Wikipedia:Reference desk/Archives/Science/2009 March 22

Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

March 22

Pick on somebody your own size...

Why is it that the largest animals, both on land (elephants) and in water (whales), don't have any natural predators (other than man, that is). I'm talking about adult animals here. So, why isn't there a predator (or group of predators) large enough to take on an adult elephant or adult blue whale ? Somehow the upper size limit for predators seems to be lower than for other animals, but why exactly is this ? StuRat (talk) 04:23, 22 March 2009 (UTC)

If the largest animals in the world were predators, they would quickly outstrip their food source, and then ensure their own demise. The situation is not unique to modern times, Tyrannosaurus, one of the largest predators ever, was still dwarfed by contemporaneous herbivorous dinosaurs; probably on a scale similar to the size difference between the largest predators and herbivorous animals today. Incidentally, Blue Whales are technically meat-eaters; they subsist on Krill, which is definately not a plant. --Jayron32.talk.contribs 04:41, 22 March 2009 (UTC)

Why couldn't there just be fewer in the predator species than their prey species ? I believe this is the normal situation in any predator-prey relationship. StuRat (talk) 04:47, 22 March 2009 (UTC)

Well, we could invent any situation we want to; except that time and time again, over history, the same patterns have emerged. We can justify these repeating patterns, by offering explanations as I have done, but offering counterexplanations (like "we SHOULD have really huge predators") doesn't make much sense, since it just appears to not work that way. Except that, as I noted above, the largest animal ever to have lived, IS A PREDATOR. Blue Whales eat other animals, live, which seems to me to be what a predator does... Even if you don't want to include that as a predator, you must admit that predators just AREN'T the largest critters in any environment and at any time, so explanations that attempt to say they should be must be flawed from the start, no? --Jayron32.talk.contribs 05:09, 22 March 2009 (UTC)

Keep in mind that the larger the animal, the longer it takes to grow a replacement. In general, anyway. Preditors can eat rabbits all day long and the population will rebound quickly. If a theoretical uber-hunter ate all the elephants within its range in could be decades before they replenished. It seems like that would leave a very low margin of error for the predator-prey balance.

In general predators prefer animals that reproduce quickly and grow up quickly. APL (talk) 06:34, 22 March 2009 (UTC)

Incidentally, while adult elephants have no natural predators other then humans, juveniles are general vunerable to big cats although the social herd nature helps to protect them.. The same appears to be the case for mammoths and saber-toothed cats and one common believe is the demise of the mammoths may have played a role in their extinction, take a read of Homotherium and Smilodon for example. Homotherium in particular says

Friesenhahn cave in Texas contained the remains of over 30 H. serum individuals, which were discovered along with the remains of between 300 and 400 juvenile Columbian Mammoths (Mammuthus columbii).[6] Besides mammoth, very few other potential prey species were found in the cave - it is therefore unlikely that Homotherium carried scavenged carcasses of already dead animals to the cave. Such specialization on prey of a particular species and age structure is not covenant with a scavenging lifestyle. For the same reason it is also unlikely that the dire wolves carried the mammoths into the cave.

Nil Einne (talk) 13:44, 22 March 2009 (UTC)

Killer Whales have been known to hunt blue whales. — DanielLC 16:55, 22 March 2009 (UTC)

Wow, they are 1/25th the mass, so that would seem rather ambitious. That's worse than a house cat hunting an adult human. StuRat (talk) 17:22, 22 March 2009 (UTC)

I think that they only go for the calves and they do hunt in packs, so maybe not so ambitious, although such attacks are said to be rare in our article. Mikenorton (talk) 17:37, 22 March 2009 (UTC)

Still, there have been cases where a dog of a similar size to a housecat has managed to kill an adult human. I'm not entirely certain - but I think that killer whales are much faster and more manoeuvrable than blue whales, and they are (obviously) much more aggressive. Blue whales are huge, yes - but I'd imagine that taking a chunk the size of a killer whale's mouth out of the body of one would cause it to die. --Kurt Shaped Box (talk) 22:33, 22 March 2009 (UTC)

There are plenty of ecosystems where the dominant predator is also the largest animal. The Killer Whale eats penguins and seals - and is easily the biggest animal that lives (continuously) in those areas. I doubt that in regions where the Great White Shark lives has any animals that are any larger. Ditto Polar Bears, ditto Grizzly Bears. I think there are plenty of ecosystems where the predator is the biggest creature around - and plenty of others where it isn't - it seems fairly random to me. As for the evolutionary pressures - I agree with the earlier respondant - if an easier living can be had hunting rabbits - why go after elephant? If the only herbivore was the elephant - then probably the carnivores would evolve to take it down. But generally a pack of animals is better at doing that...and for that, size isn't everything. SteveBaker (talk) 19:26, 22 March 2009 (UTC)

Are you sure no whales live in those oceans ? And how about large land herbivores, such as elk and moose ? They seem like they might be too big to be prey for bears, at least the adult males. As for your "if an easier living can be had hunting rabbits - why go after elephants ?", the point is that the rabbit-hunting niche is already filled by well-adapted predators, while the whale- and elephant-hunting niches are wide open. StuRat (talk) 03:34, 23 March 2009 (UTC)

Not any more, they ain't. We got there first and did it better. :) --Kurt Shaped Box (talk) 03:40, 23 March 2009 (UTC)

FYI: Biggest land animal to ever live = sauropod = 80 tonnes [1] 141.14.245.244 (talk) 15:52, 23 March 2009 (UTC)

And was there a predator that hunted the sauropods ? StuRat (talk) 23:42, 23 March 2009 (UTC)

Healthy adult sauropods (of the 'giant' type), I'd guess not. I'll bet that there were plenty of predatory dinos that could and would take a young one, or finish off a sick one, though. Predators don't generally attempt to take on prey animals that look as though they might have a good chance of defeating them in combat unless they're really desperate for food. --Kurt Shaped Box (talk) 23:58, 23 March 2009 (UTC)

I just watched a Walking with Dinosaurs episode about sauropods, and they seem to agree that, once again, adults had no predators to worry about. StuRat (talk) 05:33, 24 March 2009 (UTC)

Pyrethrins

I have sprayed a Kaffir Lime tree with a pyrethrin product to eliminate a heavy infestation of red spider mites. Since I use the leaves in cooking, IS IT SAFE to eat the food cooked using these pyrethrin-sprayed leaves? Is there a period of time after spraying not to use them, and then it is OK?

Thank you very much for your answer. Yvonne Stinson —Preceding unsigned comment added by Rajahstein (talk • contribs) 12:15, 22 March 2009 (UTC)

Pyrethrins are amongst the safest pesticides available. Having said that I'm loath to pronounce anything completely safe. You should judge for yourself from the published information about them, here are a couple of links that discuss both direct exposure [2](i.e. during application) and safety as residue in food [3]. The conclusions seem to be that there are few definite health implications but the possibility of carcinogenesis has not been ruled out. Mikenorton (talk) 12:43, 22 March 2009 (UTC)

If you do use them, I would recommend you rinse the leaves well Nil Einne (talk) 13:39, 22 March 2009 (UTC)

Next time spray the Kaffir Lime with plain water more frequently, two or three times a day if possible. Red spider mites hate moist conditions and will find it hard to survive let alone flourish. Richard Avery (talk) 08:30, 23 March 2009 (UTC)

In the instruction manual of your pesticide (or on the bottle) there is probably some direction about the use on food crops (which probably includes directions on long you have to wait). If not, at the very least there should be a telephone number for the manufacturer. I highly recommend calling them and asking their recommendation on the matter - especially with potentially hazardous things such as pesticides, I find that most manufacturers are happy to discuss how to use their product safely. -- 76.204.102.79 (talk) 03:19, 25 March 2009 (UTC)

Metal spoon in microwave

Hi. Sometimes we leave a metal spoon in our food when we put it in the microwave, and nothing happens, and the spoon is barely hot afterwards. Of course, the food must be full, solid, and in a bowl, and most of the spoon is immersed in the food so the microwave isn't heating *just* the spoon. Are there any risks that are unforseen with this practice, such as radiation being emitted outside of the microwave, or the spoon or the food storing excess radiation or an electric current, etc? Thanks. ~AH1^(TCU) 14:56, 22 March 2009 (UTC)

Microwave oven#Hazards contains language that makes me not want to repeat your experiments... 88.112.62.225 (talk) 15:10, 22 March 2009 (UTC)

It does however say "Microwaving food containing an individual smooth metal object without pointed ends (for example, a spoon) usually does not produce sparking". There is a risk of shorting if the handle gets too close to the side of the oven. I can't see how any excess radiation or electric current could be stored. Mikenorton (talk) 15:25, 22 March 2009 (UTC)

Well, there are certainly situations when this practice is "A Bad Thing" - sharp metal objects concentrate the charge at their tips and can arc - that produces all sorts of nasty, toxic gasses that you really don't want in your food - also, metal objects positioned "just so" with respect to the microwaves resonant cavity can concentrate the heat in small areas resulting in food that's cool in some areas and dangerously hot in others - that can result in small explosions when heating liquids - it can also "short out" the magnetron to some degree which will shorten it's life and might even outright destroy it. However, there are other times when none of these terrible things can happen. However, the precise reason you get one outcome versus another depends critically on exact placement of the metal, its exact shape and the precise nature of the food (if any) around it. Since we mere mortals have ZERO 'gut-feel' for what's right and what's not when it comes to invisible & intangiable things like microwaves - putting metal that was not designed specifically to be there into your microwave - is just a dumb thing to do. It says that right there in the instruction book for your oven - and there is probably another sticker someplace on the door frame that says it again...they don't do that without a reason...so just don't do it - OK? SteveBaker (talk) 19:17, 22 March 2009 (UTC)

Let me reword the OP's question a bit to understand it a bit better... "See, this one time, I crossed a busy street wearing a blindfold and blasting my I-pod. I could see nothing, I could hear nothing, and there were like 100 cars crossing the street in front of me. And yet, I didn't get hit. Doesn't this mean that all the things I read about looking where I am walking and only crossing with the light are bullshit? Like, if I managed to cross the street with a blindfold and nothing bad happened, why is there all this fuss?!?". Seriously, putting metal in a microwave is ALWAYS contraindicated, even if occasionally nothing bad happens, it is NOT a habit you want to get into... --Jayron32.talk.contribs 00:49, 23 March 2009 (UTC)

When I was a little kid, I saw a wildcat (Bobcat) in a cage at a roadside zoo. I stuck my finger through the chickenwire of the cage to tease the cat, and suffered no ill effects. Around the same time, I stuck my finger in a live electric socket, and suffered only momentary pain.Around this same time, while walking in high weeds in the southern U.S, I stepped on a snake (of unknown species) which thrashed around dramatically. Can we conclude from these anecdotal reports that these actions were a good idea? Edison (talk) 02:25, 23 March 2009 (UTC)

, still a spoon is a heck of a lot safer then a fork, so maybe the ipod was not on full blast and the blindfold let you get a glimpse of shadow vs light.65.121.141.34 (talk) 14:03, 23 March 2009 (UTC)

"Safer" != "Safe". Don't do it. SteveBaker (talk) 11:29, 24 March 2009 (UTC)

ATTN Steve Baker - do we really have complete dinosaur dna like in Jurassic Park?

Dear Steve Baker,

My question is: have we really got complete dinosaur dna like in Jurassic Park? Eventually, does it look like there is any reason we couldn't really hatch little dinos?

Thank you for your time!

Yours sincerely,

94.27.132.205 (talk) 15:27, 22 March 2009 (UTC)

I'm not sure why you are specifically asking Steve, he wasn't a palaeogeneticist (is that a word?) last time I checked. I'm pretty sure we don't have a complete genome for any dinosaurs - they didn't even have one in Jurassic Park, they had to fill in the blanks with frog DNA (why they didn't use bird DNA, I don't know... probably because the plot wouldn't have worked!), or something, which is what caused all the problems. Our article, Dinosaur#Soft tissue and DNA, suggests we haven't even got a reliable partial genome from any dinosaurs (a couple of unreliable ones, though!). --Tango (talk) 15:33, 22 March 2009 (UTC)

Hey! I have advanced degrees in palaeogenetics with all four of the universities that offer the course - paelaeogeneticists come to me when they have problems with spelling the word! and because of that, I have all fourteen alternative spellings of the term tattooed on places I'm not going to mention. SteveBaker (talk) 18:57, 22 March 2009 (UTC)

I stand corrected and humbly and deferentially beg for forgiveness, O Omniscient One! --Tango (talk) 19:45, 22 March 2009 (UTC)

I'm asking Steve Baker because he's the smartest and best-informed paleogeneticist in existence -- paleogeniticists might not exist as a profession, yet Steve Baker would be the best qualified of them all (if not best-credentialled). Thank you for the link. However, with the above points in mind, I will wait for Steve Baker's verdict. Thank you! 94.27.132.205 (talk) 15:46, 22 March 2009 (UTC)

Steve is very well read and an excellent researcher, but what gives you the idea he's a well qualified palaeogeneticist? --Tango (talk) 16:20, 22 March 2009 (UTC)

(edit conflict)Even with an animal as geologically recent as a mammoth, paleogeneticists (6660 ghits BTW) have only assembled part of the genome and in this BBC article [4] Dr Gilbert of Copenhagen's Center for Ancient Genetics says that even if we had the whole genome "technology does not currently exist to turn that biochemical information into a live animal". Mikenorton (talk) 15:50, 22 March 2009 (UTC)

If you really are only interested in answers from Steve Baker, then you should ask this Q on his talk page, not here. If you want answers from everyone, then post here, but don't address those Q's to any particular person. StuRat (talk) 16:02, 22 March 2009 (UTC)

No, we do not have complete dinosaur DNA. For full details see Bully for Brontosaurus (1991) by Stephen Jay Gould (who was a paleontologist), and well worth the price. (Sorry for not being SteveBaker.)  —B00P (talk) 17:07, 22 March 2009 (UTC)

We barely have a complete human genome, and there's no shortage of fresh, brand new, human blood. Only very tiny, and (obviously) very old samples of dinosaur blood and soft tissue have been recovered. It's not clear if it's even theoretically possible to extract a complete dinosaur genome from these samples (It's possible that the information we'd need simply doesn't exist anymore.), but even if it is, we'd need technology much more advanced than we've got now. APL (talk) 17:10, 22 March 2009 (UTC)

1. No.
2. Yes.

SteveBaker (talk) 18:57, 22 March 2009 (UTC)

I certainly feel like Moses and maybe shouldn't be asking back, but although I understand #1, could you explain the reasoning for #2? I mean, "eventually" is a long time, even if we had to combine 100,000 bits of DNA, there ARE that many in total waiting to be unearthed, no? Couldn't they be combined? If all you have is a very poor (less than VGA) webcam and want a super-super high-resolution scan of something -- couldn't you get it through 100,000 passes? Or in this case, you would have 100,000 deteorated photographs, coudln't you come up with the original based on all that? —Preceding unsigned comment added by 94.27.132.205 (talk) 19:16, 22 March 2009 (UTC)

Maybe. The problem with DNA is that, while you may have all the bits necessary, you wouldn't have any way to know what order to put them together in. Your photograph analogy doesn't quite work - a better analogy would be a puzzle for which we don't know the image we are supposed to be putting together. --Tango (talk) 19:45, 22 March 2009 (UTC)

But we do know the image! A T-Rex! 94.27.132.205 (talk) 19:47, 22 March 2009 (UTC)

I mean the image of the DNA. We are far from being able to backwards engineer DNA from observations of fossilised bones. --Tango (talk) 20:22, 22 March 2009 (UTC)

The problems with making a creature from scratch goes a long way beyond just assembling a viable DNA strand. You've also got to implant it in a suitable cell (ie one that has the right chemical environment, etc) - that has to be provoked into replicating by the right chemical setup in the mother - in the case of Dinosaurs, something has to create a huge egg - and lay it and hatch it. The way we clone animals right now is to take the egg from a closely related animal, wipe out its DNA and replace it with the new DNA. Then you implant the cell back into the female of the closely related species and wait for nature to take its course. However, we don't have any extant animals that are anything remotely like a Dinosaur. So we have no egg to implant the DNA into - and no mother dinosaur to implant the egg into. Worse still, it's very likely that all of the food that a baby dinosaur would be able to eat has long gone extinct - so you have a problem feeding it. Because we have no live dinosaurs to study - we don't even have a way to know what nutrients they need. Also, the world has changed quite a bit - different amounts of oxygen in the air - that kind of thing. Most animals get resistance to disease from their mother's antibodies - no chance of that happening here. The obstacles are spectacular...even if you could get an intact DNA strand - which isn't looking very possible from the amounts we've been able to extract. Remember that you can't just collect random DNA snippets from 500 different species spread over 160 million years and expect to be able to stitch them all back together! You need DNA from a single species...perhaps even a single sex of a single species...and over a few thousand years or so. That's asking a lot! SteveBaker (talk) 19:56, 22 March 2009 (UTC)

It doesn't need to be a huge egg, there were plenty of small species of dinosaur we could try and bring back. We don't have the technology now, but I don't see any theoretical reason why a synthetic egg wouldn't be possible to construct eventually. I think the DNA is the biggest problem, the rest can be overcome with effort but if the DNA doesn't exist, then it doesn't exist. --Tango (talk) 20:22, 22 March 2009 (UTC)

I'm no SteveBaker, but here's my take.

1.) Not yet, but theoretically possible given a well-preserved specimen. There has been some progress in sequencing the Neanderthal genome but there are still considerable gaps. Another concern is that even if you could piece together a "complete" genome for a given dino species it would almost certainly be a patch-work of pieces from different individual specimens and would utterly fail to capture the degree of genetic variation that would have existed within a population of that particular species. This would lead to considerable trouble with part 2 and any future breeding of your little dinos (which would all be genetically identical to each other -- not good for the health of the species).

2.) Without extraordinary advances in molecular biology, NO. One reason is that even if you knew the complete DNA sequence based on sequencing fragmented pieces of dino DNA, you'd still have problems assembling it into the proper chromosomes that would enable the putative dino cells to replicate. The way the sequencing of the human genome was done, large fragments of DNA contained in bacterial artificial chromosomes were sequenced and mapped to their proper chromosomes, then overlapping fragments were pieced together to generate a computational "assembly" of the genome that is now an advanced draft stage (there are still bits that haven't been sequenced due to their complexity or repetitiveness). We know the structure of human (and mouse, and fly, and dog, etc.) chromsomes because of cytogenetics, fluorescence in situ hybridization, and other such techniques -- which require intact cells and in some cases cell culture. Mapping the fragments of dino DNA to their proper locations within the dino chromosomes would essentially be impossible because of the inability to perform cytogenetic techniques. Furthermore, even if you knew where each piece was supposed to go, we don't currently have the ability to stitch together an entire chromosome "de novo" and somehow get it to assemble into its proper macromolecular structure, complete with histones and all the other DNA binding proteins that endow the DNA with the ability to be replicated in a living cell. Now, it is theoretically possible that you could get enough of the dino DNA to make a "complete" sequence and somehow "splice" it into existing chromosomes from a modern-day species (as was the plot in Jurassic Park) but this would be extraordinarily challenging (dare I say "impossible"?) for today's molecular biology. --- Medical geneticist (talk) 20:25, 22 March 2009 (UTC)

What about this iterative proposal: put the large species in a small species so that it's cramped and deformed, but alive, at birth. Then put the DNA straight back into the new girl once she's an adult (no CHANGE in the dna). It might still be cramped because of the deformity but basically should be normal. A final few generations the same way will result in a perfectly fit dino -- raised in as good a womb as you get (or whatever cold-blooded lizards have instead of wombs). What do you think of this proposal? 94.27.132.205 (talk) 20:40, 22 March 2009 (UTC)

See ALL of my objections above. You might maybe be able to get around needing a big egg that way - but you still have no cell to put the DNA into, no parent animal to implant the egg into, no food for the hatchling, no knowledge of how young dinosaurs have to be treated by their mothers - whether the temperature of the egg has to be varied during development (this turns out to be a CRUCIAL factor in the development of Turtles and Crocodiles...so it's probably critical in Dinosaurs too)...there are a million things we don't know (and arguably, cannot know) about raising a dinosaur. When you consider how many species have proven impossible to breed in zoo's - and that's with full knowledge of diet, parenting, etc, etc...this is so far from being possible. Heck, your first step would have to be in assembling lots and lots of plant DNA from species of that era and figuring out how to grow that BEFORE you even start on the actual Dinosaur. SteveBaker (talk) 21:02, 22 March 2009 (UTC)

I, for one, am very comfortable leaving it to Steve to determine whether paleogeneticists have access to complete dino DNA at this point. Edison (talk) 02:20, 23 March 2009 (UTC)

Birds are considered the modern descendants of dinosaurs so just hatch an egg and you've got yourself your own little baby dinosaur. It may be possible to get something like a dinosaur by seeing what's common between birds and crocodiles say and then cutting out a selection of those changes which are specifically for bird like features like beaks and putting in some of the more dinosaur like things that have their remnants in the junk dna and occur in crocodiles.

couldn't I just catch a bird then? —Preceding unsigned comment added by 94.27.186.235 (talk) 21:26, 23 March 2009 (UTC)

Or breed parrots? A lot of baby parrots look like mini 'raptors for the first few weeks after hatching. Probably sound a lot like them when they're begging for food too. --Kurt Shaped Box (talk) 21:41, 23 March 2009 (UTC)

I don't think you'd have too far to go to turn a Hoatzin into something pretty much dinosaur like. Dmcq (talk) 18:52, 24 March 2009 (UTC)

Re:User:Medical geneticist's concern about the inability to perform cytogenetic techniques. I completely understand why jumping right to the Cambrian would be impossible, but couldn't we just step it back slowly? Map the Dodo genome, then something from the Neogene, then a few evolutionary steps from the Paleogene, and before you know it we're right into the Cretaceous. By figuring out the genomes of a creature's ancestors we could step backwards through evolution, using the later species as a guide for arraigning the genome of the previous ones. Make the evolutionary steps small enough, and the changes from one genome to the next could be so small as to be manageable. Plasticup ^T/C 19:09, 27 March 2009 (UTC)

Falling

I was watching videos of cats falling and being okay--but some of the heights impressed me! If I fell from the same height, I'd be seriously hurt, how do they do it?!24.91.161.116 (talk) 15:48, 22 March 2009 (UTC)

See our article Cat righting reflex, it looks like it has everything you need to know. Mikenorton (talk) 15:56, 22 March 2009 (UTC)

The lighter the animal the farther it can fall without injury. With a small enough animal, like an insect, it could fall from an airplane and survive, as it's terminal velocity is too low to be, well, terminal. StuRat (talk) 15:56, 22 March 2009 (UTC)

I don't think it's just mass that's a factor, it's the ratio of mass to the area of animal projected onto a plane. Since mass is roughly proportional to volume (different animal have similar densities), which is proportional to the cube of linear size, whereas area is proportional to the square, smaller animals have an advantage over larger ones. With cats there is more to it, though, since they can self-right so their legs hit the ground first, allowing them to absorb the impact better. --Tango (talk) 18:25, 22 March 2009 (UTC)

This is of course covered in the classic essay On Being the Right Size. Algebraist 19:16, 22 March 2009 (UTC)

1 Milkshake, 2 straws

If I drink something with 2 straws in my mouth does it take more or less sucking power to get the same amount of liquid as with 1 straw. How about with 15? I'm looking to find out the most effective number of straws, where I exert the least amount of energy for the most amount of liquid pay-off.24.91.161.116 (talk) 15:51, 22 March 2009 (UTC)

I'd say one straw is best. Two would at first seem to be the same, but there is likely to be an air gap between the straws which allows some of the suction to be wasted by sucking in air. The more straws, the more likely you will have air gaps. StuRat (talk) 15:58, 22 March 2009 (UTC)

I wonder what the efficiency of sucking through a straw is... if it's very efficient to start with (and I have a feeling it might be) then adding more straws won't be able to help. The only losses I can see would be from an imperfect seal around the straw (which is probably negligible with one straw) and the usual losses associated with any muscle usage (in this case, the diaphragm). --Tango (talk) 16:40, 22 March 2009 (UTC)

It's a simple matter of conservation of energy. The liquid is raised to some height - so it gains gravitational potential energy in proportion to (mass x :height) - that's the amount of energy it costs you to lift it through that height. So, neglecting friction and such - there is no difference in the energy required. That's certainly a reasonable assumption for drinking (say) water - but milkshakes are non-Newtonian fluids and their viscosity doesn't behave in a simple way. But in any case - assuming the two straws could be said to be independent - moving X amount of liquid through one straw ought to take the same amount of energy as X amount through two. So this is really a question of efficiency - can your mouth muscles (or rib muscles or diaphragm) produce that energy more efficiently in short-high-power sucks or better in slower, low-power sucks. Think of how your car uses more gasoline if you drive around all day with the tachometer pegged at 6,000 rpm instead of 2,500 rpm. Sadly, the human body is ridiculously complicated - and so that's an insanely difficult question - so probably you need to do a series of serious (albeit delicious) experiments to figure it out. SteveBaker (talk) 18:47, 22 March 2009 (UTC)

I believe that the viscosity of a milkshake is the main factor limiting flow rate, not the potential energy between the top and bottom of the straw due to gravity. The flow should be approximately proportional to the pressure differential created by sucking (atmospheric pressure minus intra oral pressure) divided by the resistance to flow through the straw, analogous to Ohm's law for linear electrical resistances. The lips, being flexible in the normal person, can seal around two straws as well as around one, especially if they are a short distance apart so there is not a failure to seal between them. Two straws=twice the milkshake per second, with the same suction created by the mouth. Two straws is like a larger straw (but wall effects may prevent a simple relation to the area of the straw opening). The failure to linearly keep increasing the flow with more and more straws would be due to the inability of the mouth to maintain the same high suction when a high flow rate enters, as well as leakage between adjacent straws. Edison (talk) 19:06, 22 March 2009 (UTC)

WP:OR: (I couldn't help it) with 8 oz of low viscosity liquid (water) and there is a learning curve:

Trial #	Seconds, 1 straw	Seconds, 2 straws
(was 1) 1 & 2	19	19
(was 2) 3 & 4	15	15
(was 3) 5 & 6	13	13
(was 4) 7 & 8	12	11

I'm not tempted to do any high viscosity testing tonight. -hydnjo (talk) 23:59, 22 March 2009 (UTC)

Since there is, as you say, a learning curve, we need to know what order you did the trials in in order to interpret the data. --Tango (talk) 00:02, 23 March 2009 (UTC)

• I have altered the table above to provide clarity as to the trial counting:

Would the trials be numbered for some reason other than chronological sequence? // BL \\ (talk) 00:20, 23 March 2009 (UTC)

Unlikely, but the ordering of the two sets of trials is not clear at all. Algebraist 00:21, 23 March 2009 (UTC)

You can tell I am not a scientist. From the layout by itself, I assumed Trial 1 was first one straw and then two straws; Trial 2 was one straw and then two straws. You are right that it doesn't say that, though. // BL \\ (talk) 00:39, 23 March 2009 (UTC)

• I have altered the table above to provide clarity as to the trial counting: hydnjo (talk) 01:13, 23 March 2009 (UTC)

I recruited an independent referee to do the timing with a one second resolution timer. My challenge was to empty a measuring cup filled with 8 ounces of water with either one or two drinking straws by sucking the water into my mouth and then spitting it out into the adjacent sink in the fastest time. We then practiced a few times withan empty cup to be sure of the cues.

Show time: When she started the timer and said "go" I did the best I could to empty the cup as fast as possible and then declare "stop" while putting the cup down onto the counter (where it started) and then she stopped the timer. I then recorded the elapsed time. The testing trials alternated between between using one and two straws starting with one straw and finally ending with two straws (eight trials in all). The "spitting out" time seemed to go much faster than the "sucking" time that I attribute much of the "learning curve" to the "sucking" part. The apparatus consisted of a 12 ounce graduated clear glass measuring cup with a handle and "squash-proof" plastic drinking straws 7.75 inches long by 0.25 inches diameter. The water was about 48ºF. The referee thought I was nuts! -hydnjo (talk) 01:07, 23 March 2009 (UTC)

I've replaced the other responses to this question that you removed and moved your latest reply to the bottom - you managed to completely mess up the section!! (We've all done it, don't worry!)

So the conclusion we should draw from this extremely scientific and reliable experiment is that there is no significant difference between one straw and two for drinking water. Thank you for sacrificing your reputation for sanity for the sake of science - I salute you! --Tango (talk) 01:16, 23 March 2009 (UTC)

I'm enjoying your saluto in the most libationious of ways, maybe russians or something more viscous next. ;-) -hydnjo (talk) 02:38, 23 March 2009 (UTC)

Oops, Edison (below) is suggesting not spitting out! -hydnjo (talk) 02:38, 23 March 2009 (UTC)

USE A MILK SHAKE! Don't spit it out, to avoid lots of wasted time. SWALLOW IT! Water is very low viscosity, so the limiting factor is likely the ability of the tongue and jaws to pump liquid, rather than the rate of flow of a viscous liquid through one or two tubes at constant pressure. Edison (talk) 02:14, 23 March 2009 (UTC)

Whilst generally in favor of the scientific method - I can't help thinking that our most dedicated test subjects may have trouble maintaining a uniform performance after consuming approximately 8 milkshakes...and that's before we begin to concern ourselves with control groups for the influence of extra chocolate on the viscosity. SteveBaker (talk) 12:36, 23 March 2009 (UTC)

And that's before we get started in ice cream milkshakes which you end up having to "drink" with a spoon. --Tango (talk) 13:24, 23 March 2009 (UTC)

The low flow rate with a thick shake might allow consumption of a small amount per trial. 3 ounces, maybe? There would probably be lots of volunteer experimental subjects outside a malt shop/McDonalds on a nice day. Edison (talk) 18:41, 23 March 2009 (UTC)

A useful experiment might measure the flow rate of a viscous liquid through one versus two or more straws, placed such as to allow the lips to seal around them. Weigh the source vessel containing the milk shake, have the experimental subject suck on 1 or 2 straws for a short period such that mechanics of swallowing or spitting out are not a factor, and weigh the source vessel to see how much was consumed in, say 2 seconds, such that the mouth can maintain approximately constant suction. Edison (talk) 03:11, 24 March 2009 (UTC)

To add even more confusion to an unanswered question, what about straw circumference? Presumably viscosity is even more of an issue. -- MacAddct1984 ^{(talk • contribs)} 18:06, 25 March 2009 (UTC)

Injuries causing memory loss

Hi all I am researching injuries that can cause memory loss. By this I mean memory loss that occurs as a result of an accident, most likely a head injury in this case, as opposed to the likes of Alzheimer's or Parkinson's disease causing memory loss. I have read about the likes of chronic traumatic encephalopathy (punch drunk syndrome), subarachnoid haemorrhage, skull fractures and concussion causing memory loss. (Only temporary with regard to concussion). My question does anyone know if I have missed out any injuries which can result in memory loss? If so could they give me some pointers as to where I can find out more information on them? Many thanks. —Preceding unsigned comment added by 139.222.240.10 (talk) 20:45, 22 March 2009 (UTC)

We have an article, Post-traumatic amnesia, which may help. --Tango (talk) 21:13, 22 March 2009 (UTC)