Since the article said white dwarf can be 0.17, do the white dwarf dwarf being 0.17 actually exist currently, or is it just the estimation of the stars did not yet come off the main sequence. [[:Category:White dwarf stars|Is this true]] alot of white dwarf are binary stars, can 0.5 solar mass white dwarfs? is it more common for white dwarf to be single star system, or binary star system? Is white dwarf all the exact same size on single star system/non-binary star ssytem? or the Solar mass determined by white dwarf has to determine exactly how big the white dwarf has to be?--[[Special:Contributions/69.226.42.134|69.226.42.134]] ([[User talk:69.226.42.134|talk]]) 00:36, 12 April 2013 (UTC)
Since the article said white dwarf can be 0.17, do the white dwarf dwarf being 0.17 actually exist currently, or is it just the estimation of the stars did not yet come off the main sequence. [[:Category:White dwarf stars|Is this true]] alot of white dwarf are binary stars, can 0.5 solar mass white dwarfs? is it more common for white dwarf to be single star system, or binary star system? Is white dwarf all the exact same size on single star system/non-binary star ssytem? or the Solar mass determined by white dwarf has to determine exactly how big the white dwarf has to be?--[[Special:Contributions/69.226.42.134|69.226.42.134]] ([[User talk:69.226.42.134|talk]]) 00:36, 12 April 2013 (UTC)
:I struggle to see how a very small white dwarf (such of 0.17 solar masses) could form other than from a small red dwarf collapsing. Red dwarf stars live for a very long time, so none of them are dead yet. That would suggest there are no very small white dwarf stars. A lot of stars are in binary systems and they will generally remain in those systems when they die, so yes it is true that a lot of white dwarfs are in binary systems - I don't know if it is more than half, though. The size of a white dwarf is determined by the size of the star that formed it. In a binary system, there might be some transfer of matter between the stars that can change things. In a non-binary system, there obviously won't be. Does that answer most of your questions? I found them a little hard to understand... --[[User:Tango|Tango]] ([[User talk:Tango|talk]]) 11:43, 12 April 2013 (UTC)
== Bird evolution ==
== Bird evolution ==
Revision as of 11:43, 12 April 2013
Welcome to the science section of the Wikipedia reference desk.
The best answers address the question directly, and back up facts with wikilinks and links to sources. Do not edit others' comments and do not give any medical or legal advice.
If scientists believe that they or humans will eventually know everything, isn't that equivalent to a religion? Or even if they believe that they will know more than they currently do that might not always be true, so that is a belief in something without proof. Or is this Q more appropriate for the humanities desk?68.36.148.100 (talk) 00:02, 8 April 2013 (UTC)[reply]
A belief that humans will eventually know everything is indeed a declaration of faith (which is what a religion is), but what makes you think genuine scientists do belive that? I have worked closely with, and supervised, researchers working at Ph.D level. None of them believed that. Have you not heard of the expression "The more I know, the more I know what I don't know" - a favorite among researchers I know. The second part of your question reflects a common misconception about science on your part. Science is not really about asserting facts, it's more about discovering theories that fit known observations, and thus enabling calculations/predictions of results/outcomes for any practical set of conditions. An example is electromagnetics: Over 100 years of electrical engineering has never thrown up a situation where the theory gave a wrong answer. But just what a magnetic field is, or what an electric field is, is something we don't know. Until the theory does throw up a wrong answer to a situation, scientists aren't much concerned about it being merely a theory, and engineers don't care at all - for them it just works. Ratbone 124.182.150.1 (talk) 00:30, 8 April 2013 (UTC)[reply]
I doubt any scientist thinks it is possible to "know everything", regardless, I think you have two major flaws in the premises of your questions: What scientists believe is not what defines science, and similarly 'believing things without evidence' is not what defines religion. Science is based on only a very few fundamental premises, like methodological naturalism, which them selves are not "arbitrarily" chosen, but refined and condensed through hundreds of years of philosophy. Even now those fundamental premises are NOT taken for granted or completely beyond question. If there was any good reason to question or alter those fundamental premises, scientists would do so. Trying to equivocate science to religion is almost only ever done by the religious in an attempt to demote science's privileged epistemological position to 'their' level, which I think is quite funny when you think about it. You'll never hear a scientist accuse a religion of being just another "science". Vespine (talk) 00:41, 8 April 2013 (UTC)[reply]
doesn't that mean that if any scientists have this belief that it is religion to them? I hope for scientists' sake none do. I bet there are a multitude of references of legit scientists who have alluded to these "beliefs" as part of their "work"68.36.148.100 (talk) 00:49, 8 April 2013 (UTC)[reply]
You already asked this question, and we have already answered it. Why don't you go look for those references, since you have faith that they exist? Ratbone 124.182.150.1 (talk) 01:08, 8 April 2013 (UTC)[reply]
why so hostile , isn't this a legit question? Any way I'm too busy watching wrestle mania with my son. And I know those references exist but I don't do reference or bibliographies68.36.148.100 (talk) 01:18, 8 April 2013 (UTC)[reply]
Holding a belief, without any evidence, even a dogmatic one, may be a necessary condition of religion, but it's not a sufficient one. Vespine (talk) 01:48, 8 April 2013 (UTC)[reply]
Working scientists usually take for granted a set of basic assumptions that are needed to justify the scientific method: (1) that there is an objective reality shared by all rational observers; (2) that this objective reality is governed by natural laws; (3) that these laws can be discovered by means of systematic observation and experimentation. Philosophy of science seeks a deep understanding of what these underlying assumptions mean and whether they are valid.
The belief that all observers share a common reality is known as realism. It can be contrasted with anti-realism, the belief that there is no valid concept of absolute truth such that things that are true for one observer are true for all observers. The most commonly defended form of anti-realism is idealism, the belief that the mind or consciousness is the most basic essence, and that each mind generates its own reality.[17] In an idealistic world-view, what is true for one mind need not be true for other minds. — Preceding unsigned comment added by 68.36.148.100 (talk) 02:38, 8 April 2013 (UTC)[reply]
I was wondering why scientists do what they do. To make things bigger faster stronger, etc. I came to the conclusion that it is for the betterment of mankind. But obviously there are many reasons. Although ultimately there needs to be that same belief that the future state can be better than the present one. A faith in the natural universe being further understood or revealed for our benefit. 68.36.148.100 (talk) 04:16, 8 April 2013 (UTC)[reply]
If it has worked in the past and you have no good reason to think it will not work in the future, it's not necesarrily an illogical assumption. Especially if the alternative is to sit on your hands in a solipsistic coma. Also, strictly speaking, science doesn't make things better, science is used to discover things about the world. Scientific discoveries can then be applied to make things better, applied science is considered engineering, the fruits of which are technology. Vespine (talk) 04:38, 8 April 2013 (UTC)[reply]
There is a difference between natural science and supernatural science, where science is "knowing". Natural science describes the ordinary functioning of the universe according to its observable laws. Supernatural science can describe divine interventions that alter this normal functioning, or alternate universes or dimensions not accessible to experiment. However, the most important aspect of religion may be in the interpretation of what we do - often the facts are clear, but the moral reaction is anything but agreed upon. Wnt (talk) 04:42, 8 April 2013 (UTC)[reply]
Your assumption that scientists believe that they or humans will eventually know everything is a dubious premise that you have not established, and which looks a lot like a straw manfallacy. What is much less dubious is that scientists believe that through science, scientists or humans will know more than they do currently, which is all that is necessary for a career in science to be a worthwhile endeavor. And that belief is not just a matter of faith. In science, the thing that determines whether or not something is to be believed is scientific evidence, and there is rather trivially evidence that science will cause additional things to become known in the future. Scientists learn new things every day, and there is no evidence that would suggest that tomorrow, that might all stop happening.
The argument against believing certain hypotheses proposed by religions isn't really a matter of thinking that science will eventually have all the answers, so the answers given by religion should be ignored, but rather a matter of considerations like the answers that are given by religion often being contrary to the available evidence, or the answers being given by religion going against Occam's razor by hypothesizing a bunch of stuff which has no predictive value due to the hypothesized stuff being unfalsifiable. Red Act (talk) 05:45, 8 April 2013 (UTC)[reply]
Q1: If scientists believe that they or humans will eventually know everything, isn't that equivalent to a religion?
Bad premise. Scientists not only do not believe that we'll eventually know everything, they know for absolute certainty that they cannot possibly ever know everything.
We have Gödel's incompleteness theorems that says that there are things in mathematics that are true that can neither be proved nor disproved.
The total amount of information about the universe requires something at least as complex as the universe to store it all in. So we can never know every detail.
We have quantum theory that says that we can never know the precise position and momentum of a particle at the same time - and which forces randomness into the universe in fundamental ways. This will always limit our ability to know everything.
Chaos theory which proves that some systems are fundamentally unpredictable: For example: we can never predict the weather more than a few weeks or months in advance.
Science has shown that science has limits.
Q2: Or even if they believe that they will know more than they currently do that might not always be true,
It's obvious that our state of knowledge is always going to be in a state of flux. We are always learning new things - and there is little reason to suppose that we'll ever run out of things like that. But on the other hand, we're continually forgetting things too. It seems certain that one day we'll arrive at a steady state condition where we're forgetting things as fast as we're learning them - but we're nowhere near that point yet.
Q3: so that is a belief in something without proof.
No, I don't see that. Scientists don't claim that we'll eventually know everything - quite the opposite in fact. So your premise is flawed and you can't produce this conclusion from it.
One of the big differences between religious belief and scientific belief is that science is effective. You don't see industrialists gathering groups of theologians to study religious works and from the fruits of that building a better car engine or getting clean water or anything really where one can put down money and bet on which will give a better outcome. Would you say industrialists as engaging in a religious belief? What scientists do is in essence no different. Dmcq (talk) 00:35, 9 April 2013 (UTC)[reply]
Logic, creativity and ignorance
Some claim that logic can explain everything and that when new things are discovered, it is simply ignorance to that logic which has been overcome. I agree but I don't think logic always works because its basically thinking inside the box, I.e. following a set of known principles. Is my thinking correct? — Preceding unsigned comment added by 2.124.100.141 (talk) 00:35, 8 April 2013 (UTC)[reply]
Logic is an extremely broad subject, I think you might be conflating different uses of the term. At its core, formal logic is described as either valid or fallacious, that makes it clear it doesn't have anything to do with inside or outside the box. Fallacious logic will never lead to justified conclusions, it can by chance lead to correct conclusions, but they will not be justified. On the other hand, some discoveries can seem "illogical", like the fact that a photon can have seemingly incompatible properties of waves and particles, outside the box thinking was required to come to terms with that discovery, but that isn't the same meaning of the word logic. In that case, faced with the evidence that was present, outside the box thinking was in fact logical. Vespine (talk) 01:00, 8 April 2013 (UTC)[reply]
Logic doesn't imply that you cannot question your principles. Logic is mainly concerned to deduction from some assumptions to some conclusions. If the assumptions are wrong, everything is wrong. On the other hand, any explanation has to be logical. If you find a contradiction somewhere, it's time to drop some part of your theory.OsmanRF34 (talk) 01:12, 8 April 2013 (UTC)[reply]
I think these are actually very good inquisitive questions, you are starting to scratch the surface of some pretty deep philosophical ideas, about epistemology, metaphysics, etc... If you are genuienly interested, I would strongly recommend something like the free Philosophy for Beginners introduction course from Oxford University. I'm only a novice to philosophy and found these extremely enlightening. Vespine (talk) 01:21, 8 April 2013 (UTC)[reply]
Logic, by itself, cannot explain much. You need to feed it some "axioms". So, for example, no amount of logic will tell you whether the earth is flat or round - you have to feed it some observations (such as the fact that the earth's circular shadow is cast onto the moon during an eclipse - or that ships disappear over the horizon gradually, with their hulls disappearing before their masts). Logic (and more broadly, mathematics) is a tool to help you organize thoughts and data and to extract conclusions and expose weaknesses in "obvious" arguments. Science proceeds with observations and experiments - and logic and mathematics are mostly just tools to help in the process. Logic can be used to produce crazy answers if you give it crazy assumptions. For example, if you start with the assumption that zero is equal to one (or true implies false or something else which isn't true in the real world) - then the rules of logic will happily crunch away on that and produce unending streams of nonsense. This is actually occasionally useful. For example, we know that the three angles of a triangle add up to 180 degrees out here in the real world - but if you deliberately set up a logical system in which that fact is denied - then what emerges is some very interesting non-euclidean geometries that prove useful for all sorts of things. SteveBaker (talk) 16:26, 8 April 2013 (UTC)[reply]
Another way to put this is to contrast deduction with induction. (Forget Sherlock Holmes, he had them backwards.) Induction means (more or less) reasoning to a large conclusion from smaller ones. In other words, I go into the world, I see five birds of the same species, I use them to generalize for the whole species (because I cannot actually look at every member of the species). Deduction means (more or less) reasoning to small conclusions from larger ones. In other words, I know that all birds have feathers, and when asked whether a specific bird (say, a duck) has feathers, I can logically deduce that this is true, a priori. Deduction is generally the realm of formal logic: I know certain things, thus I know other things. But as you can see with my examples given, deduction alone is pretty silly when you are trying to talk about things in the real world and not hypotheticals. How do I know, a priori, that all birds have feathers? Could there be a species out there which does? Deduction alone doesn't let you answer that question. It's why induction became the name of the game for science — go out in the world, see what's there, then work backwards to find what you presume are the "real" rules, and from there you can move tentatively forward with deduction, at least up until you reach the limits of what you know. Induction isn't perfect by itself (see problem of induction — what if the five birds I looked at were, coincidentally, not at all representative?), and neither is deduction (we don't really have a formal problem of deduction but it's basically "how do you know your axioms are correct in anything other than pure philosophy or mathematics?"), but together they are pretty powerful. --Mr.98 (talk) 17:53, 8 April 2013 (UTC)[reply]
Yes, exactly. Formal logic can say:
AXIOM: All birds have feathers.
AXIOM: A duck is a kind of bird.
DEDUCTION: All ducks have feathers.
Which is great - logic told us something that we may not have known at the outset. It's not so obvious that it helped in this case - but for more complex systems where the conclusion is perhaps not so clear, application of formal logic can tell you things you didn't know and wouldn't have guessed.
But: that exact same set of formal logic can go horribly wrong:
AXIOM: All birds can fly.
AXIOM: An ostrich is a kind of bird.
DEDUCTION: All ostriches can fly.
Clearly this is an incorrect deduction - because the first axiom isn't true. This system of formal logic has no way to know that. But that doesn't make formal logic wrong or useless: what it's telling you in this case is NOT that ostriches can fly. It's saying that if all birds can fly - then ostriches can fly...which is a true statement, albeit not a very useful one!
So logic is a tool - and a very handy one - but it's not enough by itself to tell us anything at all about the world. Some poor biologist has to go out there and slog his/her way across the planet, looking at all the birds to see if there are any flightless ones out there - then come back and rewrite that first axiom. Now we have:
And the problem of our ability to deal with postulates like "Everybody agrees that a unicorn has one horn" and "Everyone agrees that unicorns do not exist" simulataneously, without being frozen like a robot in a 60s TV show mumbling "Does not compute... does not compute" Gzuckier (talk) 06:22, 9 April 2013 (UTC)[reply]
But that's not a problem with the laws/rules/mechanisms of formal logic. It's just a dumb misstatement of the axioms: "Unicorns are fictional creatures" and "Unicorns are described as having one horn" would be a better statement of those axioms - and would allow one to deduce the useful and true statement that "Some fictional creatures are described as having one horn". But if you put nonsense into a logical system - you get nonsense back out again: "All wibbles are bloings", "All bloings are pfnaargs" allows you do deduce that "All wibbles are pfnaargs"...which doesn't make you any more enlightened. But even "All elephants are tomatoes", "All tomatoes are made of pink lace" gets you "All elephants are made of pink lace" - which is clearly a false statement about the real world - but a perfectly valid deduction from those axioms. All that formal logic is telling you is that "If all of the axioms are true - then this statement is also true."
The Principle of explosion is a superb example of what happens if you have bad axioms. All you have to do to prove absolutely anything you like is to add an axiom into your system that asserts that something is both true and false. The example in that article is a good one:
"Consider two inconsistent statements - “All lemons are yellow” and "Not all lemons are yellow" - and suppose for the sake of argument that both are simultaneously true. If that's the case we can prove anything, for instance that "Santa Claus exists", by using the following argument: 1) We know that "All lemons are yellow". 2) From this we can infer that (“All lemons are yellow" OR "Santa Claus exists”) is also true. 3) If "Not all lemons are yellow", however, this proves that "Santa Claus exists" (or the statement ("All lemons are yellow" OR "Santa Claus exists") would be false)."
So the smallest error in your choice of axioms can make utter nonsense of the results. This doesn't mean that formal logic is somehow "wrong" or "useless" any more than ones' failure at using a hammer to drive a 2" length of string into a board means that a hammer is a useless tool.
I am trying to get my head around the concept of "rolled up" dimensions found in string theory. Higher dimension problems can often be visualised using a two-dimensional world as an analogue and then considering the effects of a third dimension upon it. I am having a failure of imagination here and cannot see how the third dimension could be "rolled up". I have seen Steve Baker's clever analogue of a one-dimensional world in the archives where he rolls up the second dimension into a cylinder around the one-dimensional line people, but I cannot see how this analogy is extended to two-dimensions. Further, a cylinder is three-dimensional, a third dimension was required to enable the second dimension to wrap. In a two-dimension analog would a fourth dimension be required to enable the third dimension to be wrapped? SpinningSpark 11:56, 8 April 2013 (UTC)[reply]
Its simply an analogy because we live in 3-spacial dimensions and related to this is the holographic principle, which I have not studied. Although we generally work with three spacial dimensions, I tend to think of space as one-dimensional though, because I can slice it up into countable discrete volumes with division: simply cut it up into discrete unit volumes such as bricks or tiles and then cut each of these into smaller pieces recursively into infinitesimal volumes. For me, its an interesting conceptual exercise, even if its not all that useful (its utility may be limited to object order algorithms). Of course, with the physics of string theories, one has to consider the dimension of time as well with Einstein's principles and the concept of spacetime. -Modocc (talk) 12:43, 8 April 2013 (UTC)[reply]
It has nothing to do with the holographic principle, which is about information in a volume of space. Space is not 1 dimensional in any meaningful way, even for object order algorithms (because you can't tell what a voxel's neighbors are).
To the OP: The ant on a cylinder, say a garden hose, sees 2 dimensions: one along the cylinder axis and one along the circumference. We're imaging the ant to be a 2D inhabitant of the cylinder surface. If you want the third dimension to be rolled up, our ant has to be already living in 3 dimensional space, but then (as you said) you need to embed this 3D space into a 4D space to visualize it. Our universe is one example of a curved 3D space*, but although you can measure the effects of this curvature, you can't imagine what it looks like unless you can imagine 4D. Similarly, it's pretty easy to predict what a 3D ant would see if the third dimension were rolled up: just read Flatland. --140.180.248.141 (talk) 14:31, 8 April 2013 (UTC)[reply]
*Actually, our universe is very close to having no curvature, but the point is that it would be highly curved if the universe had more mass. --140.180.248.141 (talk) 14:31, 8 April 2013 (UTC)[reply]
Sure a one-dimensional space is meaningful. As I said, a space can be divided iteratively with an algorithm. If I systematically number all the bricks and you select the ith brick, I certainly have enough information to tell you, based on the algorithm used, what its exact neighbors happen to be. Its not necessarily as efficient as linear representations, but its fundamentally sound. As for the holographic principle, its my understanding that it came into play because string theorists discovered that their different dimensional models were related. --Modocc (talk) 14:40, 8 April 2013 (UTC)[reply]
That's not workable. Sure, you can turn a 2D chessboard into a 1D representation by numbering the squares from 1 to 64 - but for an arbitrary point on a 2D plane, you need two numbers...that's fundamental. You can't represent an arbitrary point on a 2D surface with one number - or in 3-space with less than three numbers...it's impossible. The multi-dimensionality of the universe isn't something you can argue away like that. SteveBaker (talk) 15:28, 8 April 2013 (UTC)[reply]
Its simply a matter of utilizing a different representation of a line, plane or volume. I can for instance divide a line into a grid of segments by mapping them to natural numbers, for exampple: {(O,1),(0,.5),(.5,1),(0,-.5),(-.5,-1),(0,1/4),...,(1,2),(1,1.5),(1.5,2),...} For a volume, you can systematically divide the bricks into smaller units likewise with each iteration as well as continue adding unit bricks to the perimeter of the space. Note that each element is uniquely numbered, whether it be a segment, area or volume and each has the exact same dimension as other elements. Also, although points and infinities are not represented, these are not even measurable. -Modocc (talk) 15:55, 8 April 2013 (UTC)[reply]
If you're only interested in labelling every point in nD space, you can just take the decimal representations of each coordinate (x, y, z, w, etc.) and then interleave them (e.g. (0.763, 0.184, 0.952) becomes (0.719685342)). That gives you a unique symbol number for every point in the space. Double sharp (talk) 16:05, 8 April 2013 (UTC)[reply]
It's better than that: you can take a single continuous 1-dimensional curve, and use it to fill up all of space. That's called a space filling curve. This doesn't change the fact that space is 3 dimensional, and that while it might be fun and interesting to represent space with a single real number, it has no physical significance. The 3D nature of space, on the other hand, makes a fundamental difference to the laws of physics. --140.180.248.141 (talk) 16:15, 8 April 2013 (UTC)[reply]
Working with most coordinate systems definitely makes for simpler laws! Although, I tend to distinguish between whatever space is that we measure (and other things as well) and our models or representations of it. -Modocc (talk) 16:35, 8 April 2013 (UTC)[reply]
I cannot see that the 2D ant on the surface of a cylinder works as a 2D analog of the 3D situation. We cannot readily detect that our 3D space is anything other than flat. The ant, on the other hand, will pretty rapidly detect that her second dimension is anything but flat simply by circumnavigating the cylinder. And yes, I have read flatland, and its completely useless for actually understanding anything and certainly doesn't deal with rolled up dimensions. SpinningSpark 15:05, 8 April 2013 (UTC)[reply]
It's not supposed to be a 2D analog - it's a 1D analog. One dimension with a "rolled up" second dimension. The ant in the analogy is a 1D creature - aware only of the direction along the length of the hosepipe. When the "rolled up" dimension around the circumference of the hose is large - then the ant can indeed detect that it's there so he knows he's living in a rather odd 2D world. But the rolled up dimensions envisaged by things like string theory are curved up much more tightly than that...the "diameter" of these extra dimensions would be microscopic...much, MUCH less than the diameter of an atom. The 1D ant can't perceive that he's walking around the circumference of the hose because the diameter is smaller than he can see or feel or anything.
I agree that "Flatland" is a horrible analogy - it's more about the political views (including horrific class bias and appalling misogeny!) of it's author - which are quite painful to read to modern eyes. He's also confused about how his 2D world works, talking about walls, doors and roofs of his 2D houses. A *MUCH* better book about that is "Planiverse" by A.K.Dewdney - I could spend hours looking at the drawings of 2D machines, musical instruments, spacecraft and such. How does a 2D creature eat and defecate without falling in half?! It's exceedingly well thought-out and the story/plot ain't bad either. SteveBaker (talk) 15:40, 8 April 2013 (UTC)[reply]
(What's wrong with class bias and misogyny? It gives you a perspective on a historical society, allowing you to be grateful for modernity.)
To expand on what SteveBaker said, I brought up Flatland because the entire point of a "curled up" dimension is that you don't know about it until you go to the smallest lengths. If we lived in a 3D world where the third dimension was curled up, for example, we wouldn't know about it, and it would look exactly like a 2D world, aka Flatland. --140.180.248.141 (talk) 16:15, 8 April 2013 (UTC)[reply]
Yeah - by all means read Flatland if you're interested in the weird political views of the time - but if you want to get a feel for how a 2D world might be - dump that book in the trash immediately!
If we lived in a universe with a 'curled up' extra dimension, then there are several possibilities:
If we had two normal 'flat' dimensions and the radius of curvature of the 3rd dimension was much larger than the size of the visible universe, then we'd be in a world pretty much exactly like the one we live in. Without some very fancy astronomy, we'd never know it. In fact, there is a good case to be made that all three of our spatial dimensions are really like that.
If the radius of curvature of a fourth dimension were much smaller than the diameter of an atom (as string theory suggests) then we'd believe that we were living in a 3D world - and it would be exceedingly hard to devise experiments to prove otherwise (which is why we can't prove or disprove string theory right now).
If the radius of a fourth dimension was something on a "human scale" - an inch...ten feet...a mile or two...even a few tens of lightyears - then the universe would be an exceedingly weird place. It's fun to try to imagine what that would be like...but it's clear that there are no hidden dimensions that work like that in our universe.
Oh, come on, Steve. Flatland is no more about the class prejudice and misogyny of the author, than A Modest Proposal is about the author hating Irish babies. Satire: how does it work? 86.161.209.128 (talk) 08:48, 10 April 2013 (UTC)[reply]
My original analogy (I was going to repeat it - but you dug it up from the archives!) helps me to understand it...but because we have such a hard time wrapping our brains around a universe with four or more spatial dimensions - it's truly necessary to pursue a lower-dimension analog. The "hose-pipe-world" of a 1D creature with a curled up second dimension goes some way to explaining what a curled up 4th dimension might be like. As we imagine the diameter of the hose shrinking down to something less than the creature can perceive, the 1D approximation of reality for that creature is perfect. Our 1D "ant" can only meaningfully move in 1 dimension and the existence of that curled up second dimension is just not noticeable to it.
It's true that to follow that analogy, we need to visualize the plight of our 1D creature as a 3D thing - that's because the concept of "rolling up" entails curving the second dimension into a cylinder - which is a 3D object. Hence we can't imagine a 1D world with a rolled up 2nd dimension by drawing it on a flat 2D plane (like a piece of paper).
That makes visualizing a 2D world with a rolled up 3rd dimension very tough for us...we almost need a 4th dimension in order to see it in our mind's eye. That doesn't invalidate the analogy...it just poses a problem for our imaginations.
I suppose we could try though:
Imagine a large room with a very low ceiling...a REALLY large room. The ceiling is so low that we have to crawl around on our bellies to be able to live inside it. This can be considered as something close to a 2D world for us. Let's turn off gravity too (in our mental world, it operates in the 3rd dimension and that confuses this analogy).
Now imagine that there are many holes in the ceiling and floors - and that something magical happens. When you move through a hole in the floor - you reappear through a nearby hole in the ceiling...and if you climb up through a hole in the ceiling, you reappear through a nearby hole in the floor. (Just like in that video game "Portal" if you put one portal in the ceiling and the other in the floor just below it).
But it's not really "magic". What's happening is that in this world, the 3rd dimension is curled up into a loop and the "circumference" of that 3rd dimensional loop is the same as the height of the ceiling...just a couple of feet.
For you, the act of travelling through one of these holes is *almost* like nothing happened...you moved just a foot or two in the third dimension and came back more or less where you started - so moving in the 3rd dimension doesn't do much to your position within the 2D room.
Now, imagine the ceiling getting lower and lower...the effect of falling through a hole (in the 3rd dimension) has less and less effect on you.
When the 3rd dimension is microscopically thin (and the ceiling is similarly insanely low) - then moving through that 3rd dimension is just like nothing happened. Imagine the ceiling is much lower than the size of an atom...that's how big these hypothetical "curled up" dimensions must be if they really exist.
Now, instead of holes, the ceiling and floor are completely permeable...you can pass through them at will at any point - looping around the 3d dimension and arriving back almost exactly where you started.
Beings in this world would not know that there was a 3rd dimension...they would assume that the ceiling had zero height (because it's too small for them to perceive). They wouldn't be able to see any distance through the 3rd dimension because photons would also loop around it and arrive back at the same place.
Now stretch the analogy to a 3D world - with a coiled up 4th spatial dimension. We can freely move in the 4th dimension - but the motion is so slight that we can't measure it - light might travel around this 4th direction - but the curvature is so tight that you can't tell. It's a small step from that to imagine many coiled up extra dimensions...dozens of them...enough to make string theory work in fact.
It's a bit of a mental stretch - but it can be done.
The analogy makes sense, but there's something that doesn't quite sit right. According to this analogy, if the three dimensions are equivalent, I should be able to shine a flashlight (or at the atomic scale, emit a photon) at an 80 degree angle toward the ceiling, and it should spend most of its time going up and around. So why don't we see random photons from a source moving more slowly than c? Wnt (talk) 16:10, 8 April 2013 (UTC)[reply]
I wonder that too. It's an interesting question. Perhaps the problem is that you can't arrange to launch a photon in that direction to start with...(naively - the flashlight won't "fit" into the extra dimension - so it has to point nearly parallel to the unwrapped dimensions) - so the error in speed is too small to measure. Are there processes which emit photons in completely random directions? I don't think so - but I might easily be wrong. SteveBaker (talk) 16:31, 8 April 2013 (UTC)[reply]
Since it is an analogy, I wouldn't worry too much about whether or not a flashlight or other stuff fits into it. -Modocc (talk) 17:28, 8 April 2013 (UTC)[reply]
Thanks Steve, that really does make a lot of sense to me. By the way, I realised your hospipe analogy was a 1D analog (as I think my original question makes clear) but I was replying to IP 140 who seems to be offering a 2D hospipe analogy which I still think doesn't work. By by the way, I have read Planiverse as well and agree it is much more interesting from an engineering perpspective, if not a literary one. SpinningSpark 17:15, 8 April 2013 (UTC)[reply]
I was offering the exact same analogy as Steve. The ant lives on the 2D surface of a garden hose, but one of the dimensions is contracted, so it's as if the dimension didn't exist. To the ant, the world seems 1D. I believe that's exactly what Steve is saying as well. --140.180.248.141 (talk) 19:06, 8 April 2013 (UTC)[reply]
Well in that case it wasn't an answer to my question - I already understood the 1D case as I thought I made clear - so its not surprising I was confused. SpinningSpark 21:22, 8 April 2013 (UTC)[reply]
I spent exactly 1 sentence going over Steve's analogy. My point was that in Steve's analogy, the ant's "universe" is 2D, but has one rolled-up dimension. The rest of my post is about why you can't visualize a "universe" that's 3D and has 1 rolled-up dimension: because in order to visualize the curvature of a 3D universe, you need 4 dimensions, just like how you needed 3 dimensions to visualize the ant's 2D universe. Then I explained what an inhabitant of such a 3D universe with 1 rolled-up dimension would see. They would see exactly what the Flatland inhabitants would see, because they'd think their universe was 2 dimensional. Steve said essentially the same thing later on, but in more detail. --140.180.248.141 (talk) 22:14, 8 April 2013 (UTC)[reply]
Well actually I can visualise it after Steve's explanation. SpinningSpark 23:18, 8 April 2013 (UTC)[reply]
Probably the wrong desk, but I figure someone here is most likely to know the answer. My question is, what's the proper way to deal with a retracted article when writing a publication. I'm writing a thesis about a topic which has previously been studied in an article which has since been retracted. So I need to mention this article. The options I can think of are:
Mention the article but don't put it in the refs.
Mention it and reference it normally.
Mention it and reference the retraction (what's the format for that!?)
Don't mention it all, despite them basically doing the same experiments as me.
I haven't found any official guidelines, does anyone know what the best approach would be?
I would reference the article as usual: however, I would mention the fact that the article has since been retracted, either in the body of the work, or in a footnote. If you have the date of the retraction, I think I'd put that at the end of the reference, something like this: "Article X, published in the Journal of Y dated xxx, retracted in the Journal of Y dated zz". --TammyMoet (talk) 14:25, 8 April 2013 (UTC)[reply]
I don't know about "official guidelines" but it seems to me that when a paper is retracted, it is precisely because the authors or publisher no longer believe it should be referenced. Our Retraction article states that: "In science, a retraction of a published scientific article indicates that the original article should not have been published and that its data and conclusions should not be used as part of the foundation for future research. ". For me, "should not have been published" means that you should not reference it...it has (effectively) been "unpublished" and should be considered not to exist - and "should not be used as part of the foundation for future research" is a strong indication that you shouldn't be basing anything on it - and therefore should have no cause to reference it. By referencing a retracted article, you're risking people asking whether your work was in some way based upon it - which would be a huge negative for your work. As our article further notes, if the problem with the paper were not extremely serious, a "correction" would have been published...even if the author says "we messed up, this is all wrong", that would typically result in a correction rather than a retraction. Retractions are generally reserved for serious issues like plagiarism or downright intellectual fraud...and such papers really shouldn't be referenced. SteveBaker (talk) 14:51, 8 April 2013 (UTC)[reply]
My view is that a retracted article should be treated as a primary source. You can cite it to support the fact that it exists and contains certain statements, but you can't cite it as a reliable source. For example in our article on the Schön scandal it would be legitimate to cite his retracted papers when explaining the claims that he made. (As a matter of fact, though, only the retraction notices are cited in our article.) Looie496 (talk) 15:14, 8 April 2013 (UTC)[reply]
Actually I misread the question to be about Wikipedia. For a thesis, I would simply cite both the article and the retraction notice. Looie496 (talk) 15:16, 8 April 2013 (UTC)[reply]
Steve Baker has a point, but I don't agree with his approach for all circumstances. You need to consider the possiblity that your reader may discover for himself the article, but not the retraction. Retractions sometimes come long after an article was published. Why was it retracted? Did they make a simple obvious error that got thru somehow? Or was it a very difficult to spot error that a competent work in the field of study would most likey make as well? Or was it retracted because the author(s) faked their data or something? Was it retracted in error - such things can happen? Such things are difficult to spot. You don't want a reader to rely on the retracted article and junk your work, for want of a sentence or two.
How you should cite it depends on what significance it has to your work.
If your thesis agrees with the article, I suggest you cite it normally and include it in the list of references, and include a discussion stating that it was retracted and explain why you believe the retraction should not have occurred. And cite and list the retraction (which I assume was in the form of a letter to the journal in which it was published).
If the article was retracted due to faked or incorrectly recorded data, and there are lots of other directly relevant references which support that the article was wrong, then I think Steve's approach is valid.
As with any writing, whatever the logic or rules may be, there is one fundamental rule: write for your reader. If it happens that whatever your thesis discusses has not had much prior work, and so the reader is certain to discover the article if he does some kind of a search, then you must cite it and list it in your References section, and you must make it clear in your text body it has been retracted (by who? the journal editors? or the author(s)?) and cite the retraction, and list that in your references section. In such a case, you ought to give your own view on the retraction, and summarise where the author(s) went wrong, in a footnote.
Retractions are often just letters to journal editors, but may be short articles. Either way, it makes no difference, cite and list it in the same way as any other reference.
I agree that you also have a point! This isn't simple. If you replace the word "retraction" with "correction" - then I absolutely agree with you. But retractions are supposed to be for such egregious problems that the work is beyond redemption. If (as our retraction article suggests) papers are mainly retracted because of:
Plagiarism - then you should obviously be able to reference the original article from which the material was plagiarized.
Duplicate/concurrent publishing (self-plagiarism) - then it's the same deal, just reference the original work.
Serious errors amounting to scientific misconduct. Well, that's the tough one. Did the serious errors result in a paper that's totally devoid of value? You'd think so, or else a simple "correction" would have been released. The tarnished reputations associated with a retraction are sufficiently great that you'd imagine people would fall over themselves to issue a correction notice rather than retracting the entire work.
So I think the only reason to mention a retracted paper at all would be in the context of "Don't read this - it was retracted"...in which case, I'd reference the retraction notice rather than the paper itself. Remember, people often judge the worth of a paper by the number of people who referenced it - and you want to boost the notoriety of the retraction, not lead people to offer undue respect to the original paper.
The tricky corner case (and this case might fall into that category) would be when you re-did an experiment from a retracted paper - but did it "right" this time. You'd certainly want to avoid someone saying "Oh - you did it *that* way? Didn't so-and-so get their paper retracted for doing that?"...so perhaps there is a case then for explaining how come your version is acceptable. But that leads me back to wondering why a simple experimental, numerical or statistical slip up of a kind that you could fix, would result in a retraction rather than a correction of the original paper.
This is gut feeling: I don't think anyone has the right or ability to dictate good practice on this issue. I am inclined to discard the argument about inflating statistics of a retracted paper out of hand. It doesn't matter what its statistics are. That said, it would depend on the citation. If you're writing that "a widely-disseminated finding that Foo1 strongly represses Bar7 was subsequently retracted", the retraction should be enough. If you're writing that "despite the retraction of Joe Bloggs' group's work for an unrelated misconduct issue, their technician was not implicated in the matter, and we were able to replicate his high-quality immunoprecipitation data for Foo1 with an aliquot the group provided us and have subsequently confirmed the identity of the antigen with a commercial antibody", then cite both paper and retraction at the appropriate places in the sentence. Wnt (talk) 19:33, 8 April 2013 (UTC)[reply]
I If a part of the article was not up to the desirable standard, then the journal, the institution or the author would issue a partial retraction. For smaller stuff, an errata or a correction would suffice. For bigger stuff, like being marred by fraud, a total retraction. That already means that the data is not reliable, so don't use it. As [[1]] point out, citing a retracted article without knowing about it can be embarrassing. But what you are doing is citing it although you know it was retracted. That's bad practice. Don't worry about anyone finding the article anyway, since it won't be present in electronic resources. And don't worry about re-using an idea from a retracted article, since it is not copyrighted. OsmanRF34 (talk) 20:00, 8 April 2013 (UTC)[reply]
I'm concerned about your last sentence. As far as I know, copyright applies to retracted articles. I've never seen anything in copyright law that says otherwise. SteveBaker (talk) 20:42, 8 April 2013 (UTC)[reply]
The 'it' in my last sentence refers to 'idea' not to 'retracted article.' I know that the retracted article gets its copyright at the time of writing. However, no matter what flaws it had, I think the OP saw something of value in the retracted article, but it's not sure how to use it. I just meant that ideas as such are not copyrighted. If someone had a good idea and used a novel procedure, but didn't know how to implement it and massaged the data to make it 'work', then the paper will be retracted, but you still can use the same procedure in the right way. OsmanRF34 (talk) 21:27, 8 April 2013 (UTC)[reply]
It's not apparent from his question whether the OP's thesis will be about pure research or applied research. Its also not apparent whether the retracted article was published in a peer-reviewed journal having a board of editors and high repute, or a commercial journal put out by a magazine publishing company (some are peer reviewed and/or subject to subject matter expert editorial reveiew, or even a company house journal. House journals have ranged from mere carefully written advertising through to publications of very high repute, such as Bell System Technical Journal and Australian Telecommunications Research.
For research papers printed in peer reviewed journals of high repute, the probability of human error causing invalid data or invalid conclusions is low. So retractions are unusual and for serious reasons, such as faked data or other fraud. So you should carefully consider whether to ignore or cite a retracted article for the reason that Steve Baker gave.
However, plenty of articles published in commercial journals and occaisonally house journals have relavence to thesis and peer reviewed jornal articles. In commercial journals, human error can be significant, and retractions due to human error and not a deliberate attempt to defraud are relatively common, as are debates and opposing views in the form of Letters To The Editor. In such cases it is often of great value to cite both the article and the retraction, and discuss the error. Often, the error is such that another worker, expert in the field, could also make the same error and in some cases, most likely would.
You just can't be serious if you suggest that any search of the literature on a subject will always bring a reader's attention to retractions. — Preceding unsigned comment added by 124.178.45.169 (talk) 03:27, 9 April 2013 (UTC)[reply]
OsmanRF34, I'm concerned about a lot of what you wrote there. "Don't worry about anyone finding the article anyway, since it won't be present in electronic resources" just isn't true, in most cases. In the biomedical sciences, for instance, retracted articles aren't deleted or hidden from PubMed searches, but the articles are clearly annotated as 'retracted' and a reference to the retraction notice is provided. Publishers often don't delete retracted papers from journal websites, but good journals will indicate clearly – in tables of contents, abstracts or summaries, and ideally as a conspicuous notation or watermark on the PDF of the paper itself – that the paper has been retracted. Telling a reader "don't worry about re-using an idea from a retracted article, since it is not copyrighted" is missing the point—plagiarism and copyright violation are two distinct forms of misconduct that sometimes but not always overlap. (This is a problem we regularly encounter on Wikipedia, actually; there's a common misconception that one can copy as much as one likes from a public domain work without attribution, because copyright isn't engaged.) TenOfAllTrades(talk) 13:03, 10 April 2013 (UTC)[reply]
While the standards and expectations may vary by field, I'm reluctant to endorse the scorched-earth, down-the-memory-hole, it-never-happened-and-we-shall-never-speak-of-it approach. Suppose Smith et al. did (what would or should have been) an interesting experiment, but had to retract their results because they unwittingly used a contaminated reagent or defective instrument that wasn't caught in the peer review process. If Jones et al. decide to repeat Smith's experiment because Jones thinks it was a sensible, elegant approach, likely to make a worthy contribution to human knowledge, it strikes me as both deceptive and unethical for Jones not to give credit to Smith for (in effect) providing the design for Jones' experiment. Using someone else's work – published, retracted, or otherwise – without giving appropriate credit is serious academic misconduct.
The Committee on Publication Ethics offers guidelines for retractions: when they are appropriate, how they should be reported and handled. In particular, 'disappearing' a retracted publication is strongly discouraged; instead, a publication's retracted status should be made clear, but it should remain available on the record. (Ideally with an explanation for why the retraction took place, though most journals are disappointingly vague on this point.)
This paper presented at an ACRL conference offers an interesting look at what happens to the citation of papers post-retraction. Troublingly, they often continue to be cited without any indication of their retracted status, possibly because the citing authors are unaware of the retraction. Very interestingly, the paper's authors identified at least four cases where a retracted clinical study had been identified and considered for inclusion in metaanalyses (as it otherwise met the inclusion criteria laid down for incorporation into the metaanalysis; the retraction occurred because the study's authors had not received proper institutional review board approval, rather than due to any technical flaws in their work). Two of the metas discarded the study's findings as fruit of a poisoned tree; two incorporated the study's data anyway—though it's not clear whether or not these authors were fully cognizant of the studies' retractions.
It seems that a reasonable and generally-accepted method of citation is to use a normal citation format, but indicate clearly (ideally both in the text and in the references section) that the paper has been retracted. A good format might be the one used in this PLoS ONE article: the footnote number is followed by the annotation (paper now retracted) at its first appearance in the Introduction and Discussion sections, and the reference is followed by [retracted] in the references list. TenOfAllTrades(talk) 22:51, 9 April 2013 (UTC)[reply]
H 3O+ ion is a proton donor and therefore a Bronsted acid. OH− ion is a proton acceptor and therefore a Bronsted base. Ruslik_Zero 19:30, 8 April 2013 (UTC)[reply]
Acidity can be explained many ways. There are at least three prominent theories of acid-base chemistry, so you need to consider which theory you are working within before answering the question of "How does..." something about acids and bases work. It entirely depends on which model you're working within. None is wrong, but they are all different, and have their different uses. Acid–base reaction#Common acid–base theories explains all three. Incidentally, HCl is an acid according to all three theories.
The Arrhenius theory explains acids and bases based on the ability of a substance to produce certain ions in water solution. So, if something is added to water and produces hydronium ions, it is an acid, while if something is added to water and produces hydroxide ions it is a base. The basic definition of pH comes from Arrhenius theory, as it is based on ion concentrations in water solutions.
The Brønsted–Lowry theory explains acids and bases in relation to each other rather than to water, removing the restrictions of having water present to explain acids and bases. According to Brønsted–Lowry, an acid and a base are defined based on their place in a "model" reaction:
HA + B ⇌ A- + HB+
whereby HA is an acid, and B is a base. On the product side, A- and HB+ are called conjugates of the reactants, thus A- is the conjugate base of the acid HA, and visa-versa. Conjugate acid-base pairs explain Buffer solution behavior, for example. In the case of the reaction:
HCl + H2O ⇌ Cl- + H3O+
HCl is behaving as the acid, while H3O+ is the conjugate acid of the H2O.
Lewis theory explains acids and bases based on the formation of new covalent bonds. The Lewis acid-base reaction is based on electrons which migrate from species with excess electrons (usually in the form of unbonded pairs of valence electrons, or sometimes as pi bonds) towards a species that is electron deficient. The thing with the excess electrons is called the "lewis base", while the thing that is electron deficient is the "lewis acid". In this case the newly-created bond is between the hydrogen atom from the HCl molecule and the oxygen atom in the water molecule, that hydrogen atom being the lewis acid (being bonded to the more electronegative chlorine makes the hydrogen electron deficient) while the oxygen atom has excess electrons in the form of unbonded "lone" pairs, the new O-H bond that turned water into hydronium being the focus of the Lewis theory definition of acids and bases. I hope all of this helps. --Jayron32 19:54, 8 April 2013 (UTC)[reply]
So equilibrium does not exist in Arrhenius or Lewis Theory? Why isn't the relationship between metals such as NaOH (or other hydroxides such as KOH) and NaCl the same?
Who said equilibrium concepts didn't exist in Arrhenius or Lewis? I certainly didn't. Also, I'm not sure I follow your question regarding metals and hydroxides is. Could you restate it or elaborate what you're asking about? Also, it is quite different from redox: redox reactions are those which change the Oxidation state of an element. Acid base reactions don't change the oxidation state of anything (if you follow the formal rules for assigning oxidation number to atoms in any acid-base reaction, you'll find that none of them involve changes in oxidation state). But if you could restate your first two questions in detail: what exactly do you not understand or what do you need answered, that'd be great, because I can't follow what you're asking here. --Jayron32 04:21, 9 April 2013 (UTC)[reply]
Clarification for Question 1: In my grade 12 chemistry, the equilibrium sign (⇌) indicated a reaction is reversed and forward in real time. I don't remember Arrhenius and Lewis (acid-base) reactions having the possibility of reversing.
Clarification for Question 2: For example: Na+ + Cl− -> NaCl. Why can't acid-base theory(s) be applied to such a reaction (such as Cl− considered an acid (or base)).
1:Equilibrium just means that the species in the reaction are not static; that there is a dynamic interaction between a series of reversible reactions whereby the reactants (as written) make the products and the products make the reactants; but where the end result is a situation where the relative concentrations of the species are stable, even if they are continuously reacting. There is nothing in Arrhenius or Lewis theory which denies the reality of this dynamic process. I'm not sure where you got notion that somehow they denied the existence of equilibrium, that the meaning of a double arrow in one specific equation in my explanation somehow could be interpreted to mean that the other theories someone denied this reality. It is perplexing how you jumped to that conclusion, but let me assure you, they do not. I don't know what more to say on the matter as I still can't find the leaps of logic that lead to that conclusion. All three theories are compatible with observed behavior, and the reality of equilibrium is not denied by any of them.
2: They could be, specifically (and in this case only) Lewis theory explains this in terms of acid-base reactions. In the case of the reaction you just gave, Sodium is a Lewis acid and Chloride is a Lewis base. Lewis theory is decidedly more broad than the other theories. Basically, Lewis theory contains B-L theory as a special case where the acid is always the hydrogen ion, whereas B-L theory contains Arrhenius theory as a special case where one of the two reactants is always water. You can look at the three theories as building on each other, progressing from the more restrictive (Arrhenius) to the broader (Brønsted–Lowry]] to the even broader still (Lewis). But they all still work together. For example, if you place Iron (III) Chloride in water, you get a solution with a low pH. Arrhenius theory would call this an acid, unambiguously. Lewis theory explains this by showing how Iron acts as a Lewis acid, by forming Coordination complexes with hydroxide (a Lewis base) and leaving behind excess hydrogen ions. To bring it back in for simplicity's sake, Lewis theory is a "special case" and generally, when we call something an "acid" in an unqualified manner we're usually speaking about it from the perspective of Arrhenius or B-L theory; "acids" are basically molecules that give up H+ ions easily. If we want to indicate something which behaves like an acid according to the Lewis model, but not in the other models (like the Na+ in your example), we usually use the term "Lewis acid" to indicate we're using that definition, that is if something is a Lewis acid, but not a B-L acid, we always use the qualifier "Lewis" acid. Unqualified, the word "acid" always means B-L acid or Arrhenius acid (i.e. either something that is a proton donor or something that produces a low pH in water). In some contexts, a Lewis acid is called by the name electrophile, while a Lewis base is called by the name nucleophile; these terms are near perfect synonyms, and the "electrophile" and "nucleophile" terminology developed to avoid confusion with the terms "acid" and "base" (when referring to the B-L theory, for example). But that's just a semantic or linguistic distinction.
3:Because redox reactions operate under different conditions and produce different results. As I already noted, redox only involves those reactions where the oxidation state of an element is different on the product side than it is on the reactant side. In acid-base reactions, there is no change of oxidation state, so they aren't redox reactions. You can prove this to yourself by using the rules for assigning oxidation number to any acid-base reaction. Let's use those rules on the one you gave in the very first bit:
HCl + H2O ⇌ Cl- + H3O+
On the left side, in the HCl, the H has an oxidation number of +1, the Cl has an oxidation number of -1. In the water molecule, the H has an oxidation number of +1, the oxygen has an oxidation number of -2. On the right side the lone Cl ion has an obvious oxidation number of -1, and in hydronium the H has an oxidation number of +1 while the oxygen has an oxidation number of -2. Since no atom has different oxidation numbers between the left and right sides, there is no redox reaction.
Does all of that work? --Jayron32 18:16, 9 April 2013 (UTC)[reply]
Responses:
In response for Question 1: I thought → stated reactants on the left and products on the right. I guess maybe my teachers were wrong!
General response: What I don't understand is why Bronsted theory is required. I am trying to grasp the concept, but why does one compound: water, make a chemical theory, that being Bronsted theory, required?Curb Chain (talk) 20:08, 9 April 2013 (UTC)[reply]
(undent)As written, for the purpose of doing things like calculating equilibrium constants, the term "reactants" is always used for what is written on the left side of the equation even if, fundamentally, as written the reaction is not "extensive". Its just a terminology thing. Secondly, I think you mean Arrhenius theory. Water is not a necessary component in B-L theory. The reason why water-based solutions are part of Arrhenius theory is that's what Arrhenius based his much of his life's work around. He's actually famous for two things: The Arrhenius equation in kinetics, which isn't relevant to our discussion, and the concept of ions, which is. The modern understanding of what an ion is and how it works is all Arrhenius. the concept was actually first discovered and named by Michael Faraday, but he had no idea what they were or how they worked. Arrhenius worked out what is known as the dissociation theory of ions in water, that's what he won the 1903 Nobel Prize in Chemistry for. His theory explains the behavior of what we now know as electrolytes or ionic compounds by their behavior when they dissolve, or more properly dissociate, in water. His acid-base theory is merely an extension of that work, he explains acids and bases based on the concept of Self-ionization of water, which is part of his dissociation theory of ions. pH, which is just a measure of ionic strength of H+ ions, comes out of that explanation. So, Arrhenius's definition is based on water-based ions because that's what he did. As they say, if what you have is a hammer, you see every problem as a nail. Arrhenius explains acids and bases in terms of relative ionic strength in water, based on the equilibrium of the self-ionization reaction: acids (by Arrhenius) shift the equilibrium towards the hydronium side, while bases shift the equilibrium towards the hydroxide side. But the concept is intimately tied to water. Brønsted and Lowry, working some three decades later, take Arrhenius's basic model and generalize it by removing water as a necessary component. They explain acids as H+ donors and bases as H+ acceptors. Now, the Arrhenius theory is fully integrated into B-L theory as a special case whereby either the B-L acid or the B-L base is water; water is thus an amphoteric substance because it can do that. But B-L theory works to explain acid base reactions in other media, thus removing the need to explain it in context of water. For example, here's a reaction you could do fairly easily with materials in a H.S. chemistry lab:
NH3(g) + HC2H3O2(g) --> NH4C2H3O2(s)
What you do is get a container of highly concentrated ammonia solution, a container of "glacial" (highly concentrated) acetic acid, and open them inside a big glass box, like an aquarium, and what you'll see is a white powder forming in the air between the two containers. What you have here is a gas-phase Brønsted–Lowry acid-base reaction: The ammonia molecule "accepts" an H+ ion from the acetic acid molecule, forming ammonium ions and acetate ions. These ions instantly crystalize out in midair (since there's no water to dissolve them) and you get a "smoke" of ammonium acetate crystals forming. But this is an example of where B-L theory is able to more completely model acid-base reactions by expanding the definition beyond that of water-based solutions. Does that answer your questions? --Jayron32 21:32, 9 April 2013 (UTC)[reply]
So you are telling me that Arrhenius requires water (such as diluted (with water) hydrochloric acid). But how does Brønsted–Lowry theory explain Na+ + Cl− → NaCl as reaction between an acid and a base?Curb Chain (talk) 23:17, 9 April 2013 (UTC)[reply]
It doesn't. That isn't an acid-base reaction according to Brønsted–Lowry theory. Only according to Lewis theory. Remember, each theory in succession acts to expand upon the definition of acids and bases that the previous theory established. The oldest (and most restrictive) Arrhenius theory is expanded upon by the broader, and more inclusive Brønsted–Lowry theory, while Lewis theory is yet again more inclusive. There are thus chemical reactions (many, indeed) which are acid-base reactions via Lewis Theory that would not be so recognized by Brønsted–Lowry theory, but the reverse does work: every Brønsted–Lowry theory acid-base reaction is also a Lewis theory reaction. --Jayron32 03:34, 10 April 2013 (UTC)[reply]
Oh, so when we learn about these 3 theories, we are learning about the history of science. Arrhenius should not be learned, because it is not inclusive (when compared with Bronsted), and Bronsted should not be learned, because it is not inclusive when compared with Lewis. Why shouldn't we just learn Lewis, at least from a young age? So when something is very acidic and or very basic, shouldn't we just say it is very corrosive, or in some cases, reactive?Curb Chain (talk) 17:14, 10 April 2013 (UTC)[reply]
NO! Arrhenius theory is a very useful theory. You don't "ignore", you use it because it is useful. Without Arrhenius theory, you have no concept of pH, so you cannot merely pretend as though it doesn't exist. Likewise, Bronsted theory is highly useful in looking at proton-transfer reactions, which are very common and exist all over the place. No, the point is not that the older, more restrictive theories aren't useful, it's just that each of the three models takes a different perspective on acids and bases. They're all useful insofar as they allow you to gain an understanding of how acids and bases work in some way. You can't merely "not learn" the older theories, or treat them as historical artifacts, because they are useful. The only purpose of a model or a theory is to be useful. Those are all useful, so we learn all three. That would be like claiming that since the invention of the car, there's no point in teaching children to walk anymore. Regardless of the invention of more advanced means of locomotion, walking is very useful. Likewise, though Lewis theory is more advanced and modern, it doesn't make the older theories obsolete. --Jayron32 02:45, 13 April 2013 (UTC)[reply]
AIDS in non-human animals
disease like AIDS will affect the other animals as they sexually related to more than one opposite partner? — Preceding unsigned comment added by Titunsam (talk • contribs) 17:19, 8 April 2013 (UTC)[reply]
As our HIV/AIDS article explains, HIV originated in chimpanzees, and similar diseases have been found in other primates. So yes, it is possible. Looie496 (talk) 18:02, 8 April 2013 (UTC)[reply]
Does Challenger 2 and M1 Abrams have composite armor at their hull sides or it is only at the front of the hull ? — Preceding unsigned comment added by Tank Designer (talk • contribs) 19:55, 8 April 2013 (UTC)[reply]
Don't know about the Challenger, but our Abrams has composite armor all around. 24.23.196.85 (talk) 05:56, 9 April 2013 (UTC)[reply]
I'm pretty sure that the composite armour is used on all parts of both tank types. The thickness presumably varies between different parts of the tank though given that this is a standard part of tank design. Nick-D (talk) 12:01, 9 April 2013 (UTC)[reply]
Thank you everyone , but what about Russian T-72, T-80, T-90 I think they don′t have composite armor at their sides — Preceding unsigned comment added by Tank Designer (talk • contribs) 14:07, 9 April 2013 (UTC)[reply]
I happen to be knowledgeable on Russian tanks (being a Russian-American), and I know that all models of the T-80 and T-90 have composite armor, as well as the later models of the T-72. The early-model T-72s had plain hardened-steel armor, though. 24.23.196.85 (talk) 04:38, 10 April 2013 (UTC)[reply]
Very good , but why in the war of Chechnya the rebels were able to destroy the T-72 and T-80 by only using rpg-7 against side armor and exploding the ammunition of the tanks , that means the side armor is very weak to be not able to repel an rpg-7 round — Preceding unsigned comment added by Tank Designer (talk • contribs) 14:55, 10 April 2013 (UTC)
I remembered an important question , why russian army cancelled the T-80 tank from the ground forces ? (please don′t understand my questions to be aggresive) — Preceding unsigned comment added by Tank Designer (talk • contribs) 08:28, 11 April 2013 (UTC)[reply]
(1) This is not so much a question of armor as that of ammo storage -- both the T-72 and T-80 have all their shells (along with the highly explosive combustible-cased propellant charges) stored in the turret crew compartment, unlike our M-1 Abrams in which the shells are in a separate compartment at the rear with an armored partition between it and the crew compartment. So even if a shell or an RPG pierces an Abrams tank's ammo compartment and detonates the ammo, the tank could survive -- whereas if the same thing happens to a T-80, it would get blown to atoms along with the whole crew. (The Russians never did care much about the well-being of their servicemen, obviously.) (2) The T-80 burned too much gas, and broke down too often -- this is why it was retired from service. 24.23.196.85 (talk) 21:58, 11 April 2013 (UTC)[reply]
Thank you very much
not to be annoying, but had more question... (concerning hydrocarbons)
collapsing copy-paste of archived section without wiki-formatting. Looie496 (talk) 20:23, 8 April 2013 (UTC)[reply]
The following discussion has been closed. Please do not modify it.
There are oil eating microbes, and hydrocarbon seep communities, and studies that show that a large percentage of hydrocarbons on the surface are fossil derived. I am casually investigating the possibility that we are negatively affecting our organic fertility by over-harvesting fossil fuels. The "hypothesis" is that fossil fuels, while in the ground, are part of the "microbial food chain", which is in turn responsible for such aspects as soil fertility. The proposed issue is that by oil pumping, coal mining, and gas pumping (lately "fracking") are causing a loss in the ecological capabilities of harvested regions. So, fossil fuel harvesting might be contributing to desertification. As there is less food for life, there is less life. — Preceding unsigned comment added by 134.29.38.118 (talk) 20:14, 1 April 2013 (UTC)
An interesting proposition, but your entire post amounts to a statement. This Reference Desk is intended for asking questions to which responders can give (preferably referenced) factual answers: did you have a question? If so, please ask it explicitly. Conversely, this Reference Desk is not intended for hosting debates and discussions, or soliciting opinions, so if your post was an implied invitation for either of these, it is inappropriate here. {The poster formerly known as 87.81.230.195} 90.197.66.100 (talk) 21:23, 1 April 2013 (UTC)
I think the implicit question is reasonably clear, but I can't see how that could work out. Soil fertility is determined by the top few feet of soil (often much less), but hydrocarbons are found much farther down. Also some of the most fertile soils are found hundreds of miles from any known hydrocarbon deposits. Looie496 (talk) 21:46, 1 April 2013 (UTC)
Agreed. Also, fracking is a problem precisely because it contaminates the groundwater with hydrocarbons, which, under this theory, would be a good thing. StuRat (talk) 22:45, 1 April 2013 (UTC)
...assuming that the other chemicals associated with fracking are OK. Of course, having seen what happens to plants when they are exposed to crude oil, I have my doubts about this whole concept. --Guy Macon (talk) 00:09, 2 April 2013 (UTC)
In response, pollution is unnatural. Natural hydrogeological blah blah would run the hydrocarbons through bacteria, and each step would take them through some modification very slowly, but very steadily. Pollution just puts refined and broken hydrocarbons where they weren't before. There certainly are bacteria all the way up and down, we've got a lot of articles on it over the last decade or so. There are also hydrocarbon seep communities, which are unique, but then food for passing life, and what I'm talking about is basically hydrocarbon seep, but rather than through a hole or fault, just slowly via osmosis. — Preceding unsigned comment added by 66.188.222.186 (talk) 01:52, 2 April 2013 (UTC)
It takes a very special class of organisms to use hydrocarbons as their main source of food; most other organisms (including all multicellular plants and animals) not only cannot use hydrocarbons in this way, but are positively harmed by them, either directly (acute toxicity, sunlight deprivation for aquatic plants, clogging of gills in fish and of feathers in birds, etc.) or indirectly (increased BOD caused by proliferating extremophile bacteria, possible infection by same, etc.) So, in other words, an oil spill is a VERY bad thing -- and in fact, for some of the same reasons that phosphate runoff is a bad thing (which would have been a "good thing" by the OP's reasoning, too). 24.23.196.85 (talk) 01:02, 3 April 2013 (UTC)
start unanswered....
Ok, so it does indeed take a very special class of organisms to use hydrocarbons. The place we originally found them was in the reserves or in hydrocarbon seeps. I'm ballparking. When there has been an oil spill, probably (I recall) microbes then did also proliferate in these locals, and utilize these hydrocarbons. modern science has made strains that are more rapid in their use of the hydrocarbons. rewinding, and commenting also on the soil fertility. it's true, we measure fertility in the first few feet of soil, but the hydro-logical cycle of the subterranean environment means that much more of the earth has an impact on the small region which is this few feet. If there is a water table 60 feet below the surface (Depending on other geological formations) it will have an impact on the soils conditions. I am suggesting that likewise, having gas shale (such as in minnesota) 60 feet below the surface would also have an effect, and here's why. Naturally occurring within the shale are hydrocarbon "eating" microbes, which then convert the hydrocarbons into other forms of organic matter. Through osmosis, and other hydro-logical activity, some of the contents of the shale would be released towards the surface. Although this would occur very slowly, and very little at any given time, it would be like the growth of any other permanent, fixed organic community, and very continuous. My QUESTION is mostly is this accepted as common understanding, and why or why not, and what science supports our common understanding? btw, I am the original poster... thanks! — Preceding unsigned comment added by 66.188.222.186 (talk) 20:03, 8 April 2013 (UTC)[reply]
Fertility is mainly determined by levels of nitrogen, phosphorus, and potassium, along with proper pH and absence of plant toxins; see NPK rating. None of those are present at significant levels in oil or natural gas. There is lots of carbon, but plants get their carbon from atmospheric CO2, not from the soil. Looie496 (talk) 20:33, 8 April 2013 (UTC)[reply]
To answer your question: No, this is not the common scientific understanding. Your ideas are vague and hard to understand, so I cannot say exactly where you go astray of the common consensus. Though bacteria that metabolize hydrocarbons are fascinating (and currently highly studied), there is no "textbook" support for the notion that they make meaningful contributions to the biogeochemistry of terrestrial ecosystems. See also soil fertility and soil biology. As the latter article points out, this is still a very active field of research, and there are certainly things we still don't understand about the ecosystem ecology of the deep earth. SemanticMantis (talk) 02:08, 9 April 2013 (UTC)[reply]
Also note that oil, gas, and coal reserves are millions of years old, so, if they were being eaten at a significant rate, they would be gone by now. The conclusion, they can't possibly be eaten by microbes at a significant rate, at least while sequestered underground. Once on the surface, where sunlight and other forces can assist in the breakdown, then the bacteria can go wild on it. StuRat (talk) 04:57, 9 April 2013 (UTC)[reply]
Orange dwarf stars left main sequence yet
Did any orange dwarf stars left their main sequence stage yet? I thought 0.8 solar mass stars might have left main sequence. Is 0.8 sun like star or is it more like a orange dwarf star? I am confused a little bit. Because stellar classification said orange main sequence stars are between 0.6 and 0.9 solar mass, orange dwarf detailed article said it is 0.5 to 0.8 solar mass. When orange main sequence stars leave main sequence do they go to a red giant? If it goes to a red giant, will it be s smaller sized red giant, or about the similar orb as if sun might go through. When red dwarf leave its main sequence will it become a red giant? Or we don't know what will happen to these red dwarfs when it leaves its main sequence, or more likely they will shrink straight to white dwarf. I am not sure what is Subdwarf B and A is for. If that what red dwarf or orange dwarf might end its life?--69.226.42.134 (talk) 23:27, 8 April 2013 (UTC)[reply]
"According to computer simulations, the minimum mass a red dwarf must have in order to become a red giant is 0.25 solar masses; lesser massive objects, as they age, increase their surface temperatures and luminosities becoming blue dwarfs and from that finally become white dwarfs."
We only have computer simulations, since it will be 10s of billions of years before the first red dwarfs start to die.
An Orange Dwarf is a main sequence star - see K-type main-sequence star. The mass ranges are estimates, so different sources will give slightly different figures (although we should try and be consistent between Wikipedia articles...), but they are describing the same stars by a different name. That article says they remain on the main-sequence for 15-30 billion years. The universe is about 14 billion years old, so presumably none of them have left the main-sequence yet. When they do, I think they will become red giants, although our article doesn't say so (if yellow dwarfs do and large red dwarfs do, then orange dwarfs that are somewhere inbetween presumably will as well). --Tango (talk) 11:15, 9 April 2013 (UTC)[reply]
The speed of evolution depends on metallicity. Population II stars having low metallicity evolve faster than Sun-like stars. The population II stars within the mass range 0.8–0.9 Solar masses, which formed about 13 billion years ago, now undergo red giant phase. See for instance HE0107-5240, which is a red giant. Ruslik_Zero 18:55, 9 April 2013 (UTC)[reply]
Evolution of higher mass stars
I am confused about the white dwarf, neutron star and black hole stuff. I thought stars between 1.5 and 3 solar mass suppose to end to a neutron star. When a larger white main sequence star leave main sequence does it become a bright giant or only it becomes a red giant. I thought white main sequence stars (2 or 3 solar mass) will eventually become a red supergiant, or before it hits supergiant it has to go through red giant first? I always learn when large blue stars (between 3 to 8 solar mass) runs out of hydrogen it suppose to become a red supergiant. I wonder how can a blue main sequence stars (3 to 8 solar mass) become just a red giant? I thought they will eventually hit a red supergiant. i am not sure how will they end up with a white dwarf. Or before they reach neutron stars or black hole they will have to go through white dwarf first. I always learned that white and blue main sequence stars end life in neutron star or black hole. --69.226.42.134 (talk) 23:38, 8 April 2013 (UTC)[reply]
Neutron stars are that size but they are the small remnants of massive stars after they supernova. Stars which start out that size end up as white dwarfs. At least as far as I can tell from our articles which could be more clear about mass ranges. Rmhermen (talk) 03:20, 9 April 2013 (UTC)[reply]
April 9
Colour of water
Hi, there was a question once at Colour of water about why the water in the pool in the image at the right looks equally blue regardless of whether one is looking through a few centimetres (at the edge of the pool) or several feet (in the centre of the pool). "Common sense" would suggest that the more water you looked through, the bluer it would be. AFAIK, no satisfactory answer was ever provided. Does anyone have an explanation? 86.171.43.156 (talk)
Water is very faintly blue (or blue-green, in the case of sea water). So, a small amount of it will appear clear, unless blue dye has been added or something blue is behind it, like the bottom of the pool painted blue. In your example, the water in the bucket certainly doesn't look as blue. StuRat (talk) 03:00, 9 April 2013 (UTC)[reply]
When water is deep enough, it appears black. Plasmic Physics (talk) 03:19, 9 April 2013 (UTC)[reply]
I don't see how any of that answers the question. Why does the water in the bucket look much less blue than the same thickness of water at the side of the pool? (We take it on trust that the pool is tiled throughout with the same white tiles as are visible around the edge.) Why does the deepness of the blue not reduce dramatically at the sides of the pool where you are looking through an increasingly small distance of water? 86.171.43.156 (talk) 03:35, 9 April 2013 (UTC)[reply]
What do you mean? Stu just answered that in a direct manner, what part of his answer do you not understand? Plasmic Physics (talk) 03:48, 9 April 2013 (UTC)[reply]
I think they're saying that there is a point near the wall where you are only looking through as much water as is in the bucket, yet it looks far more blue. I suspect the answer is simple scattering. The water in the pool is all scattering the blue reflected off the bottom of the pool. Since the bucket is opaque and white, it will look far more clear. Vespine (talk) 04:05, 9 April 2013 (UTC)[reply]
(ec) I think I understand. He was assuming that the light 6 inches below the waterline shines straight in 6 inches, hits the edge of the pool, then reflects right back out of the pool, just as it does in the bucket. However, most of the light that hits 6 inches below the waterline is reflected downwards to the bottom of the pool, while other light reflects back up from the bottom of the pool, hits that spot 6 inches below the waterline, and back out again. Thus, this light has traveled through a lot more than 1 foot of water total, and had the redder waves absorbed, leaving a distinctly bluish tint.
A horizontal, opaque, white surface, 6 inches below the waterline, should appear white, not blue. StuRat (talk) 04:09, 9 April 2013 (UTC)[reply]
According to the caption the bucket is floating. Thus, the depth of water in the bucket is not the same as that in the pool. SpinningSpark 11:27, 9 April 2013 (UTC)[reply]
The meltwater pool on top of a glacier does look very blue. [2] --Stone (talk) 08:09, 9 April 2013 (UTC)[reply]
I think it's because your pool has a blue liner and your bucket is white. Also, if you ever look at a large swimming pool with a diving-depth deep-end it is noticeably bluer. There are also effects from disinfectants in the water, especially pools, depending on what you use. Some municipal water supplies have a greenish tint for this reason. Shadowjams (talk) 14:05, 9 April 2013 (UTC)[reply]
As I mentioned above, "we take it on trust that the pool is tiled throughout with the same white tiles as are visible around the edge". If that is not the case then all bets are off. 86.128.0.95 (talk) 17:23, 9 April 2013 (UTC) Also, the effects of tints in the water do not seem relevant to the question of why the water looks very blue right to the edge of the pool, or why the bucket (assuming it is the same water as is in the pool) is much less blue than when looking through equivalent distance of water at the edge of the pool.[reply]
It looks to me like the white tiles only go 4 rows below the edge (5 if you include the edge tiles). StuRat (talk) 17:28, 9 April 2013 (UTC)[reply]
I agree it seems a bit odd that you can't see any trace of the tile divisions below the waterline, but I still believe that the tiling (or, probably, imitation tiling) stretches down into the pool. What do other people think? 86.128.0.95 (talk) 17:55, 9 April 2013 (UTC)[reply]
Well, we're questioning the very premise of your question, and now you're trying to fiat a basic premise of the facts. I do think water in fact will scatter more light the more of it light has to go through, and I don't think that your picture is comparing apples to apples. We're surprisingly good at answering the question "why does this thing that doesn't happen happen" here at the reference desk, but you may have stumped even us this time. Shadowjams (talk) 21:43, 9 April 2013 (UTC)[reply]
If the pool has a blue liner then the whole purpose of the photo is destroyed, and the caption "Water in an indoor swimming pool appears blue against a white background, right up to the waterline. The same water inside a floating white bucket appears only slightly blue." is a deception. There seems no reason for someone to do that, which is why I take it on trust, though I cannot prove it, that the pool does not have such a liner. 86.128.0.95 (talk) 22:35, 9 April 2013 (UTC)[reply]
I think the question has been answered- more blue photons are trapped in the water medium and scattered in the pool. May I suggest the OP do some real life experiments :) Ap-uk (talk) 22:37, 9 April 2013 (UTC)[reply]
Here's an experiment you can do that I think is related (I discovered this accidentally). Take a basic white porcelain sink, with nothing in it, and fill it with a few inches of water. Then put your hand into the water. When you do, you will see (probably) that the water appears to take on a reddish tinge -- the entire pool of water, even far away from your hand. Looie496 (talk) 22:54, 9 April 2013 (UTC)[reply]
It seemed to me that Looie was pulling our legs. But, as I was about to wash the dishes, I tried this (in a regular stainless steel kitchen sink). No such red tinge occurred, of course. But what happens if a dispersant is added? It happens that I have an expired box of dispersible piroxicam (a painkiller you mix with water and drink). I stirred in several tablets until the plug was a bit hard to see. Then put a red object in. Still no red tinge!. Just a red blur around the object. I reckon StuRat has the key to it - the pool in the picture has the tiles below the water blue in colour (except for the upper three rows), just like many pools I've seen. Wickwack 124.182.36.200 (talk) 23:51, 9 April 2013 (UTC)[reply]
Of course the danger of any experiment is that it may fail if the conditions are varied. I just tried it again with my bathroom sink, and it works as described. The water in the sink appears to have a slight bluish tinge when there is nothing in it; when I put my hand in the tinge becomes reddish. Looie496 (talk) 01:49, 10 April 2013 (UTC)[reply]
I've seen this happen, but it does need to be a situation (like a shiny white sink) where your hand is very much the dominant colour, which reflects back. And it usually works best in sunny conditions. 86.161.209.128 (talk) 08:28, 10 April 2013 (UTC)[reply]
Couple things to note:
The picture has been edited/processed after capture; no information is given about what color the ambient lighting had and what processing was done to the picture.
The pool probably had a blue liner, which is quite common. (I've seen big fish tanks that measure a few feet across. I don't remember seeing any noticeable blueness when looking through the tanks sideway.)
The bucket may not be that opaque. The little blueness in the water inside the bucket may be the blue reflected light in the pool showing through.
Mus musculus anatomy and behavior, plus trap physics
Some few minutes ago, I heard the snap of the mousetrap in the kitchen, and I went out soon enough that the mouse was still twitching and its tail still moving around. This prompted a few questions in my mind that I've not been able to answer with a Google search:
Why does a trapped mouse twitch? Is it something neurological that's comparable to what causes a chicken to move uncontrollably after being beheaded?
What does a healthy Mus musculus do with its tail in daily life? Balance? I've only ever seen the species (1) in traps, or (2) running around on my floors, seemingly not using its tail.
Why do traps often flip upside down when set off by a mouse? Is the spring so powerful that its momentum forces the trap to go upside down, or is there some other explanation?
1) All animals may twitch shortly after death, including humans. The muscle cells remain alive, and have energy, for some time, but only receive random nerve impulses, so move randomly. If you apply an electric current, you can cause the twitching yourself. This is the basis for the fictional idea that you can bring the dead back to life with a lot of electricity, as in Frankenstein.
2) Yes, balance. You'd need some high speed film to see it using it as a counterbalance during quick turns, etc.
3) Yes, the momentum of the spring does it. StuRat (talk) 04:46, 9 April 2013 (UTC)[reply]
Agreed with Stu. But if you suspect the mouse is still alive, put it in a plastic bag and step on it to put it out of its misery. μηδείς (talk) 11:31, 9 April 2013 (UTC)[reply]
I can't recommend you do that, you might get prosecuted for cruelty to animals! Wnt (talk) 22:23, 13 April 2013 (UTC)[reply]
Orbital Debris
After reading the "orbital debris" article, and a lot of the references, I just can't quite understand why so much stuff stays there.
(1)Surely whenever there's a collision between objects, or even a close pass, they must both end up with a change in velocity that would eventually de-orbit them?
(2)Is a "Graveyard orbit" one that is slowly decaying away from Earth? or is it just a stable orbit that's out of the way above the valuable stuff?
(3)How big would an orbiting object have to be to actually attract other objects to itself by gravity?
I hope someone can help me with this, thanks in advance. 122.108.189.192 (talk) 07:34, 9 April 2013 (UTC)[reply]
If they collide they just get orbits which aren't so circular in general. Reducing the speed of an object that is in a circular orbit puts it into a more elliptical orbit but whatever happens unless it encounters drag from the atmosphere it eventually gets back to where it started (ignoring other gravity effects, pressure from sunlight solar wind, magnetism etc.). For low earth ones that means they will probably decay faster but for higher ones it simply means you have an expanding cloud of debris. The graveyard orbit is just one that's out of the way, I don't think of it as a complete solution myself. The stuff up there is too small and far away from each other for gravitation to have an effect that matters. Dmcq (talk) 08:19, 9 April 2013 (UTC)[reply]
There is no minimum size an object has to be to attract other objects. However, the gravitational attraction of small objects is very easily overcome by other forces. In particular tidal forces prevent the formation of bodies by gravity inside the Roche limit. SpinningSpark 11:19, 9 April 2013 (UTC)[reply]
Over time, collisions will cause objects to either go into low enough orbits that atmospheric drag causes them to re-enter and burn up, or go into high enough orbits that they stop colliding with things. However, collisions in orbit are actually very rare - it would take centuries (at least) for what is up there to clean itself up through collisions.
Graveyard orbits are just high enough orbits to be out of the way. They are potentially still a problem if you want to go through that orbit (to get to geostationary orbit, for example) or if two things in graveyard orbits collide and some of the parts get knocked into orbits that cross low earth orbit (although, the further out you go the more room there is, so such collisions are unlikely).
See Hill sphere for details of stable orbits around satellites. For objects in low earth orbit, the object would have to be denser that any naturally occuring materials for anything to orbit them (it isn't enough for an object to be very massive, it needs to be small too or orbits around it have to be too large to avoid colliding with it). There will still be an effect from gravity even if there isn't a stable orbit possible, but for any realistic satellite it won't be a measurable effect. --Tango (talk) 11:26, 9 April 2013 (UTC)[reply]
By the way, graveyard orbits for (former) geostationary satellites are only a little bit above the geostationary altitude. Because the Moon is slowing down Earth's rotation, we will have a problem again in 30 or 40 million years or so, when the geostationary height will be higher up due to the slower rotation of the Earth. But I don't know how stable the satellite's orbit is over such a timescale. Icek (talk) 14:37, 9 April 2013 (UTC)[reply]
Thank you all, that gives me a much better grasp of the situation. 122.108.189.192 (talk) 06:35, 10 April 2013 (UTC)[reply]
Simple, it's fake, the video is edited. - Lindert (talk) 14:04, 9 April 2013 (UTC)[reply]
There's so many much better fakes I can't see why this one was posted here. Dmcq (talk) 14:15, 9 April 2013 (UTC)[reply]
I agree that it's fake. However, I think it's time-lapse photography (as opposed to being edited with the glass of water replacing the glass of ice). The utility room or garage where the demo takes place must be cold enough to freeze the water over several hours. Note that it is possible to freeze water instantly, if you can make it into a supercooled liquid first (why does that link lead to an article on glass blowing ?). Or, of course, you can also just cool it very quickly, say by dumping dry ice into it (stand back !). StuRat (talk) 14:26, 9 April 2013 (UTC)[reply]
Supercooling gets there, I agree the other should probably go there too. Anyway here's a proper demonstaratio of water turning of ice quickly [4]Dmcq (talk) 14:38, 9 April 2013 (UTC)[reply]
I added "supercooling" to the dab at the top of "supercooled liquid". StuRat (talk) 15:39, 9 April 2013 (UTC) [reply]
"Demonstaratio" = a method of evaluating the effectiveness of any demonstration = (time audience spends staring at demonstration) / (time audience spends staring out the window). :-) StuRat (talk) 15:44, 9 April 2013 (UTC) [reply]
Sure, supercooled water will freeze suddenly like that - but adding the salt would have been enough to add the necessary "nucleation sites" and to cause it to freeze even faster than the demo purported to show. So we know that it wasn't super-cooled. Even if this was super-cooled water, all of the nonsense with the lighter and the straw would be superfluous - and because salt actually lowers the freezing point of water, it would make matters harder. So the odds are good that this was done in a very cold garage over many hours. The clue that this is such a simple fake is that the lighting in the background of the room and on the table changes rapidly as the ice forms - clearly indicating that this is a speeded-up video and light through some window is changing due to the sun moving across the sky. So, yeah - it's another boring YouTube fake...yawn. It's becoming *so* common for people to make these science-looking demos - and easily more than half of them are obvious fakes like this one - it's really childish and it's annoying because it un-educates gullible people - making them even more stupid than they were at the outset! SteveBaker (talk) 16:14, 9 April 2013 (UTC)[reply]
when i grew up in canada, it would get so cold the words would freeze as they came out of your mouth, and you had to collect them and carry them inside and thaw them out by the fire to find out what the other guy said. Gzuckier (talk) 19:12, 9 April 2013 (UTC) [reply]
Is that why everything Canadians say sound like "Eh"? --Wirbelwind(ヴィルヴェルヴィント) 20:22, 9 April 2013 (UTC)[reply]
It isn't supercooled ice or supercooled water, it's supersaturated solution of potassium acetate or sodium acetate. That is, there are no camera tricks, its just that someone gave a bogus explanation to a real video. I've done this demonstration a hundred times in chemistry class, though I didn't pretend what was happening was ice. See this video which largely mimics exactly what is showed above, except that it gives the actual, correct chemical explanation. --Jayron32 21:52, 9 April 2013 (UTC)[reply]
I'd have thought if that were so the crystals that were dropped into it would have acted as nucleation centres but nothing happened. I think the more obvious explanation above as indicated by the lights changing is the more probable. Dmcq (talk) 22:50, 9 April 2013 (UTC)[reply]
biology
Is there is a realation between diabetes and alzheimer's disease? — Preceding unsigned comment added by Titunsam (talk • contribs) 18:28, 9 April 2013 (UTC)[reply]
Well, it's ok to get a rough idea. If the OP is interested in actual details, PubMed is far better. The is a lot of circumstantial evidence for a link. Current thinking seems to revolve around various different aspects of diabetes, or more accurately metabolic syndrome. 1) Vascular damage 2)Metabolic damage due to hyperglycaemia, 3)Low level systemic inflammation and 4) The effects of high insulin levels on Amyloid β deposition. Now, the first three of these are definitely risk factors for developing neurodegenerative diseases, but whether they specifically promote Alzheimer's is still an open question. The last is a very interesting, possible direct causal link. Interestingly, Alzheimer's may cause central insulin resistance as well, so there may be an interaction both ways. Fgf10 (talk) 20:36, 9 April 2013 (UTC)[reply]
There's an idea floating around that Alzheimers should be considered "Type 3 Diabetes". [5][6][7] The last is a scientific article. Pull quote: "We conclude that the term “type 3 diabetes” accurately reflects the fact that AD represents a form of diabetes that selectively involves the brain and has molecular and biochemical features that overlap with both type 1 diabetes mellitus and T2DM." -- 205.175.124.30 (talk) 21:43, 9 April 2013 (UTC)[reply]
Is it true that Homo sapiens idaltu is younger than Homo sapiens sapiens?
According to several Wikipedia articles, including both Anatomically modern humans and Homo sapiens idaltu, yes. The earliest Homo sapiens sapiens fossils are believed to be dated to ~ 195,000 years ago, while the earliest Homo sapiens idaltu are dated to ~ 160,000 years ago. Of course, that's just what we know, it's possible that either or both of those dates could be pushed back if new fossils are found, but it appears, based on the (admitedly very limited) data we have right now, the oldest known Homo sapiens sapiens is older than the oldest known Homo sapiens idaltu. --Jayron32 21:57, 9 April 2013 (UTC)[reply]
Our article says sapiens idaltu has archaic features and is presumed ancestral to sapiens sapiens. μηδείς (talk) 22:05, 9 April 2013 (UTC)[reply]
Well, the article makes it more muddy than that. There are oldest HSS fossil is still older than the oldest HSI fossil (which would then require a time machine for the latter to be an ancestor of the former); analysis of features seems to point to HSI being older than HSS, but until we have that "smoking gun" of an HSI fossil which is older than 195,000 years, then that is just conjecture. On the basic chronology of the fossils we have, the oldest HSS is older than the oldest HSI. Other questions in this vein remain open. --Jayron32 22:26, 9 April 2013 (UTC)[reply]
Archaic features doesn't imply ancestral. It could just have changed less since the most recent common ancestor. --Tango (talk) 11:38, 10 April 2013 (UTC)[reply]
A scan of the recent literature indicates that the classification of idaltu as a separate subspecies is not well established. Pretty much every recent discussion uses qualifiers like "proposed" or "suggested" or "purported". Looie496 (talk) 22:42, 9 April 2013 (UTC)[reply]
Does it make sense to speak of subspecies being older or younger than each other? The split from one species into two subspecies happened at a particular (impossible to really define) time, so both are the same age. The only way they could be different ages is if there is a third subspecies involved (either they both split off from that third subspecies at different times, or the first split was into, say, HSS and HSX and then HSI split off from HSX and HSX died out. Is there a proposed third subspecies "inbetween" HSS and HSI? --Tango (talk) 11:38, 10 April 2013 (UTC)[reply]
Worry about ranges based on one specimen relies on the rather nave (in the academic sense) assumption that fossil attestation is a perfect reflection of time range. You are looking at what is a statistical sample with fossils, not a complete record. No palaeontologist believes that the first or last found fossil of a species is the first or last actual individual of a species. There are a slew of dinosaur species the last specimen of which was found a million or half a million years before the KT event and none after. That doesn't mean that dinosaurs started going extinct in anticipation of Chixulub. When only half-a-dozen specimens of a species that existed for 5 million years are known, it's highly improbable any of them will date to that species first or last decade of existence. μηδείς (talk) 17:24, 10 April 2013 (UTC)[reply]
Is this a conspiracy theory?
Is there any truth to the story that someone once invented a method of fully recharging standard alkaline batteries - but that Big Battery bought up the rights to the technology and have been sitting on it for years?
Someone mentioned this to me recently, but it sounded to me like a variation on the old 'the oil companies are intentionally keeping the water-powered car down' or 'the major pharmaceutical companies already know the cure for cancer but there's more profit for them in keeping people on chemotherapy for years, so they don't tell anyone' BS, so I was sceptical.
Sounds like bullshit to me. --Jayron32 22:50, 9 April 2013 (UTC)[reply]
There's nothing new about recharging dry cells - alkaline or regular carbon-zinc. Hobby electronics magazines now and then publish the details on how to do it - generally using a pulsed and/or periodically reversed current. The trouble is, it just isn't cost effective. Just about every type of cell (primary or secondary) has a finite life: The lifetime is determined by the fact that a given cell type has a certain approximate number of charge/discharge cycles that it can tolerate. Cells in general deteriorate while held at full charge by trickle changing as well. With dry cells the change/dicharge lietime is very short. You may only get 2 or 3 cycles before the capacity drops to a very low value. Another factor is that dry cells are designed to be leakproof, but under normal use only. If you recharge, you will likely get leakage, damaging your battery powered eqipment.
As a general principle, you can assume that the idea that big companies conceal usefull things is complete nonsense. If it works and is cost effective, somebody somewhere will let the cat out of the bag. In countries that have a strong patent regime, you generally can only patent a manufacturing process or implementation - you cannot patent a function. For example, if I invent a novel and very simple circuit to pulse-charge a battery, I could patent it. That will (in theory anyway) stop you from copying my circuit. But if you invent a completely different circuit that does exactly the same thing, and market it, my patent is not infringed, and there's absoulutely nothing I can do about you. You've rendered my patent useless. What the circuit does, ie pulse charging, cannot be patented. Patents and other forms of rights are just simply not observed in many countries anyway - especially Asian (except Japan & Korea) and communist countries. Communism fundamentally has a problem with any sort of intelectual property.
the theory I have heard is that there is the technology for a battery that lasts 30 or40 years, without recharging ever68.36.148.100 (talk) 04:16, 10 April 2013 (UTC)[reply]
Sure, but they're radioactive. See nuclear battery. Still, having one in your pocket has to make you feel warm all over. StuRat (talk) 04:26, 10 April 2013 (UTC)[reply]
Stanford's Grid Storage project is reportedly working on batteries that should last 30 or 40 years, but that's not without recharging (they are thinking of these as rechargeables that can go through >40,000 cycles without deteriorating). I can see that being easily misinterpreted as a battery that lasts 40 years period. Someguy1221 (talk) 04:33, 10 April 2013 (UTC)[reply]
Nickel-iron batteries, a very old rechargeable technology, last a very long time, typically 4 to 10 times the life of a lead-acid under similar conditions, but they are very expensive - that's why you don't see much of them. Wickwack 124.182.36.200 (talk) 04:46, 10 April 2013 (UTC)[reply]
What do you mean by 'bought the rights'? 1 There was a patent on the technology and they bought it? 2 Or they paid the inventor to shut up forever? If it was 1, the patent will be published someday and it will also expire. So the company would lose its opportunity cost of exploiting the idea. If it was 2 we won't ever know. OsmanRF34 (talk) 12:25, 10 April 2013 (UTC)[reply]
Technically if the patent exists it is already published; patents aren't secret (except in the cases of national security). Adding just to Wickwack's answer, this sort of statement also misunderstands the nature of invention, which is rarely a "one guy figures out the only way to do it and nobody else would have been able to copy him." In truth, big companies have huge industrial R&D labs, all in competition with each other, and they are all working in the same fields and reading the same literature and checking out all the new patents (and even patent applications) that come out. So the idea that one guy would do this and could be silenced... it's not likely. There have been a few cases of people discovering things really out of left field that were not really in line with what others in their line of work were doing, but they are the exception, not the rule. Invention has not really been about lone geniuses for over a century now. --Mr.98 (talk) 12:44, 10 April 2013 (UTC)[reply]
It's not a cover-up. Alkaline battery rechargers are commonplace! Just do a Google search on "buy alkaline battery charger" and you'll see dozens of them for sale for around $25 - even on Amazon.com! The reason they aren't popular is that they don't really work very well - and for most people, they aren't cost-effective. Sure, you can get *SOME* charge into a dead disposable battery - but not much. It'll go dead again much more quickly than it originally took to drain it. Also, the alkaline batteries will tend to leak - and the more times you try to recharge it, the worse these effects get.
Whether these things are cost-effective is difficult to say. Let's suppose you use 80 disposable AA's per year.
Right now, Duracel AA's cost $5 for 8 batteries - so if you just toss out your batteries, it'll cost you $50 per year.
If recharge your AA's once and then throw them away to avoid the leakage problems - and let's suppose each one gets back only half of it's original charge when you recharge it. This contraption cuts your battery purchases by 1/3rd. Now you only need 52 batteries - so you spent $25 for the charger and $33 for batteries ($58) instead of $50 on batteries alone...so you don't quite break even in the first year of use. So that battery usage rate, you'll break even after around 13 or 14 months...it's not a terrible investment.
Duracel rechargeable batteries cost $8 for four...$2 each. If you buy 8 of them, plus a charger (they are less complicated than alkaline battery rechargers - I see them for $8) - you can fully recharge each battery ten times - then you spent $16 for a year's worth of batteries and $8 for the charger instead of $50 (alkalines) or $58 (alkalines plus recharger) - and you break even after only 6 months! Much, MUCH better than with alkaline battery rechargers.
HOWEVER: The actual math depends critically on the number of batteries you need SIMULTANEOUSLY. If you only need 1 battery - but you replace it 80 times in a year - then using a rechargable battery is MASSIVELY the best choice. The initial outlay on battery and charger is $10 and you save $40 in the first year alone! But if you have enough gizmos that you need 80 batteries at once - and each one is only replaced once a year - then you can't possibly use rechargables - you spend $160 on batteries and $8 for the recharger! It would take over three years to break even!! Recharging your alkalines in that scenario would definitely be worthwhile.
So it all depends on your usage - but for most people, recharging your alkalines is just not worth the hassle. SteveBaker (talk) 15:07, 10 April 2013 (UTC)[reply]
... and it's not a new idea. I was recharging carbon-zinc batteries fifty years ago, but with very limited success. They worked for a short time in low-current applications, but I never succeeded in restoring anywhere near half the original charge. Dbfirs 18:20, 10 April 2013 (UTC)[reply]
How long until they start referring to "Big Battery" as "Big Batta"? μηδείς (talk) 17:14, 10 April 2013 (UTC)[reply]
a related question; how many times can you recharge a lemon battery? might need to make lemonade later in the day after running a light the previous evening. Gzuckier (talk) 19:02, 10 April 2013 (UTC)[reply]
Color Question.
Say I have a Orange. I know that the orange color is due to the orange photons not been absorbed into the fruit as energy.
However I had thought that the mechanism of interaction of the non orange photons was one in which the molecules at the surface of the fruit vibrate in various modes and are turned into a kind of kinetic energy. Now I read in the "color of water" article that electrons can also be involved. Is this correct and can more detail be given on this mechanism which I am assuming does not rely on electrons being promoted to higher shells? Ap-uk (talk) 22:58, 9 April 2013 (UTC)[reply]
Visible light pretty much all falls in the range of electron transitions - that is, saying "the molecules at the surface of the fruit vibrate in various modes" to absorb certain colors is not typically correct, as the the rotation and translational movement of the molecule as a whole fall in the microwave and infrared regions of the spectrum, respectively (see microwave spectroscopy and infrared spectroscopy for details). Thus the "non-orange" photons are mostly being absorbed by the electron transitions. The article electromagnetic absorption by water indicates that in the case of water, there are no electronic transitions in the visible region, but it does have absorption in the visible region due to overtones from the infrared vibrational bands. These absorb most strongly at, for example, 2662 nm, but there is weak absorbance at frequency multiples, e.g. 1331 nm and 665.5 nm, some of which fall in the red-orange-yellow end of the spectrum, resulting in a very pale (because of weak absorbance) blue color. - 71.35.98.207 (talk) 17:08, 10 April 2013 (UTC)[reply]
I guess what confuses me is that if the electrons are promoted due to the photons moving them them to a higher shell then why do they not re-emit the light? Ap-uk (talk) 17:43, 10 April 2013 (UTC)[reply]
well, they sometimes do, but due to conservation or energy or whatever the re-emitted photons have lower energy, i.e. longer wavelength. as in fluorescenceGzuckier (talk) 19:58, 10 April 2013 (UTC)[reply]
I thought quanta was a specific packet of energy, why should energy be "lost"? I don't think my oranges glow in the dark though ;) Ap-uk (talk) 20:27, 10 April 2013 (UTC)[reply]
A key thing to remember about light interacting with matter is that there are rules: momentum and energy both need to be conserved at the same time. So for example a fast-moving electron, all by itself, can't emit a photon - heck, in its frame of reference it is at rest. The same applies in reverse, so you can't just absorb a photon into an isolated electron and move it. The interaction has to be more complicated - photons can push two things apart, for example, which allows its large amount of energy to be taken up by a target while transmitting just its very small amount of momentum. For example, pushing an electron in an atom into a higher energy level. But if the electron can find other ways to slip back down in energy - by knocking into other atoms, for example - then it doesn't have to give the photon back intact. You can argue that eventually it "makes change" in photons - assuming the system stays at the same temperature, eventually all the energy taken up in big visible photons will be given back in low energy blackbody radiation, which at room temperature is infrared. Wnt (talk) 23:32, 10 April 2013 (UTC)[reply]
Can anybody help me find some information about the environment of Overlook, Portland, Oregon aka Swan Island prior to the industrialization of the 20th century and after it to the present day? Like flora and fauna. If not something about island ecosystems in the lower reaches of the Willamette River where it meets the Columbia. Again very specific, so I don't care anything about the ecosystem of Oregon in general only that specific region and if not only region similar to it on the islands of the lower reaches of the Willamette River where it meets the Columbia.--170.140.214.104 (talk) 16:20, 10 April 2013 (UTC)[reply]
Good luck. According to this source, in 1841 there was "a dense stand of oak trees" that were cut down to build the Star of Oregon. Sean.hoyland - talk 17:06, 10 April 2013 (UTC)[reply]
Searching with the term "Columbia River Estuary" might help a little. The Columbia River Estuary reaches to Bonneville on the Columbia and Willamette Falls on the Willamette, and as a topic of study tends to focus on the ecology (present and historic) of the rivers and their many islands, wetlands, floodplains. I didn't search very hard, but some possible leads: This page, [8], the slides of some presentation, says the Willamette River was much shallower, with broader wetlands along it, and that apparently the main channel went east of Swan Island instead of west as it does today (the east channel is now just an inlet/lagoon). One of the slides shows the Swan Island area's bathymetry in 1888 and 2001, another changes in "off channel habitat". It also mentions (as do many other sources) how dam building on both rivers has radically altered the river flow (flow seasonality and freshet magnitudes are greatly reduced now—that is, water flow and river levels used to change dramatically over the course of the year, but now they don't much). And this page, [9], which among other things describes historical conditions at various sites around the Willamette-Columbia confluence. As with other sources, it mentions the historic abundance of Sagittaria latifolia (wapato) on the river islands around what's now Portland. Another thing you could do is look for sources on other islands in the area that are more likely to the kind of info you want. Sauvie Island comes to mind as one for which there's likely to be a lot of info. We have a few excellent/featured pages about wetlands and small streams in the Portland area, like Columbia Slough, Johnson Creek (Willamette River), and Tryon Creek. While these pages might not answer your questions directly, they might help give a general sense of things, and their reference sections might have useful sources to check. Pfly (talk) 08:05, 11 April 2013 (UTC)[reply]
PS, you could also ask over at Wikipedia talk:WikiProject Oregon, where there are many friendly folk who know an amazing amount of stuff about Oregon and the Portland area. Pfly (talk) 05:56, 12 April 2013 (UTC)[reply]
Is there a page (maybe on the internet?) that shows/teaches how to make singapore chain, or box chain ([10]), and other designs, such as in Jewellery chain?Curb Chain (talk) 17:17, 10 April 2013 (UTC)[reply]
Are there materials that turn light into sound?
Clearly it is possible to hook up a solar cell to a loudspeaker. Shine light on the solar cell, the loudspeaker produces a tone.
Are there (artificial?) materials that do this spontaneousely? Materials that absorb light energy and re-radiate it acoustically?
81.11.175.240 (talk) 18:43, 10 April 2013 (UTC)[reply]
well this is not very general but it technically does meet the requirements: the laser light–generated using a commercial laser–ionizes a small area of water, which superheats, creating an explosion of steam that generates pulses of sound waves at about 220 decibels.Gzuckier (talk) 20:02, 10 April 2013 (UTC)[reply]
The problem which you would need to overcome is that light is electromagnetic while sound is kinetic. I also doubt hooking up a speaker to a solar cell would produce any audible tone, unless you also hooking up a tone generator. Or, maybe you could put a fan in front of the solar cell so that it is covered and exposed at an audible frequency. but then you're still not really getting "light into sound", you're generating a tone using sunlight as the "carrier wave". In a more convoluted way, we turn light into sound when we speak :) Vespine (talk) 00:49, 11 April 2013 (UTC)[reply]
A cat placed into a sunbeam will often purr. I know, I know, not right. But what I'm trying to get at here is that the transformation of electromagnetic energy into acoustic energy is probably only accomplished through some sort of complicated intermediary, such a large biological organism. For non-biological approaches, maybe something like the crack of a melting iceberg? Again, not exactly what you're asking for. --Mr.98 (talk) 01:14, 11 April 2013 (UTC)[reply]
I wonder if we could somehow involve Piezoelectricity? But that still requires voltage, not light, so not really any different to your speaker idea.... Vespine (talk) 06:01, 11 April 2013 (UTC)[reply]
Bed bug feeding frequency
Every few days I wake up with a bite and I'm wondering whether I might have bed bugs. At some point I also had a rash around my jaw which I attributed to acne. I don't know when that was though. I'm wondering how long bed bugs could go without nutrition? If I go home (I'm a student), how long should I stay away to ensure bed bugs have all died? I haven't noticed any other signs though. It might be something else biting me. Playful spider perhaps. --2.97.27.107 (talk) 21:12, 10 April 2013 (UTC)[reply]
Have a look at Bedbug#Feeding_habits. It explains they prefer to feed every 5-10 days, but in some circumstances can last much longer, up to a year. As far as I know, adaptation to rare feeding is common in blood suckers, with some ticks and fleas reliably going several months without a fresh blood meal. Also note that bedbugs can "share" their meals, by piercing the stomachs of their peers and stealing their meal. If that sounds bad, it's just the start. Bedbugs also procreate though traumatic insemination! SemanticMantis (talk) 22:28, 10 April 2013 (UTC)[reply]
Unfortunately, if your bed bugs were mature and have laid eggs, you can't just wait for the adults to die. The eggs could be in the seams of your clothing, or your luggage, or anywhere in your bedroom. Have a look at the Bed bug article for other evidence to look out for before you take drastic measures. I hope the cause is something less persistent. Dbfirs 08:23, 11 April 2013 (UTC)[reply]
Although the question isn't strictly a request for medical advice, it would probably be in your best interest to consult a professional - in this case, the Orkin Man, or some equivalent. ←Baseball BugsWhat's up, Doc?carrots→ 10:17, 11 April 2013 (UTC)[reply]
synthesising DNA
hi there, I was wondering if there was a technique which would produce the synthesis (rather than the sequencing) of a specific strand of DNA with a known sequence? Presumably using its base nucleotides? Does it work? Would it work?
could you set up a basic but high yield automated process to carry out protein synthesis from the amino acids, even for longer & more sophisticated proteins?
I'm already familiar with PCR, selecting existing sequences or alleiles for amplification or expression invitro - I'm interested in synthesising very long strands or sequences which may not be found in nature.
Not only can it be done, it is regularly done these days. If you Google "gene synthesis" you can find companies that will do it for you over the internet. Like gene sequencing, the price has dropped dramatically over the past 10 years, though it is still relatively more expensive than sequencing. --Mr.98 (talk) 23:50, 10 April 2013 (UTC)[reply]
Rabies-like symptoms in ducks
A friend of mine was pursued by an aggressive duck apparently intent on attacking, in a manner described as being reminiscent of rabies. Only mammals have rabies, though; can any diseases cause rabies-like symptoms in ducks? הסרפד (call me Hasirpad) (formerly R——bo) 22:52, 10 April 2013 (UTC)[reply]
Birds can be aggressive, especially when defending their nesting areas. Geese are notorious for attacking people. See Friendly Persuasion. RNealK (talk) 23:14, 10 April 2013 (UTC)[reply]
Sorry, I didn't provide all the details of the circumstances, which make the above explanation unlikely:
Would ducks nest in high-traffic public parks? Would a provoked duck pursue the provoker—presumably well past her nesting grounds? הסרפד (call me Hasirpad) (formerly R——bo) 23:45, 10 April 2013 (UTC)[reply]
Not only mammals can get rabies, it can infect any warm blooded animal, including birds, however apparently birds have only been infected in experiments and not found in the wild. I saw a video on YouTube of a pelican eating a seagull and the explanation someone gave is that there is a rabies like disease that pelicans can get, so maybe it wasn't rabies, but something rabies like. In Australia, there is no actual rabies virus in the wild, but we are warned about fruit bats in particular because they can carry rabies like diseases. I just did a quick Google and it appears to be this Australian bat lyssavirus: closely related to rabies. Maybe there's something similar in birds. Vespine (talk) 23:51, 10 April 2013 (UTC)[reply]
Having said that, I also think you don't need rabies or any rabies like disease to explain an aggressive duck, maybe it was just an aggressive duck? There are plenty of aggressive dogs and most don't have rabies too. Vespine (talk) 23:53, 10 April 2013 (UTC)[reply]
Once, when sitting on the ground in a public park, I was mobbed by ducks that wanted my White Castle hamburgers. Deor (talk) 00:29, 11 April 2013 (UTC)[reply]
More or less. While I was fighting some of them off with my left hand, others managed to snatch a burger from my right hand. At that point, I gave up.Deor (talk) 10:44, 11 April 2013 (UTC)[reply]
Yes, land and waterfowl will nest in public parks. Yes, they can be very aggressive, especially given they nest on the ground. Swans have killed people and there are stories of rapes. Turkey attacks were a big item in NJ last summer in various municipalities. A girlfriend of mine was terrified of ducks, and she would murmur "the ducks... the ducks..." like the ending of Apocalypse Now. My younger sisters went to the Schuykill to feed the ducks popcorn and were attacked and bitten and left in tears. Male ducks gang up on and rape females, sometimes drowning them in the process. Remember, these little monsters are just velociraptors with beaks instead of teeth. μηδείς (talk) 17:45, 11 April 2013 (UTC)[reply]
Birds are mean sons of bitches. Like Medeis says, they are the only living dinosaurs. Shadowjams (talk) 20:56, 11 April 2013 (UTC) [reply]
April 11
could a black hole exist at the center of a neutron star?
What he said. Neutron star matter is expected to be fluid, so it would presumably just flow into the black hole and be consumed over time, and you would not have a neutron star for very long. Someguy1221 (talk) 06:16, 11 April 2013 (UTC)[reply]
And by "not very long" we're probably talking milliseconds! SteveBaker (talk) 11:22, 11 April 2013 (UTC)[reply]
perhaps you're right, whether it would be milliseconds or microseconds or days or what. I wondered if rapid rotation would play a role. But subatomic particles that decay in microseconds or less are still of interest in physics. i've also heard that very small black holes don't eat much, so i'm not convinced by the mere fact of of a LOT of [fluid or otherwise] mass pressing in on a black hole inside a neutron star would for sure cause it to take in all the neutron star's mass. If the black hole were small enough, i thought the "black hole evaporation" tendency could be roughly cancelled by the ready availability of mass inside the star.{to keep the black hole going, yet have the neutron star containing it exist for a "long" period of time}76.218.104.120 (talk) 12:28, 11 April 2013 (UTC)[reply]
Black hole evaporation ius one of those unproven ideas like gravitons, string theory, branes, etc. Much may be written but far less proof exists. Rmhermen (talk) 12:57, 11 April 2013 (UTC)[reply]
Thought I would check those intuitive answers with a back of an envelope, non-relativistic, much hand waving calculation. Assume that the rate of growth of the black hole is limited by area of its event horizon, the speed of light and the density of the surrounding material. Then in a "best case" scenario (or worst case from the POV of the neutron star) we have
where r0 is the initial radius of the black hole. If rt is much greater than r0 then we have
Taking a typical density at the centre of a neutron star to be 1018 kg/m3, then I make the time taken for the black hole to absorb the whole star to be of the order of 0.2 metre seconds divided by the initial radius of the black hole. For a millimetre sized black hole, this gives a timescale of minutes rather than milliseconds. Gandalf61 (talk) 13:16, 11 April 2013 (UTC)[reply]
Your calculation neglects the (very important) fact that the density around the black hole would not remain constant during the collapse. Dauto (talk) 15:59, 11 April 2013 (UTC)[reply]
Look for instance [11] where a detailed computer simulation shows that the collapse happens in less than 10 ms. Dauto (talk) 16:16, 11 April 2013 (UTC)[reply]
Haven't looked up the paper yet, but I'd just point out a possibly very important consideration: All that mass going into the black hole is going to be accompanied by a truly spectacular release of energy. Maybe enough to blast away part of the neutron star? Don't know; it's not like I can solve the equations (or even formulate them) in my head. Does the paper take that into account? --Trovatore (talk) 16:19, 11 April 2013 (UTC)[reply]
shall i take away a "yes" to the original question--that a black hole can exist inside a neutron star, regardless of how long it lasts?76.218.104.120 (talk) 04:24, 12 April 2013 (UTC)[reply]
I hate when a potentially simple answer is complicated with obtuse mathematics and peripheral theory. It is akin to verbosity. Plasmic Physics (talk) 04:46, 12 April 2013 (UTC)[reply]
Well, I hate trivial soundbite answers because they are so facile and uninformative. I didn't know that a black hole could absorb something as massive as a neutron star in milliseconds. Now I know that (a) yes it can and (b) the scenario has been studied in detail. So I have learned something. Gandalf61 (talk) 09:04, 12 April 2013 (UTC)[reply]
With respect to the OP, it doesn't matter whether you learned something does it now? Giving a concise answer takes priority over divergent exploration of related notions. Its only fair to first answer the OP's question, before endulging in such a manner of discussion. Plasmic Physics (talk) 09:40, 12 April 2013 (UTC)[reply]
Well, I certainly don't think the OP learned anything from your trite "Not indefinitely" response, beyond the fact that you couldn't be bothered to take their question seriously. Thanks to the further discussion, we know how long it takes for the neutron star to collapse, and we have an source for that information. Gandalf61 (talk) 10:34, 12 April 2013 (UTC)[reply]
You're missing my point - the OP never inquired for an expanded answer, which is clear from his most recent post. Plasmic Physics (talk) 11:06, 12 April 2013 (UTC)[reply]
8th dimensional space
so i was looking at 8th dimensional space page the quantum entanglement and alternate realities i need help to see if i am right
so pretty much 8th dimension is saying there our many universe like ours but different at the same time and if one were to get to one of these many dimensions it would cause a tear in space causing a new reality and if one travels though many tears it cause confusion in the universe meaning the quantum entanglement if my idea of what these are are wrong let me know plases — Preceding unsigned comment added by 99.12.149.156 (talk) 03:36, 11 April 2013 (UTC)[reply]
I can't see how you got all that from our article on Eight-dimensional space, so you must have been reading this somewhere else. Sorry to tell you, but it sounds like a bunch of science fiction nonsense. Someguy1221 (talk) 06:18, 11 April 2013 (UTC)[reply]
There is some confusion here. The word "dimension" has two meanings:
In the sense of "eight dimensional universe", the meaning is like "three dimensional universe" - we'd be talking about a universe where there are more directions you could move in than just the north-south, east-west and up-down that we are normally aware of.
In the sense of "travelling between dimensions" - we're talking about "parallel universes".
Generally, scientists only use the first of those two meanings. The two meanings of the word are not connected or related in any way.
When we are considering quantum entanglement and things like certain interpretations of the Schrondinger's Cat thought experiment - then we are talking about parallel universes...not extra spatial dimensions. "Tears" that allow you to move between parallel universes are in the realms of speculation and science fiction. As far as I know, there is no evidence that they might exist from mainstream physics...quite the contrary in fact...there is reason to assume that they'd be fundamentally walled off from each other.
When we're talking about "extra dimensions" in ideas such as string theory - then we're talking about "directions you can move in".
You're basically stuck in this universe - and whether there are others (due to quantum effects, for example) is an undecided question.
There is one more scientific usage of the term "dimensionality" - the usage in the sense of degrees of freedom in a generalized coordinate system. For example, if we are describing an n-body simulation, it is common to call this a n dimensional problem, (or even more accurately, a 6-n dimensional problem, for example, accounting for velocity and position of each object in conventional dimensions x, y, and z; by extension, you can add one dimension to each degree of freedom in the problem). When we generalize a coordinate system, we can apply constraints based on physical law, and reduce the complexity of the problem to a lower dimension.
In this usage of the term, it is frequently helpful to understand the distinction between the rank and the size of a problem-space. A problem can be n-dimensional, but modeled with extra dimensions; this is called "degeneracy", and it can be helpful for practical purposes, even if it adds no new information. Nimur (talk) 21:07, 11 April 2013 (UTC)[reply]
This is almost surely a reference to http://www.tenthdimension.com/ — whether that pseudo-spatial interpretation is worth anything is beyond the scope of this comment. --Tardis (talk) 03:12, 12 April 2013 (UTC)[reply]
cyanoacrylate bond inhibitors
I recently bonded some rubber like swim fin material to itself and a glass fiber and resin material using a high quality cyanoacrylate with the manufacturer's 'filler' powder for plastics and rubber. Initially the bond seemed to hold but failed after several 20-30 minute uses on a swim fin in a chlorinated swimming pool. I am thinking that the bond may have been effected by residual chlorine compounds left on the surface prior to bonding. Other uses of the bonding product yielded exceptional results on similar rubber like materials where chlorine was not involved. Are there known adverse effects to bonding where chlorine compounds are present? What other chemical conditions might adversely affect bonding? Suggestions?
I don't see anything out there about reactions with chlorine - just about the only thing that I see might be that cyanoacrylate doesn't stick well to glass - so perhaps the glass fiber material is the cause here. That sounds like a bit of a stretch to me - but it's all I could find. SteveBaker (talk) 15:43, 11 April 2013 (UTC)[reply]
Perception of pain, which part of the brain is the gatekeeper?
I've always wondered how people can exert so much control over their perception of pain. If the stimulus is the same, the same sensory neurons fire and in the end the same regions in the brain get stimulated to an equal degree, then how is it possible to change your perception of pain, between the same stimuli? When I am on an operating table, unconscious, does my " body " still feel pain, even though I don't " know " that it is there? Can the part of my brain that is conscious effectively act as a signal limiter? Who is the gatekeeper? Has any research been done on this? 137.224.239.102 (talk) 08:45, 11 April 2013 (UTC)[reply]
Basically, the thalamus, though it isn't a conscious process. See nociception for details. - Nunh-huh 09:40, 11 April 2013 (UTC)[reply]
Many aspects of pain are still very mysterious to us, and the answers to the questions really aren't known with any clarity. Part of the difficulty is that what we call pain is actually a mixture of several aspects -- Ronald Melzack identifies three that he calls "sensory-discriminative" (sense of the intensity, location, quality and duration of the pain), "affective-motivational" (unpleasantness and urge to escape the unpleasantness), and "cognitive-evaluative" (cognitions such as appraisal, cultural values, distraction and hypnotic suggestion). (Note: I've copied that from our pain article, which is worth reading.) Each aspect is implemented by a different brain system, and differently affected by brain manipulations. We are only beginning to understand the systems and their interactions. One thing that is clear is that there is a lot of "top-down" circuitry that allows higher brain levels to modulate signals at lower levels, even down to the spinal cord. Looie496 (talk) 15:42, 11 April 2013 (UTC)[reply]
Are there drugs that boosts willpower?
Are there drugs/medicines that boosts willpower? — Preceding unsigned comment added by 50.100.191.39 (talk) 18:41, 11 April 2013 (UTC)[reply]
Certain stimulants like Ritalin have this effect. Many students who study boring subjects like law take such drugs. Count Iblis (talk) 18:54, 11 April 2013 (UTC)[reply]
Read:Dutch courage. Alcohol can depress some parts of the brain (as can some other drugs) that usually inhibit some forms of action. People that show the quality of having great will-power often have a low level of fear. Amphetamines were taken by the hand-full by American pilots during the second world war, because they did not only keep them alert but made them feel immortal and fearless, yet people may not survive very long with just that attribute. I think therefore, you may be asking about the type of will-power that brings successes. That requires a blend of other attributes. In that respect, I haven't come across any drugs that can have any long term benefit. Before anybody else steps in and pontificates, I'm not including Entheogens because these require the individual to also intellectualize (e. i., WORK) on seeking out whatever understanding they can glean from their experimental voyages. Will-power proper, I think, is a product of clear thought. Trying to think and carry out a plan of action whilst one's brain is under the influence of supposed artificial enhancements -will not achieve this. --Aspro (talk) 20:33, 11 April 2013 (UTC)[reply]
The question is ill-formed. There are various reasons besides akrasia that people lack the will power to do things--fear; lethargy; craving; compulsion. There are all sorts of drugs to treat anxiety, hunger, tiredness, OCD. So the broad answer is yes, drugs from caffeine and alcohol, to cigarettes and amphetamines, to xanax and zoloft all effect the mind. μηδείς (talk) 21:51, 11 April 2013 (UTC)[reply]
Given that a question is a request to be informed, I think that goes without saying. 202.155.85.18 (talk) 02:02, 12 April 2013 (UTC)[reply]
Launching yourself from lying on the ground to upright position using only your arms muscles
Are there people who can do this? I've seen people do so-called Muay Thai push-ups, so it seems to me that it is possible. It would require more strength than you need to do the Muay Thai push-ups, but then there are people who can do hundreds of these in a row. However, I've never seen or heard about people who can launch themselves up from lying to standing position using a push-up move. Count Iblis (talk) 19:17, 11 April 2013 (UTC)[reply]
Lying on your back or chest? I can do "kip-ups" which is lying on back to standing upright. But this involves alot of leg motion.165.212.189.187 (talk) 20:17, 11 April 2013 (UTC)[reply]
I agree it looks suspicious. For example, just before the young man gives a big push to get up to the vertical, the bottom of his T-shirt rides upwards a couple of inches for no apparent reason. Now if the whole thing were actually performed in reverse and then played backwards, I can imagine the bottom of the T-shirt riding upwards as he fell forwards and downwards, and then extending to its proper position after he came to rest. Dolphin(t) 08:16, 12 April 2013 (UTC)[reply]
April 12
Low mass white dwarf actually currently exist
Since the article said white dwarf can be 0.17, do the white dwarf dwarf being 0.17 actually exist currently, or is it just the estimation of the stars did not yet come off the main sequence. Is this true alot of white dwarf are binary stars, can 0.5 solar mass white dwarfs? is it more common for white dwarf to be single star system, or binary star system? Is white dwarf all the exact same size on single star system/non-binary star ssytem? or the Solar mass determined by white dwarf has to determine exactly how big the white dwarf has to be?--69.226.42.134 (talk) 00:36, 12 April 2013 (UTC)[reply]
I struggle to see how a very small white dwarf (such of 0.17 solar masses) could form other than from a small red dwarf collapsing. Red dwarf stars live for a very long time, so none of them are dead yet. That would suggest there are no very small white dwarf stars. A lot of stars are in binary systems and they will generally remain in those systems when they die, so yes it is true that a lot of white dwarfs are in binary systems - I don't know if it is more than half, though. The size of a white dwarf is determined by the size of the star that formed it. In a binary system, there might be some transfer of matter between the stars that can change things. In a non-binary system, there obviously won't be. Does that answer most of your questions? I found them a little hard to understand... --Tango (talk) 11:43, 12 April 2013 (UTC)[reply]
Bird evolution
Are the falcons, parrots, and sparrowsreally the closest relatives of one another, as people say? If so, who evolved from whom in this taxonomy? And also, if the falcons and the passerines are so closely related, which of the passerines are the most closely related to the falcons? (I'm guessing it would be the swallows, based on purely morphological info, but I can't be sure). Oh, and are the whippoorwills more closely related to the swifts, or to the owls? 24.23.196.85 (talk) 05:50, 12 April 2013 (UTC)[reply]
None of those groups evolved from another of them. Their most recent common ancestor was a member of neoaves but not of any of those groups (according to our articles). All falconiformes are equally closely related to all passerines. Regardless of which falcon and which passerine you pick, you get the same ancestral species as their most recent common ancestor. And according to our articles, whippoorwills are more closely related to swifts than to owls. Looie496 (talk) 06:43, 12 April 2013 (UTC)[reply]
(EC) You may be thinking of discussion surrounding some recent studies like [12][13][14][15]. You should be able to read both studies (the former may require free registration) and although they may be a little difficult for someone without a biological background to properly understand, you should get some idea and should also be able to view the various trees shown and seek help here to understand the parts which are confusing. The 2008 study (first 2 links) in particular was and is I believe regarded as fairly significant, you should be able to find a fair amount of discussion of it in blogs and other such sources, although looking for the better ones may be difficult, I think [16] is okay. As mentioned in our article Evolution of birds#Classification of modern species, this is still an area of some flux (as with quite a lot of taxonomy, particularly given the increasing ease of genomic analysis) and the 2008 study is obviously only about 5 years old although I don't know specifically how well the relationship between the species you mention is supported. I would note statements like 'who evolved from whom in this taxonomy' should generally be avoided when talking about extant species as neither extant species is going to be the same as the ancestral species. Similarly for statements like 'which of the passerines are the most closely related to the falcons' as most likely they all have the same most recent ancestral species. Nil Einne (talk) 06:51, 12 April 2013 (UTC)[reply]
Sediba's hands.
Can anyone figure out what's going on with Sediba's hands in the skeleton on the right, here? μηδείς (talk) 10:00, 12 April 2013 (UTC)[reply]
![[10]](http://www.goldfinity.com/images/Classic%20Box%20Chain.jpg){kind=link}
![[13]](http://www.sciencemag.org/content/320/5884/1763/F4.large.jpg){kind=link}