Wikipedia:Reference desk/Archives/Science/2008 August 12

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August 12

MDS , Myeloproliferative Dysplasia.

This question is for Donna Reister-Piper.

Hi Donna, you have been so kind to Gus, who I believe has spoken to you about my father who is suffering from MDS, and is currently receiving treatment using Hydroxy Urea.

We are in Adelaide, South Australia, and Gus is a relative of ours.

My father has had a Bone Marrow biopsy, and lots of blood tests.

I would like to ask you, what information can I provide to you from his case notes that would help you for his case. There are two volumes at this stage, and I would be more than happy to copy and send the information that you need, including blood tests, biopsy results and the like.

I would also be happy to pass any questions on to the Haematologist, if I can not get this information myself.

I happen to work here at the treating hospital the Royal Adelaide Hospital, so I should be able to get most of the information that you need.

Iwould like to express sincere gratitude for your help.

Thank You

Peter Spyropoulos

—Preceding unsigned comment added by Pspyropo (talk • contribs) 02:28, 12 August 2008 (UTC)

Who is Donna Reister-Piper? This is the Wikipedia Reference Desk, I don't think this is where you intended to post that message. --Tango (talk) 05:33, 12 August 2008 (UTC)

It wasn't intended to be private because it starts with "This question is for Donna Reister-Piper". Maybe said person is a Reference Desk contributor? --Bowlhover (talk) 06:23, 12 August 2008 (UTC)

genaral knowledge

Name the bird species which can only eat with its head up side down?59.98.68.47 (talk) 08:10, 12 August 2008 (UTC)

The flamingo? --Bruce1ee^talk 08:26, 12 August 2008 (UTC)

10 books in science

What ten books would you recommend to a social science or philosopher willing to learn something about science? One I have thought of is Lectures of Physics of Feynman, another is Calculus of James Stewart. I want general, complete books, not necessarily with historical value, but more like a thourough manual, covering Maths, Physics, Chemistry and Biology. Mr.K. (talk) 10:32, 12 August 2008 (UTC)

I would strongly recommend Mathematics for the Million, by Lancelot Hogben, and Facts from Figures, by M. J. Moroney as a start. DuncanHill (talk) 11:33, 12 August 2008 (UTC)

I ♥ The Flying Circus of Physics for its accessible treatment of physics in everyday life. --Sean 14:05, 12 August 2008 (UTC)

Feynman is good, but the Lectures are too technical. Try the "Six Easy Pieces" version, or something else by Feynman. 128.165.101.105 (talk) 16:41, 12 August 2008 (UTC)

I would look for a modern textbook written for a college freshman course in the particular subject (Biology, General Chemistry, ect.). The forward of a textbook often describes its intended audience or what sort of course it is designed for. For your purposes, I don't see value in looking for famous or classic names. ike9898 (talk) 17:01, 12 August 2008 (UTC)

I agree: The Feynman Lectures are amazingly well written and incredible to read...if you already know physics. To be honest, I find that they make a pretty miserable textbook. On the other hand, Surely You're Joking, Mr. Feynman! is an amazing book that is a transcript of some narrations that Richard Feynman made. It isn't instructive on the discipline itself, but I think gives some interesting insights into its culture, though I wouldn't take it as a last word. You have to keep in mind, Feynman was a (lovable) weirdo. EagleFalconn (talk) 21:06, 12 August 2008 (UTC)

Fun question! I'd suggest The Structure of Scientific Revolutions by Thomas Kuhn, A Brief History of Time by Stephen Hawking, Neurophilosophy by Patricia Churchland, Philosophy of Natural Science by Carl Hempel, and The Selfish Gene by Richard Dawkins to name a few good reads. Kuhn is an absolute must: go buy that book right now so you can earn the right to use the word "paradigm" in casual conversation. --Shaggorama (talk) 22:15, 12 August 2008 (UTC)

If you want to throw in an easy book, A Short History of Nearly Everything was quite enjoyable for me. --Kjoonlee 02:34, 13 August 2008 (UTC)

I commend your efforts if you intend to use the Stewart book. That is a fantastic calculus book that will not cut corners. The other suggestions thus far have also been great books, but they will provide more of a "philosophical insight" rather than a technical proficiency. I am of the viewpoint that you can synthesize any philosophical opinions you want to have about science with a lot more perspective if you actually get in to the gory details. I would also recommend the Tipler series [1] of introductory physics books ("Physics for Scientists and Engineers"), which are easy to understand but encourage the application of Calculus to basic physics. These books are categorized into three volumes intended to be taught as separate classes - mechanics, electromagnetism, and "modern" physics. Many physics educators debate whether this is an effective classification of physics concepts (they prefer a sort of "holistic" approach), but it has historically been the standard "sequential" way that most scientists are trained. The Feynmann lectures are really very technical; I would recommend them after you already had a thorough grounding in basic college-level physics. You will appreciate them, as well as many of the "conceptual" physics books more after you have the technical rigor. Nimur (talk) 18:07, 13 August 2008 (UTC)

Chemical Equilibrium question

Hi. I've been looking around for a while in the chem section of Wikipedia, but I can't seem to understand a few things concerning the equilibrium of reactions exactly. I was hoping for a simple tutorial, but, then again, there may be no simple way to describe this...

First, a friend of mine who's studying to be a chem teacher told me a simple rule to determine whether two diatomic salts will react or not, saying that the one with the highest electronegativity sticks with the one with the lowest (e.g. CuF + NaCl react to form CuCl + NaF, but not the other way around). Is this true in all cases?

Secondly, for salts that are not diatomic, I would have to calculate the electronegativity of the conjugate base, which, he said, was the geometric mean of the electronegativities of all atoms forming the conjugate base (e.g. for SO₄^2-, the electronegativity χ_SO4^2- = (χ_S¹ * χ_O⁴)^1/5. It seems to me that this ignores the spatial arrangement of the atoms, can it be true nonetheless?

Finally, for any reaction (n_aA + n_bB + ... -> n_pP + n_qQ + ...), with n_i being the stoichiometrical coefficients, how can I find out step by step whether the equilibrium is towards the reactants of the products?

Thanks in advance for your help, Danielsavoiu (talk) 13:08, 12 August 2008 (UTC)

1. Yes generally true.

2. You are right - but the approximation is often good, but not always.

3. See Chemical equilibrium - tables of 'energies' of the individual products and reactants can be used to get an 'energy' change for the reaction - (you need to ue the right energy depending on whether or not the reaction is contained or is open etc) - this may require more explanation so ask if so.87.102.45.156 (talk) 14:29, 12 August 2008 (UTC)

One exception to the first rule of thumb (and probably not the only exception) is where you're dealing with a metathesis reaction (old guys like me will call these double displacement reactions) that generates a precipitate from two soluble compounds. (Formation of a precipitate will pull ions out of solution and drag the chemical equilibrium to that side.) TenOfAllTrades(talk) 14:47, 12 August 2008 (UTC)

@87.102.45.76: Thanks, I had a look, but it's still a bit technical. I do not fully understand the terms entropy, enthalpy and gibbs free energy to be specific. If you could, please provide a description of these terms as for beginners and provide a formula to obtain a final result X whose sign would indicate to which side the chemical equilibrium of the reaction inclines. I presume this X is the difference in Gibbs free energy, but I still do not know how to obtain it. Something to do with bond energies, maybe?

If the gibbs energy is negative then the reaction goes to the right.( If the gibbs energy is 0 then then equilibrium is 50/50 )

Sometimes gibbs energy is not use an helmholtz free energy is used (in a sealed system for instance)

The first paragraph in entropy gives a good introduction to what it is

The very last equation in the section Chemical_equilibrium#Thermodynamics gives a relatiobship between gibbs energy and equilibrium.

Gibbs energies are calculated/estimated from experimental results and from theoretical work - again that is a book in itself.

I'm sorry I can't be more helpful today but I am very sick. Please try obtaining a book introduction on these topics. Hopefully someone else will be able to help you more.77.86.119.155 (talk) 19:53, 13 August 2008 (UTC)

@TenOfAllTrades: Thanks, I did know there would be an exception in similar cases... Danielsavoiu (talk) 16:03, 12 August 2008 (UTC)

1) I would say the most general way to answer this question would be to say that double displacement reactions take precedence (don't worry Ten, new foagies like me still call them that), and after that the rule your friend gave you. By the way, that rule falls under the Hard-soft acid base theory, which is a good place to read up on it. Mind you, both of these rules are generally true in the long term, not the short term. All sorts of crazy things happen long term. HSAB will usually win in the end.

3) The general answer is to compare the stability of the reactants to the stability of the products. This requires what is amorphously called "chemical intuition" which usually actually means "I've seen a lot of compounds and know some general trends." There is the quantitative approach above, but that requires knowing about equilibrium constants, and if you knew what those were it wouldn't be an issue. Its often relatively easy to come up with a qualitative answer, knowing definitively on a quantitative level is usually much harder to do from scratch.

EagleFalconn (talk) 20:39, 12 August 2008 (UTC)

which type of ether used for anesthesia for child in 1954

In 1954, at the age of two-and-a-half, I had an operation at a large hospital in Illinois. The anesthesia used was "ether," and I'm trying to find out which type of ether it would have been. My end goal is find out what the physical side effects would have been following the operation. I've looked at several articles about different kinds of ether on Wikipedia and don't have enough science background to tell the difference or to guess which one would have been prevalent in a major hospital at that time. Thanks for any help. —Preceding unsigned comment added by Abcol4info (talk • contribs) 16:19, 12 August 2008 (UTC)

Diethyl ether is the classic one, used as an anesthetic since the 1850s. If someone says "ether" with no further specification referring to an anesthetic, that's probably what they mean. Other ethers like methyl propyl ether and vinyl ether are also anesthetics, but they wouldn't be called simply "ether". 128.165.101.105 (talk) 16:35, 12 August 2008 (UTC)

Diethyl ether reminds me of an Osprey. -- Coneslayer (talk) 16:45, 12 August 2008 (UTC)

Sometimes when people say ether, they mean petroleum ether. ike9898 (talk) 16:55, 12 August 2008 (UTC)

True, but that's never been used as an anaesthetic to my knowledge. Algebraist 17:10, 12 August 2008 (UTC)

At the risk of violating WP:OR, after anesthesia via ether, you tend to throw up. — OtherDave (talk) 18:13, 12 August 2008 (UTC)

Ditto. Edison (talk) 23:31, 12 August 2008 (UTC)

Empyrean vs. E8

I was curious about the overall shape of the E8. What does it mean scientifcally, and why does it appear to imitate other famous symbols such as the shape in Dante's Divine Comedy ? 69.157.227.243 (talk) 16:48, 12 August 2008 (UTC)

Well, I don't think the "imitation" is very strong in that instance. It doesn't really resemble it in a strict way, other than the fact that it is a set of interlocking circles. Interlocking circles in general have been common symbols for humans for a long time (see, e.g., mandala). But that particular association seems not very specific to me in this case. Personally I think E7 looks more similar to that example than E8, but it's just a coincidence, once again. One might also spend fruitless time wondering by E7 looks vaguely like the cross-section of an atomic bomb. General resemblances between similar shapes likely has no strict meaning other than the fact that they are similar shapes. --98.217.8.46 (talk) 17:06, 12 August 2008 (UTC)

The Dynkin diagram of E8

Piping. Note the resemblance with the dynkin diagram

What you see is a graph, in the sense of dots connected by lines. Graph theory is the study of graphs. When I took a course in it, one thing the instructor insisted on is that graph theory dosn't deal with the shapes, it dosn't deal with how the dots are positioned relative to each other. Jumble the dots around, but as long as you don't break the links between them, the graph stays the same. Certain arrangements, like the one in the picture, can be useful in showing or even proving properties of the graph, but so can E8's Dynkin diagram, which looks decidedly unmystic. :More generally, an advice I heard from a mathematician is to not focus one's attention on the objects, like "But what IS the number five really?" but instead focus on the relationship between objects. That's where the real stuff is. :-) EverGreg (talk) 16:42, 13 August 2008 (UTC)

Fractals resembling natural forms is a much more interesting concept. Plasticup ^T/C 16:49, 13 August 2008 (UTC)

A conceptual problem in Physics

(I could not think of a better name for this problem, if you can be concise, kindly rename)
Problem:
Consider two earth like planets, A and B, a distance of 1 lightyear apart. Also, assume that these two planets are geosyncronous to each other. A string/rope of length 1 lightyear is tied to one of the planets A and a mass, say "x" kg is hanging on the string close to the other planet B. It is certain that no signal can travel from planet A to planet B in less that 1 year, the question is, if I cut the string at planet A, when does the mass start falling on planet B? Also, what constraints have to be kept in mind, and what assumptions have to be made? (for instance, is it possible for the mass to stay in its original place even after the string/rope is cut, as the gravitational pull of the other planet keeps the rope in "mid air"). —Preceding unsigned comment added by Akanksh (talk • contribs) 18:31, 12 August 2008 (UTC)

I wonder what the mass of the string is, also the mass of the mass, also how far above the surface of B the mass is initially. If the string length is exactly the same as the distance between the planets, the mass might be resting on the surface of B to begin with. Also, how stretchy is the string? Wanderer57 (talk) 18:57, 12 August 2008 (UTC)

(I'll be honest. I'm not going to be able to answer your question, even if you answer all of mine. But somebody else might.) Wanderer57 (talk) 18:57, 12 August 2008 (UTC)

This is close to a very common science question. The basic part of the question is: "If I have a string/rod/bar/rope connecting two things that are very far apart and I cut/pull/wiggle/twist one end, why doesn't the other end get the information instantaneously? Where's my Nobel prize for figuring out faster-than-light data transmission?" To put it simply, nothing is perfectly solid. The string is made up of mostly empty space inside of and between atoms. Each atom reacts to changes from the atoms around it, one after another. At best, you can get a change in one end of the string to reverberate down the string near the speed of light. In reality, it will be much slower (when you drop a rope, the change doesn't make a sonic boom as the change travels down the rope). So, the true answer depends highly on the makeup of the string/rope. -- kainaw™ 19:07, 12 August 2008 (UTC)

Rope is made of a bunch of atoms which are electromagnetically bound to nearby atoms. The bonds have a certain amount of elasticity, i.e. they obey Hooke's law, i.e. you can think of them as rubber bands. In the initial setup, the mass on planet B doesn't fall because the bonds in the end of the rope stretch until the restoring force (tension) counters the gravitational force. The atoms a little higher up the rope are pulled down by that elastic force and by gravity, but they don't fall because the rope above them is stretched even more. Eventually you get out of the effective range of B's gravitational field and the remainder of the rope is under roughly constant tension until you get to planet A. Now, when you remove the mass at planet A, the downward force on the nearby atoms will decrease, so they will accelerate upward, reducing the tension in the bonds above them until it starts pushing them downward, and then they'll go down again, and so on, oscillating until they reach a new equilibrium state. But in this new equilibrium state the atoms above are being pulled down less than before, and they will start doing the same thing (before the lowermost atoms have settled down, actually). And so on, propagating along the rope. But the propagation takes time—I think it will happen at the speed of sound in the rope, which I think will be around 10⁻⁵ c, so it could take 100,000 years. At any rate it will take at least one year. The atoms near planet B will continue defying gravity until the ones above them stop pulling upward, which they won't do until the ones above them stop pulling upward, and so on. It's a real life skyhook. (For some definition of "real life", anyway.) -- BenRG (talk) 19:32, 12 August 2008 (UTC)

You've mentioned everything I intended to say, but I'll post a link: http://math.ucr.edu/home/baez/physics/Relativity/SR/scissors.html --Bowlhover (talk) 22:00, 12 August 2008 (UTC)

Perhaps I'm misinterpreting Kainaw's answer, but if you simply pull on the string it wouldn't take any time at all for the guy on the other end to realize it because it's connected. Even if the string is a zillion light years across they would know it the millisecond you pulled on it because all of the string is moving. Now where is my Nobel prize?! ;) --Sam Science (talk) 01:49, 13 August 2008 (UTC)

That is exactly what I was explaining. When you pull on your end, the atoms on your end move. They then (after some time) pull on the atoms near them. Those then (after some time) pull on the atoms near them. This continues down the string until, eventually, the other end of the string notices the pull. It does not happen instantly. It happens, at best, near the speed of light. In reality, it happens slower than the speed of sound. -- kainaw™ 02:08, 13 August 2008 (UTC)

I'm still having trouble with this. When you move something, all of it moves. At exactly the same time. Now I'm picturing the rope already stretched to the max. As tight as you can stretch it without breaking. So if you pull it, the other end also pulls. It's instantly known. Let's say you're at a stoplight in a light year long limo (play along here). If you're in the back seat, you will know the absolute second the driver hits the gas. Instant, faster than light communication! The Nobel prize pays almost two million bucks, right? Now if you'll excuse me for a moment I have to call my boss (it's 2am here), and tell him to shove it. Sam Science (talk) 02:53, 13 August 2008 (UTC)

An actual limo or rope is at most several metres long. Since compression/tension forces travel at approximately the speed of sound, which is a few kilometres per second in solids, it only takes a millisecond or so for you to feel the brakes' effect or the rope pulling back. A millisecond is not long enough for you to perceive, so you believe forces travel instantaneously. As Kainaw and Ben explained, this is only an illusion and sensitive equipment can prove it false. --Bowlhover (talk) 04:09, 13 August 2008 (UTC)

And, in the case of an accident, the deceleration felt by the passengers is designed to be significantly less than that at the point of impact, due to the crumpling of the vehicle. So, the car most definitely does not move as one solid object in this case. StuRat (talk) 14:06, 13 August 2008 (UTC)

One case where the waves in seemingly solid objects are visible is earthquakes, where the p-wave (5 to 8 km/s) and s-wave have measurable speeds much slower than the speed of light (300,000 km/s), but some 20 times the speed of sound (0.343 km/s) in air. This speed is close to the speed of sound in a solid. StuRat (talk) 14:06, 13 August 2008 (UTC)

Note that in your hypothetical limo idea, 1. it would still take time for the signal from the driver's petal to make it to the engine (even if this was fancy electronics the upper limit would still be the speed of light), 2. just because the back of your limo has started to accelerate does not mean the front will have. The momentum will have to go along, atom-by-atom, until the atoms at the front know that anything has moved. You can see this happen on a different scale with long freight trains, where the back of the train is doing something very different than the front of the train (and sufficient "slack" has to be built into the system or else the changes between the different parts of the train would rip it apart—a mile-long-entirely-rigid train would tear itself apart very easily). --98.217.8.46 (talk) 17:11, 13 August 2008 (UTC)

SamScience seems to insist that solid metals move as a single unit, and remains unconvinced by our technical explanations about atomic forces and such. Maybe the easiest way to demonstrate is with a visual example. Consider a piece of sheet metal. Wobble one end of it. The sheet metal, even though it is solid, does not retain its shape perfectly. It takes a while for your wobbling to have any effect on the other end of the sheet metal. In fact, you can very precisely model the motion and the deformation of the metal. Sheet metal will propagate waves slowly enough for you to visually see the deformation. If you switched the geometries around to, say, a steel pipe, you might not be able to see the wobbling visually, but it would still happen. If your pipe / bar / limo / whatever were lightyears long, the propagation delay will not only be measurable, but the acoustic wave will be significantly slower than an electromagnetic wave, and it will damp out and attenuate due to thermal and other losses. This is why when humans built transcontinental telegraph lines, they did not try to send signals by wobbling the wire acousto-mechanically in Boston and hoping that would be able to tap out Morse Code in San Francisco. Nimur (talk) 18:25, 13 August 2008 (UTC)

Self-sacrifice in non-human animals?

Be it a soldier throwing himself on top of a live grenade in order to shield his comrades from the blast, a bodyguard taking a bullet for his president, a random passer-by jumping into the road to push a child out of the path of an oncoming car and taking the hit themselves, or someone running into a burning building to save a complete stranger, human beings sometimes make a spontaneous, conscious decision to potentially give up their own life for that of another (unrelated) individual.

Are we unique in the animal kingdom in that respect? Does science know why we do this? --Kurt Shaped Box (talk) 18:34, 12 August 2008 (UTC)

We have an article on Altruism in animals. Fribbler (talk) 18:35, 12 August 2008 (UTC)

I read the article before I posted here. It doesn't specifically address my query. Unless I'm reading it wrong. I vaguely understand altruism - but the above human behaviour would be akin to a mouse running in front of another mouse (a mouse which it had never seen before) when it saw a hawk diving from the sky with its talons extended in order that the first mouse might be saved. --Kurt Shaped Box (talk) 18:52, 12 August 2008 (UTC)

There are various documented cases of dogs pulling their owners out of burning buildings, and dolphins have been known to protect swimmers from shark attacks. --Shaggorama (talk) 21:42, 12 August 2008 (UTC)

There are some examples from the Altruism in animals article which may cover the "throw yourself on a grenade" type situations. The examples with baboons and vervet monkeys are situations where the animal incurs a risk in order to protect others. If you want a situation where death is assured, as opposed to "merely" increased in likelyhood, honeybees are the classic example. Your common honeybee has a barbed stinger, which rips itself out of the body after stinging. However, honeybees will attack dangerous animals, killing themselves while protecting the rest of the hive. If you want to nitpick about conscious decisions, you'll have to have a good delineation about where consciousness begins in the animal kingdom. -- 128.104.112.147 (talk) 22:54, 12 August 2008 (UTC)

I would contest that worker bees have no choice in the matter. They were born to serve and obey the Queen unto death and have no other purpose beyond this. I doubt that they can even understand the concept that the continued existence of the individual is a good thing for the individual. I wonder if the Queen knows? IMO, for the purposes of this question, the animal must be able to make the decision to either act, run away, or do nothing. --Kurt Shaped Box (talk) 23:08, 12 August 2008 (UTC)

First off, you're falling into the all too common fallacy of thinking that, because she's named "Queen", the queen bee has some sort of command over the hive. In reality, she is as much as a prisoner/egg-laying-machine forced into service to the hive-as-a-whole as a worker bee. At any rate, regarding the second point, there is a huge gray area as to which animal can make deliberate decisions, and which are "merely" following instinct. When a meerkat gives a warning call, is it making some sort of decision, or is it just following instinct? How can we tell? Where does instinct leave off and "consciousness" take over? Heck, when a human polishes off the rest of a jumbo order of fries, is that a conscious decision, or is it merely mindless instinct left over from our hunter-gatherer days? -- 128.104.112.147 (talk) 16:45, 13 August 2008 (UTC)

I don't think rationality or free will is even the issue here. It's impossible to rationally justify any action in a vacuum. You need a utility function or a moral code or a set of axioms of behavior or some kind of starting point. There are no logical tautologies of the form "my best course of action is such-and-such". The reason people want to live is that it's adaptive: people who survive to live another day have more offspring. That's all. It's not because any rational being will automatically desire to prolong its own existence. We instinctively want to live and we rationally want to live; it's the same thing. If we ever build intelligent robots we'll have to give them goals, and there's no reason to duplicate Homo sapiens' crazy mix of selfish and cooperative motivations. We could just make them cooperative, and we could furthermore make them value human life more than their own. And they would. Not because they're stupid, not because they're unconscious, not because they lack free will, but because their goals are different from ours. -- BenRG (talk) 01:17, 14 August 2008 (UTC)

Dear Ben, have you ever heard the expression, there are no atheists in foxholes? I get the impression that you've never been afraid for your life. I don't mean that disrespectfully. It's just that different people have had different experiences. I just think that self-preservation is a little more basic than wanting to stay alive to propagate. The other day, I was backing my car up to an air hose, and about the time I put on the brake, the car next to me started to pull forward. For a moment, it seemed that my brakes weren't working and that my car was going to roll down an imbankment into a tree. I felt fear that seemed very odd to me because I'm not a naturally afraid person. When I realized that the fear was totally unwarranted, I felt even more curious about having the feeling. Why? I still don't have a clue. Anyway, I just think that it is very natural for a person to be afraid to die, and it takes a conscious choice, for whatever reason, to sacrifice your own life for that reason alone. —Preceding unsigned comment added by 98.163.102.226 (talk) 18:12, 14 August 2008 (UTC)

A classic altruism in animals involves one bird sending out an alarm when a predator approaches, aiding the flock as a whole but calling our their own location to the predator. (Note that before you start nitpicking, the question of what "really counts" as altruism in animals is one that has been debated up and down for years by philosophers and zoologists. Let's not pretend we are going to resolve it here. There are many books on the question of altruism in animals, whether altruism itself ever truly exists, and so forth.) --98.217.8.46 (talk) 00:43, 13 August 2008 (UTC)

I wonder if animals really know about death. Through experience, an animal may learn that other animals may injure it and cause pain. And a predator kills other animals, but does it realize that could happen to itself? Andme2 (talk) 02:22, 13 August 2008 (UTC)

Well, they seem to value life, if that means anything. As for "really" understanding death, I doubt most people do... much of our response to death is no doubt instinctual, required so that we don't just blithely walk off cliffs and whatnot. Even a housefly knows that when I'm chasing after it with a fly swatter that it needs to hustle it's ass out of there... --98.217.8.46 (talk) 15:21, 13 August 2008 (UTC)

One creature that doesn't seem to value its own life is the cranefly. I know that I keep raggin' on this species here - but they don't even attempt to move when you approach to catch/swat them. I've seen the local birds just walking around and picking them up from the grass. --Kurt Shaped Box (talk) 15:41, 13 August 2008 (UTC)

I know it's obvious, but plenty of animals risk themselves to protect their young. Pretty much all mammals, for starters. Plasticup ^T/C 16:40, 13 August 2008 (UTC)

I don't know about craneflies in particular but I find it hard to believe any animal has no response to a common prey (our article mentioned birds often eat them). No response to being swated is easier to understand, if it's not a frequent threat or associated with something that's a frequent threat, they may simply not recognise it as a threat. The other issue may be that being cold-blooded animals, they may get a bit 'dopey' in the winter (I'm presuming you live in a temperate country) or otherwise temperatures outside their optimal clime. As an example, mosquitos in New Zealand even in the summer are rather easy to catch (there are few or no mosquitoes during winter, they can't survive). However before you think mosquitos are dopey easy to catch things, try living in Malaysia for a few months. Nil Einne (talk) 19:09, 13 August 2008 (UTC)

Here in England, the craneflies come out (in their thousands) in the warmth of late spring/early summer, so I don't think that it's a temperature issue. Their primary means of self-preservation seems to be the shedding of limbs when caught. They certainly can't fly away from anything that has the capability to track and give chase when it realizes that it has a mouthful of spindly leg - when they do 'fly', they pretty much go where the wind blows them, wobbling around and crashing into anything and everything. I'm not kidding here - the gulls just glide along at a ridiculously slow pace a few metres off the ground and snap them out of the air in their hundreds. --Kurt Shaped Box (talk) 00:11, 14 August 2008 (UTC)

People have already mentioned dogs pulling owners out of burning buildings. I would go further and point out it's possible to train many animals particularly domesticated ones to do a variety of things. This would include running out a road to save a child for instance (and many dogs know roads are dangerous). Police dogs will generally not hesitate to attack a criminal. I would presume they receive at least some training which teaches them "guns=bad" for example and would often know they are at risk of injury. You may argue it's not the same thing but I would disagree. Much of what you describe above are IMHO likely learnt behaviours. A bodyguard will take a bullet to save the person he/she's supposed to be protecting because it's his/her job and it's the right thing to do since the person they're supposed to be protecting is more important than them. The same bodyguard is probably generally not going to take a bullet to save the life of a homeless person. A soldier is taught about duty, comradeship etc. The same soldier is not going to jump in front of a grenade to save an enemy (he/she or his/her comrades may have thrown the grenade!). A random passerby is quite likely to jump in front of a car to save a child or perhaps 'senior citizen'. Less likely if it's a fit adult. Even less likely if it's someone they despise (e.g. most Americans are not going to jump in front of car to save Osama bin Laden). All these are what we call 'ethical' choices and they are associated with certain behaviour and a big part of it is IMHO learnt (obviously it's partially instinctive). As I've said, you can teach animals similar things. As far as we know, all other animals probably don't have quite the level of detailed thought enabling them learn and react in such detailed ways but they are still capable of learning to react in certain ways in certain situations even if it may cause harm to themselves (and as the pet examples show, an animal which developed a strong bond with an individual may try to protect it even if it wasn't specifically taught to react in that way). Nil Einne (talk) 18:55, 13 August 2008 (UTC)

I'm not going to argue with that. What a good answer (I'm not saying that the others weren't good too). Thanks a lot. --Kurt Shaped Box (talk) 00:01, 14 August 2008 (UTC)

Can a fly, or any other living thing except humans, conceive being dead - not being aware of anything? Perhaps they just live in the present.

A predator may anticipate the movements of its prey in the next few seconds, but may not think at all of the future except for that.

As for a fly moving out of the way of a fly swatter, that may just be instinct. A predator could move toward the fly to seize it, so the fly may instantly flee simply out of instinct. The instinct could apply to things as well. A horse's tail, for instance, may swish toward the fly to swat it, so the fly flees. It may instinctively flee from anything moving rapidly toward it. I don't believe it's a matter of the fly thinking it could be killed.

Creatures that have a memory may anticipate pain experienced from earlier similar circumstances and may flee to avoid pain, but not death.

I think fleeing is either a matter of instinct, or it is from a memory of earlier painful experience. Andme2 (talk) 01:07, 14 August 2008 (UTC)

(Going off on a bit of a tangent) I'm pretty sure that some animals can anticipate the future. To use an example I'm familiar with, Moluccan Cockatoos are notorious for screeching in a tone particularly offensive to human ears when their owners are not in the room in order to attract their attention. The bird will not be ignored and will keep screeching constantly until the owner enters the room. The Cockatoo apparently is taught this from an early age by unwitting owners who lavish attention on it whenever it screeches in order to 'calm it down', treating it somewhat like a human infant. The bird sees that screeching brings its keeper running every time and enjoying human contact and not understanding (or caring) that the human may have other things to do, eventually comes to the realization that 'screech = human will come to hang out with me eventually if I do it for long enough'. Seems to me that the Cockatoo can forsee the consequences of its actions. --Kurt Shaped Box (talk) 01:30, 14 August 2008 (UTC)

The cockatoo is simply remembering past experience. Just as a creature with a memory avoids pain by remembering past experience, it may also seek to repeat pleasure derived in past experience. But if it sees the death of another creature, it may not apply that eventuality to itself.

If a creature does not anticipate its own death (thinks the present will go on forever) it will not knowingly sacrifice its life for others.

Of course, instinct may cause animals to take risks for each other. For instance, a mother animal may defend its young. And a pack of wolves will attack a large and dangerous animal, instinctively aiding each other in the attack.

Or an animal may non-instinctively attack one of its own kind for food, a mate, or pack leadership. (It may also be a coward to avoid pain - that's how pack leadership is given to another.)

But a mother animal or pack animal, acting from instinct, may never think of death occuring to itself when it aids another of its own kind. The same goes for a conscious attack for food, a mate, or pack leadership. Andme2 (talk) 03:58, 14 August 2008 (UTC)

Another thing. I have never seen, in life or in photos, an animal react with horror or aversion when it sees another dead animal. Not even when the dead animal was horribly wounded. The live animal didn't seem to understand what death was. Andme2 (talk) 18:47, 14 August 2008 (UTC)

Completely anecdotal, I know - but if one of my budgies dies in my aviary, the other birds do seem quite 'subdued' whilst the dead corpse is present on the ground. --Kurt Shaped Box (talk) 00:44, 15 August 2008 (UTC)

Teeth Whitening

I have read the essay in Wikipedia regarding teeth whitening but I'm anxious to hear from people who have undergone various proceedures. Do any of them really work? Do the proceedures carried out by Dentists hurt? Do any of the "do it yourself" products really work? Which ones? Thanks, WSC —Preceding unsigned comment added by 75.85.203.191 (talk) 19:45, 12 August 2008 (UTC)

You should ask your dentist these questions. --Shaggorama (talk) 21:39, 12 August 2008 (UTC)

Given that dentists are not very forthcoming about the other side of the effects (such as weakening tooth enamel), and upkeep, try google, do research and take a list of your questions to the dentist to get to the bottom of it. In Oz there's a consumer Choice magazine that compares products so you might find something there or similar. When the dentist offered me (wasn't asked, take note) the whitening system I was impressed with 1) their selling stance; 2) the expense; and 3) the high maintenance of it. It came down to over-servicing in my book because my teeth, not glacial fluoro ceramic white, are white enough. Best of, Julia Rossi (talk) 00:13, 13 August 2008 (UTC)

I've had that gel stuff applied by a dentist ages ago. It didn't hurt. It didn't help my case, though. (I have fluorosis and ended up just needing to get veneers). --98.217.8.46 (talk) 00:39, 13 August 2008 (UTC)

There's a whole range of products available for tooth whitening, which range from quite inexpensive (and ineffective) to very expensive and quite effective. Toothpaste that claims to whiten the teeth would be at the low end, followed closely by over-the-counter gels and gel-strips, then dental treatments like laser whitening. I'd put porcelain veneers both at the top of cost and effectiveness. StuRat (talk) 13:51, 13 August 2008 (UTC)

Veneers are certainly #1 when it comes to whitening, but that's because they essentially build you new teeth out of porcelain. They're not a trivial thing, though. Aside from the cost ($500 a tooth when I had it done—somehow convinced the insurance the cover it), they also have their own other issues—they need to be replaced once a decade or so, and they can crack and fall off if you aren't careful (hard breads in particular need to be avoided, and you absolutely cannot bite your finger nails under any circumstances). If you grind your teeth at night you have to wear a bite guard, because the veneers are not anywhere as strong as your regular teeth. Anyway, just sharing my experience with them—I've had mine for about 9 years now. They look really nice, and are way better than my fluorosis teeth were, but there were many costs. I would not recommend them to people who had not exhausted other options first, as I had. (Oh, and let's not even get into the operation of having them applied, where they grind down your existing teeth first... it's a little horrific, in my opinion.) --98.217.8.46 (talk) 15:32, 13 August 2008 (UTC)

All so you can look like you have false teeth. Yay. 217.42.157.143 (talk) 19:07, 18 August 2008 (UTC)

Size of Orbitals?

Hi folks,

I'm going to be teaching an introductory general chemistry class this semester and I've been making lesson plans. I'm at the part where I talk about orbitals, and I have a question I'm not sure how to address. When speaking of the reactivity of electrons, we often talk about the size of the p-orbitals and thats why they are more reactive. But at the same time, I've asked this question before and always been told that size is ambiguous at the quantum level, which I know is crap because in my quantum class we've calculated the expectation value of the radii for some of the orbitals. I guess I'm trying to come up with a good way to answer the question, "But aren't those orbitals (say the 2s and the 2p) occupying the same space? How can two probability areas be occupying the same space? Is the 2p orbital in the 2s orbital?" Any suggestions? EagleFalconn (talk) 20:28, 12 August 2008 (UTC)

Orbital size really is ambiguous (except for nodes), but if you decide what you mean by "size", then it can be answered...you picked an expectation value, probably a probability cut-off beyond which it's too unlikely for you to care. Electrons in a p orbital (compared to s) are mostly away from the nucleus and directional, so they are less tightly held by the positive center and more able to reach out towards something else. But anyway, several orbitals do indeed occupy the same region (even for the usual "fairly likely" location/size/shapes). Overlap allows hybridization, which is a pretty important idea all the way from gen-chem through quantum discussions. Is your class only at the level of "electron filling" and atomic configurations, or have reached as far as covalent bonding? DMacks (talk) 20:36, 12 August 2008 (UTC)

The class hasn't started yet, I'm in the planning phase only. I'm taking something of a non-traditional approach. Roughly, the order I'm introducing topics is

1) Conservation of energy

2) Conservation of mass

3) Define the atom.

4) Atomic structure. Briefly the Bohr model. (about 3 minutes)

5) Wave model at more length. Types of orbitals, filling order by energy, motivation for orbitals existing, why they fill in the order they do, Pauli exclusion, Hund's rule.

6) Kinetic/Thermodynamically stable states

7) Stability of states as applied to chemical reactions.

8) Balancing chemical reactions as motivated by conservation of mass

9) Hybridization

10) Atomic radii/Electronegativity

11) Predicting simple reaction products as an application of hybridization, to motivate Lewis structures.

EagleFalconn (talk) 20:51, 12 August 2008 (UTC)

One problem which has a simple explanation is that the terminology "space" is sometimes mis-used. (i.e. "two electrons cannot share the same space" - this is not correct!) For example, Pauli Exclusion Principle dictates nothing about spatial exclusivity. It strictly operates in the realm of quantum state, which may be related to spatial location, but is not equivalent. So, for example, if someone asks whether 2s and 2p orbitals are "in the same place", you may tell them that they do contain overlapping spatial locations, but they are not in the same quantum state; further, encourage them to understand that in Quantum Mechanics, spatial location is often less important than quantum state as far as determining or predicting the system's behavior - and that is why we do not have well-defined "positions" for so many cases. Nimur (talk) 18:33, 13 August 2008 (UTC)

That's a very good distinction! It helps to keep in mind "could be in the same place at various times" from doing the same thing at the same place and time". You could even use the term "momentum" (no need to call it "angular momentum") to describe the two electrons in different orbitals doing different things (and therefore "different from each other") even if they might be in the same place. DMacks (talk) 18:52, 13 August 2008 (UTC)

In general orbitals that are higher in energy are on average further away from the nucleus. So if your p orbitals are higher in energy than s you can use that.

Two gases can occupy the same space, as can smells, lights you name it. Use an analogy.77.86.119.155 (talk) 19:32, 13 August 2008 (UTC)

Per Atom the outermost electron can be as far as half a millimeter from the nucleus. Edison (talk) 01:17, 14 August 2008 (UTC)

There is a probability of an electron from an atom on Earth being on Mars....but the common diagrams of orbitals describe the 90% confidence level.--Shniken (talk) 14:07, 14 August 2008 (UTC)

I just deleted that sentence from the article since it seems pretty misleading; naturally occurring atoms don't get anywhere close to that size. To the original poster, you have to be a little careful when talking about the expected radius of an orbital. The most likely place to find a 1s electron is inside the nucleus. The most likely radius at which to find it is the Bohr radius. The expectation value of the radius is 1.5 times the Bohr radius (if I calculated correctly). But the electron is actually spread all over the place, as shown in pictures like this, and none of the radii I just quoted accurately captures "where it spends its time". It's also worth mentioning that 1s electrons don't orbit the nucleus in any way shape or form. The only reason they're ever found far from the nucleus is the uncertainty principle. -- BenRG (talk) 16:43, 14 August 2008 (UTC)