Wikipedia:Reference desk/Archives/Science/2007 November 19

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November 19

Are clearer lakes necessarily more "healthier" than less clear ones?

I was looking at http://lakeaccess.org/russ/turbidity.htm and became confused. It seems that a clearer lake is healthier in terms of the quality of life for wildlife, etc., but at the end of the article, it says, "unproductive lakes are usually much clearer than productive lakes." Can someone explaine this to me? 24.125.31.205 (talk)

An unproductive lake, one with nothing living in it, wouldn't have any algae to muck it up, for one. Someguy1221 (talk) 02:21, 19 November 2007 (UTC)

I read your link, and the way I read it productivity is not necessarily a good thing. I think he meant that in the absence of suspended inorganic particulates, the Secchi disk will measure the amount of algae in the water, basically. To have some algae is a sign of life, but too much algae is bad (see Eutrophication). I think you can have an "overproductive" lake, but he doesn't mention that right there. I think he's talking about a relatively healthy lake in regard to the Secchi disk and clarity. --Milkbreath (talk) 03:58, 19 November 2007 (UTC)

Heavy acid rain can lead to an acidic lake with little or no life. Such a lake is very clear, but hardly healthy. Heavy pollution by human sewage can lead to a very unhealthy lake that is very turbid. Neither high nor low turbidity is a sure indicator of health. To answer your title question: "No". --mglg_(talk) 04:28, 19 November 2007 (UTC)

"Healthy" for whom? A lake that's utterly choked with algae to the point where fish can't live in it isn't too healthy for the fish - but clearly the algae are exceedingly happy. Certainly a lake with no algae in it at all must be suffering some kind of problem. In a "balanced" lake ecology - there should be a food chain that roughly says that incoming sunlight powers the algae (which are green photosynthesisers) - which is eaten by the smaller herbivorous fish, insects, etc - which in turn are eaten by the bigger carnivorous fish - which are ultimately recycled by the scavengers. An utterly sparkling clear lake with no algae whatever can't possibly be functioning correctly because it's not getting a net energy input from the sun.

But I can tell you that if I stop chlorinating my swimming pool for even a week in the summer, algae will be happy to re-colonise it and after three weeks, they'll have turned it into a thick green, opaque soup. However, once the temperature drops, the growth rate of the algae slows way down - and once we're below about 10degC, one good shot of chlorine will keep the pool clear for maybe a month - but they still gradually re-colonise the pool.

So if a lake has no algae in it at all, there must be something actively killing them off - and fairly agressively too because no matter how many lethal chemicals (that are especially designed to kill the little brutes) I put into my backyard pool, they still bounce back in no time flat! SteveBaker (talk) 15:13, 19 November 2007 (UTC)

Error with finding the elasticity of rubber?

I've done an experiment to find the (Young's) modulus of elasticity of a rubber band, and have found the result to be 255 KPa (0.000255 GPa) - this is a factor of 50 out of the minimum accepted value of rubber, which is 0.01 - 0.1 GPa. I'm sure that I've done the experiment correctly - does the rubber which I'm using (which I assume is artificial rubber) have such a large difference from natural rubber (which I assume is what Wikipedia uses to define it's 0.01 - 0.1 GPa) - or is it likely that I've made an error? Robert (talk) 12:49, 19 November 2007 (UTC)

It's hard to know for sure what's going on here - but Rubber is tricky stuff - as our article on Young's modulus points out, it's a non-linear material - the young's modulus for rubber varies depending on the strain you apply to it. It's also very sensitive to temperature changes - and it's very hard to stretch the stuff without it getting hotter and messing up the results. Artificial rubber is also a lot different from natural rubber - and will generally have been vulcanized - so that would certainly make a difference. There are plenty of reasons why you may not have gotten the 'accepted' value and still have done a perfectly reasonable experiment. SteveBaker (talk) 14:58, 19 November 2007 (UTC)

Yeah, the nonlinearity was my first thought as to what the problem might be. However, the nonlinearity of rubber is in the opposite direction of the error he's getting -- if you double the stress on a rubber band, you will less than double the strain. So stretching the rubber band too much in the experiment will give too large of a Young's modulus, not too low.

The rubber band article says that most rubber bands are still primarily made with (vulcanized) natural rubber. MrRedact (talk) 15:19, 19 November 2007 (UTC)

But perhaps this experiment is not putting enough strain on the rubber compared to the "standard" test? Our article on rubber mentions four different artificial rubbers: styrene-butadiene, butadiene, chloroprene and ethylene-propylene-diene - any of which might or might not be vulcanised to greater or lesser degrees - and to have enlarged or reduced temperature sensitivities. I'm always reminded of the Space Shuttle Challenger disaster - which Richard Feynman so memorably demonstrated was caused by the 'rubber' O-rings having a wildly different young's modulus in the cold weather of the day of the launch compared to the properties they were expected to have. So there is clearly huge scope here for getting off-the-chart results compared to natural rubber. SteveBaker (talk) 15:55, 19 November 2007 (UTC)

To get the Young's modulus of rubber you have to use very small elongations (strains). This is only an approximation since a true value is not really valid for elastomers. Rubber bands are almost certainly made of natural rubber, which strain crystallizes at large strain. As pointed out above, this would give you an artificially high modulus value. Delmlsfan (talk) 00:11, 20 November 2007 (UTC)

Curved Frizzy Hair

Scientifically Why does hair become curved & frizzy ? What is a natural way (*not artifical) to change this characteristic without hair damaging ??

The section on Texture in our Hair article covers the cause of naturally curly hair. The humidity of the air is the most significant factor in making hair change shape - high humidity tends to make the hair return to it's natural curve. Doing something to change the shape of your hair could hardly be described as "natural" no matter what it is because "natural" is how it was before you started messing with it! There is a lot of nonsense spoken in the hair care industry about damaging (or 'feeding' or 'repairing') hair. The fact is that hair is a dead material - there are no live cells in it or anything like that. Most of the things you do are altering the moisture content (think of curling tongs - they drive the moisture out of your hair to force it into a particular shape - as soon as the hair gets wet again (or in humid air) it's going to spring back to it's natural shape) - or mechanically gluing it together (such as hair sprays and such) - or altering the amount of oils in the hair (which affects how easily it can take up or lose water). SteveBaker (talk) 15:41, 19 November 2007 (UTC)

Technically, hair does have living cells in its roots, but that's under the skin, and isn't effected by shampoo or conditioner. — Daniel 16:48, 20 November 2007 (UTC)

Brain Power Limited or Unlimited??

Is it true that we use only 10% of our brain and if we can use more we will unlock abnormal powers ? if it is true , is their a way to unlock more % usage of the brain ?? —Preceding unsigned comment added by 86.51.3.194 (talk) 14:44, 19 November 2007 (UTC)

No, we do not use 10% of our brains. Percentage usage isn't a good way of measuring anything if only because your brain is specialized, to some degree. You can't use your Brain_stem to make mathematical calculations or to think harder about the motives of a coworker. Increased "percentage" is a fool's errand. Cultivating more attention would be one of the few ways you can increase your "brainpower", or at least use the brainpower you already have.--droptone (talk) 14:50, 19 November 2007 (UTC)

No - that's not true. We can now observe the brain in action using all sorts of clever scanners and there is no evidence what so ever of that. This is one of those urban legends that grows in the retelling. The Snopes urban legend site has an article covers it pretty well: http://www.snopes.com/science/stats/10percent.asp - but just ask yourself: Why would we have evolved freakishly large brains if we could function perfectly well with brains ten times smaller? SteveBaker (talk) 14:51, 19 November 2007 (UTC)

Snopes is fine, but I'm more of a The Straight Dope fan: "Do we really use only 10 percent of our brains?" Short answer: No. This is also explained in Human brain#Common misconceptions. -- HiEv 17:19, 19 November 2007 (UTC)

Note that even if it were the case that only 10% were used, it wouldn't at all mean that conservation-of-energy-violating powers would be possible with the rest. --24.147.86.187 (talk) 16:00, 19 November 2007 (UTC)

Agreed. And if it was so easy to have "abnormal powers" by simply using more brain, why wouldn't we, or other animals, have evolved to take advantage of that? In any case, telekinesis, ESP, telepathy, and other such powers appear to be fiction, as there is no reliable evidence that they exist. There, in fact, is a $1 million (USD) prize for anyone who can demonstrate such powers that has remained unclaimed for decades now. See James Randi Educational Foundation#The One Million Dollar Paranormal Challenge for details. -- HiEv 17:38, 19 November 2007 (UTC)

Autistic savants show, that the human brain has extraordinary capabilities, that are naturally supressed in normal persons. They also show, that these abilities are suppressed for a good reason, as most of them require special help in their daily life. This does not mean that unused brain areas are activated, most savants have on the contrary defect brain areas. The 10% number is complete bullshit, why not 11, 26 or 99? The phrase gives no measurement procedure, so the number is meaningless. —Preceding unsigned comment added by 153.96.188.2 (talk) 17:29, 19 November 2007 (UTC)

It's most often the case that savants are getting their amazing mental abilities in some very narrow area of learning at the cost of some terrible deficiency in almost every other area. This actually lends credibility to the idea that we're using 100% of our brains already - because people with the ability to memorize phone books but who cannot learn how to dial a phone are evidently filling up the (say) 90% of their brains that they aren't using for useful things to learn irrelevent junk. I've just been listening to a biography of Einstein (on CD to pass the time on long car trips) and it's really obvious that whilst he was amazingly good at physics and a passable violin player, he was quite utterly useless at absolutely everything else. SteveBaker (talk) 19:09, 19 November 2007 (UTC)

I've always wondered whether the 10:1 ratio has historically had anything to do with glial cells. As far as cell number, only 10% of our brain is composed of brain cells, while the other 90% is composed of supporting cells. Wikipedia's article on the histology of the brain provides additional information. (EhJJ) 03:49, 20 November 2007 (UTC)

It's possible that some such claim is the original cause of this myth - but since you can't think with glial cells - it's certainly not the case that there is some 90% of your brain just sitting there waiting to be used. SteveBaker (talk) 21:44, 20 November 2007 (UTC)

Compared to other animals, are humans physically strong or weak for our mass?

^topic says it all 64.236.121.129 (talk) 16:53, 19 November 2007 (UTC)

We’re in the middle. Suppose you define an animal’s "strength" as being the mass that it is capable of lifting. Then as a general rule of thumb, smaller animals tend to have a greater strength-to-mass ratio than larger animals. So for example, elephants can't lift as much as their own mass, humans can lift roughly as much as their own mass, and ants can lift multiple times their own mass. MrRedact (talk) 17:26, 19 November 2007 (UTC)

I guess what I meant was, compared to other animals of similar mass, how do we compare to them? 64.236.121.129 (talk) 17:52, 19 November 2007 (UTC)

I don't know the answer in general, but compared to chimps we're wimps. It's hard to get animals to perform strength tests, but in one test a 135 pound (~61 kg) female chimpanzee pulled an incredible 1,260 pounds (~571 kg) one-handed. Other chimps have dead lifted 600 pounds (~272 kg) with ease. See: "Can a 90-lb. chimp clobber a full-grown man?" for details. -- HiEv 18:00, 19 November 2007 (UTC)

Just as I thought. Humans are pathetic strength wise. 64.236.121.129 (talk) 18:32, 19 November 2007 (UTC)

Time to start working on cross-species head transplants...Someguy1221 (talk) 19:24, 19 November 2007 (UTC)

Or genetic engineering 64.236.121.129 (talk) 19:50, 19 November 2007 (UTC)

Also - could you do this? (see pic) --Kurt Shaped Box (talk) 19:32, 19 November 2007 (UTC)

If I had a bloody great hook bolted to the front of my face - yes! It doesn't require any strength whatever to just hang from a rigid beak. SteveBaker (talk) 20:47, 19 November 2007 (UTC)

Even so, have you considered the strain on your neck of supporting your full bodyweight minus the weight of your head? --Kurt Shaped Box (talk) 20:57, 19 November 2007 (UTC)

Check out the picture to the right - we've all seen that done in circus acts - they swings around too - adding centrifugal force to the problem. So sure, a human can do it. SteveBaker (talk) 22:37, 19 November 2007 (UTC)

That's not really a measure of strength - but the reason the bird can do that is twofold:

1. It's a bird. It has hollow bones and is generally built to be as light as possible.
2. The strength of the muscles in the neck is a function of the cross-sectional area - so it increases with the square of the size of the animal - but the weight the animal has to support is proportional to the cube of the size of the animal. Scale that parrot up to human size (let's say 10x larger) and it'll weigh 1000 times as much but only have a neck 100x stronger.

The parrot can do that - not because it's strong - but because it's small and very, very light. One of my dogs can do the same thing (well, for maybe 10 seconds or so) - she weighs in at 30lbs - and it's a VASTLY more impressive trick! SteveBaker (talk) 22:29, 19 November 2007 (UTC)

Observe the young lady to the right! SteveBaker (talk) 22:34, 19 November 2007 (UTC)

Humans aren't particularly strong or fast runners, but we have high endurance. Otherwise, I think that evolution shaped us to be generalists. We can climb a tree, but not as well as other apes. We can run, but not as fast as a horse. We can swim, but not as well as a dolphin. We can climb a mountain, but not as well as a mountain goat. We can hunt, but not very well without tools. -- JSBillings 19:51, 19 November 2007 (UTC)

Jack of all trades, master of none... Except intelligence. 64.236.121.129 (talk) 20:01, 19 November 2007 (UTC)

Man versus Horse Marathon. Keria (talk) 20:38, 19 November 2007 (UTC)

Yes - exactly. We are better than most similar animals at endurance events. We can't outrun a cheetah in a 2 minute sprint - but a cheetah can't complete a 26 mile marathon in 3 to 5 hours. SteveBaker (talk) 20:52, 19 November 2007 (UTC)

See Persistence hunting. --Milkbreath (talk) 21:32, 19 November 2007 (UTC)

As a matter of interest, can anyone here crack a macadamia nut with their teeth? --Kurt Shaped Box (talk) 20:49, 19 November 2007 (UTC)

The human jaw is strong enough, ask me again when I get my titanium implants. Someguy1221 (talk) 21:21, 19 November 2007 (UTC)

Whoopty-do. This guy pulled a 300-ton train with his teeth. TenOfAllTrades(talk) 21:40, 19 November 2007 (UTC)

Sadly, he did it on level ground - so all the weight of the train was conveniently supported on the rails. Since trains deliberately park with all of their inter-wagon couplings slack, you only have to overcome the inertial resistance of one car at a time - plus the total rolling resistance. Since we don't know how much accelleration he was able to impart, overcoming inertia was not a huge issue if he does it slowly enough - so it's basically just the rolling resistance - which for the super-smooth wheels of a railroad car at low speed is exceedingly small. If he could pull a 1 ton bag of sand up a 1:10 slope, then I'd be impressed. This speaks more to our inability to pay attention to the physics than it is a testament to his strenght. (Although it's fairly impressive anyway). SteveBaker (talk) 22:20, 19 November 2007 (UTC)

IIRC, the world's highest ranked master of Kung Fu's Iron Penis form (yes - that really does exist!) can pull a train with his member. I don't know if that's actually any more difficult from an anatomical standpoint than using the teeth... --Kurt Shaped Box (talk) 22:27, 19 November 2007 (UTC)

Don't forget as well that humans make up for this by having big brains. You don't need to have claws if you know how to sharpen a rock. --24.147.86.187 (talk) 22:49, 19 November 2007 (UTC)

Very interesting to hear how strong chimps are. They are small enough to hold in your arms sometimes, but amazingly stronger than humans. Imagine how strong a gorilla is. 69.34.167.233 (talk) 01:22, 20 November 2007 (UTC)

I'm sure I've seen on TV a tug-o-war contest between a sumo wrestler and a orangutan. Both contestants had something to brace their feet against. The orangutan could hold the sumo wrestler even with one hand, and when it used both hands it won easily. I wish I could remember where I saw this. I think it was on a show with all sorts of other human-vs-animal events. 72.10.110.107 (talk) 15:42, 21 November 2007 (UTC)

If you put food in a total vacuum, will it last forever, and still be edible?

^topic 64.236.121.129 (talk) 17:07, 19 November 2007 (UTC)

There's a related question and interesting discussion here: Reference desk/Science (24 Nov 2006) — Decomposition on the moon and in outer space. Sancho 18:16, 19 November 2007 (UTC)

Plenty of foods are vacuum-packed to preserve them - some last a long time - but no vacuum ever stays perfect because the packaging is going to allow some air to diffuse inwards. Also, this excludes air from the packaging but doesn't leave a hard vacuum because the food is merely pushed against the packaging material which exerts a normal air pressure onto it. The main thing that's going to happen in a true vacuum (say a bell-jar that's been evacuated) is that the food will eventually completely dry out. Whether that leaves it edible is dependent on what the food was in the first place - but most foods are not going to come out looking as appetizing as when they went in! Some bacteria are able to survive in a vacuum - so some kinds would be able to continue to cause some decay...but once the water is all gone - that's pretty much going to stop them dead in their tracks. I can't really think of a reason why (for example) beef jerky wouldn't continue to be just as inedible as it is now after a million years in a vacuum. —Preceding unsigned comment added by SteveBaker (talk • contribs) 18:55, 19 November 2007 (UTC)

The question, then, is how fast spontaneous decay processes (in the complete absence of water) will turn that beef jerky into a pile of dust. Someguy1221 (talk) 19:41, 19 November 2007 (UTC)

I recollect that radioactive decay of contained potassium, or irradiation with cosmic rays or neutrinos will eventually damage living material that is frozen. This would affect dried products, so they would not last for ever. I suppose the polymers would break down, but what would be the final result? perhaps some kind of amorphous carbon, or something like the organic moleculses found in interstellar space? This could take many billions of years. And no it would not be edible after total radiation breakdown. Graeme Bartlett (talk) 20:08, 19 November 2007 (UTC)

Thomas Edison used the vacuum pump technology he created for making light bulbs to vacuum preserve food in 1881, per "A streak of luck'" by Robert Conot (1979), page 172. A steak was sealed in a jar with five hours of vacuum pumping and shipped to England. It acquired a "fermented, alcoholic flavor" which did not prevent the enjoyment of it by his associate Gouraud. Grouse and other fowl were also vacuum-preserved, as were peaches, steaks and chops. In time, they all developed a state of "fermented putrefaction" and Edison discontinued the research. In that era, game was often allowed to putrify in an effort to tenderize it: pheasant was "hung" until the tail feathers fell off due to putrifaction before cooking. [1] Of course food poisoning such as botulism and salmonella can kill you if you consume improperly stored food, so none of this is offered as endorsement of such techniques, and official governmental standards for food storage and preparation should be fully complied with. Edison (talk) 15:13, 20 November 2007 (UTC)

I very much doubt that those early vacuum pumps got the pressure down anywhere near far enough. Even with a 90% vacuum, there would be plenty of oxygen around to allow bacteria to continue to work. SteveBaker (talk) 21:42, 20 November 2007 (UTC)

See [2] where it says that by 1879 Edison using Geissler and Sprengel vacuum pumps could achieve 1 milliTorr of vacuum, or 1/760000 atmosphere. Rather than a mere 90% vacuum, this is a better than 99.999% vacuum. The technology was used in lightbulbs to remove oxygen, which would have prevented a useful lifetime for the carbon filament. But a steak is not a carbon filament, and after the air was exhausted from the container, the water in the meat or fruit should have gone to vapor form, drying it somewhat. When the pump stopped after the 5 hours, the vacuum level would have dropped, but little oxygen should have been present other than in the form of water vapor. It is not documented how high a vacuum was actually obtained in the food preservation experiments, what with the outgassing of the water vapors from the food. The microorganisms in the meat might have initiated anerobic decomposition. Edison (talk) 22:00, 20 November 2007 (UTC)

Wow - I'm amazed their pumps were that good back then! So much for that theory! The other thing that just struck me is that the people who received the food mentioned: "fermented, alcoholic flavor" - and fermentation is an anaerobic process. SteveBaker (talk) 00:42, 21 November 2007 (UTC)

Err, I don't really think that vaccuum packaging of food is going to be commerically practical. For example, if you tried to pack potato chips in vaccum bag, the bag wold be almost completely flat, as the outside air will try to eiliminate any space that the vaccuum takes up. In the end, you might find squished potato crumbs. Yummy! Have you ever tried creating a vaccuum pocket in a sealed bag? The air immediately squishes that pocket and causes the plastic to squish upon itself. Unless you can store the chips in an airtight box; but then the air pressure from the outside will be so tight it will be almost impossible to open it! If you do get it open, BOOM! Volcanic potato explosion! Tasty! If the water does eventually evaporate, however, it might eventually disperse into the no-concentration vaccuum, and eventually you might get water vapour gas instead of a true vaccuum, because if it was sealed enough the water has no way of getting out. Withought water, our food would probably just be a crumbly powder. Hope this helps. Thanks. ~AH1^(TCU) 01:28, 21 November 2007 (UTC)

Ground coffee has been vacuum packed for years. I've no idea what level of vacuum is attained, but the can is rigid enough to avoid being crushed by atmospheric pressure. This is in contradistinction to the old Mr. Wizard demo of boiling water in a metal can, removing it from the flame and capping it, then seeing it crushed by air pressure as the steam inside condenses. Some coffee is actually vacuum packed in plastic pouches, so for non-potatochip "uncrushable" foods, vacuum packing seems common. The vacuum keeps air from making the coffee stale, but wouldn't is cause the oils which give coffee its flavor to outgas? People with home vacuum sealing equipment store all sorts of food in vacuum (actual pressure level unknown. Food like cheese or meat can be in a plastic pouch (refrigerated) and fragile food goes in plastic jars. It is supposed to prevent freezer-burn. Edison (talk) 17:19, 21 November 2007 (UTC)

There can be a problem with CO2 outgassing, to which there are multiple approaches: Seal it in vacuum when fairly fresh, allowing room for the CO2 to release into (since CO2 isn't going to cause the coffee to go stale) (this can lead to bags popping), wait for the CO2 to be released, then vacuum pack (means the coffee is a little less fresh, but is sealed in a compact foil 'brick' that won't pop), or add a cunning valve to the pack. While the oils are volatile, a vacuum isn't being drawn on the coffee for very long so there shouldn't be time for much of the oils to evaporate. Once they're sealed in a tight brick (or in a relatively high-pressure CO2 atmosphere), they're not going anywhere... Skittle (talk) 18:18, 21 November 2007 (UTC)

Just to be clear, many coffee bags actually have the cunning valve Skittle mentioned above. I don't drink coffee, so I don't know how widespread they are in retail packages, but they're quite common in the 2.27kg and 5.45kg foodservice bags. Being larger quantities, there's obviously a greater need for that kind of thing - the larger amount is worth more $$$ and there's also more gas getting released. Matt Deres (talk) 21:35, 21 November 2007 (UTC)

What is the fastest form of propulsion through water?

Which is the fastest, and why don't they use it on large ships? 64.236.121.129 (talk) 17:19, 19 November 2007 (UTC)

I believe that water speed records are held by hydroplanes. Questions of scalability and efficiency preclude that sort of performance on large vessels (though large vessels do often use propellors powered by turbine engines, so they're not entirely dissimilar, either). — Lomn 18:05, 19 November 2007 (UTC)

The fastest way for an object to travel through water at the moment is using supercavitation. It is used only on very recent torpedoes. I think the reason it cannot be used yet on big ships is because of the ammount of energy needed to enclose part or the entirety of the hull in a bubble of air and the too small improvement working experimental technology brings. See supercavitation propeller and underwater speed record. For big ships see the newscientist article here Keria (talk) 18:37, 19 November 2007 (UTC)

Certainly the trick to going fast through water is not to go through the water! Hydroplanes, hovercraft and such are the fastest. But there is a bizarre trick called supercavitation that would allow a submarine to go faster than the speed of sound - it's claimed to have been used on some torpedoes - but it's still only a theoretical possibility for larger vessels.

The reason these techniques aren't more widely used is simple: Fastest isn't always the number one design criteria. If the most important thing in designing (say) an oil tanker was speed then they'd be the shape and size of powerboats and hold maybe 10 barrels of oil (and use 20 barrels of gasoline in getting it from source to destination)! In fact, there are many other considerations in the design of a ship that may be more important than speed: Payload, cost, fuel efficiency, safety, lifespan, whether it can pass through the Panama/Suez canals, what docks it can dock at, how many crew it needs...speed may be way down on the list of priorities. SteveBaker (talk) 18:46, 19 November 2007 (UTC)

Researchers ignoring other researchers

I was told by one of my Dutch lecturer's that while European and Japanese researchers were generally quite cooperative when contacted about the research/papers etc., he was frequently ignored by Americans (he also added the disclaimer that it was just in his experience). If Journal's require researchers to make their reagents available to other researchers, perhaps there are other rules governing this behaviour? --Seans Potato Business 19:28, 19 November 2007 (UTC)

The general idea is that a paper written for a quality, peer-reviewed journal on a particular set of experimental results should contain enough information to allow someone reasonably well versed in the area of study to reproduce the experiment without any other information - if that's true then there is really no need for the original authors to go out of their way to help people - although generally, they would want to do so because having someone else reproduce your results is a big help in getting them accepted. Of course if a dozen other labs have already confirmed your findings, you might not want to be bothered with getting yet more confirmation.

Of course this approach isn't always possible in practice - if (for example) a cosmologist is relying on the data from the Hubble Space Telescope - then while there might in theory be enough information to reproduce the results, building one's own space telescope isn't always a practical matter. In those circumstances, it would be reasonable to ask for access to the results from the telescope in order to do one's own analysis of it.

What field is your lecturer working in?

SteveBaker (talk) 19:56, 19 November 2007 (UTC)

What do you mean by ignored? Do you mean they didn't contact him with chances to collaborate? Do you mean they did not respond or acknowledge his research? I assume your lecturer worked in chemistry (or some sub-field), by the word "reagents". Is this correct?--droptone (talk) 20:43, 19 November 2007 (UTC)

• As far as I know laboratories are not required to share reagents, but in my own experience people tend to share substances and information to make optimal use of each other's strong points. The group I'm working with has a collaboration going with another group. Unfortunately, science is also a race to be the first to publish something ground-breaking, so it's understandable if not everyone is keen to work together, after all your collaborator could beat you to publication. - Mgm|^(talk) 21:06, 19 November 2007 (UTC)

Lecturer is working in immunology. When I said ignored, I meant that they don't return his email (I'm not sure what sort of things he's been emailing them about). In my (limited) experience, not all journal articles are clear, and since so many researchers don't have English as a first language, what appear to be language mistakes not infrequently also lend ambiguity to certain parts including methodology. Furthermore, according to some lecturers and PhD students I've spoken to, researchers will sometimes tend to deliberately obscure methodology/leave out details etc., to make it harder for others. This (and other) revelations have all come in the past three months or so, while I've been studying in the Netherlands. I never heard any of this while I was in England (there could be a variety of reasons). All in all, there doesn't appear to be as much professionalism as I'd hoped and people seem more interested in themselves than the progression of science. Not everyone can make constant major breakthroughs. While I realise that competition can yield faster results in certain situations, I don't think that the current state of affairs is the most conducive to quick and high-quality results. --Seans Potato Business 21:30, 19 November 2007 (UTC)

If an asteroid/meteor killed off the dinosaurs, why didn't it kill off the other animals too?

Other animals like aligators, dragonflys, mosquitos, and rats existed at the same time as dinosaurs. Why weren't they wiped out by the asteroid/meteor too? 64.236.121.129 (talk) 19:56, 19 November 2007 (UTC)

Many other animals were made extinct in the K-T extinction event. Those that depended on food chains that had photosynthesis as their base perished. Rats can eat anything and mosquitoes can eat bacteria that would still be around, decomposing dead stuff. Presumably alligators ate things that ate dead stuff too, as did the birds and mammals that survived. I don't know what dragonflies eat! Graeme Bartlett (talk) 20:28, 19 November 2007 (UTC)

(From our article: Dragonflies typically eat mosquitoes, midges and other small insects like flies, bees, and butterflies.) SteveBaker (talk) 20:40, 19 November 2007 (UTC)

Apparently half of the crocodile families died out, only those that lived in burrows and freshwater lived. Graeme Bartlett (talk) 20:31, 19 November 2007 (UTC)

(ec) Simply put, really big organisms don't fare well when most other life is wiped out. See Cretaceous–Tertiary extinction event. It might also be instructive to look at a biomass pyramid. Very large animals, as well as any animal high up on the pyramid, requires exceedingly large masses of plant matter to sustain them, directly or indirectly (indirectly by sustaining the animal's own food source). When the bulk of plant matter dies, any such organism doesn't stand a chance. Further, many small mammals did go extinct during this event. Many of the ones who survived, in addition to being small, could presumably burrow for protection from some of the generally bad conditions that may have abounded after the impact. As for aligators and similar species, the largest among them went extinct at this time. There are explanations for how large insects got wiped out, but I can't recall at the moment. Someguy1221 (talk) 20:36, 19 November 2007 (UTC)

The really large insects were not wiped out by an extinction event - they had already evolved down into smaller insects. The huge insects were around in a period when the oxygen content of the air was much higher (needed because insects rely of diffusion of oxygen into their bodies because they don't have lungs or gills). When the oxygen content gradually dropped to its present levels, the gigantic insects had to gradually evolve into being the size they are today. SteveBaker (talk) 20:44, 19 November 2007 (UTC)

There is also a theory that the event itself wasn't so terrible - but that iridium from the meteor was responsible for destroying their ability to form hard-shelled eggs - which would certainly account for dinosaur extinction - but mammalian survival. Alligators lay eggs too - but they are soft-shelled. However, that doesn't explain how we still have birds - which evolved from dinosaurs. SteveBaker (talk) 20:40, 19 November 2007 (UTC)

im guessing that it was pretty cold afterwards....and im also guessing that being reptiles (?) and so cold-blooded the dinos caught a nasty flu and died :P......and well mammles are warm blooded so they just got a cold and didnt complain too much and lived for ever more...... —Preceding unsigned comment added by 81.76.80.99 (talk) 21:59, 19 November 2007 (UTC)

Some theropod dinosaurs are believed to be warm blooded actually. 64.236.121.129 (talk) 23:28, 19 November 2007 (UTC)

According to the book The Eternal Frontier by Tim Flannery, North America bore the brunt of the Chicxulub Impact. While the rest of the world suffered from global repercussions, North America was essentially "fried". Its forests almost totally destroyed. Its tropical conifer forests were wiped out and about 80% of its flowering plants as well (and those insects which had come to depend on flowering plants). In areas protected to one degree or another (the lee of the Sierra Nevadas and the far north) the surviving plant species ended up eventually recolonizing the continent. An interesting theory is that because at the time of the impact the continent's northern region was at the North Pole, and that it was warm enough for forests to thrive even at the poles, deciduous trees, adapted to live in the dark half the year, ended up becoming the dominate colonizing tree and over time spreading over a wide range, especially at the planet cooled. The idea being that the Chicxulub Impact made the rise of deciduous forests possible by destroying the existing tropical conifers of North America. Another point is that people often talk of "species extinction" as a result of this event. A factor often overlooked is the radical change in the distribution of surviving species over the planet. Apparently the impact caused the extinction of a great many species, of plants especially, in the northern hemisphere, but not as many in the southern. According to Flannery, and other sources I can't recall offhand, a great deal of the present day differences between northern and southern plant and animal distribution can be traced to Chicxulub. Plants, and especially trees, are the most obvious example, since they evolve fairly slowly and don't move very fast :) -- animal differences apparently include the survival of more many species of marsupials in the south than in the north. Pfly (talk) 06:36, 20 November 2007 (UTC)

Science

how can inert gases renew? —Preceding unsigned comment added by 84.36.154.72 (talk) 20:02, 19 November 2007 (UTC)

Inert gases don't deteriorate by reacting with something, but they could be contaminated or become diluted. You could distill them again, to separate the good gas. I don't know if any one does this though, or just vents the useless gas to the air. Graeme Bartlett (talk) 20:15, 19 November 2007 (UTC)

Yes...but only VERY slowly. Some of them form as a result of radioactive decay from other elements. Helium forms in the earth's crust (very slowly) as a byproduct of the decay of Uranium and Thorium. Neon is similarly thought to come from the decay of some exotic isotopes of Magnesium - which in turn are by-products of Uranium decay. Argon comes from the decay of radioactive Potassium isotopes...and so on. SteveBaker (talk) 20:30, 19 November 2007 (UTC)

And helium is the only one that actually gets lost from the Earth in significant quantities, because it's light enough to rise to the top of the atmosphere and drift away in the solar wind. See Helium#Natural abundance. The other noble gases are heavy enough that they stay in the atmosphere, effectively for good. —Keenan Pepper 04:40, 20 November 2007 (UTC)

genetic engineering

Is it possible for genetic engineering to do things like cause breasts or testes to drop off or the ovaries or prostate to be reabsorbed into the body at a certain age like 30 when they are no longer of any practical benefit as a way to reduce the risk from developing cancer? —Preceding unsigned comment added by 71.100.4.186 (talk) 20:57, 19 November 2007 (UTC)

No. Someguy1221 (talk) 21:03, 19 November 2007 (UTC)

Ok, slightly more detailed answer. Genetic engineering can presently do nothing but add or remove (or knockup or knockdown) a coding sequence for an RNA. This typically does nothing more (directly) than alter the presence of a particular protein in the target cells. While this can make pigs glow (and many other neat things), you can't presently significantly alter the functionality of entire organs. Someguy1221 (talk) 21:08, 19 November 2007 (UTC)

As a potential way to do it, it would be interesting to attempt to design an artificial set of genes to make a target organ initiate preprogrammed cell-death in its entirety (upon exposure to a suitable signal molecule). You'd have to ensure your gene only enters the target organ, and enters all of it. I'd also be concerned about what the outcome of apoptosing an entire organ would be, which might make this infeasible. So maybe this isn't so far off from what we can do now, but it's not necessarily a good idea. Someguy1221 (talk) 21:18, 19 November 2007 (UTC)

If simply removing those organs worked - we'd have people standing in line to have them removed surgically. The trouble is that even after they've ceased to have reproductive benefits (although testes still function perfectly well into old age), they still provide all sorts of hormones - without which we don't do so well. SteveBaker (talk) 22:44, 19 November 2007 (UTC)

Thirty? Wow, that makes me depressed. Means I've got 6 years to get married and start a family before my boyfriend's testes will be "no longer useful" - and I'm only halfway through college. Kuronue | Talk 19:30, 21 November 2007 (UTC)

Power Production

hello,

right, im looking for some numbers guys:

• firstly, a typical electrical output ( in MW please) of a typical coal, oil, gas and nuclear power station in the UK
• secondly, the typical output at set windespeeds (eg 10, 15, 20mph etc) of a typical wind turbine, again in the UK, like the offshore ones,
• thirdly the cost of constructing one of the above mentioned wind turbines, (offshore and onshore), in GBP if possible

thanks, --81.76.80.99 (talk) 21:56, 19 November 2007 (UTC)

Google can answer all your questions pretty quickly... - Katavothron (talk) 20:39, 20 November 2007 (UTC)

That's true of nearly everything that's asked here. Not everyone is good with search engines - or in assessing the quality of the answers they find. If you can't answer the question in a helpful manner, please don't bother replying. SteveBaker (talk) —Preceding comment was added at 21:33, 20 November 2007 (UTC)

Sorry, but I perceive a difference between a knowledge-related question that requires some understanding to relate correctly and a question requiring the parroting off of statistics that are trivially obtainable. Not to discourage anyone else from finding the numbers for the OP, of course... - Katavothron (talk) 21:36, 20 November 2007 (UTC)

Ehh.. Sorry for coming off a bit grumpy; I just took the "search first" rule at the top of this page to heart. Feel free to delete my message if it comes across as unnecessarily abrasive. - Katavothron (talk) 21:56, 20 November 2007 (UTC)

what comes out?

what comes out of little boys' penises? roughly age 8-9, after sexual stimulation? My friends and I were talking about a recent case in Georgia, USA where an 8 year old and 2 9 year old boys raped an 11 year old girl, and whether if any definitive proof would be left behind. Coolotter88 (talk) 22:36, 19 November 2007 (UTC)

Most likely nothing identifiable: see the second paragraph here (why isn't this a separate section title? oh well). According to puberty, sperm production doesn't start until the first day or so, so there's unlikely to be that sort of DNA evidence (few 9 years have started puberty, though I don't doubt a rare few have). -Wooty [Woot?] [Spam! Spam! Wonderful spam!] 22:51, 19 November 2007 (UTC)

I would think pre-ejaculate -- MacAddct  1984 ^{(talk • contribs)} 23:00, 19 November 2007 (UTC)

It would be semen without the sperm. This includes fluids from the prostate gland, the seminal vesicles, and the bulbourethral glands. Since these fluids are made up of body cells, and since they're be ejected in pre-pubic ejaculations, there would be DNA in them that the police can use. --Bowlhover (talk) 08:48, 20 November 2007 (UTC)

Carbon dioxide and water

Since like dissolves with like, why does carbon dioxide disolve in water (forming carbonic acid) even though CO2 is non-polar but ethanol disolves in water as they're both polar? Is it anything to do with polar bonds? Thanks 86.145.105.1 (talk) 22:50, 19 November 2007 (UTC)

The nugget of the answer is in your question. Think of the situation as two steps rather than one. First, the carbon dioxide reacts with water to form carbonic acid; second, carbonic acid dissolves and dissociates in water. TenOfAllTrades(talk) 00:14, 20 November 2007 (UTC)

Also, look closer at the article on carbonic acid. CO2 is hardly soluble in water under most conditions, so it does follow the "like dissolves in like" principle. By contrast, ethanol is 100% miscible in water. Delmlsfan (talk) 03:30, 20 November 2007 (UTC)

As for the carbon dioxide itself, its lone pairs allow it to make weak bonds to hydrogen in water, even though molecularly it isn't polar. This helps explain why carbon dioxide, while quite insoluble in water, is roughly 100 times more soluble than something like nitrogen gas. Someguy1221 (talk) 04:24, 20 November 2007 (UTC)