit. But 'lbs' is a unit of mass and people felt compeled to explain that to you, resultig in long-winded explanations. Dauto (talk) 01:21, 4 May 2009 (UTC)

To be fair, some of us learned in school that pounds are a unit of force and not mass. I was quite surprised when I learned that this was actually wrong. --Anonymous, 05:50 UTC, May 4, 2009.

It is very common to refer to pounds-force as simply "pounds". It may be only ref deskers that actually know the difference! --Tango (talk) 12:54, 4 May 2009 (UTC)

Not many people know their weight in Newtons either...so similar problems exist in the metric world. At least with lb and lbf, the numerical part is identical. How many people still use kiloponds? To do things 'right' in the metric world requires using Newtons and now the numerical value isn't the same as the (incorrect) kilogram number. Aaarrrggghhh! SteveBaker (talk) 13:11, 4 May 2009 (UTC)

I don't think the problem is with the units, the problem is with the dimensions. People say "weight" when they mean "mass". They are using the correct units for the measurement they are actually talking about, they just give it the wrong name. --Tango (talk) 16:40, 4 May 2009 (UTC)

In school, I was taught that pounds is a unit of weight, grams is a unit of mass. A Quest For Knowledge (talk) 13:52, 4 May 2009 (UTC)

You were taught wrong. For a start, weight isn't a dimension, so there aren't really "units of weight". Weight is just a type of force. You don't talk about "units of friction" or "units of tension" or "units of electrostatic repulsion", they all have the same units, the units of force. Pounds is a unit of mass, pounds-force is a unit of force (the name is a clue!). People sometimes abbreviate "pounds-force" to "pounds" when it is clear from context that they mean the force, but it is sloppy. --Tango (talk) 16:40, 4 May 2009 (UTC)

Wow, interesting. I stand corrected. Thanks! BTW, this page has nice info (not that you need it, Tango). [5] 18:20, 4 May 2009 (UTC)

Earth #1 and earth #2 each attract the other. Would this double their mutual attraction (pull toward the other body) and thus the weight of each of them? I don't think so. When we speak of weight, we are referring to the mutual attraction. In everyday life, the object that is not the earth has so little mass that we can ignore its pull on the earth. But that pull exists. When we drop something, the earth moves up toward it just a little bit.
Weight has to do with two objects and the distance between them.. Mass has to do with one object and Newton's second law of motion. – GlowWorm. —Preceding unsigned comment added by 98.21.109.223 (talk) 01:38, 4 May 2009 (UTC)

Indeed, "weight" is the force between the two bodies. That can be thought of as one attracting the other, the other attracting the one or a combination of the two - the difference is simply what coordinate system you choose to work in (we usually fix the Earth and measure everything relative to it, so we don't consider forces on the Earth, but that's just a convenient convention). --Tango (talk) 12:56, 4 May 2009 (UTC)

See my earlier response to Dauto. I don't think it's that simple. SteveBaker (talk) 13:06, 4 May 2009 (UTC)

See my response to your response, it really is that simple! --Tango (talk) 14:45, 4 May 2009 (UTC)

In the UK, we are taught that "pound" is a unit of force. Thought experiment for SteveBaker:-

Take an object, say an apple, and put it on the scales. The scales read "1 pound". According to Newton's law of universal gravitation, the earth exerts a force of one pound on the apple. The apple exerts a force of one pound on the earth. Now turn the scales upside down and put the apple on top. The scales read "1 pound". [Actually the scales will read more than one pound, because of the weight of the scales themselves that had been ignored by zeroing the scales when they were the right side up.] The earth continues to exert the same force on the apple: one pound; the apple exerts the same force on the earth: one pound. The scales measure the gravitational force that one object exerts on the other. Axl ¤ [Talk] 16:36, 4 May 2009 (UTC)

Surely the non-uniformity of gravity has to be taken in account when finding the force a duplicate earth would excert on the earth? I obtain 1.7*10^45 Newton. (Do the conversion to your archaic units yourself :-) ). —Preceding unsigned comment added by 81.11.182.18 (talk) 16:45, 4 May 2009 (UTC)

Hmm, I get a value of 31.1 x 10⁶ Newtons. Axl ¤ [Talk] 17:38, 4 May 2009 (UTC)

Hmm, I get a value of about 1.5x10²⁵N (for the value displayed on the bathroom scales - assuming you had some that measure in Newtons). The mass of the Earth is 6x10²⁴kg. To convert that to Newtons we would usually multiply by 9.81, however the centres of gravity are twice as far apart as usual, so we need to divide by two squared (4) as well. --Tango (talk) 17:50, 4 May 2009 (UTC)

Tango, your mistake: the gravitational field strength of the earth is 9.81 N/kg only at the surface of the earth. It is better to use Newton's law of universal gravitation. Axl ¤ [Talk] 18:02, 4 May 2009 (UTC)

Newton's universal law of gravitation is difficult to use, though (as in, you need a calculator, or at least pen and paper). My method required looking up one Wikipedia infobox and some simple mental arithmetic. Why doesn't dividing by 4 work? The gravitational field strength twice as far away is 1/4 as strong, you then multiply that field strength by the mass of the object in question to get the force. --Tango (talk) 18:08, 4 May 2009 (UTC)

Ack, you're quite right, Tango. I checked through my working and I multiplied by two instead of squaring. :-( Sorry. Axl ¤ [Talk] 18:57, 4 May 2009 (UTC)

1. Newton showed that "an object with a spherically symmetric distribution of mass exerts the same gravitational attraction on external bodies as if all the object's mass were concentrated at a point at its centre" (see Newton's law of universal gravitation#Bodies with spatial extent)
2. Try Googling "G*((mass of the earth)^2)/((diameter of the earth)^2) in lbf"

--Heron (talk) 18:59, 4 May 2009 (UTC)

Yes, you can do that, but if you are comfortable with what all the different numbers that are flying around actually mean, you don't need to. The reason I used 9.81 (well, actually I used 10, which is more than precise enough for these purposes) is because I knew that was most of Newton's law done for me. It is G*M/r² where M is the Earth's mass and r is its radius, so I knew I just needed to multiply by the Earth's mass again and double the radius (which means dividing by 4, since it is squared and in the denominator). All of that I could do in my head. If you go back to basics and use Newton's law you are actually just deriving the number 9.81 and then doing exactly what I did - I just skipped a step. People use calculators as an excuse not to think, they are rarely actually needed unless you want really precise answers - a few seconds thought about how best to do the question can usually get it into a form that can be done with mental arithmetic or, at worst, pen and paper. --Tango (talk) 21:37, 4 May 2009 (UTC)

Note to Tango - I corrected your reply to stop the rest of the page being rendered incorrectly - you used <sup>2<sup> instead of ² . Exxolon (talk) 21:42, 4 May 2009 (UTC)

Oops! Thank you. I almost always type that wrong, but usually spot it straight away and correct it, I must have missed that one! --Tango (talk) 22:57, 4 May 2009 (UTC)

My high school and college physics courses taught that "pound" was a unit of force. Period.A "pound of sugar" on Earth would be a "'fraction of a pound" of sugar on the Moon or many pounds of sugar on a more massive planet. A "kilogram"of sugar" stayed the same (unless it turned to caramel on a hot planet). To answer otherwise was to get the question marked "incorrect." "Pound-mass" was the term used (rarely) for the equivalent mass. I looked at some old physics books at Google books, and pounds were used for mass or force a hundred or more years ago. Edison (talk) 03:11, 5 May 2009 (UTC)

We have a discussion of the issue here. It is very common to use "pound" as a unit of force when it is clear from context, so I guess I can't really complain about that, but to say it is exclusively a unit of force just seems wrong to me. Schools ought to teach the difference between pound-force and pound-mass and teach pupils to make it clear what they are talking about. --Tango (talk) 13:10, 5 May 2009 (UTC)

Interesting. I assume Edison was taught in the USA because, in the UK, I was taught that pound was a unit of mass, and that I should use "pound-weight" or "pound-force" (or even "poundal"?) for forces. I also was taught to convert to grammes and grammes-weight! (I had heard of Newton). Dbfirs 13:18, 5 May 2009 (UTC)

I read the OP as asking: what's the sum if we add up (as magnitudes, not vectors) the weights of all the pieces of the Earth? Because each increment of volume (if not centred on the core) does have a weight relative to the rest of the Earth. —Tamfang (talk) 05:23, 10 May 2009 (UTC)

Is milk marked as hazardous

When transporting milk in the UK, is is marked as hazardous or non-hazardous, because of its environmental impact once spilled?

82.19.53.148 (talk) 19:08, 3 May 2009 (UTC)

I'm guessing that this is raw milk - not yet pasteurized - which means that it could potentially have some disease-causing agents in it. It's a pretty small risk - but in the UK, we have European Community rules which may well disallow the sale or consumption of raw milk - and thereby require (through typically bizarre euro-logic) a hazard warning sticker. SteveBaker (talk) 19:18, 3 May 2009 (UTC)

I believe I have seen milk tankers marked "non-hazardous food product" or something similar. SpinningSpark 20:24, 3 May 2009 (UTC)

The EC does pass some strange things but in most of the cases I've checked I agree with the EC rather than Britain. In others Britain makes a strange interpretation of an EC regulation or applies it where it was never intended. And in a small but important minority it does look like someone has got something wrong through probably for political reasons. My main complaint is that it is too hidebound to pass something new and controversial like for instance controlling fisheries properly. If the current crop of control freaks in Westminster disappeared and Britain was run directly by the EC I wouldn't mind. Dmcq (talk) 10:19, 4 May 2009 (UTC)

I don't think your political essay is actually providing an answer to the question. SpinningSpark 10:51, 4 May 2009 (UTC)

Oh sorry. You're quite right in that even some foodstuffs can be hazardous but I'm pretty certain milk is not one of them. If milk has gone off it is normally just used as a fertilizer and sprayed on a field. One can't just dump large quantities of even non-hazardous things like milk down the drain though. Dmcq (talk) 12:53, 4 May 2009 (UTC)

I work for a large supermarket chain in the UK. I'm not entirely sure if this relates to all milk, but milk which has passed its use-by date, which is contaminated or is otherwise unsuitable for sale is classed as a Category 3 Animal By Product. Under current legislation it has to be marked up as being 'Category 3 - Unfit for Human Consumption' and has to be removed by a specialist carrier, who will then arrange for it to be rendered, composted, or destroyed by other means. This was introduced, I believe, following the BSE crisis, when it was found that the infective element in animal by-products could hypothetically be re-introduced into the food chain if it was simply dumped or disposed of by regular waste disposal means (such as tipping it down a drain or landfilling it). Also, common sense would suggest that if a milk tanker was to crash and spill its load, huge quantities of milk flowing into local rivers could have the potential to kill fish and other marine biology. Therefore, I would further assume these are the reasons it may carry hazard warnings russ (talk) 23:55, 4 May 2009 (UTC)

Here's a link: Animal By-Products Regulations, the regulations date from 2003. It is quite a bit more strict than I remember. It isn't a hazard though, see Dangerous goods or the European regulations referenced from there. Hazardous really does mean you should stay well away if anything happens to it. Dmcq (talk) 07:35, 5 May 2009 (UTC)

I worked at a grocery store in highschool several years ago and we just dumped the stuff down the sink. 65.121.141.34 (talk) 13:13, 5 May 2009 (UTC)

how do I frickin slice bread???

omg I'm the worst frickin bread slicer in the world. Everyone else can do it, but when i try, the stuff just like ends up a pastiche of little pieces and a WHOLE lot of crumbs. And by that I mean the plate is like 60% crumbs, 40% little itty bitty islands of bread. When I look up the rest of my extended family is looking at me like I've been shaking the baby. Now, I buy myself sliced bread, for obvious reasons, but sometimes I don't have control over the situation, and I need to know how to slice bread, I don't want to be in these kinds of jams again. I have tried every technique from choking the bread to barely touching it with the one hand, with the other hand I've tried everything from firm quick to light quick to light slow to firm slow it's like either I'm not cutting into the bread or I'm mauling the thing. The very best I can do is like tweeze a little triangle of it between my thumb and forefinger and then I can cut that no problem. I end up with like this pyramid of bread (not flat) and then can proceed to butter its several sides. There just has to be a better way. Any hints guys? 94.27.137.46 (talk) 19:35, 3 May 2009 (UTC)

Use a sharp knife, a sawing motion, and little pressure. --Stephan Schulz (talk) 20:09, 3 May 2009 (UTC)

the knife is sharp, it cuts everything else just fine at my hand, and at everyone else's it cuts the bread fine too. As for sawing motion... as opposed to what? I don't really see what this contrasts with.... A little pressure: tried it. Tried all different kinds of pressure, no use.

Also, only cut through part way, then turn the loaf 90° and start a new cut from that side, and so on. That will tend to prevent the knife breaking out of the bread before you get to the bottom, or cutting deeper into the loaf than you intended. Also, try watching someone who is good at it, the best way to learn is from someone who actually knows, not from theory. SpinningSpark 20:22, 3 May 2009 (UTC)

Be sure to use a proper bread knife[6]. They are generally long with a serrated edge. To be the hero of your family, invest in an electric one[7]. Cuddlyable3 (talk) 21:01, 3 May 2009 (UTC)

I'm going to try the cut-and-turn thing. But the other people, the good bread cutters, definitely don't do that. I've tried imitating them but then the effect is even worse than when I just try my best. 94.27.137.46 (talk) 20:56, 3 May 2009 (UTC)

In my experience, there are exactly two practical uses for an electric knife, and this is one of them. The fact that you have two serrated blades oscillating against each other means that you have to exert almost NO downward force on the loaf. It's a worthwhile investment even if you don't make a lot of your own bread, because there's NOTHING like a slice of fresh bread still warm from the over, with a bit of real butter on it!

--DaHorsesMouth (talk) 21:13, 3 May 2009 (UTC)

If you're imitating people who succeed, but you're not succeeding, then it's not a question of your technique but of how you execute it. We would probably have to see you in action to figure out what the problem is. My best guess is that your hands are shaky, but who knows? Looie496 (talk) 21:29, 3 May 2009 (UTC)

I'd say that the advice posted here is the greatest thing since sliced bread. --Mark PEA (talk) 22:32, 3 May 2009 (UTC)

If I had to guess I'd say you're pressing down too hard. Surprisingly little force should be required, if you try to force it you'll just crush the bread. APL (talk) 22:47, 3 May 2009 (UTC)

I have found that if the serrated bread knife is at a 45 degree angle, and the cut is started on the top corner opposite where you stand, you can get uniform slices by watching that the cut stays the desired distance from the face (cut surface) both at the top and at the bottom opposite you. If you just apply the knife across the top, the cut line will angle so that you cut wedge shaped slices. Historically, sliced bread was introduced in 1928. When World War 2 started, the U.S. government in January, 1943 banned the sale of presliced bread, but consumers argued that presliced loaves saved wheat by reducing waste, and sliced bread was again allowed to be sold in March, 1943. Edison (talk) 01:44, 4 May 2009 (UTC)

Thank you for what is the most scientific advice given so far, but I just tried it and am currently eating a piece of bread in five pieces with a lot of crumbs under it, I had to butter the five pieces separately and put separate toppings on them for my "sandwich". I can't live like this. Please try to describe your method again, this is just not working :( 94.27.226.57 (talk) 11:07, 4 May 2009 (UTC)

<image removed because it violated WP:IUP and WP:NFC>Clarityfiend (talk) 04:37, 4 May 2009 (UTC)

Sorry, dude, but I had to remove the image, per policy. For the record, it was funny as hell. But rules is rules... No Mr. Bond, I expect you to die... --Jayron32.talk.contribs 05:01, 4 May 2009 (UTC)

According to our article, World War 2 started in 1939, not 1943. It was just that the Americans did not notice and we had to start without them. SpinningSpark 07:56, 4 May 2009 (UTC)

Poor phrasing. The U.S. government allowed bakeries to slice bread until January 1943. Then the U.S. brought the war in the Pacific to an end in 1945 with Weapons of Mass Destruction, but sliced bread lovers may not have noticed, since their pre-sliced bread had once again become available in March, 1943. Perhaps as they munched on uniformly sliced bread pieces in August 1945, they heard of Hiroshima, Nagasaki and the Japanese surrender on the radio, and mumbled "Wow! Nukes! The greatest thing since sliced bread!" Edison (talk) 03:00, 5 May 2009 (UTC)

Is it possible that our OP is trying to make slices that are far too thin? Can you make a half-inch-thick 'slab' without making a horrible mess? SteveBaker (talk) 12:35, 4 May 2009 (UTC)

I find that when I slice bread the way I naturally hold the knife results in the slice getting thinner and thinner as I go down. I have to consciously avoid that by paying attention to the width of the slice and tilting the knife appropriately. Perhaps you have a similar problem? --Tango (talk) 12:52, 4 May 2009 (UTC)

That happens to me when I slice cheese - but that's because our cheese knife has one flat face (on the left side of the blade) and the opposite face has a sloping angle on it coming down to the serrated edge. Since I'm left-handed - that slope deflects my cut to one side. To compensate for that - you have to lean the knife at an angle - and with hard cheeses, that causes the slices to disintegrate because of the lateral force applied to the slice before it becomes fully separated from the slab. The world owes me a left-handed cheese knife! I can't imagine that being the cause with bread because it's so much softer - but if have this problem and you are left-handed, then a close examination of your knife might be revealing! SteveBaker (talk) 13:21, 4 May 2009 (UTC)

No, I don't have any good excuse like that, I'm just rubbish at slicing bread! It's not difficult to make sure you tilt the knife appropriately, it just requires paying attention. It would be nice to be able to slice break absent-mindedly, but I'll live! --Tango (talk) 14:02, 4 May 2009 (UTC)

Steve, your problem is rather easy to fix: just hold the sharp end so that the flat side is against the cheese. Or you could slice from the other end of the cheese, but that's not nearly so amusing to me... Matt Deres (talk) 19:40, 4 May 2009 (UTC)

I also should get one of those handicapped license plates, due to my inability to slice bread. I can make thick slices fine, but sandwich-thin slices never work out. I use pre-sliced bread for that. For bread machine bread, which I normally eat with just butter, there's no need to be that thin. (If a thick slice is too much, I'll cut it the other way, into halves or even quarters.)

Letting the bread sit until it gets cold makes it easier to slice, but then you miss out on that "fresh out of the oven" taste. With my bread machine I always get rock hard crusts and super-soft interiors, which makes thin slices virtually impossible. Also note that there is a special "bread knife" which should be used to slice bread. Just being sharp isn't enough, it needs the proper type of cutting edge. StuRat (talk) 15:36, 4 May 2009 (UTC)

Cutting hot freshly baked bread is, indeed, very difficult. Just giving it a few minutes to cool can make a big difference, though, and it is still warm enough to be delicious. But I agree, there is no need to cut thin slices of such bread - its delicious, eat lots of it! --Tango (talk) 15:39, 4 May 2009 (UTC)

Ditto the serrated (toothed) edge. For a slice with an even thickness, hold the knife blade perpendicular to the cutting surface (i.e. straight up-and-down, 90°, right angle to the countertop). Try a mitre box that will align the knife till you get used to it. -- Deborahjay (talk) 16:46, 4 May 2009 (UTC)

Thin slices and hot bread is an almost impossible thing to handle - especially if it's typical home-made bread where the crust is relatively hard and the interior very soft (until it's cooled at least). In such cases, an electric carving knife might help. The problem with a hand-held knife is that as you drag the blade back and forth by several inches - the soft interior of the bread finds it easier to stick to the knife and move back and forth with it (result...disaster) than it does to maintain it's internal cohesiveness. Using an electric carving knife limits the amount of motion to a quarter inch or so - and the fact that they have two parallel blades moving against one another means that its trapping the tiny pieces of bread between two serrations and 'scissoring' them - rather than pulling it back and forth by several inches and thereby tearing it apart. However, this is still a tough problem. Thicker slices are definitely called for in warm, crusty bread. (Darn - now I have to wipe the drool off of my keyboard...note to self - don't answer foodie questions too close to lunchtime!) SteveBaker (talk) 19:07, 4 May 2009 (UTC)

Reportedly putting the knife in the freezer for a couple of minutes before cutting might help with fresh bread (s.o. else's OR). Other than that, train at home: start off by doing very short and fast to and fro blade movements at a corner. - Think you a fiddling a series of very fast short notes on a violin. Use the knife like a bow, no pressure. Let the cutting edge do the cutting. Once you got the hang of that modify length of cutting stroke, speed and downward pressure till you get satisfactory results. Take your time. First slice 1 minute? - No sweat.

@SteveBaker Cheese knife, was it? A bit of overtime pay should cover this one [8]. (Be sure to hang a sign for visitors somewhere in the house. We have this thing with our LH scissors, pens and peelers when RH people drop by.) 76.111.32.140 (talk) 21:22, 4 May 2009 (UTC)

Looking back at the OP's question, where they note that everyone else can do it but they can't - dude, you're too tense about it. I think you're trying to hold the bread down, whereas actually you should be kind of holding the bread up a little bit while you do that violin thing noted above. Don't attack the bread (and I have a 30-year-old bread knife!). Watch the other people to see where they put their hand on the bread and how they saw the knife. Then fill in the gaps - you have to support the loaf when you break in at the top, if you start crushing it, you're screwed. Franamax (talk) 11:42, 5 May 2009 (UTC)

Endergonic but exothermic reaction

Such reactions are possible and there is some case involving water but off the top of my head I cannot think of what reaction it is. Is it water melting or what? Thanks —Preceding unsigned comment added by 24.171.145.63 (talk) 19:40, 3 May 2009 (UTC)

I have a feeling it may be acidity; if the pKa (at 20 C) is just at the right value, it will be energetically endothermic to lose the hydrogen proton, but exergonic to do so. The reverse reaction is exothermic but endergonic. Elimination reactions at sufficiently high heat are also another good bet. John Riemann Soong (talk) 20:15, 3 May 2009 (UTC)

There are lots of reactions like that involving water. My favorite example is dissolving ammonium nitrate in a small amount of water, which is exergonic (so it occurs spontaneously) but very endothermic (you can use it to freeze water). The reverse is endergonic but exothermic. See [9], which starts with two solid salts but is basically the same reaction. —Keenan Pepper 20:48, 3 May 2009 (UTC)

Hmm, as temperature decreases won't the entropy term decrease in magnitude? So at some point it starts being endergonic too. (Presumably that sets up the equilibrium point, if all the ammonium nitrate isn't dissolved.) John Riemann Soong (talk) 04:56, 4 May 2009 (UTC)

Thanks but I was asking about something to do with water by itself (i.e water freezing) —Preceding unsigned comment added by 24.171.145.63 (talk) 23:32, 3 May 2009 (UTC)

It's probably condensation or freezing, in that case. In fact, it's often why water doesn't freeze or condense at 100% RH, but at supersaturated conditions (or supercooled conditions). Only then does condensation or melting occur. As I would understand it. Adding a heterogeneous compound (for cloud seeding) would lower the free energy required for nucleation. Of course, this is all temperature-dependent. If temperature is lowered enough, the entropy term stops becoming significant, so the exothermic term takes over, the reaction is exergonic and the reaction occurs (until it gets too hot and the reaction stops).

You can probably drive many weather systems, e.g. such as thunderstorms, midlatitude cyclones (around a low pressure area) or hurricanes this way. When you make condensation or freezing exergonic, heat is released, which powers a system through latent heat, giving weather systems their energy. If an air mass gets too hot, net condensation or freezing stops (remember net, as unfavourable reactions can still occur) -- but if it's still warmer than the environment temperature, it will rise, temperature will drop again (and so will solubility), releasing more heat energy... (and also creating a pressure gradient). The normal condition I would bet, is that condensation is endergonic at equilibrium temperatures. Which is why the water in the air doesn't spontaneously rain on you. If it's not endergonic, then it will condense until it reaches equilibrium. [From how I see it.] John Riemann Soong (talk) 04:56, 4 May 2009 (UTC)

Unecessary use of radioalablled nucleotides?

For a scientific journal article I'm reading, the method used to determine the quantity of modified DNA was "cycle-limited" PCR using radioactive nucleotides, followed by denaturation and reanealing followed by treatment with an enzyme (CEL I) which recognises and cleaves (double-stranded, I guess) wherever it finds a mismatch. The DNA is then run on a polyacrylamide gel and visualised overnight with a phosphoimaging screen. This was published in 2008. My question is why do they use radiolablled nucleotides and not just stain with ethidium bromide or something else? (the paper is PMID 18657511, incase you're interested). ----Seans Potato Business 21:32, 3 May 2009 (UTC)

Let me pose the question the other way; what is the objection to using it? Is there some inherant disadvantage to using the radioactive labeling method that the ethidium bromide method does better? --Jayron32.talk.contribs 01:08, 4 May 2009 (UTC)

Presumably, getting nucleotides that are radioactively labelled might be more expensive. John Riemann Soong (talk) 05:53, 4 May 2009 (UTC)

Anyone know what the detection limit is for ethidium bromide staining versus using radiolabeled nucleotides? Someguy1221 (talk) 07:14, 4 May 2009 (UTC)

Normally, you would try to use as little radioactive material as possible in a lab. So I would think if there would have been an easy alternative like ethidium iodide or bromide, they would have used it. One advantage of radioactive labeling and exposition overnight I can think of is the higher sensitivity: You can raise the exposition time to get brighter spots on the plate, if you want to detect very small amounts of DNA, but with ethidium staining in my experience this does not work well (the camera is not very sensitive and the images of the gel normally have a high background, meaning a higher exposition will just give you an image that is more and more white). TheMaster17 (talk) 09:21, 4 May 2009 (UTC)

My guess is sensitivity also. I think you would struggle to see EtBr stained DNA using this technique. Rockpocket 19:12, 4 May 2009 (UTC)