I've looked around for this on here. What exactly holds the quaternary structure of a protein together. All I could find on here was that the monomers are not normally covalently linked, then the article talked about many methods of determining the quarternary structure. Any help is much appreciated, thanks...Oh, and while I may currently be doing an assignment on proteins and enzymes, this is actually a personal interest question that has cropped up while doing it. <small><span class="autosigned">—Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[User:Alaphent|Alaphent]] ([[User talk:Alaphent|talk]] • [[Special:Contributions/Alaphent|contribs]]) 09:53, 17 June 2009 (UTC)</span></small><!-- Template:Unsigned --> <!--Autosigned by SineBot-->
I've looked around for this on here. What exactly holds the quaternary structure of a protein together. All I could find on here was that the monomers are not normally covalently linked, then the article talked about many methods of determining the quarternary structure. Any help is much appreciated, thanks...Oh, and while I may currently be doing an assignment on proteins and enzymes, this is actually a personal interest question that has cropped up while doing it. <small><span class="autosigned">—Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[User:Alaphent|Alaphent]] ([[User talk:Alaphent|talk]] • [[Special:Contributions/Alaphent|contribs]]) 09:53, 17 June 2009 (UTC)</span></small><!-- Template:Unsigned --> <!--Autosigned by SineBot-->
:[[Secondary structure]] is the general 3D form form of local segments of polypeptides, formed when [[hydrogen bond]]ing occurs between hydrogens of an [[amino]] group and [[lone pair]]s of a [[carboxy]] group. [[Disulfide]] bonds can also contribute to secondary structure. [[Tertiary structure]] is the 3D form of the entire polypeptide/protein. [[Quaternary structure]] is when multiple tertiary structures come together to form a working complex. Examples include [[insulin]] (in some states) and [[haemoglobin]] (a [[tetramer]] with an iron ion bound). --[[User:Mark PEA|Mark PEA]] ([[User talk:Mark PEA|talk]]) 11:15, 17 June 2009 (UTC)
:[[Secondary structure]] is the general 3D form form of local segments of polypeptides, formed when [[hydrogen bond]]ing occurs between hydrogens of an [[amino]] group and [[lone pair]]s of a [[carboxy]] group. [[Disulfide]] bonds can also contribute to secondary structure. [[Tertiary structure]] is the 3D form of the entire polypeptide/protein. [[Quaternary structure]] is when multiple tertiary structures come together to form a working complex. Examples include [[insulin]] (in some states) and [[haemoglobin]] (a [[tetramer]] with an iron ion bound). --[[User:Mark PEA|Mark PEA]] ([[User talk:Mark PEA|talk]]) 11:15, 17 June 2009 (UTC)
== why do hurricanes slow down? ==
what stops hurricanes carrying on exponentially? if there is the energy for them to get to the size they do, why doesn't it carry on increasing? i am not a scientist at all, but i was thinking maybe it has something to do with friction, though i have no idea if this is relevant to air particles. is it to do with air pressure? as it moves into low pressure areas it kind of disperses?
cheers
nick
Revision as of 11:17, 17 June 2009
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.
This was a problem from a physics book I vaguely remember; I never quite figured it out and someone else's question reminded me.
A bus is accelerating forward. A balloon is tied to a string attached to a chair. Why does the balloon go forward as well. If I remember correctly it was from one of the Feynman lectures on physics book so I doubt the question is wrong. But to me it would seem the balloon should go backwards, not forwards. Any possible explanations that involve simple Newtonian mechanics (nothing about fluids or pressure; I don't think it said WHAT the balloon was filled with but I'm assuming standard balloon with helium.24.171.145.63 (talk) 03:16, 11 June 2009 (UTC)[reply]
:By who's perspective? To a person on the bus, the balloon will drift backwards, until the string stops it, and then it will go forwards with the bus. However, to a person standing on the street, the balloon will drift forwards but at a rate slower than the bus does, since the air in the bus generates a small amount of friction on the balloon, and will push if forward slightly. --Jayron32.talk.contribs03:28, 11 June 2009 (UTC)[reply]
No Jayron, the balloon actually moves foward (even from the perspective of the person inside the bus) because the air around the balloon is heavier than the balloon and moves backward forcing the balloon forward (just as it falls downward, forcing the balloon upward). Dauto (talk) 03:48, 11 June 2009 (UTC)[reply]
Actually ... when the bus accelerates several forces will affect the ballon's motion:
the motion of the bus, pulling the string -- the most significant force, causing the balloon to move forwards with the bus
the balloon's inertial mass -- causing it to drift backwards relative to the passengers
assuming calm atmospheric conditions (no wind), air pressure or friction would be a small factor opposing the balloon's drifting motion —Preceding unsigned comment added by Ropata (talk • contribs) 09:35, 11 June 2009 (UTC)[reply]
Also, the bus will pull the string in the opposite direction the balloon is being pushed. If it is indeed moving forward, the bus will pull the balloon back. — DanielLC14:10, 11 June 2009 (UTC)[reply]
Yes bouyancy is the key here. The gas in the balloon is lighter than air (which is why it's floating). Imagine a cork floating in a glass of water in the bus. As the bus accelerates forwards - the water in the glass sloshes towards the back of the bus - which forces the lighter cork to move forwards. That's very easy to visualize because you can see the water. However, the same thing is happening with the balloon which is floating in the air. When the bus accelerates, the air sloshes towards the back of the bus - forcing the balloon to move forwards...it seems counter-intuitive - but that's because we're not used to seeing things that are lighter than air. SteveBaker (talk) 12:06, 11 June 2009 (UTC)[reply]
We need to state that we are referring to a balloon that has positive buoyancy--it would rise toward the ceiling if untied. My daughter's physics class was given this problem, and the debate was so fierce that she drove to a store, purchased a balloon, and verified by experiment that the balloon goes forward. I pointed out to her that one result of general relativity is that accelerated frames of reference are indistinguishable, if the buoyant force opposes gravity, it must also oppose any other acceleration. on the bus, if you tie a plumb bob and a balloon to the same pivot point, the two strings will form a straight line in steady state tilt or steady state acceleration. -Arch dude (talk) 13:03, 11 June 2009 (UTC)[reply]
Yes, the equivalence principle is the easy way to see this. A bus accelerating forward is equivalent to a bus tilted backward (in both cases you're pressed into your seat). A helium balloon has to behave the same relative to the frame of the bus in both cases, and that means moving diagonally in the front-ceiling direction. -- BenRG (talk) 16:17, 11 June 2009 (UTC)[reply]
Why would the balloon move forward? I don't understand the part about the air inside the bus "sloshing" backwards. Yes, there will be "sloshing," but will it be only backwards? I think such "sloshing" will be complex, going around the seats and any other complexity to what otherwise might be a simple geometric volume. Supposing instead of a bus, we were considering a hollow cylinder. And instead of windows, which might be opened or closed, we considered the cylinder totally closed. Would the balloon still move forward? If so, that would be assuming that the air at the back of the cylinder became more dense, or compressed, than the air at the front of the cylinder. But is this really the case, to any appreciable degree, at acceleration rates concerning busses? I have my doubts about that. In theory that sort of reasoning might apply. But I am not so sure it applies in a bus accelerating from a standstill, no matter how fast the driver attempted to accelerate the bus. I think a more likely explanation for the balloon moving forward might be complex air currents resulting especially from open windows. But I am not sure. Bus stop (talk) 16:37, 11 June 2009 (UTC)[reply]
Yes, even in your cylinder example, it would happen. Yes, the acceleration causes an increase in density at the rear of the bus. If the bus starts turning left, the density will increase on the right and the balloon wil move to the left.--Sphilbrick (talk) 16:42, 11 June 2009 (UTC)[reply]
Yes, that's exactly what happens. The air at the back of the balloon becomes more dense than the air at the front of it creating a pressure gradient force on the balloon that's enought to push it forwards. This is entirely equivalent to the vertical pressure gradient that makes the balloon float. Dauto (talk) 18:24, 11 June 2009 (UTC)[reply]
Do you understand why the balloon floats in the first place? The reason it moves forward under acceleration is exactly the same as the reason it floats. In a completely sealed cylinder in steady-state 1G forward acceleration, the balloon will be at an angle of 45 degrees even though there is no air movement whatsoever. You really need to purchase a balloon and get someone else to drive you and accelerate. The effect is dramatic, not subtle at all. -Arch dude (talk) 19:55, 11 June 2009 (UTC)[reply]
Another way to approach this problem is using the Equivalence principle:("we [...] assume the complete physical equivalence of a gravitational field and a corresponding acceleration of the reference system." - Einstein, 1907). If the vehicle is accelerating at say 9.8m/s/s it may equivalently be modeled as a gravitational field of 1g, within this vehicle, oriented opposite to the direction of the acceleration vector. This creates a pressure gradient ( just like gravity creates a pressure gradient in fluids) which causes the balloon to move forward - just as a hydrogen balloon would rise up as a result of the pressure gradient created by gravity.
Dilip rajeev (talk) 20:02, 16 June 2009 (UTC)[reply]
If I understand genetics correctly (hopefully I do) then everything that makes a person male comes from their father via the Y chromosome, whereas what makes a person female comes from one X chromosome of the mother and father respectively.
Therefore does this fact of nature indicate that generally men (or male animals even, if this helps rule out the cultural and psychology influences) would prefer the birth of a son?
In other words, a father completely influences the male characteristics of his sons but only half the female characteristics of his daughters. So in the interest of passing on one's genes (which according to The Selfish Gene and natural selection indicates is the main reason for competition for mates and for having children) wouldn't men prefer sons while women would be indifferent? Perhaps this also explains why inheritance laws have typically favored sons in most cultures? TheFutureAwaits (talk) 09:54, 11 June 2009 (UTC)[reply]
It seems to me that since males have no female parts, they wouldn't influence a female offspring at all. Rather, the fathers female ancestors gens, plus the mothers genes, would control the female parts.
My apologies if I'm stating the obvious, but men are XY and women are XX. Therefore men do influence half of what makes their daughters female (in terms of sex chromosomes; female being the "default" sex is an issue beyond the scope of this question). You know:
Xm1Ym1 (father) + Xf1Xf2 (mother)
could result in Xm1Xf1 (female) , Xm1Xf2 (female), Ym1Xf1 (male) or Ym1Xf2 (male).
Of course the man's X chromosome came from their own mother but the man's Y came from his father; we could got back generation after generation but I don't see how this impacts the original question: Do men favor son's because they completely contribute what makes their sons male but only contribute half of what makes their daughters female. TheFutureAwaits (talk) 10:53, 11 June 2009 (UTC)[reply]
The XY chromosome system is the sex-determination system in most mammals, but not in all animals - birds have an entirely different genetic system (see ZW sex-determination system); some reptiles have a non-genetic temperature-dependent sex determination; some fish and molluscs can even change sex. So in evolutionary terms the Y chromsome is a fairly recent arrival. Even if we stick to mammals, a father contributes more genetic material to his daughters than to his sons (the X chromosome is 153 million base pairs long; the Y chromosome only 60 million base pairs) so an evolutionary argument could predict favouring daughters over sons. OTOH, if there are fewer males than females in the adult population, then a son will produce more grandchildren, on average, than a daughter ... Gandalf61 (talk) 11:02, 11 June 2009 (UTC)[reply]
There are ~25,000 genes that affect a person's physical characteristics, most of which are NOT on the X or Y chromosome. Early in embryogenesis, the gender is completely indeterminate -- males and females all have the same embryonic tissues (Mullerian ducts and Wolffian ducts) that will go on to form the basic internal genital structures through the process of sex determination and sex differentiation. The embryonic genital tubercle and genital folds will develop into the external genital structures. Therefore, you should think of the Y chromosome as having a "switch" (the SRY gene) that turns on a complex genetic program that results in the embryonic gonads becoming testes in a male, whereas the absence of the SRY gene (which is true in XX females but also in Turner syndrome and Swyer syndrome) the default is to form ovaries. Everything follows from that point in development -- testes produce antimullerian hormone that causes regression of the female internal structures, and testosterone that promotes development of characteristic male external genitalia. In the absence of these signals (and probably in the presence of some X-linked gene signals), the system defaults to a female phenotype. Most of the genes that are involved in this process are actually NOT on the sex chromosomes, so would allow contributions from both parents, even though the switch that starts off the process is on the Y. Why would it make sense for the small number of genes on the Y chromosome to be more "selfish" than all the others? There are far more genes on the autosomes. --- Medical geneticist (talk) 11:41, 11 June 2009 (UTC)[reply]
Aren't you overlooking the importance of the SRY "switch"? It seems rather easy to argue gender has a profound effect on many other genes. My hypothesis is that men would favor sons as they are genetically and ultimately phenotypically more related to their fathers versus daughters. The gene/chromosome is exclusive to one parent and has a massive influence on the development of the individual. TheFutureAwaits (talk) 12:05, 11 June 2009 (UTC)[reply]
OK - these explanations have gone WAY off the rails. It's not complicated:
Women have two X chromosomes - men have one X and one Y. The child gets one of the mother's sex chromosomes and one of the father's - but it's random which one. So if the baby is a girl, she got one of her mother's X chromosomes (it's random which one) and the X chromosome from her father. If the baby is a boy - he gets one of his mother's X chromosomes (again, at random) and the Y chromosome from the father. Either way - the kid got one of the two genes from the mother and one from the father so that is no reason to prefer to have a boy child.
Where the confusion lies is that someone here thinks that a girl baby could get both of her X chromosomes from the mother and a baby boy could get both the X and the Y from the father. That's NOT what happens! But if that were the case then in the case of a girl, it would be true to say that there are two possibilities: Both X's from mommy or one X from mommy and one from daddy. There would therefore hypothetically be (on average) 75% of the genetic material in girls coming from the mother and 25% from the father. In the case of a boy - there would certainly have to have gotten the Y from the father but the X could come from either parent - so on average, 75% of the genetic material in boys would come from the father and 25% from the mother. It would then make evolutionary sense for the father to 'prefer' boys to girls because on average they'd contain more of his genetic material. I think that's what the OP imagines. But that's not what happens.
If fathers prefer their boy offspring to their girls (and I'm not convinced of that) - it's more likely to be that it is the traditional role of the father to pass on male-dominated skills (hunting, tracking, boat-building, beer-drinking, whatever) to their sons and for women to pass on traditionally female-oriented skills (nagging, shopping, etc??<shrug>) to their daughters - so it would perhaps make evolutionary sense for the males to preferentially bond with their sons and the females to bond with their daughters. SteveBaker (talk) 12:26, 11 June 2009 (UTC)[reply]
I don't disagree with any of the above but I just want to point out that, unless I'm missing something, evolutionary arguments regarding sex-preference don't add up. The only way a gene causing men to prefer sons would be selected for is if it caused such a strong preference that it made men kill their daughters (or render them infertile somehow). Can such a gene be selected otherwise? Zain Ebrahim (talk) 13:13, 11 June 2009 (UTC)[reply]
Okay, this is getting silly. No one here (at least that I'm aware of) thinks both X's come from the mother. See what I posted above in response to Drew...
Xm1Ym1 (father) + Xf1Xf2 (mother)
could result in Xm1Xf1 (female) , Xm1Xf2 (female), Ym1Xf1 (male) or Ym1Xf2 (male).
It seems like a simple misunderstanding but Steve, I would appreciate if you would cross out that section of your discussion since no one is advocating that point of view.
Anyway, what I AM saying is the Y chromosome is ultimately responsible for the creation of a male child. The father is the only one with a Y chromosome and thus 100% responsible for the gender characteristics of a male (XY) child (X from the mother, Y from the father). In the case of a daughter both parents contribute equally to the gender characteristics as one X comes from the mother and one from the father.
Therefore as a father is wholly responsible for the male characteristics of the son but only 50% responsible for the gender characteristics of a daughter it follows that men would prefer sons. TheFutureAwaits (talk) 13:40, 11 June 2009 (UTC)[reply]
The gender is decided by the Y chromosome, but the characteristics are decided by the combination. Let me pose a hypothetical question that may make things a little clearer. What would happen if someone where born with two Y chromosomes?DrewSmithWhat I've done14:02, 11 June 2009 (UTC)[reply]
That's not possible, the embryo would fail to develop. XYY can occur but YY can not as there are many genes on X which people require to live. However I am not sure this hypothetical applies to the question... I think the terminology may be throwing people off. Also Drew, can you provide a citation or example for confirmation of your statement "The gender is decided by the Y chromosome, but the characteristics are decided by the combination."?
The male gender characteristics are the result of the activation of a male phenotype by the SRY gene. Therefore what makes a person male and all the male characteristics (not ALL characteristics but those which are unique to males) are caused by the Y chromosome which comes from the father. Does this clear up any confusion on the point I am trying to make? TheFutureAwaits (talk) 14:44, 11 June 2009 (UTC)[reply]
According to The XYY Man he'd be some kind of a super-hero. In reality, he'd have XYY syndrome which I suggest you read. Note that there are also XXX girls...(which, strangely, seem to be advertised a helluva lot in certain parts of downtown Dallas). If you're suggesting someone with two Y chromosomes and no X - they'd certainly never get as far as being born because there are a shit-load of genes on the X chromosome that you can't survive without - so the question is moot. SteveBaker (talk) 14:41, 11 June 2009 (UTC)[reply]
That point of view makes no sense to me. An X chromosome has more genes than a Y chromosome which means that a man actually passes more of his genes to his dauthers than to his sons so, if anything, that naive application of the selfish gene principle would lead to men prefering their dauthers. Dauto (talk) 14:37, 11 June 2009 (UTC)[reply]
Except I'm not refering to the number of genes, but rather to the impact the SRY gene has on the resulting phenotype caused by all the other genes. The Selfish Gene was an earlier work of Dawkins which he expanded on in The Extended Phenotype which may explain a bit more the theory behind my reasoning. Essentially the father has a much greater impact on the phenotype of a son versus a daugther as everything which makes that son male comes from the father. For daughters the contribution is shared equally. TheFutureAwaits (talk) 14:50, 11 June 2009 (UTC)[reply]
"Everything which makes that son male comes from the father" is a trick of language. It has no scientific meaning. The father's genetic material determines the sex of the child, whether male or female. The father supplies 50% of the genetic material whether the child is male or female (slightly less than 50% for a male). That includes 50% of the genes that are preferentially expressed in males and 50% of the genes that are preferentially expressed in females. The mother and father contribute equally to the phenotype of a male child and they contribute equally to the phenotype of a female child. -- BenRG (talk) 15:24, 11 June 2009 (UTC)[reply]
Halleujah! This is what I've been getting at the whole time. I can't claim expertise in this stuff though and the articles actually seem a bit sparse, so can anybody explain whether any evidence confirm or contradicts my hypothesis that the father has a much greater impact on the phenotype of a son versus a daugther as everything which makes that son male comes from the father and thus men would prefer sons? TheFutureAwaits (talk) 15:43, 11 June 2009 (UTC)[reply]
Your hypothesis is false. As MedicalGeneticist explained (but maybe in too complicated a way), the things that make a man male are scattered all over the genome. The Y chromosome is tiny, and the main thing it contains is a set of "switches" whose function is to activate the male-related genes on other chromosomes. In females, these genes are present but they don't get activated. The contents of the Y chromosome differ very little across people. Therefore, the mother and father both have essentially equal impacts on the phenotype of a son. Looie496 (talk) 16:16, 11 June 2009 (UTC)[reply]
Yet the switch makes all the difference. When the other genes are not activated then they do not impact the phenotype so ultimately the father DOES make a larger determination. TheFutureAwaits (talk) 16:28, 11 June 2009 (UTC)[reply]
Clearly you're not refering to the number of genes. My point is that you probabily should be refering to the number of genes, unless you can show us that the inheritance of that single gene present in the Y chromosome is more relevant than the inheritance of all the genes present in the X chromosome which you haven't done so far, as far as I can see. Just saying that you are not talking about my point doesn't make it go away, mind you. Dauto (talk) 16:21, 11 June 2009 (UTC)[reply]
See above, it's more important because this gene controls the activation of the other genes you are refering to. If they aren't activated the phenotype doesn't change so ultimately the fact that it controls the activation makes it more important than the pure number of inactive genes. TheFutureAwaits (talk) 16:28, 11 June 2009 (UTC)[reply]
I think it's rather obvious if something has control over a process then it is rather important. Not necessarily more important than the process but in this case it influences the outcome of gender, something the other genes don't do. I would also argue the fact that it alone determines gender makes it extremely important. The differences that result biologically because of gender are very far reaching. TheFutureAwaits (talk) 18:52, 11 June 2009 (UTC)[reply]
Well, I would argue that since all that gene does is determine gender that makes it extremely unimportant as far as it concerns the matter of wheather a father would prefer a son or a dauther. You've simply asserted the oposite point of view but without giving any real reasons for us to accept it. On the other hand I know for a fact that fathers love their dauthers. Dauto (talk) 19:06, 11 June 2009 (UTC)[reply]
Getting back to the original question about "selfish genes" and wanting to pass on one's genes, the idea that a male should prefer sons based on wanting to pass on his genes has been adequately refuted. A male actually passes on slightly more genes to his daughters since the X chromosome carries more genes. Look at the Y chromosome article -- in some species, there are only 4 genes on the Y chromosome. Your argument attaches too much importance to the SRY gene. What if I "hypothesized" that people with orange eyes would rather have children with orange eyes because the "orange eye gene" is selfish? It just doesn't make sense. There are enough social/cultural reasons given for sex preference in offspring that your theory about a genetic basis just doesn't add anything useful. --- Medical geneticist (talk) 17:19, 11 June 2009 (UTC)[reply]
If the SRY gene determines gender then it influences a person's morphology more than pretty much any other gene (yes there are HOX genes but these don't get passed on only half the time). So what I'm saying is it is reasonable the "selfishness" of this gene would be extremely influencial. As a consequence of a gene contributed by only one parent the child's morphology is vastly changed.
If a father has a son everything that makes that son male comes from the father. If a father has a daughter the gender characteristics are cause by both the mother and father. Therefore, a father wishing to pass on his genes would prefer sons as the sons will pass on his male characteristics to their children, daughters will not. TheFutureAwaits (talk) 19:01, 11 June 2009 (UTC)[reply]
A father wishing to pass on his genes would prefer a daughter as the daughter will have more of his genes than a son. Being a male is not that important, really. Dauto (talk) 19:13, 11 June 2009 (UTC)[reply]
This is becoming a circular argument, as I said earlier it's not about the number of genes it's about the end result. Let's try this: do you agree that the gender of a child is determined by the genetic contribution of only the father? TheFutureAwaits (talk) 20:23, 11 June 2009 (UTC)[reply]
No one is arguing that the contribution of the SRY gene is unimportant in determining the gender. It is a critical switch between a male and female phenotype. However, you are incorrect in your assertion that "everything that makes that son male comes from the father". Have a look at the androgen receptor and androgen insensitivity syndrome articles and then tell me whether you still think that the mother does not contribute to the male phenotype in her sons. --- Medical geneticist (talk) 20:48, 11 June 2009 (UTC)[reply]
Androgen receptors are present in men and women; the information is interesting but it doesn't refute the fact that only the contributions of the father determine whether a male is born. The father is solely responsible for whether the switch is triggered and child becomes a boy or a girl. That's where the importance lies; all the genes that interact as a result of this trigger are still dependent on SRY in the first place. TheFutureAwaits (talk) 21:12, 11 June 2009 (UTC)[reply]
Besides, the genes themselves don't care about the phenotypical outcome as long as they get to be inthe next generation. That's what's meant by selfish gene. And all those genes on the X chromosome are selfish and want to be in the next generation and don't care that much wheather it is a male or a female. The SRY gene is outnumbered and, despite of what you said, I think that does matter. Dauto (talk) 21:30, 11 June 2009 (UTC)[reply]
Going back to the first principles of evolution, suppose a mutation occurs on the Y chromosome being passed on to a son. The son with the mutated Y chromosome has a 50% chance of passing it on to a child; he'll definitely pass it to sons and definitely not pass it to daughters.
Now suppose a mutation occurs on the X chromosome being passed on to a daughter. That daughter has a 50% chance of passing it on to a child; all her children receive an X from her, but only half will receive the mutated X. So both sons and daughters have a 50% chance of giving the mutation to their children. Being on the Y chromosome offers no advantage. --Bowlhover (talk) 03:22, 12 June 2009 (UTC)[reply]
How can you make black through mixing colors?
Hi all,
If you had only primary colors available, would it be possible to mix them together in such a way to make perfect black? (We can assume hypothetically perfect primary colors.) If not, what colors are needed in order to produce perfect black?
It depends. Are we talking about Addition of Colors? (Like mixing colored light) Or are we talking about Subtraction of Colors? (Like mixing paint). Check out Color mixing to learn the difference. But briefly, if you're subtracting colors, then yes, you can mix red, blue and greenYellow, Magenta and Cyan, to form black. But if you're adding colors, then mixing red,blue and green will form white. APL (talk) 13:28, 11 June 2009 (UTC)[reply]
(ec) In theory, yes, see color mixing#subtractive mixing. In reality, you end up with some kind of dark mud colour because some light is still being reflected. This is the reason printers always use three colours plus black in full colour printing - the "mixed black" is just not good enough for quality documents. SpinningSpark13:30, 11 June 2009 (UTC)[reply]
Our article is also a little misleading, you might get a nice dark black as shown with subtractive mixing using filters but it won't happen with pigments as the article claims. I might just go edit that. SpinningSpark13:37, 11 June 2009 (UTC)[reply]
For additive mixing - mixing light - such as you do on a computer screen - then using zero amounts of the three primary colors gets you black. For subtractive mixing - paint, dyes, etc - you'd theoretically use the maximum amount of all of the primary colors. The problem with subtractive mixing is that firstly, the three primary colors that you'd ideally want are not perfectly manufacturable with available chemicals - and secondly that the means by which dyes, inks and paint pigments work means that they really cannot do a perfect job. SteveBaker (talk) 14:32, 11 June 2009 (UTC)[reply]
I can mix a good subtractive black with clear pigments in acrylic paints. I seldom want flat black because it rarely occurs in nature, but I can mix it. I spent an hour learning how. Most of the time, however, I want black with an edge, a punch, and that means a red-black, a blue-black or whatever suits the painting. // BL \\ (talk) 03:31, 12 June 2009 (UTC)[reply]
Is this person mentally challenged?
Someone online told me a few days ago that the solution to the world's problems was to "have a party for everyone." Now, obviously if you can't diagnosed OPs, you can't diagnose people. :-) But, is this a normal thing for an adult to think? (Okay, I'll admit they may just be saying they're an adult - but you'd think someone pretending to be an adult wouldn't be talking about magically bringing Mideast peace by having a party for everyone.)
What psychological reason would a person have for believing that by jsut throwing a party and inviting everyone, that: A. the people will come; and, B. that they'll put aside so much hatred? I know that in some cases, ordinary citizens have come together peacefully, but that's not the same thing as everyone stopping it.209.244.30.221 (talk) 15:00, 11 June 2009 (UTC)[reply]
Perhaps he was referring to a party in his mouth in which obviously everyone is invited. It's actual not a horrible idea; a world peace day celebration couldn't cause much harm. TheFutureAwaits (talk) 15:11, 11 June 2009 (UTC)[reply]
Unless someone used it to cover their sneak attack. Then it would just make things worse. I think people make the mistake that all of the world leaders are rational, which may or may not be the case. 65.121.141.34 (talk) —Preceding undated comment added 15:36, 11 June 2009 (UTC).[reply]
This sentiment also embodies the naive assumption that all wars, violence, and feuds are fundamentally "bad" for everybody, and that if we just agreed to stop having wars, violence, and feuds, everyone would be happier. Unfortunately, human history has shown us many times that wars are often beneficial to one or more responsible players. These players have no incentive to stop the war/violence/feud. Most often, they are able to separate themselves from the negative repercussions of conflict, either via force projection, effective defense, or some other method. They can then reap all the benefits while subjected to minimal harm, and are inclined to perpetuate the conflict indefinitely (until some strategic situational change). Nimur (talk) 16:04, 11 June 2009 (UTC)[reply]
Attempting a serious response: People mature psychologically in different ways. Some people may have difficulty formulating a realistic Theory of mind and fail to appreciate the potential threat of coercing various hostile tribes to attend a mass "social" gathering. However, people who voluntarily attend such a gathering would presumably share your friend's hope that we can all get along.
Several political movements have attempted to overcome the inherent fractiousness of human nature, by setting a singular purpose for their followers. Marxism teaches that religion, culture, and ethnicity are secondary to the great historical class struggle for economic justice. Christianity teaches that money, sex and power are secondary to the holy injunction to live a life worthy of Heaven. Secular humanism teaches that autonomy and freedom of thought are among the highest virtues, and the individual actualizes their dreams by hard work and merit. Dictatorships (benevolent or otherwise) demand that the subject peoples submit to the will of the sovereign. All these systems have inherent flaws because humans exhibit behaviour spanning from wonderful atruism to despicable evil.
The only way we can all "just get along" is if/when a large enough proportion of the population decides themselves to do so, through their shared belief and values. Otherwise humanity is always going to be a troublesome collection of competing tribes. ~~ Ropata (talk) 17:50, 11 June 2009 (UTC)[reply]
The OP friend's call to "have a party for everyone" has been interpreted as "throw a party for everyone" which is difficult to do. However if the caller meant "have a political party for everyone" they may be postulating that democracy would solve the world's problems better without political parties. Far from implying mental disease, that is a critical viewpoint that merits consideration. It supports the idea of Direct democracy whereby citizens vote on issues directly without intermediate representatives or parties. Examples of direct democracies are seen in Landsgemeinde in some Swiss cantons and in many countries an occasional referendum (plebiscite) that is held to resolve a specific issue. There are obvious practical difficulties with controlling government this way. However the speaker may have had a more ominous idea that only one political party should be permitted for everyone i.e. a single-party state such as a communist state or a form of fascism. All these are political standpoints that should be open to debate, though inapropriate for this Science desk, but there is a bad precedent for equating dissident political opinion with mental disease. Cuddlyable3 (talk) 20:26, 11 June 2009 (UTC)[reply]
I think the one that works is not "have a party for everyone" but is "everyone has a party together and likes it" but that won't feed people who are hungry :( ~ R.T.G20:28, 11 June 2009 (UTC)[reply]
Well I would assume this party has snacks and drinks, but yeah long term, they still have no food. And on a more serious note, you would have a very difficult time hosting a party for everyone on earth not only logistically, but also without gravely insulting at least one group. That means, your catering can have no alchohol or you will insult the Muslims, no pork products for the same reason. No beef because of Hindus. In fact, better go no meat at all for the vegans. Now you upset just about everyone else who was hoping for some beer and pizza. My point is that if you can't even get the catering to work out for all these groups, how do you expect them to work more serious issues out? I do not know this person and can not tell if they were serious, but they appear to be hopelessly idealistic. 65.121.141.34 (talk) 20:50, 11 June 2009 (UTC)[reply]
The best part about throwing an everybody-in-the-world party is that there are no neighbors to complain about the noise. APL (talk) 21:02, 11 June 2009 (UTC)[reply]
Back to te original question. I doubt the person was serious. However, taking the question at face value, and assuming they were serious, I would have to say that, yes, this person is perfectly sane, but most likely wrong. There are many mature, rationale, successful (have an apartment and car) adults who would do nothing but party if given the chance. Now how many of those people are in politics? :)
On a side note, war is not a bad thing. War distracts countries from developing dangerous technologies. War boosts the economy. War keeps the population under control. War is an outlet for aggression. Without war, society would collapse. Now bring on the insults and rebuttals, because I know they are coming.DrewSmithWhat I've done03:44, 12 June 2009 (UTC)[reply]
Rebuttal... Wars are excellent routes for technological advances. No one cares about the money you are spending on it, and you have a very strong motivation to develop new stuff to get the bad guys. 65.121.141.34 (talk) 13:19, 12 June 2009 (UTC)[reply]
God forgive me but you pluck ones out to represent all of the differing opinions/religions etc. but you make sure 100% they will not kill or even badly injure each other ever. You put them all on a spacecraft like the Arthur C Clarke Rama with all they need to sustain themselves or party and tell them they are going to a far away star. Then just throw them into orbit and watch them like Big Brother. You have picked them all out correctly so none dominates, none suffers too severe depressions, competitiveness is mild and the environment gets adequate care (which means excellent care really). You sit back and watch them all and they instinctively produce the solution to human differences. Maybe thats what the Earth is already. ~ R.T.G15:33, 12 June 2009 (UTC)[reply]
How do you select them so that you know that they will never kill or intentionally injure each other? I suspect even the Amish (about as pacifist a group I have ever seen) probably have the rare murder. 65.121.141.34 (talk) 16:37, 12 June 2009 (UTC)[reply]
WW2 was a good motivator for scientific progress, but is that typical of all wars? WW2 was a special case in many ways. For example, what technological advances has the civil war in Darfur produced? APL (talk) 18:46, 12 June 2009 (UTC)[reply]
You mean Darfur Sudan??? Probably because everyone else did the technological advances that they are using in their war 20+ years ago. 65.121.141.34 (talk) 19:53, 12 June 2009 (UTC)[reply]
Probably a combo of science and humanities. Anyway my comment on distracting countries from developing dangerous tech was a little misleading. Example: the A bomb would have been completed a lot sooner if not for WW2. The war diverted valuable funding away from the manhatten project.DrewSmithWhat I've done03:54, 14 June 2009 (UTC)[reply]
Quick one on Darfur; There was a truck discovered with a modifyed suspension so it didnt bounce so much when it was mounted with a Dushka and used as a platform for a fire baseChromagnum (talk) 10:37, 17 June 2009 (UTC)[reply]
June 12
Cancer in Whales
I was wondering why whales don't die early from cancer but in fact can be very long lived and as usual have found it is a question other people have asked before and actually it's called Peto's Paradox. I haven't seen any statistics on it though. Do people study of whales that are caught to determine if they have tumours?
And silly me. I was thinking with all the coal mining going on there, there was bound to be higher rates of lung cancer. OK, that was the worst joke EVER. I didn't even laugh at that.--Jayron32.talk.contribs03:22, 12 June 2009 (UTC)[reply]
As to the why, I was reading about Bowhead Whales and how they can live over 200 years and are 50 tons in weight. If one in eight of people die of cancer then even if we ignore the extra time a cancer has to grow but each person weight bit of the whale has that chance of a malignant cancer then overall their chance of escaping it would be something like (1 - 1/8) to the power of (50*2000/200) which google calculator tells me is about 10-29, i.e. they should all die of cancer and it's a wonder they live so long. By the way that's very interesting about chimps having a much lower rate. Dmcq (talk) 08:36, 12 June 2009 (UTC)[reply]
I guess, more properly stated, my question really is why would anybody expect the whale cancer rate per cell to be the same as a human cancer rate per cell? I don't see why it should be. In fact I think it should be expected to be a much slower rate given that a huge animal like that is necessarily going to have a much slower methabolic rate per cell. Dauto (talk) 13:10, 12 June 2009 (UTC)[reply]
Per Dauto's remark, the assumption of a uniform risk of malignant transformation per unit body weight does not bear scrutiny. Even within the human body, different tissues (and, for that matter, different cell types within those tissues) have vastly different probabilities of becoming cancers. Malignant tumours derived from fat cells (liposarcomas and their ilk) are exceedingly rare, whereas cancers of the mucosal lining of the colon and rectum (colorectal cancer) are depressingly common. While one should be cautious about carrying these assumptions across species, it is likely that all that whale blubber – accounting for up to half the mass of the bowhead whale – is resistant to malignant transformation. TenOfAllTrades(talk) 14:12, 12 June 2009 (UTC)[reply]
As to the rate per cell the whale lives far longer so that should offset its slower metabolic rate, thats why I didn't put in a factor for their longer life. Also since the cells divide many more times there's more opportunity for them to go wrong I'd have thought even in normal growth. As to the different tissues the whales have the same tissues so corresponding organs can be compared, they have colons and rectums too only far far larger. Dmcq (talk) 14:45, 12 June 2009 (UTC)[reply]
Speculation: high metabolic rate + relatively low volume of cells = high possibility that for humans, cancer is going to kill you. Whales are low rate and high volume, even if one had cancer, would it become large enough to kill it? More interesting as Dmcq points are are high rate, low-volume animals that don't have cancer problems. --98.217.14.211 (talk) 15:40, 12 June 2009 (UTC)[reply]
I don't see that the size makes much difference once a cancer has gone malignant. It'll spread and multiply and the only difference the victim's size makes is that it'll take a little bit longer to kill a bigger one.
Going backwards from whales to humans I get that if humans had an equivalent rate then death from cancer would have to be about 0.2% or less - which sounds much more reasonable and attainable by evolution than the 10-29 chance of surviving for whales I got the other way round. It still means whales must have some very good anti-cancer protection. I would have thought also it implies any evolutionary clock for whales would run much slower than expected for smaller mammals which mightn't be too hard to check. Dmcq (talk) 17:52, 12 June 2009 (UTC)[reply]
Well, Bovines are very resistant to all kinds of cancer. Whales are much closer to cattle (both are Ferungulata) than to humans. This does not mean that they have the same defenses, but it does make it at least plausible that whales have good cancer resistance. --Stephan Schulz (talk) 22:25, 12 June 2009 (UTC)[reply]
Where did you get that cows were resistant to cancer? I didn't find statistics but a web search seemed to show that cancer in cows was quite common and it having gone malignant was a common cause for condemning meat. And it's not as though they have long lives. Dmcq (talk) 09:43, 13 June 2009 (UTC)[reply]
I got it from the Science Magazine Podcast from April 24th (first interview, on the sequencing of the cattle genome - "cattle rarely develop spontaneous cancers [...] and almost never auto-immune diseases") - about 7'47" into the program. Archive,mp3. Sorry, not much more there, and I cannot make out the name of the researcher. --Stephan Schulz (talk) 10:16, 13 June 2009 (UTC)[reply]
I couldn't find a podcast on that date but it is a veyr interesting site. Seemingly people with Down's syndrome only get half the rate of cancer and primates in general get only a tenth of the cancer of humans. The authors seem to think our cancer protection has been compromised in the interest of growing a bigger brain. The primate rate is only ten times as much as I was calculating a whale had so well within the reach of whale evolution I'd have thought considering it isn't anywhere near so important for primates. So I consider the question as probably resolved. Cancer rates can be very variable and human rates are particularly bad considering our size and lifespan. Dmcq (talk) 12:24, 13 June 2009 (UTC)[reply]
Sorry about the link - I mixed up the Science and the Nature Podcast sites (I had to check both to find the Podcast again). The Science Archive page is [feed://www.sciencemag.org/rss/podcast.xml], but Wikipedia does not render that as a clickable link. The mp3 link above should work. --Stephan Schulz (talk) 13:19, 13 June 2009 (UTC)[reply]
Formation and evolution of the solar system#Moon-ring system said Europa, Io is tidally lock from Jupiter. is Titan tidally lock from Saturn? Does that mean Europa is moving further away from Jupiter? Is Titan moving away from Saturn? Pluto is also tidally lock with Charon. Does that mean eventually their moon will escape away from planet, until the moon escapes and become a own planet. Even the source isn't too clear.--69.226.38.106 (talk) 04:01, 12 June 2009 (UTC)[reply]
The ratios have nothing to do with the movement closer to and farther from the respective planets; the ratios have to do with the nature of the tidal lock. The ratio 3:2 means that the object makes three rotations per two orbits; 2:3 would mean two rotations per three orbits. As far as moving away from or towards the planet, you would have to know whether or not the moon's rotational speed is getting faster or slower as a result of the tidal lock. If the moon had to slow down to become locked, then, by conservation of angular momentum, it will be move FASTER in its orbit, thus drifting away from its planet. If it had to speed up its rotation, then it will have to slow down its orbit, and will drift towards its planet. This is all explained in the article. --Jayron32.talk.contribs05:28, 12 June 2009 (UTC)[reply]
Jayron's answer is slightly imprecise but he pointed to the article (Tidal acceleration) that explains all that in detail. To answer the OP's questions: Yes, Europa is moving away from Jupiter but not because it is tidally locked. It does so because it's orbit around Jupiter is prograde with a period longer than Jupiter's rotational period. samething is true for Titan. Triton, on the other hand has a retrograde orbit and is therefore moving closer to Neptune. Charon's orbit is stable because Pluto itself is also tidally locked. Dauto (talk) 06:01, 12 June 2009 (UTC)[reply]
Ok having read the article on this; i was thinking wouldnt the gravitational pull of the planet counter this making it more of a Elastic Orbit? it moves further away but gets pulled back in?Chromagnum (talk) 10:45, 17 June 2009 (UTC)[reply]
There's a picture of some at the start of the Poles article. I don't see what you're seeing. Perhaps you have an old picture that has gone a bit yellow? Dmcq (talk) 12:49, 12 June 2009 (UTC)[reply]
No, I saw a guy today who was obviously Polish/Slavic and he looked almost exactly the same as white British except with a yellow tone to his skin that white British people generally lack.--Kempist (talk) 13:11, 12 June 2009 (UTC)[reply]
Not sure what you are referring to. Most Poles are Slavs, and so share similar characteristics to other Slavs, such as Russians or Ukranians. However, Poland is surround by nations of different ethnicities, so there is bound to be a wide variation in appearances as people intermarry. Consider that the Magyars of Hungary and the Estonians are both Uralic peoples originally from Central Asia, while the Germans likely originated on the Baltic shores of Scandanavia. The fact is there is far more variance than assumed in an "ethnic" group, and such definitions are fluid and hard to nail down. What makes Nicholas Sarkozy French and Alberto Fujimori Peruvian and Linda Ronstadt Mexican-American is not just genetic lineage, but also environment. A person is Polish because they live in Poland, even if all eight of their great grandparents came from other countries... --Jayron32.talk.contribs13:25, 12 June 2009 (UTC)[reply]
Discussing peoples in Europe is particularly dicey because they don't seem to have stayed put for any considerable length of time. IMHO quite a few Polish people have a pasty to rosy complexion. Compare Images Voelkerwanderungkarte.png, Karte völkerwanderung.jpg, Invasions of the Roman Empire 1.png71.236.26.74 (talk) 15:42, 12 June 2009 (UTC)[reply]
I just had a look at the corresponding pictures in the British people and Poles articles. Comparing them against each other there is an overall slight difference in the shape of the heads I think but otherwise nothing at all obvious I think. Have you seen a lot of people from Poland? it doesn't sound like it if you're talking about one person, and you sure they were from Poland rather than it being obvious somehow? After all it's quite possible for individuals to have a yellower skin either from ancestry or kidney disease or a tan or there's just a great variation amongst people. Some of those British or Polish people in the pictures could be interchanged quite easily without anyone noticing I think. Dmcq (talk) 14:30, 12 June 2009 (UTC)[reply]
I've seen plenty of yellow looking British and I didn't think they were Chinese. Heavy drinkers. The Poles come over here and bang they are drinking around the clock (sometimes) you too would be gone yellow. Some of that yellow is natural anyway even if you were pure black. You think this is a yellow colour but you also think that the best way to pronounce Belgique is Belgi-um. If you look at those and still see yellow, go to the fourth row down, compare the elderly orient-asian man with the elderly caucasian man. There is plenty of yellow in the skin colour but it is typical. Yellow/brown/pink (white man). You are just a bit of a snob, sorry. Don't worry about it it's good for you. ~ R.T.G15:56, 12 June 2009 (UTC)[reply]
Since nobody has yet openly stated it, the original poster should be aware of a few things:
This sort of comparative racial ethnography is widely discredited by modern scientific analysis. (As mentioned above, mass migrations and population diffusion are so prevalent that they render the 19th-century ethnic archetypes wholly inaccurate).
Cultural definitions are more relevant than biological distinctions. Take a look at Polish people and Chinese people. Most anthropologists do not use skin pigment as a primary indicator of cultural identity.
The use of the term Chinaman may be construed as pejorative (offensive) in most contexts. Our article discusses the debate surrounding use of this term.
The lumping of skin-color and a generally offensive term suggest that the question is not asked in good faith.
Our general policy is to assume good faith on your part - possibly, this original poster is not aware of the implications of such a question - and in deference to the possibility that English is not your first language, or you are unfamiliar with cultural norms, I have posted this response as such. However, racially offensive questions are not very well received. While we don't censor such questions, because we value free speech, I think this question is inappropriate and unscientific. If you have a specific scientific question about ethnic or cultural identity; or if you have a specific question about human skin pigments, you should rephrase your question. Nimur (talk) 18:00, 12 June 2009 (UTC)[reply]
Out of curiousity, are there visible differences between Koreans, Chinese and Japanese? IOW, if you see an Asian person, can you tell which country they are from? For example, can you tell that Jin from Lost really is Korean? A Quest For Knowledge (talk) 18:18, 12 June 2009 (UTC)[reply]
I see nothing racially offensive about the content of the question though I know some people treat people of other races badly for no other good reason than their color. Personally I'm prejudiced in that I have liked both the Poles and Chinese I have come across, it's my negative prejudices I have to be a bit more careful about. And by the way yes I can tell Koreans Chinese and Japanese apart quite easily normally. Dmcq (talk) 18:32, 12 June 2009 (UTC)[reply]
really? I have asked this question of numerous japanese and Chinese people (and one mongolian) and they all said they could not tell the difference between Chinese and Japanese people until they heard a person speak (or only based on cues such as clothing). Don't many people depend on this fact? Spies, Korean-born-Japanese-pop-stars etc - if there are obvious visible differences, then the vast majority of people seem to be missing them. But then i am pretty sure that no English person could really identify a Pole under controlled conditions - people think they can because of subconcious social cues.YobMod19:07, 12 June 2009 (UTC)[reply]
Well there are lots of different types of Chinese people so you get all sorts but I must admit I'm very surprised. My first language was Chinese though I'm not Chinese myself so that probably helps with seeing them as different. Dmcq (talk) 19:22, 12 June 2009 (UTC)[reply]
There's a test at [1]. I didn't do as well as I though I would and seemingly lots of nationals from those countries do worse. Dmcq (talk) 20:44, 12 June 2009 (UTC)[reply]
I've read that carotene-based tanning products are popular in parts of Europe. That can give an unusual cast to someone's skin color. APL (talk) 18:40, 12 June 2009 (UTC)[reply]
From a biological point of view, you are adult since puberty. Thinking logically, having an identity or empathy are not signs that you are an adult, not matter how desirable these characteristics are.--Mr.K.(talk)12:42, 12 June 2009 (UTC)[reply]
Psychologically, such character traits may be used to distinguish adolescents and adults (depending on which theories are believed), which is called "psychological age". Cf. "chronological age", "biological age" and "social age". Chronological age is the most simple to detirmine, as one just counts from birth, but may not always be the most useful. Biological age has useful developmental markers such as puberty, but these may not correspond to social age - is a sexually functional 12 year old an adult? The answer is always culturally dependant. A 25 year old man could have the psychologically adaptive capabilities of a child, and his adult status may depend upon situations (eg. he is adult enough for sex, but all his money is stored in a trust fund controlled by others). So the scientific answer is "it depends on which science, and why the age is needed".YobMod13:15, 12 June 2009 (UTC)[reply]
(EC with yobmod)However, from a sociological point of view, what makes one person capable of taking on adult responsibilities varies greatly from society to society, and people will tend to act as they are expected; thus when a society expects a 14-year old to be an adult, one will often find a 16-year old having adult-like psychology. When another society places the age at 18, they will find most 16-year olds to have child-like psychology. And the biological definition of adulthood is not a bright-line. Puberty is a process, and I would venture that it is the end of puberty, and not the start, that is a better definition of full adulthood, but reasonable people may disagree on when that occurs. --Jayron32.talk.contribs13:17, 12 June 2009 (UTC)[reply]
Jepp - i didn't go into social age, but the textbook i am getting this from distinguishes that from psychological age. Social age means taking on responsibilites associated with a certain age, whereas psychological age is detirmined by "adaptive behavioural strategies". I don't think changing the social role necessarily changes the psychological age - teenage mother's need extra support as their social age is far advanced while their pschological age is not (and to some extent is dependant on biological age).YobMod13:29, 12 June 2009 (UTC)[reply]
(outdent)One hugely influential psych theory that differentiates between adolescenthood, young adulthood, middle adulthood etc is Erikson's stages of psychosocial development. And biological changes associated with growth continue much past puberty - chest hair growth for example may not have even started by age 19.YobMod13:29, 12 June 2009 (UTC)[reply]
There is a lot of evidence that brain development is not complete at age 18 - particularly the areas relating to self-restraint and risk-taking. Some studies show that full maturity does not arrive until perhaps age 25:
But we start to get into a fuzzy argument here - after all, people even later in life (in their 40's and 50's) start to change mental recall strategies from raw memory (which begins to fade) to using intelligence/logic-based strategies (which continues to strengthen). Should we argue that "brain development" continues into your 40's and 50's and declare all 30 to 40 year olds "under age" for some activities demanding cold, hard logic? Surely not?! But it's also arguable that humans evolved in a situation where they'd mostly be dead by age 25 (average longevity in the bronze age was 18 years!) - and even in ancient Rome, Greece and medieval europe 25 was about the average life-expectancy, so if brain development is still happening at age 25 - should we not consider 18 year-olds to be the "normal adults" (with their high risk-taking and poor self-restraint being considered "normal") and the 30+ year olds to be "post-adult" and incapable of considering "normal" degrees of risk? It's just a matter of terminology in the end. What we should perhaps be asking is whether it makes sense to impose limits on 17 to 19 year-olds because of this risk-taking difference. Limiting alcohol use and access to fast, dangerous machines might make sense even if we decided they were to be called "adult" because a "normal" level of risk-taking is still too risky when the stakes are that high. SteveBaker (talk) 16:20, 12 June 2009 (UTC)[reply]
Steve, although the average life expectancy in those times was 25 years or less, this was mostly a result of the large numbers of children born who did not make it to adulthood. A lot of times, if a person got past that first part, they would often live 50+ years. 65.121.141.34 (talk) 16:33, 12 June 2009 (UTC)[reply]
Why is it when I cut limes, my hands are never sticky? Actually, when I cut limes sometimes I don't wash my hands because they smell nice afterwards? Is it the low sugar content? If so, what type of sugar? --Reticuli88 (talk) 18:59, 12 June 2009 (UTC)[reply]
To answer your question, when you cut out limes, oranges or lemons your knife and your hands will never be sitcky, because it is not made of oils such as meat, chickens, or barbeques. When you wash dishes or hands with citrus fruits, watermelons, apples, or grapes all you have to do is rinse with water, but you don't have to clean it with your soap.--69.226.38.106 (talk) 22:20, 12 June 2009 (UTC)[reply]
May I ask a follow-up question, regarding the washing of fruit? It's common knowledge that one should wash, say an apple or grapefruit before eating, even though you don't necessarily eat the skin of the grapefruit - but my girlfriend has a tendency to wash an apple with washing-up liquid before eating it - a little drop on the sponge, wipe fruit, rinse fruit thoroughly. I find it awful. Is this practiced/common/uncommon/unspeakable? --Ouro (blah blah) 06:40, 13 June 2009 (UTC)[reply]
Fruit gets washed mostly to get pesticide residues and waxes (the "make the fruit look pretty on display at the store stuff"). Dishwashing liquid can contain lots of chemicals and you can't know how they might react with those you wish to get rid of. In addition those chemicals only get tested for irritating skin, not for what they do if the get ingested. In case your friend doesn't like the results she gets with plain water and a brush she might try adding a bit of baking soda. It's safe to eat (for all but a very few people with certain medical problems) and if nothing else has a slight Abrasive effect. A study (sorry can't get at it) has found that vegetable washes they advertise aren't any more effective than plain water and a brush. 71.236.26.74 (talk) 07:09, 13 June 2009 (UTC)[reply]
One has to wonder: if residue from dishwashing soap is harmful to ingest, what about the residue left on washed plates, bowls, and silverware and subsequently transferred to the food served on them? -- 128.104.112.114 (talk) 21:02, 13 June 2009 (UTC)[reply]
Here's a summary of the study I couldn't get at. [2] They even did study dishwashing liquid which I hadn't remembered. As you can see it didn't show any beneficial effect. They didn't study residues from it though. I think there's a study on that out there somewhere, but the one I'm thinking of might be outdated by now. Rinsing your dishes after washing is a good idea. --71.236.26.74 (talk) 21:55, 13 June 2009 (UTC)[reply]
warm "blooded" plants
In his speculations about the possibility of the most ultimate spread of life into space in Infinite in All Directions, Freeman Dyson discussed the advantages of warmbloodedness and mused on the fact that plants have never evolved this trait. What conceivable advantages for plants could such a trait have? --Halcatalyst (talk) 22:46, 12 June 2009 (UTC)[reply]
Plants have evolved other safeguards against temperature changes besides "warmbloodedness". The ability to maintain a constant temperature, aka basal metabolism is a fantastically wasteful process. You basically are eating all day just to keep your temperature up. There are certainly advantages to it, but seeing as plants evolved other systems to deal with the ups and downs of the external temperature, it doesn't seem like there was much need for them to evolve this trait, given the obvious disadvantages that come along with it. --Jayron32.talk.contribs23:12, 12 June 2009 (UTC)[reply]
I do believe it is lotus plants that elevate their temperature above the night-time surroundings. That to me would qualify as "warm-blooded" and it does convey an evolutionary advantage. I may need a few minutes to get the links though. (Especially since the 7th game of the Stanley Cup final series starts in a half-hour) Franamax (talk) 23:24, 12 June 2009 (UTC)[reply]
Whew, just in time. It is "Thermoregulating lotus flowers", R. Seymour & P. Schultze-Motel, Nature 383, 305 (26 September 1996) doi:10.1038/383305a0 My Nature subscription only lets me access fulltext back to '97, but as I remember the content, the plant upregulates to 2-3 degrees above ambient temperature. Anthems are starting, the game is on, must go now. :) Franamax (talk) 00:08, 13 June 2009 (UTC)[reply]
Warm bloodedness makes a more active life possible. You have to eat more, but you also have the energy to find the food. Plants, however, are rooted in the earth, which seriously limits their mobility and makes such a lifestyle unlikely. Unless they uproot themselves, like the Triffids. So it would make most sense if that trait evolved first. But I don't know of any real plants that can do this. The best chance of this happening seems to me to be in the water, where plants can float around and then still get their nutrients the plant way. Once they do that, the ability to swim may become an advantage, in which case warm bloodedness starts to make sense.
But then there is the necessity for muscles, which will be needed to use this energy. One way for plants to move is by growing. But then they would have to do that at an incredible pace and most of their energy would have to go into growing (and then splitting off in several plants, I imagine, something that plants are good at). The only other way that plants can move that I can think of is the way certain carnivorous plants do it. The descriptions sounds a bit like the way muscles work (note that I'm not a biologist). And the way the signal is passed on even sounds a bit like a nervous system, which seems to me to be another necessity, for rapid response to the environment. Give these plants another million years of evolution, and who knows..... DirkvdM (talk) 07:32, 13 June 2009 (UTC)[reply]
But none of those things actually require warm-bloodedness - the vast majority of animals that do these things are cold-blooded (or no blooded). Undersea life does not seem to have the same activity levels as land-based animals anyway - presumably most fish and crustaceans do not experience the daily temperature and associated activity levels of reptiles.YobMod07:15, 14 June 2009 (UTC)[reply]
As I recall, Dyson thought "warmblooded" plants would have some kind of advantage in deep space. I'm trying to get at what that advantage could possibly be. --Halcatalyst (talk) 20:57, 13 June 2009 (UTC)[reply]
To make things harder, most plants have a high surface area to volume ratio compared to warm blooded animals, which means they are even less energy efficient in maintaining their heat. Contributions/65.121.141.34 (talk) 13:54, 15 June 2009 (UTC)[reply]
June 13
What is this bug?
In the past two days, I've seen two of these little guys crawling around. Because I was too terrified to get a picture, I've done this awful MSPaint approximation. They're about 3/4 of a cm long, and the spots look like little fuzzy bits, and are arranged in a rectangle, with the darker orange on the outside and the beige on the inside. There is no shell or wings or anything, and they're not shiny. I'm in Toronto, Canada. I've never seen anything like it in my life -- what are they? And should I be worried? --✶♏ݣ01:23, 13 June 2009 (UTC)[reply]
That drawing and your description makes me think these might be ladybird(ladybug)larvae. There are many species of which the Harlequin ladybird is causing a little concern in the UK following its invasion from mainland Europe over the last few years. Here[3]is an image of a Harlequin Ladybird larva. What I don't know is how common these beetles are in Canada. You have little need to be worried on a personal level as they eat aphids and other small creatures, unfortunately including the larvae of other ladybird species. Richard Avery (talk) 07:18, 13 June 2009 (UTC)[reply]
Yes, it looks like it's probably some kind of juvenile ladybug. Frightening -- I hate ladybugs. (And all bugs. But ladybugs hold a special fury for me due to their invasion of 2003, and the fact that they tend to land on people.) Thanks guys. I guess I should be on the lookout for another ladybug invasion this summer. --✶♏ݣ23:39, 13 June 2009 (UTC)[reply]
Those ridges are called rugae. They are meant to help break down the food you are chewing, as food is pressed up against them during mastication.—Preceding unsigned comment added by Ropata (talk • contribs) 06:20, 13 June 2009 (UTC)[reply]
When I naively looked at pictures of dinosaurs , I think I see a pattern. There seems to be two types of dinosaurs.
1. Dinosaurs that walk/move on two legs
2. Dinosaurs the walk/move on fours legs.
It seems to me untrained mind that all the herbivore dinosaurs walk on four legs while all the carnivore dinosaurs walk on two legs.
This to me seems really really odd, if you are a carnivore then you need all the speed in the world to catch your prey. Therefore you must run faster by using all four of your legs, running on two legs is really stupid.
No carnivores today would run on two legs because your prey would run away faster than you can chase them.
I approach this question and I came up with 3 ideas. I want everyone to criticize me ideas and suggest new ones.
Three Basic Ideas.
1. Carnivore dinosaurs run on two legs because they have a long thick tail. Because they evolve into having long thick tails, they are unable to run on four legs therefore they must run on two legs to balance their tails.
2. Carnivore dinosaurs are blind, therefore they run on four legs. As they are blind they must hunt with their nose (sense of smell) therefore their front legs must be short as they move around with their noses to the ground.
3. Carnivore dinosaurs only hunt in shallow streams, as they must move in shallow streams, the fastest way to move around is on two legs rather than on four legs. So they hide underwater and slowly move closer to their prey and pop up in the last minute to run on two legs towards their prey. This makes a lot of sense to me as I practice running on four legs on a shallow stream and it is very difficult.
First, I doubt that your hypothesis is right. Many birds (cladistically two-legged dinos) are herbivores. And why would you assume that a 4-legged animal is necessarily faster than a 2-legged on? Humans are excellent long-distance runners (well, trained humans ;-), Ostriches can run at over 70km/h. Take a look at some kangaroos occasionally. Not all carnivores run their pry down in a sprint - there are endurance hunters, scavengers, and lurkers as well. And of course, to catch prey it is enough to be faster than the slowest prey - in fact, if anything the prey would have an incentive to evolve for speed ("The fox is running for its next meal, but the hare..."). --Stephan Schulz (talk) 09:19, 13 June 2009 (UTC)[reply]
Running on two legs does not make sense because it actually increases the amount of air friction as the dinosaur chases it's prey. If it had run on four legs, it will minimize the air friction and have a streamline aerodynamic form and get a better grip on the ground. 122.107.207.98 (talk) 11:23, 13 June 2009 (UTC)[reply]
Both aerodynamics and traction are only a small part of the equation. In fact, among primarily walking/running animals, I'm hard-pressed to think of a two-legged slow mover - all the slow animals seem to have 4 legs. Walking on two legs requires permanent balancing, and therefore a more active metabolism. --Stephan Schulz (talk) 12:04, 13 June 2009 (UTC)[reply]
Two monks (the biped kind) were walking through a jungle when a fierce carnivourous dinosaur jumped out at them. One of the monks calmly changed his sandals for a pair of Nike trainers that he happened to have. His companion said "Brother, what is the use of running shoes? Surely you realize that you cannot run faster than the fierce carnivourous dinosaur!" The first monk replied "I know that. I just have to run faster than you." Cuddlyable3 (talk) 11:28, 13 June 2009 (UTC)[reply]
Air resistance is pretty negligable at the 10 to 20mph these guys might maybe have been able to reach - so that's irrelevent. There are super-fast 2 legged animals (ostriches, certainly) and super-fast 4-legged ones (Cheetah for example). There are also 2 legged animals with massive endurance (humans possibly have the longest walking endurance of any land animal) and 4 legged ones that are almost as good (horses, for example). I don't think speed enters into the equation here - and as others have pointed out, you can be a carnivore and only eat things that are already dead!
I suspect the reason for two-legged gait being better is that your head can be up higher while still having a stong neck, massive jaws and teeth. Getting your head up higher allows you to see further and pick up scent from the air better - that's great if you're hunting live animals, or if you're hoping to find that Stegosaurus that died of old age earlier today. But if you are the brutally-killing kind of carnivore then you need to get up on top of your prey to sink teeth in and use your weight to push it to the ground - and for that, it helps to have your principle weapons and body weight held as high up as possible. If you look at the way quadruped canivores like lions and tigers work in modern times - they jump on top of their prey and sink their teeth into the back of the neck. They can do that with four legs because their prey animals are pretty small - and at those small sizes, jumping is a definite possibility. Something weighing a couple of hundred pounds can jump fairly high - but a 7 ton T-rex isn't remotely going to be able do that! It's an odd fact that almost all animals from the flea to the elephant can only jump about a foot into the air from a standing start. Getting a foot higher is useful if you're a lion taking down a gazelle - but if you're a 30' tall carnivore trying to take down one of those gigantic herbivores and you can only jump 1 foot - then it's pretty much useless. Hence if you need all the height you can get, a two-legged gait makes a lot of sense.
Someone should also explain about bird-hipped dinosaurs versus the lizard-hipped kind. I forget the details - but I bet that matters.
As for the two different types of dinosaurs, see ornithischian (bird-hipped) and saurischian (lizard-hipped). To generalise, ornithischian dinosaurs were usually four-legged and herbivorous, while saurischians included the sauropods (long-necked four-legged dinosaurs, usually herbivorous, some omnivorous) and the therapods (two-legged, carnivorous or omnivorous). The late-Cretaceous dromaeosaurid (therapod) dinosaurs included the ones that developed the most "advanced" brains, and are rather similar to today's birds. ~AH1(TCU)22:26, 13 June 2009 (UTC)[reply]
The way I see it is they evolved to be two legged to sharpen their hunting technique. What is the key thing dinos do in the movies? They jump really high, and pin their prey beneath them. Four leggers, on the other hand rarely hunt this way. In fact the mor efficient hunters tend to hide in the bushes and make extremely long range jumps, rather than the high jumps used by dinos. Could you imagine anything that walks on four legs making this kind of jump?DrewSmithWhat I've done09:19, 14 June 2009 (UTC)[reply]
The OP is incorrect to claim that "if you are a carnivore then you need all the speed in the world to catch your prey." because for success a predator needs other characteristics that may be incompatible with having maximum speed. Some useful abilities for a predator are maneuvrability, having size and colouration that are appropriate for lying in ambush or stalking close to a prey, finely tuned senses of sight and smell, a cooperative pack strategy, a combination of muscles + teeth + claws sufficient to triumph against the prey and the sense not to take on losing battles. Mating between predators happens only after some delicate negotiation. Cuddlyable3 (talk) 12:03, 14 June 2009 (UTC)[reply]
How hot is boiling water?
I was watching QI last night when Hugh Fearnley-Whittingstall mentioned that water on a "rolling-boil" was much hotter than water that was simmering. I have never really understood the difference between boiling and simmering, because in both cases the water is turning into vapour and therefore presumably reaching 100C, and I would not have expected that it would go over 100C (at least not by very much). Now I am wondering whether, on a rolling boil, whether so much heat is being put into the bottom of the pan that the water actually is getting much hotter (as HFW states) than 100C, before it gets a chance to vapourise. I read Boiling_water#Boiling_in_cookery but it does not seem to give a definite answer. Can anyway help clarify what actually happens please? Frank Bruno's Laugh (talk) 09:21, 13 June 2009 (UTC)[reply]
Yes, actually you're right, I was! I watched both last night and I guess I merged the two together. This is what happens when you waste your life watching panel shows! :) Frank Bruno's Laugh (talk) 12:03, 13 June 2009 (UTC)[reply]
Pressure at the bottom of an open saucepan of water is higher than atmospheric due to the weight of water above. This raises the boiling temperature slightly. With heat applied from below there is continual vaporisation of water at the base from which bubbles of vapour rise and are replaced by new water. This process absorbs considerable heat energy due to the latent heat of vapourisation that water requires. Superheated steam could be generated only by such a huge inflow of heat that vapour is generated faster than can be replaced by liquid. Cuddlyable3 (talk) 11:14, 13 June 2009 (UTC)[reply]
Thanks. Based upon my scuba experience, I believe that, very roughly, 10m over water exerts the same pressure as 1 atmosphere. Asssuming that the water in the pan is maybe 10cm, that would seem to indicate only a 1% rise in pressure at the very botton of the pan. In comparison, accoring to Pressure cooker raising the pressure to 2 atmospheres would lead to a boiling point of 122C, so I am guessing that the depth of water will have an incredibly small impact on the potential water temperature. Is that correct? I had a quick read of Latent heat of vaporization, but I'm not sure I really understand. It seems, as you say, that a lot of energy is required to actually vapourise the water (5 times more than is required to raise it from 0 to 100C?), but how does that actually affect the temperature of the water (and of the vapour that is formed) and how does that transfer to the food?
I am assuming, probably incorrectly, that the food absorbs heat primarily from the water, and that the water itself is still around 100C. Is the vapour much hotter, and does that heat also transfer to the food. Thank again for your help. Frank Bruno's Laugh (talk) 11:30, 13 June 2009 (UTC)[reply]
When you keep heating water, from say 250C, the temperature also rises uniformly, approximately given by the equation, Heat = Constant * (Change in Temperature). This goes on till you reach the boiling point of water, say at atmospheric pressure, at 1000. When you further heat water, the temperature does NOT rise. It remains at 100, the heat is absorbed to convert the water into steam. When all the water is converted to steam, only then does the temperature again rise. This extra heat supplied to raise the temperature from 100 onwards is called Latent Heat of Vaporization. I just thought i would explain this, I'm not sure about the other parts of the question. I presume the entire water would be at a constant 1000C. Rkr1991 (talk) 12:34, 13 June 2009 (UTC)[reply]
(ec) No it is credible not incredible that the depth of water has a small impact on the boiling temperature. Absorbing the latent heat of vaporisation does not raise the water temperature, it just changes the water's state from liquid to vapour. As long as the vapour bubbles disconnect from the heat source (base) as fast as they are formed they are not hotter than the boiling temperature. Since the thermal capacity of liquid water is higher than the expanded vapour you are correct to assume the food absorbs heat primarily from the liquid (it's all called water). Cuddlyable3 (talk) 12:41, 13 June 2009 (UTC)[reply]
The variations in air pressure due to weather (pressure, humidity, etc), and your current altitude, probably affect the boiling temperature of water much more than the 10 cm or water pressure. Also, impurities in the water (such as trace quantities of salts and carbonates) also probably affect the boiling temperature much more than the 10 cm of water pressure. You can easily probe the water with a thermometer to find out what temperature it is when various levels of boiling activity become prominent. I know that my water is not receiving heat uniformly, because I can see nucleation sites forming preferentially tracking the shape of my electric stove's heater coil (even if I slosh the water around or move the pan) - so even this heat conduction effect seems to be more important than the static water pressure.
In truth, the thermodynamics of a "simple pot of water" are very complicated - a huge number of competing phenomena, including water convection, cohesion, heat conduction, heat radiation, phase change and latent heat of vaporization, bubble-formation and fluid interaction, etc. All of these require elaborate statistics and calculus (fluid mechanics) to solve "exactly" (if such a thing can be solved exactly). The true temperature of the water when boiling is approximately 100 degrees Celsius, but at best this is a macroscopic average over the entire pot of water. Nimur (talk) 15:30, 13 June 2009 (UTC)[reply]
Actually I think that both are correct [4], not sure if usage varies by location. In the video that I linked at the bottom of this section, HFW does seem to be saying "rolling" (not sure if you can view the video), so maybe "rolling" is more prevalent in the UK. Frank Bruno's Laugh (talk) 11:06, 14 June 2009 (UTC)[reply]
Although the first time I mentioned it in my opening question you are right that I did say "bowl"! :) Luckily I used the correct spelling later in the question, so hopefully I don't look like a complete dunce! :) Frank Bruno's Laugh (talk) 11:09, 14 June 2009 (UTC)[reply]
As most writers above seem to agree, a rolling boil is within a gnat's whisker of 100 °C. WP says that simmering starts somewhere between 82 and 94 °C. So on average HFW appears to be right. --Heron (talk) 17:19, 13 June 2009 (UTC)[reply]
At normal pressures - the water can't get above roughly 100 degC without turning to steam - so the energy supplied by the stove top can't increase the temperature any further without first boiling all of the water away. I suppose any steam bubbles sticking to the bottom of the pan could get a little hotter than 100 degC before they floated up to the surface - but not by much because the surface tension of the water will tend to keep at least a thin layer of water between the pan and the bubble.
But I do know that in a water-cooled car engine, if there is no detergent in the water, bubbles of steam will form in some of the narrower passageways through the engine block and the temperature of the metal around them can spike quite high. That's why it's undesirable to fill your radiator with pure water without either "water-wetting-agents" or antifreeze. That's because the bubbles get trapped inside those narrow tubes and can't easily rise to the surface as they would in a pan of water on the stove.
What I suspect is being implied in the original post here is not that the water is literally hotter when it's boiling - but that things in the pan get cooked faster by 100 degC water that's boiling than 99.999 degC water that's just a fraction short of boiling. That is certainly a true statement - but it's about heat energy - not temperature. The reason is that when a steam bubble hits whatever is being cooked - which is still at less than 100 degC (presumably) - then the steam will rapidly condense back into water. When it does that - the steam gives up it's "latent heat of condensation" and a LOT of energy is transferred to your food as steam at 100.00001 C condenses into water at 99.99999 C. Transferring energy into the food cooks it quickly - even though the water keeps the temperature at a solid 100 degrees.
People who get almost-boiling water spilled on themselves don't suffer too much injury - but it doesn't take much steam at almost the exact same temperature to cause severe burns.
Whoa! It doesn't take much boiling water either. Where I live, "they" now advise people that water heaters should be set no higher than 50°C, on the grounds that 60°C is hot enough to be a significant safety risk to a person who doesn't react fast enough. I'm willing to take that risk, but that's not the point: an equivalent mass of steam may be worse than 100°C water, but the water can be bad enough. --Anon, 20:40 UTC, June 13, 2009.
As Heron pointed out, not all the water in a simmering pot is boiling - this is connected to what Nimur discusses further up. So the overall temperature of the water is cooler than in a pot at a rolling boil - where just about all the water is boiling. This isn't a matter of 0.00001°C, as discussed in the article Heron linked to. 80.41.126.158 (talk) 19:03, 13 June 2009 (UTC)[reply]
Thanks for all of the above. I'm tempted to go and buy a thermometer now and check the temperature at different stages of boiling (still confused, because I always consider "simmering" in terms of "bring to the boil, then simmer", suggesting that the water is boiling - but I guess there are different stages of simmering too). BTW the original comments from HFW can be found here @ 27:20 (for the next 7 days and, I think, only for people on a UK IP address). Frank Bruno's Laugh (talk) 10:56, 14 June 2009 (UTC)[reply]
Suicide Question
Hello,Im not seeking medical advice, just a curiosity, whats the best method of commiting suicide if you are locked in a room whit absolutely no tools (only your body)? (Not my case , if im writing this I have electricity and I can finish myself of this way.
DST
It's good that you don't seek medical advice because Wikipedia won't give it. The best method is not to entertain a morbid curiosity. Cuddlyable3 (talk) 11:20, 13 June 2009 (UTC)[reply]
There are plenty of ways to kill yourself under those circumstances. I'm not sure what you mean by "best". The most efficient? The least painless? Both are hard to gauge. I'm going to assume that simply dying of starvation and dehydration wouldn't be an option, for whatever reason -- so that implies that there's a kind of a time limit in which you need to get this done. In any case, under those circumstances, it's definitely going to get really ugly, and it's going to take some serious, serious will to die. I'm pretty sure most of us couldn't do it, because it's just too goddamn hard.
But there are options. If you have clothes, you could hang yourself or try to choke yourself with them -- but perhaps you're naked, what with the "absolutely no tools" parameter in place, and unfortunately, that's about as easy as it gets. You could chew through the arteries in your arms and bleed to death. You could bash your head against the wall or against a sharp corner if there's some sturdy furniture around. You could try to throw yourself down and land on your head so you break your neck -- again, probably easier if you had some furniture around, so you could jump off it. You could probably break your own neck with your hands. You could crush your own larynx and choke to death. You could simply punch yourself over and over again until you do some real damage.
I mean, as long as your body still obeys your commands, there are things you can do to damage yourself very badly. But none of these methods are easy, and all of this would be extremely difficult to do, not only because of the physical challenges involved but because this kind of stuff really goes against the grain: the instinct for self-preservation is going to make the kind of extended effort this kind of thing requires very, very difficult. That's why people who commit suicide generally do it in a way that's either fairly peaceful or fairly quick -- if all you need to do is jerk your finger or jump once, that's relatively easy. Repeatedly smashing your fist into your own body as hard as you can in the hopes of rupturing some internal organs or cracking a rib so it'll puncture a lung -- for example -- is a different story.
But even if you were to attempt something like this, it's hard to guarantee success; if you hesitate at the wrong moment, or don't have the willpower to go through with it, or just make a mistake, you could just incapacitate yourself instead of dying, and take too long to die. It's not a problem if no one is coming to stop you, of course, but if that was the case, you could just stop eating and drinking and let dehydration take care of it.
So what's the best method? I don't know. Personally, I wouldn't recommend any of them, because I'm not that kind of crazy, but rest assured that if you're locked away in that cell and 24 hours from now the alien invaders are going to march in and drag you to the Brain Probe to find the secrets of Earth's defense network from the deepest recesses of your mind, there are things you can try and, if you have the willpower and a basic understanding of what parts of your body are vital, and you're a little lucky, you can do it. Probably. -- Captain Disdain (talk) 12:11, 13 June 2009 (UTC)[reply]
We have an article called Guantanamo suicide attempts, which details the successful and unsuccessful suicide methods of several prisoners locked in a room with no meaningful tools. Many of them attempted to strangle or hang themselves with their own clothing. Many managed to fashion a knife or sharp object. Many have undetermined or unreported method of suicide. Nimur (talk) 15:18, 13 June 2009 (UTC)[reply]
If you'd like to volunteer for a Darwin Award you could try to verify the urban myth whether you can obstruct your airways with your tongue. Commonly referred to as "swallowing one's tongue". There are retching reflexes that should prevent that, but there's suspicion that running out of air might possibly interfere with that function. Another unreliable method would be to try to create a blockage in the Superficial temporal artery and hope for that to disrupt the major cartoid arteries. 71.236.26.74 (talk) 21:07, 13 June 2009 (UTC)[reply]
Hold your breath. Pinching your nose may help. In the meanwhile, if you change your mind, stop the procedure and start breathing again. --pma (talk) 22:51, 14 June 2009 (UTC)[reply]
I'm not sure if you're joking here, but I'm nearly certain you will pass out and begin breathing again if you try to commit suicide by holding your breath. Diogenes of Sinope, a Greek philosopher, is famously said to have killed himself by holding his breath, but the claims are dubious. —Pie4all88TC21:36, 18 June 2009 (UTC)[reply]
In any kind of suicide, you would want a technique that guarantees that you wont be left alive but brain-damaged or mutilated. I would guess that in the conditions described, an effective way may be to bite and chew the blood vessels in your wrists open. 78.147.253.196 (talk) 10:37, 17 June 2009 (UTC)[reply]
It was 1/3 for humans in Ireland a few years ago. Not deaths, just 'adults that will have cancer at some time in their life'. No link sorry. ~ R.T.G12:12, 13 June 2009 (UTC)[reply]
I'm afraid I couldn't find any reliable figures even for cats and dogs where you'd have thought the statistics would be best and you can be sold insurance and treatment. Dmcq (talk) 12:34, 14 June 2009 (UTC)[reply]
I get the impression that its way higher for humsns. Perhaps the chemicals formed during high-temperature cooking (not boiling) are to blame. 78.147.253.196 (talk) 10:33, 17 June 2009 (UTC)[reply]
I've heard statements like this from a number of people, and historically this topic is rife for speculation and conspiracy theories. Consider this though: the risk of cancer in any organism increases as that organism ages because errors and mutations build up over time, as much due to internal reasons (oxidative damage or copy errors during mitosis, for example) as external ones (environmental carcinogens), and since fewer humans die of disease or predation than most other animals, it's often cancer that does us in. Further, since more and more conditions are treatable and/or preventable now than, say, in our grandparents' time, cancer is more and more often the cause of death rather than things like chronic obstructive pulmonary disease, diabetes, or measles. For that reason, it's tempting to think that the rate of cancer is increasing, when it's much closer to the truth to say that death by other causes are generally decreasing. Thus, the observed increase in cancer rates is more a reflection of the overall increase in the average human life expectancy than the fact that we like to cook our meat. (Caveat: don't take this to mean that environmental carcinogens don't do anything, they just aren't quite the bugbear that people often make them out to be). – ClockworkSoul16:44, 19 June 2009 (UTC)[reply]
Air hunger / winded when stuck in lungs
Some times when I get struck in the lungs, such as being punched in the lungs, I get winded/air hunger. I understand that this only happens when there is too much carbon dioxide. How does getting punched trigger too much co2? Is it because the lung is contracted so the pressure increases and body thinks it detects a high level of carbon dioxide? Does anyone know typically at what level above normal atmosphere air hunger typical triggers at?--58.111.132.138 (talk) 11:45, 13 June 2009 (UTC)[reply]
The wikipedia article on air hunger defines it as the sensation or urge to breathe, and says that it is usually from a build up of carbon dioxide, but that doesn't sound like what you are describing. Us humans have three mechanisms that trigger breathing. One is based on stretch receptors that sense how often we expand our chest. This is the mechanism that most people must fight against to hold their breath, and is often neglected in citation of a second mechanism in which breathing frequency is controlled by the amount of carbon dioxide in the blood. This mechanism is important for long periods of breath holding, and unconscious people (such as in pearl divers and ICU patients) and controls our overall breathing rate more than it does each individual breath. It also keeps us breathing when we sleep. The third, and by far the weakest mechanism is based on the amount of oxygen in the blood. This so-called "anoxic drive" is really only important in that it is something to be avoided in patients who get oxygen therapy for long periods of time and at high concentrations. The air hunger that you describe sounds like the first one, and likely has nothing to do with carbon dioxide. When one is struck in the stomach or chest, the muscle that controls most of our breathing, called the diaphragm, can be suddenly stretched in a way that causes it to spasm or be temporarily paralyzed. This is often called "losing one's wind" or "having the wind knocked out of oneself", and is similar in cause if not duration to a hiccup. When this happens, we must use our far less effective chest wall muscles to exchange air for the short duration of the spasm, and the inability breath deep to stretch those stretch receptors, in addition to being just plain scary, leads to the distinctly uncomfortable "air hunger" that I believe you are describing. Tuckerekcut (talk) 14:05, 13 June 2009 (UTC)[reply]
Wikipedia really does have an article on everything, including getting the wind knocked out of you. Maybe we should redirect/rename that article to something more scientific. It is a common name for a mild (or severe) injury to the thoracic diaphragm, the muscle responsible for inflating and deflating the thoracic cavity (and the lungs, by proxy). When injured, this muscle may temporarily spasm or experience paralysis. Naturally, the severity of this injury ranges from mild to life-threatening. We can not give medical advice or diagnose your injuries, so if you are worried about repeated trauma, you should consult your medical doctor. Nimur (talk) 15:22, 13 June 2009 (UTC)[reply]
What is the nature of the big bang?
There is a theory that for the Big Bang to make sense in a universe, it would have to be equal parts implosion (sorry, define that as equal parts shrinking internally), both internal and external elasticity, accounting for all angles of everything. Supposedly that would be more difficult to prove/disprove than the bang itself. Is that a preposturous thing to consider? ~ R.T.G18:21, 13 June 2009 (UTC)[reply]
For every action there is an equal and opposite reaction, for all matter there is, possibly, an anti-matter. If the bang/fusion were so all-encompassing, it could be very precise. That would give it a definite center. That could make it a skin or a layer. Perhaps there is a light which has been receding? ~ R.T.G21:08, 13 June 2009 (UTC)[reply]
You still don't get it do you? Just making a long string of fanciful scientific sounding words does not a meaningful statement make. Just answer me that following question: How is the law of action and reaction and the existence of antimatter related to your vague idea of a expanding shell arounding a shrinking center. Be specific and use logic. Dauto (talk) 21:23, 13 June 2009 (UTC)[reply]
RTG, your recent questions at this refdesk resemble Chomsky's "Colorless green ideas sleep furiously", in that the string of word can be interpreted to have some metaphorical meaning in some technical sense, but are in plain-speak nonsensical. I would echo the advice you have been previously given that you will be better off spending your time reading some basic high-school physics text, instead of wasting it on idle and pseudo-scientific speculation. You can find a list of useful physics textbooks here. If you don't wish to borrow or buy one of those books, you can read some of the free texts listed here or even browse wikipedia - although personally I would recommend against such a slapdash approach. Hope this helps. Abecedare (talk) 21:29, 13 June 2009 (UTC)[reply]
I am suggesting that there would need to be something in that center. We have anti-everything else in theory and practice so where is the anti-light? ~ R.T.G21:38, 13 June 2009 (UTC)[reply]
I still can't tell exactly what you're talking about in regards to a centre. I also cannot tell why you're saying there has to be something there, nor what that has to do with light. That seems to all be nonsense. As for "anti-light", you may be confused as to what an antiparticle is. An antiparticle has the opposite electric to its non-antiparticle companion. Photons have no electric charge, so they have no anti. -- Consumed Crustacean (talk) 21:48, 13 June 2009 (UTC)[reply]
I concur that RTG isn't clear on antiparticles, but your definition doesn't hold, either. Antineutrons have been known for 50 years and have no charge (just like their standard counterparts). We don't expect "anti-light" because light isn't composed of hadrons, of which antiparticles are a subset. — Lomn23:43, 13 June 2009 (UTC)[reply]
Yeah, that's true enough. Antineutrons aren't elementary though; the antiquarks composing the antineutrons do have electric (and color) charge, which is flipped. -- Consumed Crustacean (talk) 23:53, 13 June 2009 (UTC)[reply]
That's not right either, in two accounts. First, some elementary fermions are neutral - we call them neutrinos - and they may turn out to be their anti-particles or not. We don't know that yet. Second, some gauge bosons have anti-particles which are distinc from themselves. The anti W+ is the W-, for instance. Even some chargeless bosons may not be their antiparticles such as some of the gluons. The particle-antiparticle thing is a symmetry of nature and some particles simply are their own "reflection" through that symmetry. A good analogy is given by looking at gloves and socks on a mirror. The righthand glove turns into the lefthand glove on a mirror and vice-versa. The rightfoot sock and leftfoot sock are identical. Socks are their own antiparticles. Gloves are not. Dauto (talk) 01:19, 14 June 2009 (UTC)[reply]
Fun fact : RTG first wrote "insulting" before he changed it to "preposterous".
RTG you're just mentioning a bunch of concepts and stringing them into sentences with no meaning and then asking us for debate.
Big Bang provides a good overview. Its not really within the remit of a Reference desk to consider the merits or otherwise of theories. We just provide references to such theories. If one is lacking, then there is little we can do to assist you. Is there are specific subject or reference you are interested in? Rockpocket
I don't think RTG is trolling, floating ideas to prod debate, or asking bad-faith questions. I think he has merely never studied or read a book about the subject and has many incorrect impressions, is all. RTG, I recommend A Brief History of Time, by Stephen Hawking — the book, not the documentary. If you can stick with it then I recommend taking some related courses at your local community college. Tempshill (talk) 05:06, 14 June 2009 (UTC)[reply]
APL and Pocketrocket are right. I thought some of you were being awfully rude but this is not a study group or a discussion center. I am just saying stuff like "What if that lines is curved?" I have read some Stephen Hawking, Tempshill, and it is very good but to go to college with that sort of thing is a matter of mathematics not just idle curiosity. I am just making personal amusement here, please forget about it. ~ R.T.G13:02, 14 June 2009 (UTC)[reply]
A 5 kilometer race is not an extremely strenuous run, but the answer depends entirely on how you have been training. An optimal training regimen will vary based on a lot of things, like your age, weight, and diet (not to mention your health and medical conditions - consult a doctor, etc). Even if you are training for strenuous run conditioning, it's often best to run no more than every other day. This gives your muscles time to recuperate and generally gives better performance (endurance and sprint capability). Our article about running may help give some ideas about run conditioning training. Nimur (talk) 21:26, 13 June 2009 (UTC)[reply]
The article supercompensation describes the theory behind timing one's training exercise to maximise fitness "on the big day". It also cautions that there is no one right period for the effects described. Therefore an answer to the OPs question should not be given by Wikipedia. The supercompensation theory may be useful only if the phases described have been actually observed and timed in an individual, ideally by a skilled sports coach. Cuddlyable3 (talk) 21:33, 13 June 2009 (UTC)[reply]
I think the standard answer is that the day before a race, it's best to run just enough to keep yourself loose. It matters less for a 5K than for longer distances, but it will still help. Looie496 (talk) 02:16, 14 June 2009 (UTC)[reply]
about death
Can we will be able to overcome over death.can we find out its answer .Here i m not talking about death of universe with change in entropy . —Preceding unsigned comment added by 119.154.10.21 (talk) 21:53, 13 June 2009 (UTC)[reply]
Have you read death? As far as I know when we die we are no more, just like before we were born. Other people believe all sorts of things like that one has an immortal spirit. Even if the universe was eternal I see no way a person could be immortal and have a meaningful existence. Either they could accumulate more and more experiences without any bound or they would stay their original limited selves and forever in effect keep repeating the same old things and not develop. If they develop without bound they would not be the original person. I suppose it would be reassuring though not to have death looming as an immediate anxiety. Dmcq (talk) 23:35, 13 June 2009 (UTC)[reply]
Personally I'm a bit sad about the fact that one day I must die, but the thought that everybody must die as well, greatly cheers me up. Up to now, natural death is the safer way we have to get rid of the worst people around. --pma (talk) 23:43, 13 June 2009 (UTC)[reply]
Much more serious (but possibly exceeding the horizon of the science desk) is the question: "Will we be able to overcome birth?" Other people, as implied by user:Dmcq above, speculate idly that there may be life after birth, yet evidence from any prenatal curly position is not conclusive. --Cookatoo.ergo.ZooM (talk) 23:59, 13 June 2009 (UTC)[reply]
I wonder if, by "overcome" the OP is referring to preventing or indefinitely postponing death, rather than surviving it in some form? If so, the work of the Methuselah Foundation may be of some interest to you. The reason we die - assuming disease or misfortune doesn't get us first - is due to the cellular and physiological effects of aging. If you can over-come aging, then you can overcome death (theoretically, in reality you would also have to overcome cancer or else that would get you eventually). Outline of life extension provides some strategies towards this goal.
The good thing about death is that it provides the ultimate I told you so moment of vindication, for either those who do, or do not, believe in an afterlife. The bad thing is that there is no-one of the other persuasion around to gloat over. Rockpocket00:32, 14 June 2009 (UTC)[reply]
The theory behind that goes something along the lines of plugging in the minute electrical pulses along our spines and transferring it into a computer. In reality this would prove to be extremely dangerous, and may not even produce results.
How does one "plug" into a spine? Seems to me (I'm no expert, not by a long shot) that this would be very delicate and dangerous. One false move and the spine would be damaged, thus paralyzing, or even killing the subject.
It seems like it may be futile because those electrical pulses probably don't contain our "soul". More accurately, they don't hold our memories, our self awareness, or anything that could be identify it as an individual. Even if you could get them into a computer, whats to say it'll actually do anything?
Which presents another problem. Taking the electric pulses would kill the body. So if it doesn't work you've got a dead guy, and possibly a fried computer. Ultimate "oh shit" moment, no?DrewSmithWhat I've done04:50, 14 June 2009 (UTC)[reply]
Attaching electrodes to spines of living people and sending electrical pulses along them has already been done, so is not necesarrily deadly, and would seem conceptually reversible (The only example i know of though was a programm using the technique to install experimental orgasm controllers in women, which had some success.). Measuring an electrical pulse could be done without erasing it, so that would seem soluble to. Which then leaves the questions of "soul", which of course have no scientific answer anyway.YobMod06:59, 14 June 2009 (UTC)[reply]
No, sending the pulses isn't deadly, but if you take them all out, and leave nothing (which I'm assuming you would have to do to create "existance" on the computer) wouldn't the body die? And I was using "soul" in a non-religious, non-scientific way. I meant the essence of who you are. If you kill the body but don't capture the "soul" it was all for nothing.DrewSmithWhat I've done09:27, 14 June 2009 (UTC)[reply]
The synaptic gap is a complex electrochemical signaling pathway, but it can be modeled as a high-impedance voltage source. You can connect many electrical loads in parallel to a single voltage source without any trouble - that is an operating principle of an ECG or EEG. (In other words, when the electrical pulse "goes in to the cardiogram machine", it also "goes in to the heart muscle" in parallel, with negligible loss of power. There is no need to worry that the neural electric signals will get "sucked into the machine" forever. Take a look at parallel circuit. A more realistic problem, as has been pointed out, is that we don't really know what signal we are looking at when we probe a nerve, and we can say with pretty good certainty that the electric pulses on the spinal nerve are not "the soul" (they are probably not even related to any cognitive process at all). The spine is primarily used to relay control messages and sensory input between the brain and the rest of the body. Nimur (talk) 14:29, 14 June 2009 (UTC)[reply]
Sticking one's personality into a computer seems like a bit of egotism to me. Unless you killed the original person there would then be two people starting off with the same memories. Dmcq (talk) 11:43, 14 June 2009 (UTC)[reply]
2050 is a LONG time away in computer technology. If you look back 40 years and see where computers were in 1970 and use that to extrapolate to 2050 - I have no problem believing we could have computers of reasonable size and cost that would have the power to run a neural network simulation of an entire human brain. This issue came up in the Ref desk a few years ago - and I calculated that if Moore's law continues than a suitable computer could be purchased for a million dollars (present value) by about 2035 - it would have the capacity to simulate the brain - but perhaps not in "realtime" (so the simulated human would think rather slowly). By 2040, everyone could afford one - and by 2050, an affordable machine would be cheap and faster than a real human brain. So the computer technology side of things is a done deal...it'll happen so long as Moore's law continues (which, admittedly, can't be forever). Since we know the real brain has the computational power to fit that much computer in that volume of space - I have little doubt that we could do it in the space of (say) a 10' x 10' x 10' cube...which is plenty small enough. So people who have a million dollars put away (which is a surprisingly large number of people) could be "retiring" into a computer in 25 years. The problem of thinking slowly is not so great - but once the brain is inside the computer - the underlying computer hardware can be upgraded over the years until their thought rates catch up (and ultimately exceed) that of living, biological people.
The trickier question is how and when do we put your brain into the computer? Some kind of non-invasive brain-scanning machine that could somehow figure out all of the interconnections and such would be idea. If it could do the job in a matter of hours, while we sleep perhaps, then you could make a 'backup copy' of your brain every night - and when you die - you'll only have lost the memories formed in the last day...which are probably best forgotten anyway. However, I suspect that people might want their brain scans to be taken while they are in the prime of their mental acuity - and that starts a complicated moral/ethical matter of when to stop recording...since any memories made after that point would be lost.
But that assumes that this 'brain recording' process is non-invasive and fast (and cheap!). If it's non-invasive but slow (or ruinously expensive), you might have to go get your brain scanned once a year or once a decade. If it's not non-invasive (like maybe you have to slice the brain into thin slices in order to get the data) then clearly you can't do this until you're already dead. Now the moral/ethical part gets even tougher...would people choose to commit suicide at a young age when their brain is functioning at it's peak in order that their electronic "afterlife" would be more productive? I don't know - but I don't think it particularly complicates things.
The business of the lack of a "soul" is something I completely discount. This is a scientific matter - not religious claptrap. Everything that makes our brains tick is due to the configuration of the neurons - and that can be completely simulated given enough computing horsepower.
Another issue relates to "quality of life" for these electronic people. Can we interface cameras, microphones, taste and touch sensors into these electronic gizmo's? Would robotic bodies be an appropriate thing to attempt? Would we instead build a virtual world for these virtual people to inhabit? I could certainly imagine the latter...something like "The Matrix" - an elaborate multiplayer computer game in which the inhabitants are driven by people who are now inhabiting these computers.
For the electronic brain - there would be no reasonable difference between the living person and the electronic version - their thought patterns can be identical - they will feel that they are still alive, they'll have all of their memories - and the means to form new ones - their dearest friends and relatives would recognize them by the things they say - the way they think. The electronic person would be able to hold down a job - which would be necessary in order to pay for electricity, software backups and replacement computer parts.
Some very exciting things become possible - you could choose to run your brain at varying clock rates. If you're bored - you can "fast-forward" to the next interesting thing. You could pause your brain for years, decades, centuries and "time travel" to the future. You could send an empty computer on a slow rocket to the nearest star - and when it gets there, transmit your brain pattern to it. You'd be able to travel around the universe at the speed of light...but in zero time as far as you are concerned. One moment you're here on earth...then ZZAPP! and you're in orbit around Alpha Centaurii. Of course, when you come back with your new memories and holiday snaps - 8 years have gone by here on earth - but your (dead) friends and relatives can fast-forward through that if they miss you - and for you, it seems like no time has passed.
Being able to make copies of yourself is an interesting and difficult thing. If the computers involved are merely simulating a human brain using mathematical models of biological neurons - then there would probably be no way for your two copies to be merged back together again...so you couldn't (for example) have a copy go on vacation while the original stays home - then merge them back together again and have memories of both things...that (I think) makes it less interesting to make copies...but it's obviously possible - and more ethical/moral dilemmas are bound to happen as a consequence.
There is also the possibility of running your electronic brain faster than realtime. This would be one way to make a living - being able to think at (say) ten times the speed of a living human would give you some significant advantages in the job market. Electronic people with more money would be able to upgrade their computers more frequently - and have faster models than poorer people. Rich people would be able to hold down better jobs...not much changes there, I guess.
In the long term - there might be trillions of electronic people - and only billions of biological people. It might be that we come to think of these brief biological years as a kind of childhood...but the need to look after these trillions of computers - provide power, spare parts. upgrades...that would soon come to dominate the "work" of mankind. But with robotic maintenance workers - maybe even that isn't a problem.
For people who come to tire of life in this electronic form - suicide is a simple matter. But the ability to "fast forward" your life would probably mean that these people don't choose to kill themselves - but merely slow down their brains more and more to travel futher and further into the future - in the hope that something better comes along. In this form, "fast-forwarding" people would consume virtually zero resources - their minds could be archived for years on "backup" memory (like the hard-drive on your PC) - and only reloaded once in a while as requested before they slept. Much of mankind might be in backup memory form for most of the time - waking up only once a century to see what's new.
A lot depends on the technology of the brain scanning machine. That's really the only technological hurdle...we have brain scanners that work at larger scales - I could imagine them getting more and more precise - until they could resolve individual neural connections. There is active research in these areas. I wouldn't be surprised to see this happen by 2050...and the closer we get to it - and the more people who realise that the long-sought goal of immortality is within our grasp - the more that research will be pushed.
I think this can happen - and within the lifetimes of many of the people reading this page. Sadly - the math says that I probably won't live long enough to make use of it...darn! But I think there is every possibility that if you are (say) 30 years old or younger today - then you could wind up living as long as you want...but not in your biological body.
Nice to meet you, Mr. Kurzweil; it's an honor to work with you here on the refdesk. Wish you hadn't been pseudonymous for all this time. Tempshill (talk) 16:43, 14 June 2009 (UTC)[reply]
Ouch! I'm pretty sure that accusing someone of being Ray Kurzweil falls under the WP:NPA rules! :-( 17:58, 14 June 2009 (UTC)
Well Steve, I'm optimistic for the future that you envision, because it seems like progress to me; but I really wonder if Moore's Law is actually even relevant on the technology roadmap to making this happen. I see more important obstacles than hardware capacity standing between our present society and a computerized, brain-in-robot-body utopia.
Without doubt, computers are rapidly accelerating (even the last few years of thermal nightmares, clock-rate growth-pains, and economic downturn have not been able to slow the pace by much). Disk storage is so huge it's laughable (at the lab on Friday, they just threw out several sets of 300 GB disks because they're "outdated" and not cost effective!) And with a sizable server room, we can stuff petaflops and zetabytes and gigabytes of bandwidth.
But what about software? Every day I work with brilliant physicists who still don't know the meaning of "pthread" - so when we provide them a rack of 400 cpus, they use them one-at-a-time (not always, but more often than we'd like). We're at a crossroads of computer interfacing technology - it's becoming harder and harder to stay at the cozy abstraction layer we have been in for a decade or more, because harnessing these new computer technologies means getting down and dirty with the hardware model. 300x faster FFTs, you say, but what's NUMA again? And we're solving "conventional" programming challenges - number crunching type problems. Faster number-crunching machines do not immediately solve all problems - even problems that are already formulated as number-crunching problems!
You're sort of skipping the step where a crew of bio-/genetico-/computer-/software-/electronics-engineers take the primitive state of understanding of human neurology, and translate it into an engineering schematic for the hardware and software of the computer of 2050. To do this, we need several key accomplishments - first, we need to really really understand the biology behind the brain. How much do we have to replicate and simulate? Individual cells? Neural blocks? Neural connectivity schemes? Or maybe just a "low-pass filtered" version of some kind of psychoneural model. For all we know, we might need to simulate every neuron's intricate internal cellular chemistry, down to the femto-mole concentrations of neurotransmitters - or worse, we might need to simulate the genetic code and protein folding arrangement. We don't even know what we need to simulate, because the best efforts of a hundred years of psychology and neuroscience still haven't answered the basic questions about what exactly a thought is made of.
Once we have the elaborate biology of brain function worked out, we then have the arduous task of generalizing it (so that it applies equally well to all human brains, not just a few test cases). The Human Genome Project has shown us that this is non-trivial. (And, they only have some 4 billion "bits" worth of information! The whole human genome for one individual fits uncompressed on a DVD-R!) I can't really comprehend how much "state" you need to save if you want to recreate the finite state machine that is a 45-year old human - there are hundreds of thousands of words, millions of sentences, who knows how to count how many images, sounds, sensory perceptions - all stored in the brain. What if there is a different packing format for every individual? You might have to start with a physics/chemistry simulator of the basic genetic code, and "press play" to see how the neuro-chemistry unfolds, given those sets of genes; and then you have to generate an custom-built interpreter for that individual's mind.
Now mainstreaming this so that every person can afford this technology is the next challenge. Imagine the issues surrounding reliability and stability. When you have (as SteveBaker predicted) a trillion individuals, what sort of bit-error-rate is acceptable? What mean-time-between-failure is acceptable for a project with a million-year lifespan? What tradeoffs in reliability are acceptable if it means that we can mass-produce this technology and allow more people to store their brains (albeit with more risks?) Thus ensues a complex moral/ethical debate.
I don't know if we have 25 or 50 years before the technology is available. I think it's so difficult to guess because we only have half of the technology (the computer-side) in a form which we can quantize and measure. The biology, neurology, and psychology is so far from mature, that it could be centuries - or never - before it's ready. We don't even know. For all our best guesses, we might have already surpassed the human cognitive ability with a mainstream computer - but without the software to emulate human behavior, we can't run a comparative benchmark suite. Most of the time, when I evaluate a nifty new image recognition program or semantic natural language processor, it doesn't require a hardware upgrade - but new abilities are granted to my almighty, infinitely programmablehandheld computing device.
You're sort of skipping the step where a crew of bio-/genetico-/computer-/software-/electronics-engineers take the primitive state of understanding of human neurology, and translate it into an engineering schematic for the hardware and software of the computer of 2050.
Well, the 2035 estimate assumes that present neural network simulation software would be employed to completely brute-force simulate the brain by replicating the actions of every single neuron. Biologists understand what an individual neuron does - you apply these stimulii - some time later, it fires or not and some signals head outwards...there is some recovery curve or other. Sure there will be questions of blood flow and such like - but our brains seem pretty resiliant to changes in those kinds of parameters. There would presumably need to be careful measurement of the performance of various kinds of neuron - but it's not that tough. Doubtless, advances in understanding the brain at the middle-levels (higher than "neuron" but lower than "the frontal lobe does this and the temporal lobe does that") would result in massive simplifications in software and reductions in hardware - but the brute-force approach ought to work - and it's easy to crunch the math to predict when we might get there.
I can't really comprehend how much "state" you need to save if you want to recreate the finite state machine that is a 45-year old human - there are hundreds of thousands of words, millions of sentences, who knows how to count how many images, sounds, sensory perceptions - all stored in the brain.
Well, we know how many neurons there are - and how many connections each one has to it's neighbours. That tells you how much storage space you need for the network - and it's do-able with another 25 years of Moore's law expansion for a $1,000,000 hardware outlay. The rate at which neurons fire gives you a way to measure the amount of CPU time you need - it's huge - but it's very parallelisable...this allows us to use a lot of simple CPU's to provide the horsepower we need. It's do-able.
What if there is a different packing format for every individual?
The naive plan that I propose would entail simulating all of the connections between that individuals' neurons. That's all of the memories (although perhaps not the short-term memory) - all of the learned algorithms - the lot. We number all of the neurons - and for each one make a list of all the other neurons it connects to - the lengths of those connections and whether they are excitatory or inhibitory. This connection pattern is obviously unique to that individual - and will change day by day and hour by hour as memories are formed. We'd need to understand how new connections are formed.
You might have to start with a physics/chemistry simulator of the basic genetic code, and "press play" to see how the neuro-chemistry unfolds, given those sets of genes; and then you have to generate an custom-built interpreter for that individual's mind.
No - that's truly impossible...if it can't be done at the level of neurons - it's certainly impractical to look to yet lower levels.
Imagine the issues surrounding reliability and stability. When you have (as SteveBaker predicted) a trillion individuals, what sort of bit-error-rate is acceptable?
Real neurons are incredibly unreliable - they die of old age - diseases kill them. The brain has enough redundancy and plasticity to survive that. Our software simulation will have that same property. So small errors in these gargantuan computers would be survivable...perhaps even necessary to an accurate simulation! We need to occasionally make mistakes or we won't be human. However, wholesale failure of an entire computer could be serious - like a car wreck. Fortunately, we can make backup copies. You could have the exact state of your software brain backed up (onto "hard disk" - or whatever we have in 2050) on a regular basis. A "car wreck" scale of computer failure would result in you losing a few days of memories - but not much worse.
Thus ensues a complex moral/ethical debate.
I don't doubt the moral/ethical issues...they are exceedingly complex. However, we'll have a decade between the technology first seeming "real" before the first people will be using it - and to start with, it's going to take immense computing resources (perhaps a warehousefull) for "early adopters" - so only the very rich (or perhaps very accomplished/valuable) individuals will be able to have it. It'll be another decade after that before the average person would be able to afford it. That's plenty of time for the ethical issues to be worked out.
I wonder how quickly the brains will have to be imaged and at what resolutions to extract the data with enough fidelity. APL (talk) 06:31, 15 June 2009 (UTC)[reply]
That's a serious concern. I used to think that brains were like computers in that they had software and hardware - and (as with a computer) if you turn it off, the sofware just vanishes and everything the machine was doing at that instant was lost. However, brains are a bit more complicated. It seems that only short-term memory is represented as electrical signals zipping around some kind of closed-loop pathway - but everything that is more than a few minutes old is retained by physically rewiring the neurons. That being the case (and perhaps the jury is still out on this one), we'd only have to replicate the connectivity of the neurons to have the brain be able to 'reboot' successfully with only short-term memory loss. I don't know enough brain biology to be certain of that - but I believe it to be true. SteveBaker (talk) 13:34, 15 June 2009 (UTC)[reply]
Well, we know how many neurons there are - and how many connections each one has to it's neighbours. That tells you how much storage space you need for the network
What about the key issue of plasticity (both neural and synaptic)? Brains physically change. The brain you had this morning is not the same brain, in terms of the number of neurons and the connections each one has, that you have now. Neurons are born and die, they grow and shrink, they fire and wire. Its very likely it is those very changes that encodes the part of you - your memories, what you sensed, learned, forgot and how you felt - that was formed today.
So even if we could scan a brain and somehow make sense of what all the neurons in the present synaptic configuration meant at that given moment, its likely that would only provide us with a snapshot in time, analogous to the information a screen-shot gives you about a movie. To understand the movie you need to watch frame after frame after frame, in the correct order. Likewise you might only be able to understand how the plasticity of the brain encodes the information present by doing scan after scan after scan and comparing the changes. But even if you scanned your brain every day from birth until the day of your death, would you still be able to understand its plasticity well enough to predict how it would wire in a completely novel situation? Say, for example, if you found yourself face to face with a great white shark while going for a dip in the sea, how could you possibly predict how your brain would wire in response to that. What frame of reference would you use? Going back to the movie analogy, consider a good twist ending. You can watch every single frame, and - up to that final scene - still not fully predict how it will end and be totally amazed when something unexpected is revealed.
I predict we will be able to artificially model human brains one day, but never be able to recreate the unpredictable wonder that is human consciousness. Predictable movies are boring movies, so I'll enjoy every second of the original on the big screen and pass on the straight-to-DVD, cash-in sequel, thanks. Rockpocket06:17, 15 June 2009 (UTC)[reply]
But surely accurately modeling the brain would entail modeling even the unpredictable aspects? It's not as if our brains suddenly break the laws of physics every time we have an unexpected thought? APL (talk) 17:53, 15 June 2009 (UTC)[reply]
What about the key issue of plasticity (both neural and synaptic)? Brains physically change. The brain you had this morning is not the same brain, in terms of the number of neurons and the connections each one has, that you have now.
Our software simulation would have to allow dynamic reconnection of simulated neurons - but that's not a hard thing to do. Bear in mind that we already have software that simulates neural networks - they can easily accomodate on-the-fly rewiring...creation and deletion of neurons. I don't think this is an obstacle. Remember - I'm not talking about building some custom computer chip which mimics the wiring of your brain. I'm talking about using a general purpose computer so simulate those connections using tables of data. Naively: You'd have a big array of neuron data - with one entry for each neuron. Each neuron gets a number and inside its data structure would be a long list of the numbers of all of the other neurons it connects to (the synapses). When the neuron 'fires' you'd loop through the list of connections and apply an excitatory or inhibitory signal to each of the synapses - changing the data structure for the neurons you just changed the state of. Over and over again...very fast. Adding new connections to our software brain is a simple matter of changing the list of synapses that this neuron connects to. We would (of course) need to understand what causes new connections to form - at the neural level. That may take some biology that we don't understand yet - but we have 40 years to figure it out and when you consider the state of our understanding of the brain back in 1970, I think we have time.
Say, for example, if you found yourself face to face with a great white shark while going for a dip in the sea, how could you possibly predict how your brain would wire in response to that.
Well, I presume that each neuron is mindlessly following a set of rules that some piece of biochemistry makes it follow. Perhaps the concentration of chemicals along a frequently used pathway results in a stimulus for neurons to grow their dendrites in that direction - resulting in shorter connections where the information flow is densest. I'm no biologist - so I don't know whether that's what happens - but the answer is one of chemistry and cell growth - not some complicated question about sharks and swimming. The neurons are just simple switching machines...not unlike the 'gates' in an electronic circuit - except for this rewiring business.
I predict we will be able to artificially model human brains one day, but never be able to recreate the unpredictable wonder that is human consciousness.
Unpredictability comes from complexity - as well as from randomness. Computer software can already be so complex as to seem unpredictable by any reasonable measure. Our "brain computer" would be similar in size and complexity to the entire Internet. Chaos theory can easily ensure that degree of seeming randomness because the processes we'd be simulating would suffer from 'sensitive dependence on initial conditions'. I'm sure that if we could do this at all, the person involved would be 100% convinced that they were still "alive". The extent to which we could make things seem "normal" for them is a tricky question...the immediate lack of the normal senses of sight, sound, touch, smell, taste, proprioception, etc would be a big problem. The simulated brain would need to learn how to connect to it's new senses...cameras, microphones, etc. We could perhaps plan for this in advance by planting electronic devices into the living brain which people would learn to use before death - and which could continue to function in precisely the same way in the simulated brain. We know that blind people can be given "sight" by connecting electronics directly to nerves in the retina - and even to other parts of the body.
13:34, 15 June 2009 (UTC)
I think the system identification problem is far tougher than the "system simulation" problem discussed above. I am curious to know what technology can possibly be used to "scan the brain" at a sufficient spatial, temporal and functional resolution. Is there one available today that simply needs to be "grown", or do we need to come up with something(s) qualitatively new ? Abecedare (talk) 07:38, 15 June 2009 (UTC)[reply]
I guess you could freeze the brain and take thin slices. If everything necessary to reproducing the brain survived such a process I don't suppose it would be too difficult to automate scanning the slices and generating an electronic replica. It sounds about possible with todays technology. Doing it without killing a person sounds a lot more difficult but it might be possible with nanomachines going around in the blood and reporting back to scanners around the head. There's also the possibility of replacing bits of the brain gradually with prosthesis so one day without a visible transition a person is all imlemented in silicon. Dmcq (talk) 11:56, 15 June 2009 (UTC)[reply]
I agree that the 'scanning' problem is a tough one. It's the hardest because (in a sense) the other part of the problem is already solved. We know we'll be able to build computers big enough - and we know that simulating something as fundamentally simple as a neuron can be done. We know that small errors in that simulation aren't critical because we know that the brain still functions after considerable damage, under changes in chemical environment and so forth. Scanning is hard because we haven't even started to look at that technology.
We have brain scanners that can look at large-scale structures - perhaps (I don't know) a really precise PET scanner or CT scanner could image such small structures given 40 years of technology advances. There is certainly plenty of research into ever more precise brain imaging...it's not unreasonable to assume that we could do that. Nanotechnology (meaning nanotechnology robots and computers) would certainly make the destructive imaging of brain very do-able - but I'm doubtful that this technology will come to fruition.
The idea of replacing the brain a bit at a time is an intriguing one. We know that you could chop out a sizeable chunk (say 1%) of someone's brain and that they'd still be "themselves" - able to think, function, etc. If we replaced that 1% with some computer circuitry representing a neural simulation of about the same number of neurons - and did so in such a way that the living brain could make use of it just as if it were biological neurons - then perhaps brain plasticity would result in that 1% being used for thinking and memory storage in the future. Do this 1% at a time and after 100 such operations - the person is living entirely inside the computer. My concern is that the rate at which this might happen could be too slow. If it took the person a year for their brain to adapt to the new circuitry (which seems reasonable) - it might take 100 years to replace the brain at 1% per year. You'd have to do it in small steps or else there might be massive memory loss at each stage.
For our purpose we need to be able to measure not only the structure of the neuronal network but also synaptic strength that is thought to encode memory, and perhaps other neuronal and synaptic characteristics. None of the technologies listed above are likely to be ever able to do this - the reason being a fundamental mismatch, not just technological barriers that can be resolved by throwing enough money at the problem. For instance the spatial resolution of a MR scanner is not only at (at least) 9-orders of magnitude worse than what would be required to visualize a neuron - the contrast mechanism (T1/T2 relaxation times in anatomical scans, or the haemodynamic response in fMRI) are essentially bulk tissue phenomenon and hence will never be scalable down to a neuron resolution. The contrast mechanism in CT scans (X-ray attenuation coefficient) is even more limited, while PET measure the degree of absorption of the injected radionuclide, which again is a bulk effect. Finally, slicing and freeze drying a brain may preserve the structural properties of the tissue, but many of the functional properties are destroyed.
In short, I think a fundamentally new enabling technology in order to identify and record the brain state. Personally I think most computer scientists underestimate the difficulty of this "wet sciences" problem. I have no doubt that it will be eventually solved by but I'll be (pleasantly) shocked if it happens in 30-50 year time-frame, even in a laboratory setting. Abecedare (talk) 19:10, 15 June 2009 (UTC)[reply]
Awesome information (albeit a bit depressing!). Thanks! I guess we computer folk had better get a move on with the nanotech robots then. :-( SteveBaker (talk) 00:42, 16 June 2009 (UTC)[reply]
Just wanted to thank everyone for this interesting and informative discussion about mankind's oldest concern in the modern age. And to think, all this from a poorly-worded question from an anon! —Pie4all88TC21:51, 16 June 2009 (UTC)[reply]
June 14
Betalgeuse + supernova
According to Betelgeuse#Betelgeuse's fate, it is quite likely that the star Betelgeuse would go supernova within the next hundred years (if I infer properly from the numbers provided). According to the article, the star's rotation is not near the Earth, so there is no chance of damage to the ecosystem. Two questions:
Would such an explosion cause problems for telecommunications and other electronic devices
I don't think it will cause any problems for electronic devices: after all, it's more than 500 light-years away, and besides, the Earth's ionosphere will probably block most of the radiation that does reach the Earth. Just my opinion though, I'm not a professional astrophysicist.
I'm guessing a kiloparsec is 1000 parsecs? If so, and this one is only 200 parsecs, then it would probably be worse than the 1kiloparsec mass extinction prediction.DrewSmithWhat I've done09:59, 14 June 2009 (UTC)[reply]
Correct. Since Betalgeuse is approxamately 650 light years away, we wouldnt know it exploded until ~650 years after that happened. Livewireo (talk) 19:51, 15 June 2009 (UTC)[reply]
Betelgeuse has shunk in diameter by 15% in the past 15 years! Another example of a star to go supernova in the near future, although with a larger explosion (possibly a hypernova) but farther away but as a binary star but its axis is also not pointed toward us, is Eta Carinae. Currently, the closest star to us that is predicted to undergo a type Ibc or II supernova in the future is Spica, which would shine at the intensity of nearly the full moon; Betelgeuse would be a bit dimmer but would leave a bright nebula. ~AH1(TCU)01:33, 16 June 2009 (UTC)[reply]
Artificial breeding to save endangered species
Suppose you have a species that's on the brink of extinction. To save the species, all surviving members are gathered and artificially bred to boost the population. There's a problem, though — there's only 1 male among the surviving individuals. Is there an optimal pattern of breeding, if the goal is to increase the genetic diversity of the offspring? —Preceding unsigned comment added by 98.114.98.148 (talk) 01:41, 14 June 2009 (UTC)[reply]
Put em in a cage, and let the dude get gangbanged. Jokes aside, the optimal breeding pattern is to put the male in a cage with as many females as he seems happy around. Add one female per day (or even per week) and observe the males attitude. When he starts to be aprehensive about the schedule time to add a female, stop adding them.DrewSmithWhat I've done03:57, 14 June 2009 (UTC)[reply]
If there is just one male left - then the breed is already gone. The lack of genetic diversity in subsequent generations would doom them. SteveBaker (talk) 04:11, 14 June 2009 (UTC)[reply]
I think there are many dog/cat breeds that came from one breeding pair, so i also think that having only one male dooming the species needs a source. The only certain limit to diversity would be in the Y chromosome, no?YobMod06:51, 14 June 2009 (UTC)[reply]
You probably want to think that one through a little more, Steve. You are incorrect, and there are plenty of practical examples to demonstrate that. One is BALB/c. These mice are for all intents and purposes isogenic - there is negligible genetic diversity among the entire strain - and yet are far from "doomed", indeed they continue to survive quite happily when bred together for over 200 generations. Note these mice are purposely inbred, but if you were trying to repopulate a species, you would purposely outbreed to maintain as much genetic diversity as possible. You would probably want to have enough fertile females that are genetically diverse to ensure you avoided creating too much of an artificial selective sweep. From this harem mating with your single male, agnate half-brother/half-sister pairings would have only a 12.5% coefficient of kinship, no big deal. You would then HapMap the offspring from the subsequent generations and set up crosses to minimize homozygosity. With careful management, the genetic diversity of your new population will correlate with the genetic diversity of your starting population, irrespective that all but one were the same sex.
Thus if certain other conditions are met, then a single male could be perfectly sufficient to repopulate a species. But even if you only had one male and one female, with a little bit of luck you could still propagate the species (albeit the repopulated species will be a not quite the same as it was before, for example BALB/c mice are noticeably different from a mouse you might catch living in your house, but they are all still mice). Rockpocket08:18, 14 June 2009 (UTC)[reply]
And who are we to play god? Barring predators, (which I'm assuming you wouldn't be dumb enough to include predators in your cage) I think the animals themselves would best be able to choose a proper mate. They know better than we do what traits they "like", i.e. traits that are benificial to survival. If you put a male lab in the same cage with a healthy female and a crippled female, he would mate with the healthy female first, and most often. Again, I say just put em all in a big cage and let em have an orgy.DrewSmithWhat I've done09:33, 14 June 2009 (UTC)[reply]
Ummm... you're slightly missing the point here, Drew. It isn't really about how to mate the one remaining male but how to manage the subsequent matings between half-sib offspring. Rockpocket's answer is best. What is being described is the reverse of what mouse researchers use to generate congenic mouse strains by using genetic markers to select the "best" pairings (i.e. between half-sibs, cousins, second-cousins, etc. that have the least amount of genetic information in common), and thus to increase the genetic diversity of the resulting population as much as possible. --- Medical geneticist (talk) 10:35, 14 June 2009 (UTC)[reply]
And I say let them choose. Diversity will happen over time, they don't have to be diverse right from the start.
Mate selection works statistically and on an evolutionary time-scale. With only one male left to choose for himself, there is no way to be certain he would mate with all the females to ensure genetic diversity, nor that he would choose the most "fit" for survival or reproductive success. If he did this 51% of the time, this would be enough for natural selection to work, but you cannot apply a statistical outcome to an isolated case. If he is asexual or monogamous or gay, you have just doomed the species for a philosophical stand! In fact for monogamous species, leaving them to an orgy would be the worst idea.YobMod12:51, 14 June 2009 (UTC)[reply]
It probably is a good idea to let the predators amongst them once their numbers are a bit up. Otherwise natural selection would start choosing them for a cage environment. Dmcq (talk) 11:51, 14 June 2009 (UTC)[reply]
But as evolutionary changes take many many generations, this would seem a very far off and unlikely problem compared to preserving genetic divirsity, without which disease is likely to kill them all far more quickly.YobMod12:57, 14 June 2009 (UTC)[reply]
Critical velocities for Lockheed Electra 10-E?
Hello everyone, I'd like to know the stall speed and Vmc (minimum control speed, the lowest airspeed at which the pilot can maintain lateral control in case of engine failure) for the Lockheed L-10 Electra with a 3,600 lb. overload, as was the case with Amelia Earhart's plane on takeoff from Lae, New Guinea. I'm writing a song about Amelia, and I need those numbers to see if one of the lines is realistic or not (I've already been forced to take some liberties with the facts, and I don't want to do that any more than I have to). How I came up with 3,600 lbs of overload: ~7,100 lbs. airframe/engines/equipment + 6,600 lbs. (1,100 gal. * 6 lbs/gal) fuel + ~130 lbs. pilot (tall, thin woman) + ~170 lbs. navigator + ~100 lbs. or so of navigational equipment = ~14,100 lbs. gross weight; 14,100 - 10,500 max. takeoff weight = 3,600 lbs. overload. What I really want to know is, given these numbers, would it be possible to fly below Vmc without stalling out (not that anyone would choose to)? Also, I would really appreciate it if you could also calculate the speed that a Lockheed Electra 10-E with a 3,600 lb. overload would achieve after a takeoff run of 3,000 feet on a rough gravel runway at full power (1,100 hp combined power for both engines); would it be greater than Vmc, or less than Vmc? Thanks a lot!
Oh, and by the way, does Vmc change significantly with the load? I'm not a professional pilot, but I know that stall speed certainly increases with the load, does Vmc do the same?
Judging by the time that Amelia would have realized that she had overflown Howland, it is quite conceivable that most of the fuel would have been burnt off. Some of the Itasca personnel were quite sure that her radio messages coming in loud and clear put her in the vicinity of the island. If the next hour involved a "crawl" back over navigation tracks, conceivably, Amelia would have reduced speed to above stalling speed: 65 kts/120 km/h (clean). If she let down flaps, stalling speed would be reduced slightly by approximately 5 kts. She would not have put down the gear. As to actual Vmc of the Lockheed 10 Electra, it is comparable to the PA-30 Twin Comanche, where the number is 90 mph and it's the left engine that's critical. Observers on Lae saw the Electra stagger into the air with its overloaded condition, so that the Vmc was probably adjusted to consider airframe configuration, accessories, air density and loading which all make a difference. FWiW Bzuk (talk) 04:07, 14 June 2009 (UTC).[reply]
I would be quite surprised if it were possible to figure this out. Finding data like this on a fairly obscure antique is going to be tough - but much, much worse - Earhart had heavily modified her plane - so the odds are very good that the details of it's performance weren't caefully measured even at the time. Since the plane itself was evidently lost in whatever befell Earhart - we'll probably never know. SteveBaker (talk) 04:09, 14 June 2009 (UTC)[reply]
Bzuk -- thanks for the info about Vmc, it was very helpful of you. As for the stall speed, I was actually asking for the stall speed on takeoff with all that extra weight, would it still be so much lower than Vmc or would the overload bring it closer to Vmc? (BTW, you can forget that I ever asked about the airspeed after the 3,000 foot takeoff run, I can now calculate it with the data that I have.) Clear skies to you, and best regards!
I've done the calculations just this morning and came up with the following (very approximate) numbers:
--Stall speed (clean, overloaded): Depending on whether 65 kts. is the stall speed at empty weight or maximum takeoff weight, stall speed at 14,100 lbs. total weight will be either 72-74 kts. (if 65 kts. at maximum takeoff weight) or around 90 kts. (if 65 kts. at empty weight).
--Vmc was probably slightly higher than 90 kts. due to the hot weather conditions (between 90-95 kts).
--The actual velocity at the moment of takeoff is only a ballpark figure because I was only able to get a very rough estimate of rolling resistance, but the number I got was somewhere around 90 kts (FWIW). In other words, AE was literally threading the needle in terms of the plane's performance envelope: one wrong move on her part could easily have led either to a departure stall, or to an uncontrolled descent to the ocean's surface, or to a loss of lateral control. Just the fact that she even made it off that short, rough runway with such a big overload proves what a good pilot she was by that time.
Well anyway, thank you very much for the info. Clear skies to you, and best regards!
Where I live, a yard waste service carries away all the grass clippings and tree cuttings and food waste that I care to throw into our yard waste bin, and it's all mixed together with the neighbors' yard waste and at some 'central' location is turned into compost, at which point I believe it's sold to local nurseries and garden supply stores. Surely my yard waste contains thousands of seeds of weeds, and I'm sure the inferior yard waste of my unscrupulous neighbors is teeming with seeds of some of those noxious weeds that are impossible to get rid of once you've got them. My question: Is there some process (natural or otherwise) that occurs in composting that wrecks the seeds? Or am I dooming myself to additional hours of backbreaking labor every weekend by using compost? Tempshill (talk) 04:49, 14 June 2009 (UTC)[reply]
Depends on the method used to make the compost. If they burn it and use the ashes, the seeds are toast (pardon the pun). If, on the other hand, they mulch, decay, or use any other method of composting, the seeds would likely survive. Especially through mulching.
This is also a problem when you mow your yard. If you simply mow over the weeds, you spread the seeds, and infect more of your yard with weeds.
My theory (I haven't tried it yet) would be to comb over every inch of your yard, plucking as many weeds as possible. Let it grow for awhile. This makes the weeds much easier to find as they grow a lot taller than grass. Pick more weeds. Now mow, and repeat the process. Combine with any form of weedicides (pardon the term) that you want. If you use compost, burn it and spread the ashes instead of just spreading the live compost. This will kill everything in the compost, but the nutrients are still there.DrewSmithWhat I've done04:58, 14 June 2009 (UTC)[reply]
If you care about runoff (You probably should) skip the herbicide step. Be careful about using ashes in your garden. It is true that ashes contain a large part of the original nutrients, but indiscriminate use of ashes can drastically influence the soil's PH which might end up hurting more than helping. Dauto (talk) 05:27, 14 June 2009 (UTC)[reply]
Commercially produced compost heats the original materials to such a point that renders seeds useless. It's a bit early on a Sunday morning - I can't find the relevant reference yet...maybe someone can help out here? --TammyMoet (talk) 07:56, 14 June 2009 (UTC)[reply]
That depends on who is doing the composting, and where. For example, in hawaii we our local companies compost using the decaying method (letting the compost sit forever until it stinks. Well, thats what it seems like anyway, it's probably a lot more scientific). Some also simply mulch it and resell it. Even traditionally heated compost has been known to have still active seeds (granted, not nearly the numbers of other methods).DrewSmithWhat I've done09:00, 14 June 2009 (UTC)[reply]
Decomposition bacteria can work at temperatures over 60 degrees that will kill most seeds, and they produce the heat as they consume the material. Graeme Bartlett (talk) 09:20, 14 June 2009 (UTC)[reply]
turning a hot compost pile at SBI don't have a source on hand, but yes, if the compost is properly aerated over a period of time the thermophyllic bacteria can raise the temperatures to 65 C, which kills all but very large seeds, as well as many fungal spores and harmful bacteria (such as salmonella, which can be in animal manures).
As far as the process involved, the normal aerobic soil bacteria raise the heat in the pile to a certain temperature as a byproduct of their metabolism (just like you get hot when exercising), after which the thermophyllic (heat-loving) bacteria are able to function. The thermopyllic bacteria then take over, raising the temperature much higher and essentially pasteurizing the pile. The NOP standards for certified compost in the US require the pile to be kept hot (131-170 F) for at least 15 days, turning every 3 days to ensure adequate oxygen (anaerobic bacteria do not produce as much heat). --SB_Johnny | talk09:46, 14 June 2009 (UTC)[reply]
This is really bothering me. When I Googled the question "What is the volume of all the water on Earth, I see a lot of different references. The vast majority seem to state that the volume of all the water on Earth is described as being about 1.3 billion kilometers. Now when I visualize 1.3 billion kilometers, I visualize a cube measuring 1.2 billion kilometers wide, 1.3 billion kilometers in width, and 1.3 billion kilometers high. If I am correct, the Earth itself is no where near 1.3 billion kilometers wide, and since our sun is something like 93 million miles from the Earth, this cube of 1.3 billion kilometers would exceed the distance by 11 or 12 times. What am I missing here?
Thank you for all your help,
Jim Lyle —Preceding unsigned comment added by 66.184.45.161 (talk) 04:55, 14 June 2009 (UTC)[reply]
That is not what 1.3 billion cubic kilometres means. It means 1.3 billion lots of one cubic kilometre, where one cubic kilometre is a cube 1 kilometre to each side. Thus the amount of water on earth is equivalent to a cube about 1090km to each side. Algebraist05:00, 14 June 2009 (UTC)[reply]
(EC)I think your numbers are rigt, but your explanation is basically affirming what he says. If you want to visualise it as "one giant cube" take the cube root of 1.3 bill which is roughly 1091. So each side of your cube would be around 1091Km's. Make it alittle simpler to understand?DrewSmithWhat I've done05:18, 14 June 2009 (UTC)[reply]
I would be surprised to see any reference, let alone "a lot of different references", that quantify a volume in kilometers because that is nonsense. Cuddlyable3 (talk) 11:15, 14 June 2009 (UTC)[reply]
When I Googled "What is the volume of all the water on Earth" (without quotes) all of the results seem to give the answer in cubic metres [6] (except the first one, which gives the area). Interestingly, the fifth result is exactly the same post on Yahoo answers [7] and Googling with quotes give only that question on Yahoo. Frank Bruno's Laugh (talk) 11:32, 14 June 2009 (UTC)[reply]
Exactly what I thought but WolframAlphaing "all water", "earth water", etc etc gave me no answer, seems to be picky about exactly how you phrase your question. Aaadddaaammm (talk) 11:25, 15 June 2009 (UTC)[reply]
Is an unicellular organism a tautology?
This question has always popped up in my mind whenever someone speaks about unicellular organisms. Since it is only made up of one cell, what differs such an organism from a single cell? If there is no difference, why do we have two names for one thing in the same expression, i.e. why do we use this obvious tautology? // 85.229.103.178 (talk) 06:30, 14 June 2009 (UTC)[reply]
The distinction is more between unicellular and multicellular organisms (like, say, humans). A multicellular organism is made up of lots of cells, which aren't organisms in their own right, hence there is no tautology. Confusing Manifestation(Say hi!) 08:01, 14 June 2009 (UTC)[reply]
Further to that, some cells from multicellular organisms can "live" as single cells - HeLa, for example - but these are not considered an organism (at least not by most people). This is quite an important distinction that can be made using the apparent tautology Rockpocket08:55, 14 June 2009 (UTC)[reply]
what are the properties or components or chemicals are used for obtaining good quality of starch from maize corn?
After seperation of starch from corn which are other material or chemicals are added to create biopolymer?
What are the processes or method for making bioplastic from maize corn? —Preceding unsigned comment added by Hirenmalvi (talk • contribs) 07:27, 14 June 2009 (UTC)[reply]
Can someone explain what metric expansion of space entails in the following situation? Say you have a crystal lattice in which atoms are regularly spaced. Since the crystal lattice is embedded in space, does an expansion of space cause the inter-atom distance to increase? If a large crystal is shaped such that a light pulse emitted from a source embedded in the crystal will later come back to the source, will expansion of space manifest as an increase in the time it takes a light pulse to come back to the same point? —Preceding unsigned comment added by 98.114.146.108 (talk) 12:09, 14 June 2009 (UTC)[reply]
No. The expansion isn't a force pushing things apart, it's just leftover inertia from the inflationary epoch. The article "metric expansion of space" should be renamed to something more accurate like "expansion of the universe". The cosmological constant (if there really is one) is an exception; you can think of it as a slight modification to the self-gravitation of the object. The force is smaller than in a universe without the cosmological constant by a fractional amount roughly equal to the density of the crystal divided by 10-29 g/cm3. This is well outside the bounds of detectability, of course. (I don't know if we can even detect the self-gravitation, much less a decrease of one part in 1029.) -- BenRG (talk) 13:12, 14 June 2009 (UTC)[reply]
(EC) May I assume you are talking about cosmic expansion? If that's the case, the answer is no, that expansion does not entail the expansion of objects like a crystal latice within space. Dauto (talk) 13:15, 14 June 2009 (UTC)[reply]
Space is stretching - but over small distances, the speed of that expansion is negligable. The forces between the atoms in the crystal can easily keep the lattice together. It's only over vast distances when the force of gravity is so gentle that things on the scale of galaxies can be moved further apart. SteveBaker (talk) 13:48, 14 June 2009 (UTC)[reply]
The reason your lattice stays together is because of strong electron bonds. Those are strong enough the offset the very small counter-force of the expansion of space. On massive, massive scales, things like galaxies will be moved by the expansion of space, but not pulled apart. Common example is an ant on a balloon—the ant doesn't rip apart, because the forces that hold the ant together are much stronger than the forces causing the surface of the balloon to stretch. If you had a lot of ants on the surface of a very big balloon (a problematic endeavor) and you inflated it, each ant would perceive the other ants moving away from them, but no ants would be pulled apart. --98.217.14.211 (talk) 13:53, 14 June 2009 (UTC)[reply]
No, the Hubble expansion is not a force. It doesn't have the right units to be a force—it's a velocity per unit distance, not an acceleration. It is not pushing the lattice apart, not even by a tiny amount. The expansion rate is changing, and those changes are due to forces which do also act on the lattice, namely self-gravitation and cosmological repulsion. Of those, self-gravitation dominates overwhelmingly in ordinary circumstances—it's roughly 1029 times larger for a substance with the density of water. So the net effect of the forces implicated in universal expansion is to decrease the interatomic distance of a crystal by a very small amount. -- BenRG (talk) 14:18, 14 June 2009 (UTC)[reply]
I'm not using force here in a technical sense. I'm just trying to conjure up an image for them of the relative ability of things to affect the position of things. One sees a galaxy zooming away from us—it's not actually zooming in the sense of being pushed, but it is easier to make sense of as an analogy to a pushing force. --98.217.14.211 (talk) 14:23, 14 June 2009 (UTC)[reply]
I'm pretty sure the OP understood that an outward force/push/pull on the crystal would just cause a change in the equilibrium lattice spacing, not a gradual expansion. Nonetheless there is no such effect. An ant on a stretching rubber sheet would find its legs being forced apart, but nothing analogous happens as the universe expands. -- BenRG (talk) 14:40, 14 June 2009 (UTC)[reply]
Eating high volume and fibrous food can fill you up enough to not feel hungry, while easily having low enough calories to cause weight loss. Alternately, a normal varied diet can be eaten and weight still loss if doing enough excercise. Imo, people don't fail at sensible healthy diets because they are hungry, but becasue they crave certain comfort foods or are used to over-eating. They may intepret that as hunger, but it isn't really.YobMod12:35, 14 June 2009 (UTC)[reply]
That is why he said hungry, not hungary. Incidentally if this is for yourself your local GP will happily dole out diet advice, and that might be a good idea if you live in a country with free healthcare. Contributions/212.219.8.233 (talk) 10:06, 15 June 2009 (UTC)[reply]
It isn't usually possible to lose weight without feeling hungry except by getting some sort of disease, but it's possible to lose weight without depriving yourself of food, by exercising in the right way. If you can work up to running five miles a day, or go on a long backpacking trip, you will probably lose weight even if you eat as much as you want to. Looie496 (talk) 16:08, 15 June 2009 (UTC)[reply]
How amount of UV in sunlight differs between time of day, season, and various places in north or south Britain
I'm looking for some figures for how the amount of damaging UV varies along the above dimensions please. As well as being affected by latitude, the amount might be affected by the amount of cloud cover, although I have heard that cloud cover makes little difference. 78.151.102.179 (talk) 12:52, 14 June 2009 (UTC)[reply]
There are really three things to take into account:
The amount of sunlight intercepted by the earth per square meter of the surface is proportional to the sine of the latitude - so there is less sunlight at more northerly latitudes.
At more northerly latitudes, the light has to pass through more air - so more of it gets scattered. You can calculate that using the Beer–Lambert law.
As you say: The amount of cloud and humidity in the atmosphere also has an effect (although not so large as the others) - and differing weather patterns between the northern and southern parts of Britain might therefore make a difference.
I wonder how I could include similar effects due to the time of day? Does anyone know a formula for the earth's tilt angle in relation to the month of year? 78.147.253.196 (talk) 10:29, 17 June 2009 (UTC)[reply]
Thermodynamics chemistry
Van't Hoff reaction isotherm and van't Hoff equation are different ?
If it is how can I deduce van't Hoff equation from van't Hoff reaction isotherm?Supriyochowdhury (talk) 15:05, 14 June 2009 (UTC)[reply]
Unfortunately, we don't seem to have an article on the van 't Hoff isotherm, but Googling it turns up several sites ([8],[9], [10], [11](page 269 in the last)) From these I surmise that the van 't Hoff reaction isotherm refers to the equation giving the free energy change for a reaction system which is not in equilibrium: , where Q has the same form as the equilibrium constant but uses the current, non-equilibrium activities (concentrations). If you define the first term on the right hand side as , and use the relation , you can get the last equation on the van 't Hoff equation page. If you then take the derivative with respect to T (or 1/T), you obtain the first (or second) equation on that page. -- 128.104.112.114 (talk) 19:26, 14 June 2009 (UTC)[reply]
Household science-themed activities for 18-26 year olds
Hi guys, this week I need to run a Science themed night for my Rover crew (probably about a dozen or fewer 18-26 year olds) and I'm pretty stuck for ideas. What kind of stuff can I do cheaply and not-too-destructively, that will demonstrate interesting or surprising science ideas? "Wow" factor is a definite plus, and preferably it should be something that they themselves can participate in rather than a long sequence of demonstrations. Maelin (Talk | Contribs) 15:51, 14 June 2009 (UTC)[reply]
The guy who made the Periodic Table Table writes (or wrote) a column for Popular Science about spectacular experiments you shouldn't do because they're probably too dangerous. As a public service, I will point you to his website anyway. Tempshill (talk) 16:33, 14 June 2009 (UTC)[reply]
I'm collecting those sorts of ideas - so far, I have three good ones that meet your criteria. They all require only things you'd find around the house - all three seem impossible at first sight - all three work very well - none of them need cost you a penny - none are destructive:
Measuring the thickness of a human hair using a laserpointer and a tape measure.
Measuring the speed of light using chocolate chips and a microwave oven.
I always thought it was pretty cool to invert a bowl of slaked cornflour (that's cornstarch in the US, and if it's slaked it's mixed with water to form a smooth paste - a bit more runny than glue) over someone's head. If you do it fast enough it sets. You can also make sure it sets by banging the bowl on the table first. I think it's something to do with it being a colloidal solution. It should appeal to the child in every young adult - well you could always get them to bet on the outcome! --TammyMoet (talk) 18:54, 14 June 2009 (UTC)[reply]
You could extract DNA from peas or kiwis (the fruit, not the people or the bird - though come to think of it - if you could find an Antipodean willing to donate a cheek swab, you could do a cool comparison between the DNA of the fruit and the person to demonstrate the ubiquity of DNA as the basis for life). Rockpocket21:05, 14 June 2009 (UTC)[reply]
The article you link from says that you need a lot of material to extract a visible amount of DNA from using this technique - so a cheek-swab isn't going to cut it. It's certainly cool that you can extract DNA using such simple methods though. The end of the experiment seems like a bit of an anticlimax...so you've got this white stringy stuff...now what? It seems like you should be able to create an evil clone army with it or something! SteveBaker (talk) 14:41, 15 June 2009 (UTC)[reply]
Lacking the "science factor", but high in the "wow factor", get an old microwave and put stuff in it - CDs, lightbulbs, tinfoil, candles. Please note that this could be very dangerous, I don't know, I just know it looks cool, and when I've done it, the microwave hasn't exploded. Aaadddaaammm (talk) 11:15, 15 June 2009 (UTC)[reply]
Grapes cut nearly in half and splayed out flat with just a thin piece of skin connecting the pieces, produce an impressive result when microwaved. If you're going to microwave a CD - don't use a recordable one - it needs to be a prerecorded disk to get the most impressive results. But PLEASE make sure everyone wears eye protection - and don't be surprised if it wrecks your microwave oven. SteveBaker (talk) 14:41, 15 June 2009 (UTC)[reply]
That really seems unlikely to me. But if it worries you - keep a fire extinguisher in your kitchen (you should do that anyway). Any grape-induced microwave pyrotechnics can easily be extinguished with a CO2 extinguisher...and because there are MANY other things in your kitchen that could catch fire - you need one of those even if you aren't doing parlor tricks. SteveBaker (talk) 14:41, 16 June 2009 (UTC)[reply]
(undent) Aluminium and a solution of sodium hydroxide make hydrogen (and quite a bit of heat). You can quarter fill a wine bottle with sodium hydroxide solution, weigh it down and sit it in a bucket of water (as coolant) then roll up a piece of aluminium foil and stick it in the bottle. You can then put a balloon's neck over the neck of the bottle, it'll fill slowly. Do this outside, and note that the balloon will also have steam + NaOH in it. To fill a balloon with cooler hydrogen (and no steam) use wit and engineering to filter the hydrogen through water. My setup had a sealed plastic container containing the reagents, a tube carrying the hydrogen/steam from that into the bottom of a a 1 litre drink bottle; the drink bottle was 3/4 filled with water, and the balloon was filled from the bottle. Anyway, you can then do as you wish with the balloon full of hydrogen. The pop test is traditional. --Polysylabic Pseudonym (talk) 05:28, 17 June 2009 (UTC)[reply]
Falling from a motorcycle
If I fall from a motorcycle, does it really matter at what speed I am? Provided I don't hit a tree or other similar obstacle, my speed is parallel to the floor, so not that relevant, right?--Mr.K.(talk)17:33, 14 June 2009 (UTC)[reply]
I know nothing about this subject, but friction would increase with speed. It would be the difference between scraping a layer or two of skin and scraping off a considerable amount of muscle, wouldn't it? Plus, the more momentum you have the more likely you are to start rolling uncontrollably at high sped, risking sudden impacts and thus broken bones, etc. Vimescarrot (talk) 17:50, 14 June 2009 (UTC)[reply]
What do you mean "fall from a motorcycle"? Are we just talking about letting go of the handlebars and somehow just tumbling off the bike? I am not a biker, but I think that sort of accident is rare. APL (talk) 18:12, 14 June 2009 (UTC)[reply]
The problem is this: When you're on the motorbike - your body has a certain amount of kinetic energy, which is proportional to the SQUARE of your speed. If you drive twice as fast you have four times the amount of energy. At 100mph you have 100 times more kinetic energy than at 10mph. When you fall off - bounce around a bit - then stop, that energy has to be dissipated somehow. How does it dissipate? Well, friction turns some of it to heat - the rest is consumed in ripping, smashing, tearing and otherwise breaking you and whatever you're still attached to. Certainly, the more slowly that energy is dissipated, the better. Hitting a tree will dissipate all of it in a tiny fraction of a second...sliding smoothely along the road will dissipate it much more slowly. However, what we can say is that it's not good! As for rolling - the frictional force of your body against the road is pretty much the same, no matter your speed - which means it'll take longer to come to a stop if you're going faster. But your speed is higher - so the rotational torque is higher too. Hence, you'll certainly be more inclined to roll. The faster you roll, the more centrifugal force is going to throw your limbs outwards - which means they'll be more inclined to get broken.
It's safe to say that the faster you're going when you fall off - the worse the consequences...and because (in the end) it's all about dissipating energy - it's probably going to be four times worse at twice the speed.
I think I may be the first biker to comment on this, and its not a very scientific answer. Whatever speed you fall off at, it will hurt. If you're not wearing appropriate safety gear (and I mean leathers or kevlar) your speed parrellel to the floor is what I'd be most worried about. Denim will not protect mate, you can fall over wearing jeans and tear a whole in them. The wavey hand science above is all correct though. Dont it into your head that spead doesn't matter, I can testify to the fact that it doest notm and that falling off ALWAYS hurts. If you want to learn to ride fast safely, there are a whole host of advanced rider courses.Alaphent (talk) 19:47, 14 June 2009 (UTC)[reply]
If you see racing motorcyclists fall, you do indeed see them slide along the ground (a very considerable way); remarkably often they are only slightly bruised. So it's possible, but it's a difficult thing to achieve. In their favour, the professionals have: a) very long runoffs, so plenty of room to scrape down to zero without hitting a telephone pole b) really good suits and other safety gear c) they often put the bike down; better to be doing a slide along the ground than pinwheeling around after a collision; d) they know how to fall (because they've all done it a lot); they know how to get onto their back (where the spine protector will eat the damage) and to avoid rolling (which, as Steve says, will break limbs). And of course they almost always come off at corners, when the speed is relatively low and they're already virtually on the ground anyway. If it was only a bit safer you could get a pretty good new sport out of it: fire bikers out of a gun and watch them slide along the tarmac - they get points for style and for tricks. 87.115.144.38 (talk) 20:17, 14 June 2009 (UTC)[reply]
Speaking as someone who has fallen off a motorbike I can confirm that;
it does definitely hurt
there is an awful lot of damage (lost skin and flesh) even at low speed if you are stupid enough not to wear any safety equipment (tee-shirt and sandals don't count)
(in the context of this post) I am stupid
it probably does get worse to v2 but I'm not going to experiment
Of course your speed matters. It's sort of appalling that this has not been beaten in to your head, as a motorcycle driver. Because a motorcycle driver is categorically the least safe driver (both by his/her own actions, and because of some unforgiving physics), it is extremely important that you understand how dangerous speeding is.
First, if you speed, you are more likely to be involved in a crash.
Second, if you are involved in a crash, your speed will be the primary predictive factor in the severity of injuries and death that you will sustain yourself and inflict on other drivers. As a motorcyclist, your statistics are unfortunately weighted towards inflicting death and injury on yourself, rather than other vehicles. As a motorcyclist, you will be 6 times as likely to be in a fatal accident than an automobile driver. Speeding on a motorcycle is correlated with fatal accidents 1.5x as much as it is for automobiles. If you are a driver of a "sport bike" (typically, one which you ride leaning forward, with a faster top speed and acceleration than a Touring or Cruiser bike), you are in the category of "most statistically likely to die" of any motor vehicle operator, passenger, or bystander.
When you crash, your speed will be the primary parameter of the impact. (This is more important than incidence angle for many reasons). There is the simple matter of kinetic energy to dissipate - which increases as velocity squared. As mentioned above, if you drive twice as fast, you will have four times as much energy.
Okay, first, it's not uncommon for motorcycles to crash by hitting a slick spot and sliding, without hitting anything. If you are completely covered in leather and helmet, and the terrain is completely flat, and you don't try to stop yourself with your hands, and you don't get tangled up with the motorcycle, you are likely to slide without major damage even at high speed. But if you hit even a small obstacle or start tumbling, lots of nasty things can happen. Looie496 (talk) 15:54, 15 June 2009 (UTC)[reply]
Curvature of Space
Space is curved. Does the curve extend to form a circle? If so, does the curve exist in all directions to form a sphere? If that also is so, what is outside the sphere? Can it be said there is no outside? Where does the third dimension, in the everyday sense of the word, fit into this? – GlowWorm.
It is difficult to answer the question because "space" by definition is a void without form. That means no curves, no lines, nothing. The other stuff is just floating about in that space. If God loves us, or we love him enough, maybe some of it does form that complete loop. I hope so. Apparently a black hole could curve light in such a way that you can see its other side (as though you were hovering over England but could see bits of Australia and Antartica around the edges!) Nobody can say if the universe has an outside because, not only can we not see it's outer edges, we cannot even see that which is in our view (see Dark matter). Dimensions as we know them are classed as three to help us with mathematical equations (up-down, left-right, in-out) but in reality all objects with mass are curved, without linear form. No up-down, left-right, only across and in that across, only in one direction. You will not be able to calculate the volume of an area if you think in one dimension but that is the only dimension you will ever have. ~ R.T.G21:49, 14 June 2009 (UTC)[reply]
RTG: Please stop answering questions you have no clue about. Nearly every sentence of what you wrote is wrong: Space is curved - so it has curves (duh!) - you can trace them by following the paths of lightbeams. Space does what space does without the help of god or gods - there is no shred of evidence for gods of any kind - and all of the physics of space-time works perfectly well without divine intervention. Black holes can only theoretically curve light into a closed loop (see Photon sphere) it's not possible in practice because "photon spheres" are unstable - otherwise black holes only bend light like any other gravitational source - nothing remarkable going on there. The universe cannot have an "outside" because that too would (by definition) be a part of the universe. The word "universe" pretty much means "everything" (as you'd know if you took the time to read the very first sentence of our article universe). "Dimensions as we know them are classed as three to help us with mathematical equations" is a meaningless statement. Mathematics can comfortably cope with any number of dimensions - we routinely use four (for space-time) and string theorists go with dozens of dimensions. No - the reason we talk about space as having three dimensions because we can uniquely identify every point in space with three numbers - those don't have to be up-down, left-right, in-out - they could be azimuth, elevation and range...or any of an infinite number of other coordinate systems - however, all of them need exactly three numbers ("dimensions") - hence, "three dimensional". You say that "all objects with mass are curved" - that's nonsense - a proton, for example, has mass - but has zero size - it can't be "curved". Space around objects that have mass is curved. I have no clue what you are babbling about measuring the "volume of an area"...by definition, an area is a measure of a surface - a two dimensional entity - volume relates to three dimensions. Please - don't answer questions unless you are clear on what you are saying in response. SteveBaker (talk) 03:40, 15 June 2009 (UTC)[reply]
The proton does too have a size. I agree with everything else you said (specially the point about RTG not answering questions about things he doesn't understand). Dauto (talk) 07:02, 15 June 2009 (UTC)[reply]
Sure Steve. "Space" is not the definition of a void, and matter can be described as having as many dimensions as you like so long as it is not the one I mention. See Gravitational lens for the best Einstein theory about how a black hole might curve "light", GloWorm, and don't kid yourself that Steve knows what shape a proton is, or that we know if a proton "...has mass - but has zero size ..." (that doesn't actually make sense but you can definitely calculate the theory using mathematics). There is no experiment to show an object (or a space) to have zero size. It is possible to calculate zero through maths but, like Steve says, it is also possible to calculate infinite dimensions through math. Math is not reality. Infinite dimensions and time travel are as feasable as extending your life by transferring you brain onto a neural net (it's a double negative, it still is not your brain) all you can hope is that some part of it keeps on going and that, my friend, is 1 to the power of higher. Like I said, we cannot observe most of the universe that is within our viewing range so the best theories on the outside or the shape of it are all sci-fi. ~ R.T.G08:45, 15 June 2009 (UTC)[reply]
And while you're at it, RTG, please don't change the order of the posts, as you just did by moving Steve's and Dauto's comments away from under your comment and to the bottom of this topic, which I have corrected along with this response. Steve's comment was a direct response to your response, and it's far easier for people to follow the discussion when it's organized as a dialogue, instead of placing the newest posts at the bottom. By preserving that order, we can separate the threads of this discussion and make it easier for new readers to follow things, which becomes increasingly important as the discussion gets more in-depth and diverse. Your edit summary said, "reverting the order of the posts to their original state", but that's not what you did -- you changed the order of the posts. -- Captain Disdain (talk) 08:49, 15 June 2009 (UTC)[reply]
OK Captain Disdain, and how about you check the order of the posts before "Steve" posted and fix them up right for me? no? Didn't think so. ~ R.T.G08:54, 15 June 2009 (UTC)[reply]
Steve posted in an entirely correct manner. He separated the discussion you are having from the other (related) discussion below, which makes this whole thing more readable. Had he posted at the bottom of this topic, it would've made for a more confusing conversation. There's nothing to fix. -- Captain Disdain (talk) 09:07, 15 June 2009 (UTC)[reply]
OK. In a 3-dimensional coordinate system three numbers are needed to define the position of a point in space in relation to the point of origin. However, to define the position of an object in space a fourth number is needed – time. For instance, an airplane may be at a certain azimuth, elevation and range in relation to a point of origin. However, it is also necessary to state the time at which it is there. The same would apply to any other coordinate system. The position of a point in space can be defined by the quantity of numbers required by the coordinate system (number of dimensions). But to define the position of an object the time at which it is there must also be stated. An object can move. A point in space cannot move. – GlowWorm.
To state my last point differently, a moving object moves from point to point in space. When we state its position at a particular time, we are really stating the point in space at which it is situated. - GlowWorm.
There is a really great picture on Special relativity for thinking about a "point in space" called "Diagram 1". Time is great for co-ordination but it is merely the name we give to tapping our feet in the rhythm and counting, no more real than that action. It is possible that your continuous loop will bring the universe back to the same place one day but plotting a point in yesterday, and expecting it to be there, that is "Gods and indistinguishable from Gods" only. When you find a place that is a day of the week, you will surely be able to return to it. ~ R.T.G11:48, 15 June 2009 (UTC)[reply]
The idea that the universe could loop around and repeat itself exactly is utterly discredited. The idea was that if the universe ended in a "Big Crunch" (the opposite of a "Big Bang") then the "next" universe would start with another big bang from the singularity created by the end of the this one (see Cyclic model). Since the properties of this true singularity would (hypothetically) have precisely the same starting state as the previous one (so the theory proposed), all subsequent events would unfold identically - and all of history would repeat endlessly. However, the "Big Crunch" is now firmly disproved - and in any case quantum randomness would ensure that the universe would not repeat exactly the same way anyhow. Your idea that time is just something we dreamed up is patent nonsense. There are plenty of things that depend on time that were doing their thing long before we came along. Time is required in order for there to be a change in entropy - and everything really depends on that. RTG: Please stop posting your own random daydreams and try to stick to actual science - you aren't helping our questioners with this stream-of-consciousness babble. Your last five or six answers here on the science desk have all been horribly wrong in really fundamental ways. SteveBaker (talk) 13:08, 15 June 2009 (UTC)[reply]
Space is without substance by its very definition. All things things within space, you say, are under some curving effects, they are not space. Time has no more substance than space. Space = go read a dictionary. Time, refer us to the substance of time, Steve. (I am not the only person posting here that space and time have no substance) Can I not ask questions around here because I am not good enough, a babbler, full of BS, streaming conciousness (what are you on>?), am I stringing random words about colours and teapots, come on Steve what insult have you for me this time or is it Dauto in for the intermission? ~ R.T.G14:27, 15 June 2009 (UTC)[reply]
It is not really appropriate for you to completely redefine the concept of "spacetime" while answering a question on the reference desk. If you have a problem with the great physicists of our age, I recommend you take it up with them, and when you've made them see the light, and they write papers about it, then you could reference those papers here and prove to the world that you were right all along. APL (talk) 16:37, 15 June 2009 (UTC)[reply]
What? When did I insult you RTG? listen, Steve may have been unecessarily harsh but he is right that the ref. desk is not a soap box ffor you to express you uninformed opinion about things you don't really understand. Remember earlier when you complained about being constantly bombarded by inconsistent titbits of misinformation? Well, now you're being part of the bombardment. Don't expect the folks here at the ref. desk to take that lightly. Dauto (talk) 18:23, 15 June 2009 (UTC)[reply]
Your first comment to me, Dauto, was to "...say something that normal people can understand." You say Steve acted unessecarily yet he was "right". You say that after insisting that I make contradictory and insensible statements. Do you see what I am telling you? You both say that my disagreements with you on fundamental principles are unnacceptable and yet, right here on this post, you are contradicted all over (see next post down, for instance). As Ben says, I am really not suitable to answer very many questions about anything here but why should I be slapped in the face and not slap back? You are not stronger than me, friend. If this post can't be finally enough for you, you are on your own. You certainly haven't won me over, wether it is important to you or not. I am not following you. This is likely to be the last post I ever direct at you. I will not be sad if you win a prize. I will not be happy if you cannot add teaching into your method of instruction but, please God, I will never know. ~ R.T.G19:45, 15 June 2009 (UTC)[reply]
When did I isult you? I don't think I did. When did I slap you in the face? I don't think I did. All I did was to point out that your posts are hard to understand and that you don't know enough to understand many of those things you like talking about and that you shouldn't answer questions about subjects you don't understand. None of that is offensive. Heck, I even took the time to right a very careful response to one of your post to help you see why you are falling short. Dauto (talk) 20:32, 15 June 2009 (UTC)[reply]
Big Crunch scenarios aren't ruled out—it depends on the nature of the dark energy, and there are fairly natural models where the energy density eventually goes negative, after which the universe recollapses (see astro-ph/0409264). And there are other cyclic models that don't involve a recollapse, like Penrose's wacky conformal cyclic cosmology. But RTG, I have to agree with the others who've said that you shouldn't be answering cosmology questions here. -- BenRG (talk) 19:23, 15 June 2009 (UTC)[reply]
Does the curve extend to form a circle? Nobody knows. The hypothesis is called "Multiply connected Universe", a term taken from topology (see Shape of the Universe). Think of it like this: A ring is a one dimensional structure, where every straight path leads back to the origin. A sphere is a two dimensional structure, where every straight path leads back to the origin. The universe could be a three dimensional structure, where every straight path leads back to the origin. That's hard visualize as a geometry, but very easy to do with vectors and modulo arithmetic. It has interesting physical effects. For example gravity between two objects would act from multiple sides, first from the front side, then, when the force has travelled around the universe, from the back side. It could expain the accelerated expansion of the universe and disprove the dark energy theory, but that is not widely believed. http://cat.inist.fr/?aModele=afficheN&cpsidt=18523179
That paper (on the arXiv here) is obviously wrong and shouldn't have passed peer review. They compare an infinite universe that's empty except for one supercluster (inhomogeneous, average density zero) to a compact universe containing the same supercluster (homogeneous, average density nonzero) and find a difference in the gravitational field. If they'd given their infinite universe the same matter distribution as their compact universe then the difference would have disappeared (aside from anisotropies). They conclude that their effect can't explain the dark energy anyway, but in fact the effect doesn't even exist. -- BenRG (talk) 19:23, 15 June 2009 (UTC)[reply]
Space is not curved, though Spacetime is. (You have to have a mathematical model that demonstrates it, according to our article). In classical Newtonian physics the question can't come up, because space and time are regarded as imponderables which merely set the stage for motion. Einstein's model, which made space and time a single concept, associated curvature with the force of gravity. This had nothing to do with spheres and circles; there is no relationship between general relativity and geometry. --Halcatalyst (talk) 01:46, 15 June 2009 (UTC)[reply]
Isn't some of this theory, or hypothesis? Some things are theorized, are they not? Other things are considered to be known beyond a shadow of a doubt. For instance, the existence of dark matter in the universe has I think recently come under question. I don't know if curvature or the absence of curvature as a quality of space is really known with assuredness. Bus stop (talk) 18:36, 15 June 2009 (UTC)[reply]
Yes, somethings are considered hypothesis while others are considered to be known beyond a shadow of a doubt, as you said. General Relativity falls on that second cathegory. Dauto (talk) 18:47, 15 June 2009 (UTC)[reply]
Bus stop, while researchers are still active in trying to extend and complete the theory of General Relativity and integrate it it with Quantum Mechanics, the central bulk is really beyond dispute; its predictions have been experimentally confirmed numerous times over the last ~90 years. See Tests of general relativity, which discusses several experiments that have measured the curvature of space-time (or, the bending of light) in presence of gravitational bodies. Abecedare (talk) 19:33, 15 June 2009 (UTC)[reply]
With regard to what is "outside the universe", drawings are sometimes used to depict the various theories about the shape of the universe. (Some of these drawings are shown in the Wikepedia article "Shape of the Universe".) All these drawings raise the question of what is outside the shape depicted. The drawings themselves have white space around them. The white space is misleading. It does not represent space outside the universe. The complete depiction of the universe stops at the outer edge of the actual drawing. – GlowWorm.
Most(?) of us have played games where, if you move your spaceship off one edge of the screen, it reappears on the opposite edge. The principle can be extended to a three-dimensional box. (Someone living in that universe would not see boundaries.) What is the 'outside' of that universe? —Tamfang (talk) 19:55, 16 June 2009 (UTC)[reply]
June 15
natural refraction of sound?
I read that that sound refraction often happens in the morning over bodies of water, where the water and lower air are still cold, and the higher air is warmer. The claim was made that this allowed people to hear further than they normally would and amplified the sound. There are then claims that people have had normal conversations from incredible distances, like 400 meters. Can the curved refraction actually focus the sound to create amplification at certain points? Or are these stories just made up? I would have thought that the refracted sound would not travel any further than normal sound during the day when all the air was heated - so how could people be talking in normal voices 400m away? Also does anyone know of any other situations in sound refraction occurs naturally or situations where sound is amplified (ie. focused so that the amplitude is above what would expect) naturally?--Dacium (talk) 01:07, 15 June 2009 (UTC)[reply]
Certainly sound refracts through air of different densities (and therefore temperatures). In uniform air, the energy of the sound wave expands outwards in a sphere (think ripples on a pond - but in 3D) - as the sound waves move outwards, the radius of the sphere grows and the energy is spread out over an ever increasing area. As the distance from the source doubles - the area quadruples - so the sound becomes four times quieter. One mechanism by which a particular temperature profile over water could increase the volume of the sound would be if the sound were refracted from layers above the water - and bounced back off of the water surface - such that the sound waves would expand outwards in a cylinder. That would mean that doubling the distance would only halve the volume of the sound - so it would travel MUCH further and still be heard. This is somewhat like a 'waveguide' or 'optical fiber' or laser works for radio/light. By constraining the way that the waves can spread out, the energy can travel further. SteveBaker (talk) 03:51, 15 June 2009 (UTC)[reply]
In principle, sound waves can experience total internal reflection at the air/water or the cold-air/hot air interface and reach places where they might not have reached otherwise. The reflected wave can also add to the directly receive sound and (possibly) amplify the received signal - however there will be considerable phase difference (delay) between the direct and reflected waves, which means that we will hear an "echo" rather than an amplified sound. We will need to plug in the exact temperature profile (and the consequent changes in the refractive index), to determine if this "in principle phenomenon" is actually observed in practical settings. Abecedare (talk) 04:05, 15 June 2009 (UTC)[reply]
I believe the refraction and long distance surface propagation of sound occurs when the air is generally cooler than the water resulting in a gradient of warm air near the surface. The cooler air is slightly more dense and thus conducts sound slightly faster, resulting in the wave tending to focus back towards the surface. This would result in the cylinder-like propagation described by SteveBaker above. This is also why this effect is often observed in the late evening as the air cools, but the water remains warm. -- Tcncv (talk) 04:29, 15 June 2009 (UTC)[reply]
Hmmm, "cooler air is slightly more dense and thus conducts sound slightly faster" is not true. Speed of sound in air, increases with temperature (proportional to ), so we need the colder air layer to be near the water surface in order for the sound to refract back down. Abecedare (talk) 04:54, 15 June 2009 (UTC)[reply]
Abecedare is right, the sound speed increases with the temperature. Hot air at the bottom and cold air on top would have the opposite effect (which sometimes is actually observed in deserts). The sound ends up deflected upwards and it becomes almost impossible to hear anything more than just a few dozen meters away. It's the silence of the desert! —Preceding unsigned comment added by Dauto (talk • contribs) 06:18, 15 June 2009 (UTC)[reply]
If you were in a desert at night, with no real wind, you could quite easily holler over a long distance. Bodies of water are often in a valley, shielded from much noise outside a specific area. It is probably a little quieter a couple of hours before morning starts. I don't know if that helps. ~ R.T.G09:04, 15 June 2009 (UTC)[reply]
No - as Dauto points out deserts tend to be quiet because their temperature profile is the opposite of that over water. The air above the ground refracts the sound away from the ground...something that it also does to light...hence mirages. Plus, if it's a sandy desert, the ground will absorb sound rather than reflect it back up...if it's a rocky desert then the sound will likely be scattered by the rocks. The deserts I've visited in Arizona and New Mexico do indeed seem very quiet places. What makes water (particularly calm water) so effective at doing this is that it has a smooth, predominantly horizontal surface that reflects the sound back upwards. With the air diffracting the sound downwards and the water reflecting it back up - you produce this 'wave-guide' effect that prevents the sound from propagating in three dimensions - and by constraining it to two dimensions (well, kinda), allows it to propagate further. A very narrow canyon with smooth, near-vertical walls might maybe produce the same effect - but a gentler valley would not...particularly if it's predominantly lined with softer, sound-absorbing materials like grass and other vegetation. SteveBaker (talk) 12:42, 15 June 2009 (UTC)[reply]
Dang! (Kick self.) Wrong agiin. Sorry about that. I guess I need to do some better fact checking before I speak. -- Tcncv (talk) 23:14, 15 June 2009 (UTC)[reply]
Should I turn on the lights at night when using my computer?
I'm not aware of any conclusive studies. Opinion is widely divided amongst computer programmers and other long-term computer users. Personally, I like light - but it's gotta be arranged so it doesn't glare off of the screen. I don't think it matters. Avoiding eye-strain is certainly important - but the best thing you can do is to take at least a couple of 5 minute breaks every hour...focus on something far from the screen - take a walk - stretch - etc. SteveBaker (talk) 04:00, 15 June 2009 (UTC)[reply]
Many scientific studies have produced conflicting results about the long-term impacts of eyestrain on vision. It seems to be inconclusive. It is not even clear whether light or dark in the periphery of your computer monitor has any effect on eyestrain, let alone whether that induces any vision trouble. Take a look at Myopia#Theories - see the cited sources there, and note that there is not a consensus among scientists and medical doctors. Nimur (talk) 04:07, 15 June 2009 (UTC)[reply]
Yes, turn them on. It will help prevent you from tripping on wires, barking your shins, and putting things down in the wrong place. Can't tell you anything about eyestrain, though. (I prefer them on, FWIW.) B00P (talk) 03:05, 16 June 2009 (UTC)[reply]
There's an article in today's Onion about how 90% of waking hours are spent staring at glowing rectangles. For those who don't know, The Onion is satire, but this one sounds depressingly close to being accurate. One would really have to expect there to be consequences of some sort from that. --Trovatore (talk) 03:12, 16 June 2009 (UTC)[reply]
supplier for polyvinyl alcohol & dextrin adhesive
Research shows me that the above adhesive ( polyvinyl alcohol & dextrin)is that which is used on postage stamps. I believe this may be the same adhesive used on self sealing envelopes. I am in need for a supplier for an ultra peelable adhesive similar to the postage stamp adhesive.
I have exhausted my search options for that particular adhesive supplier.
3M markets post it adhesive in spray cans [12] There may be similar products out there and most office supply stores or arts suppliers would have s.th. like it. The chemical composition is not what you were looking for and you should use this product in a well ventilated area. Hope this helps. 71.236.26.74 (talk) 06:16, 16 June 2009 (UTC)[reply]
The term for the glue is Mucilage and if I remember right, we used Legumes glue or Peanut glue when I was in school to make stamps. Mind you these are for the lick-and-stick type, not the self-adhesive. ZabMilenkoHow am I driving?10:48, 16 June 2009 (UTC)[reply]
Why would you tie your hands behind your back like that? Quantum Mechanics is already hard enought even with mathematics.Dauto (talk) 06:23, 15 June 2009 (UTC)[reply]
I think it depends on the interest level of the student and his free time available for this. If he/she is not a serious student, then i don't think learning with all the mathematics is necessary, just the principle, as learning the mathematics itself would take considerable amount of time. Personally, I would recommend the Vignettes in Physics, Quantum Revolution by G.Venkataraman, a set of three books, which beautifully explain in qualitative terms the implications of Quantum Theory - Look for it in your local book store. I read it and thoroughly enjoyed it. Rkr1991 (talk) 07:02, 15 June 2009 (UTC)[reply]
The QWERTY keyboard layout was devised and created in the early 1870s by Christopher Sholes, a newspaper editor and printer who lived in Milwaukee. ... His "Type Writer" had its printing point located beneath the paper carriage, and so was invisible to the operator. Consequently, the tendency of the typebars to clash and jam if struck in rapid succession was an especially serious problem, in that the mishap would only be discovered when the typist raised the carriage to inspect what had been typed. ... Sholes struggled for the next six years to perfect his invention, making many trial-and-error rearrangements of the original machine's alphabetical key arrangement in an effort to reduce the frequency of typebar clashes... Eventually he arrived at a four-row, upper case keyboard approaching the modern QWERTY standard.
(ec)They mimic the positions of typewriter keys - and those were originally laid out in an effort to improve typing speeds by limiting the distances your fingers have to move to hit the most frequent English word spellings. See QWERTY for details. Someone here will probably tell you that the keyboard layout was actually designed to slow down typists - but that's an urban legend. Someone will also probably try to tell us that "Dvorak Simplified Keyboard" layout is faster - but that's also untrue. SteveBaker (talk) 04:44, 15 June 2009 (UTC)[reply]
A lot of the early studies on Dvorak were either faked, rigged or just so poorly run as to be meaningless. Their results caused quite a few people to switch - and given the effort required to do that, those adopters continue to support it with great fervor - mostly because of the urban legend about QWERTY being specifically designed to slow typists down in order to avoid jamming the early typewriters - which turns out to be very far from the truth - or that it was designed so that typewriter salesmen could type the word "typewriter" using only the top row of keys without moving their fingers. However, more recent, carefully run studies show zero benefits of any kind for Dvorak. As a result, it's just a pain in the neck to have to support it. Users of it have to suffer the difficulties of being unable to use other people's keyboards efficiently - and having to switch back to QWERTY for things like PDA keyboards and the like. It's a nasty con trick perpetrated on the community - and it needs to die. SteveBaker (talk) 12:29, 15 June 2009 (UTC)[reply]
Without questioning the fact that there are many urban legends surrounding QWERTY's origins and Dvorak's advantages, I'll disagree with you on your conclusion, Steve. I have typed with both keyboards for over a decade - QWERTY at work, Dvorak at home - and I'll testify that Dvorak is more comfortable & ergonomic. For me, that translates to a little faster, but that's not generalizable. But I (and my wife, who also is ambikeyboardous) don't suffer any of your supposed nasty effects of this "con". jeffjon (talk) 20:19, 15 June 2009 (UTC)[reply]
Well, it has more common letters on the home row; J is among the rarest. If I were designing a layout from scratch, the first thing I'd do is partition the letters so that common digraphs like ED are split between the hands ... —Tamfang (talk) 19:41, 16 June 2009 (UTC)[reply]
But if the layout of Dvorak were that much superior from a statistical letter placement perspective, it would be faster - not just "more comfortable" - and studies done over the past few years have shown conclusively that they aren't faster. SteveBaker (talk) 20:20, 16 June 2009 (UTC)[reply]
Yeah - they are amazingly difficult to type on if you aren't used to them. I've used a French AZERTY keyboard for a couple of weeks and I swear it's harder than Dvorak...it's just enough like QWERTY to fool you into thinking you can type quickly! SteveBaker (talk) 20:20, 16 June 2009 (UTC)[reply]
It depends. Many articles are online, both significant older ones, but in particular newer ones, e.g. via arXiv or simply from the authors home page. "Full mathematical details" are usually in PhD theses, which can be online or available via a good scientific library, possibly via Interlibrary loan. --Stephan Schulz (talk) 11:22, 15 June 2009 (UTC)[reply]
If you live near a university (or are a student of one) they should have journal papers that you can have a look at (you probably won't be allowed to borrow them). Also, the university may have online access to journal papers that you can download. - Akamad (talk) 12:41, 15 June 2009 (UTC)[reply]
The original questioner asked for the thesis specifically - did you mean the doctoral dissertation? These are published by the original university, and may be available for free through a research library. You may also be able to access them online (for free or for a charge, depending on may factors). Universities in the United States publish doctoral dissertations through a clearinghouse, ProQuest, which is the distributor for almost all archived dissertations. You can search through 125 billion digital documents, including dissertations, from ProQuest's online access page (you may need to pay a fee or visit a library or research institution with a subscription). ProQuest republishes doctoral dissertations from all accredited universities in the United States, and has online archives of all dissertations since 1938 and a large percentage of all U.S. dissertations since the early 19th century. The original research institution and the author also usually retain the rights to republish their dissertations in other formats as well - so you may be able to find the thesis elsewhere. Nimur (talk) 16:09, 15 June 2009 (UTC)
Note that this company is not merely another opportunistic Web 2.0 data aggregator - it is the official repository for dissertations by government contract to the Library of Congress. Nimur (talk) 16:15, 15 June 2009 (UTC)[reply]
Number of Synapses in Newborns
I've searched - but was not able to find - the number of synapses in newborns (or number of avarage synapses per neuron). Adults (as well as newborns) have about 1011 neurons with (in adults) about 1014 synapses (1000 S./N.). For 3-year-olds I have found numbers of 15.000 S./N. and for newborns about 2500 S./N. (synaptic plasticity). Can this be confirmed (i.e. large number in the beginning, then even an increase, and finally settling to an "operational number" of about 1000 S./N.) with references? Curious ... --Grey Geezer 11:57, 15 June 2009 (UTC) —Preceding unsigned comment added by Grey Geezer (talk • contribs)
Thanks for the reference. Numbers are different, however, the tendency seems to be the same. Will read. --Grey Geezer 16:14, 15 June 2009 (UTC) —Preceding unsigned comment added by Grey Geezer (talk • contribs)
Weird Street Drug
My friend is trying to convince me that in the early '90's, there was this street drug that made you sexually orgasm almost instantly. He said that it was originally developed for astronauts whose stay in space is long term. Did/does such a drug ever exist/ed? --Reticuli88 (talk) 13:23, 15 June 2009 (UTC)[reply]
Unless you have a reference, don't make that claim. There is evidence that clomipramine can cause yawning-induced orgasms, but this is only in a small number of depressed patients [13][14]. It would be good if others can find more references for this, specifically with a larger sample and in a more reputable journal. On another note, clomipramine isn't a street-drug, and I haven't a clue what it has to do with astronauts. In the majority of cases, clomipramine (and other TCAs/SSRIs) actually causes sexual dysfunction. (EDIT: 1641GMT: Here are a couple of SD refs (but every pharmacology textbook will mention it): [15][16], sorry for lateness, I had to leave immediately so didn't have time to find refs at first). --Mark PEA (talk) 14:34, 15 June 2009 (UTC)[reply]
When astronauts head into space the effect of Earth's gravity tails of pretty quickly I believe. Earth is over 12000km in diameter and is 5.9736 × 1024 kg but just 400km above the surface gravity tails off about 10%. With this is mind I can't get my head around why Mercury, being so close to the Sun hasn't been pulled in when the Sun still has enough gravitational force to keep Pluto in orbit when it's so far away. If it's possible to keep the explanation simple I'd appreciate it, I know very little about physics :-)
Thanks all --16:19, 15 June 2009 (UTC)Contributions/87.115.23.15 (talk)
Basically the answer is that Mercury moves a lot faster than Pluto. It spins around the Sun so fast that the gravitational force from the Sun is just enough to counterbalance Mercury's tendency to go shooting off into space. Looie496 (talk) 16:38, 15 June 2009 (UTC)[reply]
(EC) Two points:
First: Your understanding of how quickly earth's gravity tails off is inacurate. Gravity actually follows an inverse square law (That is, the strength of a body's gravitational pull is proportinal to the inverse of the square of the distace to that body). So at 400 km above the ground earth's gravity is still 88.5% as strong as at ground level.
Second (and more important): Both Mercury and Pluto are in orbit around the sun. its true that the sun's tug on mercury is much stronger than on Pluto, but it is also true that Pluto is moving more slowly around the sun. In both situations the sun's gravitational tug is just right to provide the centripetal force necessary to keep the planets on a (approximately) circular orbit. Circular motion might be a good read for you. Dauto (talk) 16:49, 15 June 2009 (UTC)[reply]
My understanding of the OP's phrase "gravity tails off about 10%" is that the gravity is reduced by 10%, not to 10%, so s/he is approximately correct. --Sean17:07, 15 June 2009 (UTC)[reply]
Thanks for quick replies all, seems obvious now you've explained it :-) That circular motion link was a bit much for me Dauto but I might read it again when I'm more awake, and thanks Sean, I did mean reduced by 10%. Could I ask for an expansion on the original question... I take it that when the universe solar system was forming the planets achieved a natural equilibrium? Matter closer to the Sun (accretion disc?) was orbiting faster, matter further away orbiting more slowly so that as the planets formed they naturally fell into the 'appropriate' orbit according to velocity, mass and distance from the Sun? (EDIT): What I mean is the planets didn't form and then fall into their current orbits, they actually formed apprximately where they are now? --Contributions/87.115.23.15 (talk) 17:37, 15 June 2009 (UTC)[reply]
Yes, that's correct. The planets were formed already in orbit around the (young) sun. They did not necessarily form exactly where they are now because at those early times there was a lot of debris floating around the solar system and interaction with all that debris is believed to have made the plats wander away from their original orbits. But once most of that debris was cleared away the planets orbits have remained pretty much stable ever since. Dauto (talk) 18:43, 15 June 2009 (UTC)[reply]
Why does the barrel of a pistol or rifle rise - as opposed to jerking any which way, down, left, right, etc. when fired? I understand recoil, but not why a barrel moves upward when fired. Contributions/167.153.5.107 (talk) 16:50, 15 June 2009 (UTC)[reply]
I would imagine it's because the bullet, when it fires, pushes against the upper part of the weapon closet to your body. Therefore, it's not so much going up as it is pivoting around your hand. -- MacAddct1984(talk • contribs)17:08, 15 June 2009 (UTC)[reply]
This is exactly right. If you fire a gun upside down, it'll jerk down, as seen in this clip. If the barrel was located exactly in the center of your grip, then it wouldn't jerk up or down, it'd just push against your hand. -- Captain Disdain (talk) 23:32, 15 June 2009 (UTC)[reply]
...and the shock of that would hurt. The pivoting of your wrist acts as a shock absorber. A barrel at the center of the grip, when fired, would feel like slamming your hand into a wall. I believe the reason a rifle doesn't exert the same level of shock is because the rifle has a lot more mass. ~Amatulić (talk) 00:48, 16 June 2009 (UTC)[reply]
Yeah, it would hurt (and it could even do actual damage). It'd also make aiming a little more difficult (proper sights would help, of course, but with varying distances, things would get problematic), and handgun design in general would become more complicated, at least with modern semi-automatics, because right now the slide has room to move freely back with each shot. If that movement took place in the center of the grip, you'd have to do a lot of re-design, because of course you couldn't have the slide hitting the user's hand. -- Captain Disdain (talk) 05:55, 16 June 2009 (UTC)[reply]
An interesting side note is that in the military, and police force, they teach you to shoot a pistol with your arms locked, instead of elbows bent. Doing this reduces the amount of muscle it takes to get the pistol back into firing position, thus enabling you to fire faster. The reason this works is that with your arms locked, your entire arm moves upwards. Then, gravity takes effect, and begins to bring te pistol back down for you. With your elbow bent, however, the recoil would make your arm bend further, pushing your elbow down, and your wrist up. This creates the added exertion of bringing your elbow back up, and extending your elbow again. DrewSmithWhat I've done13:10, 16 June 2009 (UTC)[reply]
OR: Many moons ago one of my professors came to work with a bandage in the middle of his forehead. He'd been at the firing range the prior evening firing his .38 when the person next to him let him fire their .44 magnum. My professor habitually (based on his experience with the .38) bent his elbows when he fired the .44 - and the dramatic recoil brought the pistol to his forehead with embarassing and somewhat painful results. --Scray (talk) 20:19, 16 June 2009 (UTC)[reply]
question about stability of ecamsule
For a while now I’ve been searching for information on the stability of sunscreens containing avobenzone when exposed to makeup containing titanium dioxide and iron oxides. I found one article online: see http://www.koboproductsinc.com/Downloads/NYSCC-Avobenzone.pdf
However, I don’t know if the information found in that article applies to ecamsule. I’ve read, for example, that since the avobenzone in la roche posay’s anthelios xl is stabilized, it won’t degrade in the presence of mineral makeups, but I can’t find anything definitive on this subject. Since most women wear makeup and since it’s almost impossible to find makeup that doesn’t contain titanium dioxide and iron oxides, I wonder why more studies have not been done regarding this issue. My big question is, does wearing makeup degrade the ecamsule or the form of avobenzone used in mexoryl sunscreens?Lunaeva (talk) 17:41, 15 June 2009 (UTC) comment added by Lunaeva (talk • contribs) 17:36, 15 June 2009 (UTC)[reply]
post-splenectomy immunication schedule
I know splenectomy patients (with no part of the spleen remaining) need vaccinations periodically for the rest of their lives, but what vaccinations and how often, please? (Later readers of responses hereto should note that they are general and not intended as personal advice, for which you should consult your physician (or osteopath).)—msh210℠17:42, 15 June 2009 (UTC)[reply]
I don't see it there, actually. Where are you seeing it? (What I do see there is vaccinations needed immediately after a splenectomy (or before), but I asked about recurrent immunizations for life.)—msh210℠21:14, 16 June 2009 (UTC)[reply]
It's basically the same for all mammals. This page will give you some details, and shows an artificial vagina for harvesting rabbit semen, which might be about the right size for a ferret (I'm not familiar with ferret cock, personally). --Sean18:40, 15 June 2009 (UTC)[reply]
I'm a little concerned about any application of ferret sperm which a) does not involve making more ferrets and b) which cannot be discussed in public... --Jayron32.talk.contribs17:41, 16 June 2009 (UTC)[reply]
Yes, it reminds me somewhat of National_Lampoon's_Van_Wilder 'In one infamous scene, Van and his friends replace the cream inside some cannoli with dog semen and send them to Richard's fraternity, where the frat brothers begin eating and don't realize what it really is until it's too late'. Hoping I'm wrong! --87.115.23.15 (talk) 17:49, 16 June 2009 (UTC)[reply]
In all seriousness, if its a prank like that, there are methods at hand which can obtain mammalian sperm which don't involve very complex procedures. I'm not sure that, culinarily speaking, ferret sperm and say, your sperm, are all that different... Don't know though, I haven't really tried that particular application of either of them. --Jayron32.talk.contribs18:27, 16 June 2009 (UTC)[reply]
I think that "Black Footed" ferrets are being repopulated artificially, so you might be able to find some paper describing how it's done. I can't find it with a quick Google though, only articles that gloss over that important step. APL (talk) 18:11, 16 June 2009 (UTC)[reply]
parasitic worms
Would it be genetically modified parasitic worms (mainly by limiting lifespan and reproduction) be useful as a weight loss aid, or would they not steal enough nutrients to have an effect if there are only a few worms? Contributions/65.121.141.34 (talk) 20:00, 15 June 2009 (UTC)[reply]
I believe similar Q's were asked here previously, and the answer was that it's a bad idea because they steal vitamins and minerals, not just calories. So, you would risk malnutrition with such a "treatment". StuRat (talk) 20:15, 15 June 2009 (UTC)[reply]
googling gave several results (including a couple that are more relevant to the ferret Q above:-) This looks like one of the more relevant ones [18] The device seems to work similarly to an old Seismometer. I'm not sure it would be worth a page, but there should be some mention in a paragraph on history of medicine somewhere. (volunteers step forward, please)Contributions/71.236.26.74 (talk) 20:31, 15 June 2009 (UTC)[reply]
Yes - they were used like pen recorders. You'd coat a class cylinder with smoke and use a sharp needle to scrape a line through the smoke as the cylinder slowly rotated. Just the thing for a seisemometer, certainly. SteveBaker (talk) 23:46, 15 June 2009 (UTC)[reply]
In general an ink pen could similarly record data on a paper chart, though perhaps with more friction. A smoked cylinder could have been used in a spirometer, to record the volume of exhaled air, indexing lung capacity. Asmoked cilinder was used in 19th century reaction time experiments, as by Donders, and in pre-phonograph sound recordings, as the Phonautograph. Edison (talk) 01:26, 16 June 2009 (UTC)[reply]
A stylus capable of scratching smoke from a rotating cylinder could have lower mass than a siphon ink pen, and thus a higher frequency response. Edison (talk) 16:02, 16 June 2009 (UTC)[reply]
I also find myself wondering why a smoked cylinder would have been preferable to ink and paper. Perhaps before the invention of the ball point pen it wasn't easy to get a continuous flow of ink from the pen to the paper ? Since the modern ball point wasn't invented until 1938, and didn't become widely available until after WW2, maybe that would explain the use of smoked cylinders in the 1930s.StuRat (talk) 19:28, 16 June 2009 (UTC)[reply]
I wondered about that too. The classic twitching needle things don't look that high-tech by 1930's standards. When I was a kid in school, we had one that had a little ink reservoir for each pen and ink that travelled to the tip via capilliary action like a fountain pen. That technology would have been around in the tenth century - so it would hardly have been difficult in the 1930's! One thing I wondered was whether they might want to take multiple permanent copies from the drum by wrapping it with a piece of photographic film and placing a light inside the glass cylinder to expose it. In an era before photocopiers - I suppose that might have made sense. But it's hard to say why this technique was used. SteveBaker (talk) 19:54, 16 June 2009 (UTC)[reply]
Remembering my first couple of Fountain pens, they leaked, the ink kept clogging and they were quite unreliable. This was quite a few decades after they were first marketed but before we got those with ink cartridges. Just because a technology is available doesn't mean it's a good choice. 68.208.122.33 (talk) 01:32, 17 June 2009 (UTC)[reply]
Fountain pens have been around for 150 years - even the kind with replaceable cartridges. Quite a few decades! What I think changed in our lifetimes is that the price of reasonable quality pens has steadily dropped with mass-production and modern plastics. I have a really nice German fountain pen that belonged to my grandfather. It's close to 100 years old - and it's every bit as good as a high quality modern pen...but it probably cost a fortune even when it was new. Sadly, I'm left-handed - and writing with a fountain pen is pretty much out of the question! SteveBaker (talk) 02:30, 17 June 2009 (UTC)[reply]
immovable object and irresistable force - revisited
A while back there was some discussion about the immovable object/irresistable force paradigm. The original poster wondered if such an event were to occur, wouldn't they just cancel each other out. Anyway, while I was in my Aikido class I had a thought: what if we think differently? In other words, in pondering this question, we think in terms of either the irresistable force being stopped by the immovable object or the immovable object diffusing the irresistable force. What about the idea of redirecting? In other words, what if the imovable object turned on it's axis and redirected the irresistable force? We tend to think of moving as back and forth or sideways; therefore, simply rotating on it's axis is not really "moving" in the classical sense. Also, we tend to think of "resisting" as stopping all movement rather than redirecting it. I am suggesting that if this paradigm could exist then the idea of rotation/redirection would maintain the purity of both immovable and irresistable. What do others think? —Preceding unsigned comment added by 69.77.185.91 (talk) 21:48, 15 June 2009 (UTC)[reply]
The paradox isn't a real one since no object is immovable. (Interestingly, all forces are irresistible, though.) In the real world, an object can often redirect a force and a force can often redirect an object. StuRat (talk) 22:19, 15 June 2009 (UTC)[reply]
This reminds me I once felt I had a solution to the paradox. I'm sure it needs tightening up, and it may (almost inevitably) be flawed, but here it is:
Imagine object, something like a ray, moving through space. A ray doesn't have mass, but this object may - the point is it can exert a force and some may insist that this requires mass. Imagine it is moving through space at some speed - the amount is irrelevant, but for the purpose of concreteness, assume 1 m/s. When the head of the ray hits a small object, it just pushes it aside. When it encounters a larger object, it "piles up" behind the object, until the accumulated force moves the object. For any movable object, the ray encounters the object and the head of the ray is stopped for a time, until it amasses enough force to move the object. We can assume that the length of time is proportional to the resistive force. Note that while the head of the ray stops for a finite period of time when it encounters an object, the weighed average of the mass continues to move at 1 m/s, as almost all (in the mathematical sense) of the ray is still moving. (I realize I just calculated a weighed average over an infinite length, at that may get me in trouble.)
So we have defined an object that is irresistible. When it encounters a normal object, a finite portion of the object comes to rest for a finite period of time, but the overall object does not stop, and eventually moves the object.
So now what happens when the irresistible force meets an immovable object? The head of the ray is stopped, and begins piling up. But while the object never moves, the ray (arguably) never stops.
I don't fully expect anyone to decide this paradox has now been convincingly resolved, but it's my stab at it - in my mind, I've defined an irresistible object, and immovable object, and described what happens when they meet. The result doesn't cause one to re-assess the label of immovable, because the object doesn't move. Nor does it cause one to re-assess the label of irresistible, as it has moved every other object it encounters, and even after encountering this object, it is still moving. --SPhilbrickT22:45, 15 June 2009 (UTC)[reply]
The fact that the trailing parts of this ray are still moving doesn't make it irresistible. It's only that if it can move the object, and in your example, it doesn't. Clarityfiend (talk) 23:26, 15 June 2009 (UTC)[reply]
I guess it depends on what you mean by "resisting" the irresistable. I would argue that merely changing the path of it would constitute resistance. But this is a stupid argument - it's not a paradox - it's just wrong. There is not - nor cannot possibly be - either an irresistable force or an immovable object. So no paradox. SteveBaker (talk) 23:44, 15 June 2009 (UTC)[reply]
Relativity disagrees. Either the concept of the universe not moving is meaningless (which I believe is truly the case) - or if you could somehow show that its "not moving" - then I could pick a frame of references where it's moving along just fine. SteveBaker (talk) 01:29, 16 June 2009 (UTC)[reply]
You don't defeat it that easily, "immovable" in this context means that its motion cannot be changed relative to the frame of reference chosen. Changing the frame of reference has not changed the motion by applying a force. By that argument, even supposing a truly immovable object within the universe, one could "move" it by switching co-ordinates, an obvious cheat. SpinningSpark06:30, 16 June 2009 (UTC)[reply]
I disagree with your summary. There cannot be BOTH an irresistible force and an immovable object, but there is no paradox if one or the other exists.--SPhilbrickT00:18, 16 June 2009 (UTC)[reply]
Just because there is no paradox - doesn't mean that either can exist. A purple, elephant juggling mongoose isn't a paradox - and there aren't any of those either! SteveBaker (talk) 01:26, 16 June 2009 (UTC)[reply]
Fair enough. But simply asserting something isn't proof. In fact, I'll argue the opposite. Classify all objects in the universe by how hard they are to move. Consider the object with the largest value. Is there a force in the universe that can move it? If no, it is immovable. If yes, then the force is irresistible.--SPhilbrickT12:33, 16 June 2009 (UTC)[reply]
This question made me wonder, what is the most immovable object in reality and how would it fair against the most irresistible force. For an "object", I want something that is a coherent single entity, so I choose a supermassive black hole. For a force, I'd prefer a "contact" force in the spirit of things that push. A supernova jet seems like a logical choice. So, today's bonus round question, how large a change in velocity would the black hole experience if it ate a supernova jet? Dragons flight (talk) 05:48, 16 June 2009 (UTC)[reply]
A black hole is in no way immovable or irresistible. It has finite mass, just like anything else, and a=f/m applies just like it does to anything else. Two black holes colliding will conserve momentum, and the characteristics of the resulting black hole will not mirror either of its progenitors. — Lomn13:01, 16 June 2009 (UTC)[reply]
There is no distinction! A black hole, like all matter, is movable, which is to say that it is not immovable. As StuRat correctly notes above, all forces are irresistible, which is to say that none are in any fashion resisted. There are no degrees or shades of grey. There are many cases where the effect of a force is so small as to be unmeasurable, but unmeasurable is not a synonym for nonexistent. — Lomn14:15, 16 June 2009 (UTC)[reply]
With this more reasonable question, I think we can reason it out using proper science and logic and stuff:
Because we have relativity to consider, you can't say that any object is not moving ("immovable") because that just depends on your choice of reference frame. What we mean when when we say that an object is "the most immovable" is really that it's "the most difficult to accelerate". Furthermore, the hypothetical "irresistable" object has to have the same property - it can't be slowed down or deflected...so there is really no difference between an immovable object and an irresistable one - it just depends on your frame of reference. That narrows our search. We only have to find the object that's hardest to accelerate - and it must be both the most irresistable and the most immovable.
F=ma - Force equals mass times acceleration. So the 'most' unacceleratable object is either the most massive one - or one which somehow is most successful at avoiding having forces imposed upon it.
So we have two routes to trying to pick our candidate - either something insanely massive - or something which is somehow immune to the most forces:
If you go the "heavy" route then a super-massive black hole pretty much has to be it - because any reasonably compact object that is more massive than a super-massive black hole will inevitably become a black hole (perhaps a 'super-duper-massive black hole'!) An object like a galaxy is quite likely to be heavier than a black hole - but it's hardly something you'd count as an "object" in the terms of something immovable or irresistable because it's parts are so loosely connected. So without doubt - the answer on this side of the argument is the most supermassive black hole we can lay our hands on...nothing else is possible.
If you go for "immune to forces" - then you can perhaps think of things like the neutrino - which has no electric charge - so it's immune to magnetism and such like - it does have a TINY mass, so affected by gravity and (IIRC) it ignores the 'strong' force. So it's really only significantly affected by gravity and the weak force...which is (guess what!) weak.
If you were to try to move a stationary neutrino by shooting lasers at it - or trying to move it with magnets - you'd be out of luck. You could try whacking it with something impressive - like, say, an entire planet moving at close to the speed of light - and it would hardly move at all...so it's pretty amazingly 'immovable' - and if you slam a neutrino into an entire planet at close to the speed of light - the neutrino hardly ever notices - which makes it fairly 'irresistable'. But the same could be said for a supermassive black hole.
So you get to choose - Neutrino or super-massive black hole? Neither is completely immovable/irresistable - but both are impressively close!
Steve, I think the miscommunication is that when you say it's impossible to have either an immovable object or an irresistible force, you mean physically impossible. What the paradox shows is that to have both at the same time (at least, if the force acts on the object) is logically impossible; this is a different notion, or at least there's a widely accepted current of thought that considers it a different notion. --Trovatore (talk) 02:10, 17 June 2009 (UTC)[reply]
Just wondering, why would the force mv^2/R be directed away from the apex? Wouldn't there have to be a normal force N equaling mv^2/R directed towards the apex ie towards the centre of the circle? —Preceding unsigned comment added by 74.15.138.134 (talk) 00:43, 16 June 2009 (UTC)[reply]
You are right. The centripetal force is directed towards the center. I doesn't have to be a normal force. Any force towards the center will do. Dauto (talk) 01:14, 16 June 2009 (UTC)[reply]
Note: I just realized that the link doesn't take people to where I want them to go. Please, go to exercises and go to "ball and cone". —Preceding unsigned comment added by 74.15.138.134 (talk) 02:10, 16 June 2009 (UTC)[reply]
I think (I haven't seen the question yet) the solution would have been in the reference frame of the revolving object, which causes a centrifugal force mv2/R away from the centre, balanced by the normal force, towards the center. A more complete explanation can be given after I see the question. Rkr1991 (talk) 04:48, 16 June 2009 (UTC)[reply]
Hmmm...well, if you treat it from the reference frame of someone else, it doesn't seem to work. How would you do this from an inertia reference frame? 74.15.138.134 (talk) 05:38, 16 June 2009 (UTC)[reply]
Well there isn't much of a difference. If you understand the above solution, that shouldn't be a problem. All you do is forget about that centrifugal force, all the other forces are just the same. The only difference is that in the normal direction, you will be writing sum of all the forces to be mv2/R instead of zero. That's all. So the equations essentially remain the same. And I see you have signed your post.:-) Rkr1991 (talk) 06:20, 16 June 2009 (UTC)[reply]
The published solution oddly omits the normal force - possibly because it has no component parallel to the cone's surface, but it would still be nice to see it mentioned. Working in an inertial frame of reference:
We have two forces acting on the ball; the normal force N and gravity mg.
The particle is not accelerating vertically, so N cos(θ) = mg.
The particle is not in equilibrium in a horizontal plane - we require a net centripetal force mv2/R. So N sin(θ) = mv2/R. (Note that centripetal force is horizontal, not normal to the cone's surface, because centre of ball's orbit is in plane of ball's motion, which is horizontal)
Actually wait. How can the normal force, which is perpendicular to the surface (and hence doesn't have a component parallel to the surface) cancel out the component of gravity parallel to the surface? 64.254.236.98 (talk) 17:08, 16 June 2009 (UTC)[reply]
It doesn't. Nothing "cancels" the component of gravity parallel to the surface. Nothing needs to because the ball is not in equilibrium; it is accelerating towards the axis of the cone. The only direction in which the net force on the ball is zero is vertically; this is because the ball's motion is in a horizontal plane, so it is not accelerating vertically. Gandalf61 (talk) 19:17, 16 June 2009 (UTC)[reply]
There's a race called Krikkets who have spent their entire civilisation unaware of the 'universe'
I'm wondering when Humans first became aware that those twinkly things at night weren't like the clouds, that is, mere pretty decorations on this world (obviously clous are more significant than decoration, but my point is that they aren't off the planet)
One of my favorite alternate universes to contemplate is if the Earth was always overcast. This would mean no stars or planets would ever be visible and the Sun (and maybe Moon) wouldn't appear as a circle but only as a bright spot in the clouds. How would astronomy develop ? Would we even figure out that the Earth is round ? (We might still be able to see tall ships drop over the horizon as they sail away, but a continuously foggy condition could obscure even this observation.) StuRat (talk) 13:06, 16 June 2009 (UTC)[reply]
I think there'd be significant curiosity in what this difuse glowing object in the sky was. Also cartography would definitely conclude the Earth is round in not so much time. Factor in flight to all this and I don't think we'd be that impared on a cloudy Earth.Aaadddaaammm (talk) 16:50, 16 June 2009 (UTC)[reply]
The ability to safely navigate the oceans without astronomical navigation would be quite difficult, and a continuously foggy world would make for constant shipwrecks. As for planes, take-off and landing would be quite dangerous if it was always foggy, although perhaps a water landing could be done safely (but getting back to shore would be another issue). Navigation would also be quite a problem. Gyros and/or radio location beacons would need to be used. Cars would also be dangerous in "foggy world", so perhaps trains (and maybe barges pulled along canals) would be the only reliable form of transportation. StuRat (talk) 19:37, 16 June 2009 (UTC)[reply]
You cannot know that we can observe everything. For all you know, there may be a class of phenomena which we cannot observe that, if observed, would show us a much larger multiverse. Thus the beings that move from dimension to dimension pity us because we are restricted to a single dimensions and we are not even aware of it. Tautologically, this hypothesis is not scientific because it is not falsifiable. -Arch dude (talk) 13:28, 16 June 2009 (UTC)[reply]
If that were true - there would have to be an entirely new mechanism for viewing. We've explored the electromagnetic spectrum from end to end - and observed what there is to observe along the way (with varying degrees of precision of course). For there to be more "things" to see - the seeing would have to be with some unimagined energy/information transfer mechanism that's not related to gravity/electromagnetism/weak/strong forces. Also, the energy being transferred by this mysterious means would have to be accounted for in some new way because we're currently able to account for most of the energy involved in physical processes. However, for all of that, it's not impossible that what you say is true. This is what makes the whole 'dark energy/dark matter' business so interesting. It implies that there is indeed some entirely different kind of process going on that we only know about because of "accounting errors" in things we do know about. SteveBaker (talk) 13:59, 16 June 2009 (UTC)[reply]
That's not a new "mechanism for viewing", or you could say "sense". We can sense electromagnetic radiation (sight and touch/heat), chemical compounds (smell and taste), physical force (touch). This is a pretty small list, there are a whole lot of other things we could sense. Taste and smell don't even factor into the energy calculations so it could be anything. Aaadddaaammm (talk) 16:45, 16 June 2009 (UTC)[reply]
chemical potetial
Give me a derivation which show the variation of chemical potential with temperature.chemical potetial of a component of a system drecrease with increase in temperature - is it true ?Supriyochowdhury (talk) 06:54, 16 June 2009 (UTC)[reply]
Welcome to the Wikipedia Reference Desk. Your question appears to be a homework question. I apologize if this is a misinterpretation, but it is our aim here not to do people's homework for them, but to merely aid them in doing it themselves. Letting someone else do your homework does not help you learn nearly as much as doing it yourself. Please attempt to solve the problem or answer the question yourself first. If you need help with a specific part of your homework, feel free to tell us where you are stuck and ask for help. If you need help grasping the concept of a problem, by all means let us know. -- Captain Disdain (talk) 07:21, 16 June 2009 (UTC)[reply]
I'm not answering this specifically unless it turns out its not homework, but I've never had a problem helping people find the answers to their homework. Have you tried looking in any of the basic physical chemistry textbooks such as Atkins' Elements of Physical Chemistry? Or perhaps your course textbook may have the information you are seeking. If not, try reading your lecture notes to find the answers in there. It's where I find them more often than not. If all these fail, then try the wikipedia article on chemical potential. However wikipedia articles on subjects such as these often assume chemistry knowledge beyond that assumed by an introductory textbook. If the problem really persists, email the lecturer or if you have a supervisor/mentor/tutor at your college or uni try them. They don't just have academic knowledge, they have teaching knowledge and it can always help to talk through the stages of a problem with someone.
This answer isn't to say that I don't know the answer to this, I just don't think you would gain much by me or anyone else just spouting a few formulae.
Myalgia usually refers to an underlying disorder or other long term situation (alcohol abuse, medication, RSI) that triggers it off (i.e. not 1 exercise session). Does microtrauma help, although that applies according to how hard you push yourself, not your level of fitness. --87.115.23.15 (talk) 18:02, 16 June 2009 (UTC)[reply]
Myalgia as a medical term is a synonym for muscle pain - it's that simple. Similarly, arthralgia is joint pain. --Scray (talk) 20:13, 16 June 2009 (UTC)[reply]
What is RVS Steel?
A Google search of RVS Steel reveals many products manufactured from this material (many of them Dutch) but none provides information on what type or grade of steel this is or gives any reference to a national or international material specification.
We can't give medical advice, but I think it's safe to say you need to be quite flexible to be able to do this in the first place, and you shouldn't continue if it is painful. Alternate the legs occasionally to avoid discomfort.--Shantavira|feed me16:20, 16 June 2009 (UTC)[reply]
Either prey or mates. There's only really three good reasons to be brightly colored: 1) To attract prey 2) To attract a mate 3) To look poisonous so other things won't eat you. Take your pick. --Jayron32.talk.contribs17:35, 16 June 2009 (UTC)[reply]
I would think for advertising strength and virility since only the males are brightly coloured (usually). As an aside, the male dragonflies eyes are larger than those of the females. They actually touch at the top of the head! I would think that is so because he has too always watch for rival males.
67.193.179.241 (talk) 22:53, 16 June 2009 (UTC) Rana sylvatica[reply]
Do you mean the Perseids? As always, they'll peak on the night of August 12-13, and the best time to see them in Toronto (where I live) is around 3 a.m. on August 13. --Bowlhover (talk) 22:55, 16 June 2009 (UTC)[reply]
I did mean the Perseids, thanks. Of course the peak is not exactly the same day each year, which is why I was asking. Apparently the morning of Aug 12 will be the best this year, though with interference from the Moon. --Trovatore (talk) 22:58, 16 June 2009 (UTC)[reply]
Often the exact time of the peak isn't as important as local factors in determining the best time to go out. It is generally best to view between midnight and dawn, local time, although I can't remember why (something to do with the directions the meteors will be coming in). You also want to view when the radiant is as high in the sky as possible and when the moon is out of the way. --Tango (talk) 23:36, 16 June 2009 (UTC)[reply]
Aug 12 - oops! I somehow got the impression that the peak is almost always somewhere around Aug. 13 morning, but I guess that's not true. --Bowlhover (talk) 00:15, 17 June 2009 (UTC)[reply]
Yes, unfortunately these are somewhat incompatible this year, as moonrise will be around midnight. But this link suggests there could be a decent show anyway. --Trovatore (talk) 23:39, 16 June 2009 (UTC)[reply]
For the Perseids, I find it's best to go out around 3 a.m. because the radiant is high in the sky at the moment, and because going out at 3 a.m. gives plenty of time to observe before dawn. Of course there are advantages to observing earlier: you get to see the slow and long-lasting earthgrazers, the ones that enter the atmosphere at a shallow angle, and this year the Moon won't interfere. --Bowlhover (talk) 00:15, 17 June 2009 (UTC)[reply]
Thanks much. I'm hoping to be backpacking in the Sierras that night, and if the weather cooperates we can just lie in our sleeping bags on top of a ground cloth and watch the sky. I did that once as a boy during a meteor shower, and it was unforgettable. --Trovatore (talk) 01:25, 17 June 2009 (UTC)[reply]
June 17
Does TeVeS or STVG explain LIGO?
Despite years of operation, LIGO has yet to have a single unambiguous detection event. Meanwhile, TeVeS and STVG have been developed, which can explain galaxy rotation curves without the need for dark matter, and which avoid some of the problems that plagued earlier alternative gravity theories. Does either TeVeS or STVG modify gravity theory at interstellar distances in ways that would explain why LIGO can’t seem to detect gravity waves? Or are TeVeS and STVG both close enough to unmodified general relativity that it shouldn’t affect LIGO? Red Act (talk) 00:16, 17 June 2009 (UTC)[reply]
All these modified gravity theory have a hard time explaining some of the evidence for dark matter such as the Bullet Cluster, so they may be part of an explanation but don't preclude the need for some form of dark matter. Dauto (talk) 00:38, 17 June 2009 (UTC)[reply]
I don’t know about TeVeS, but the STVG article says that STVG successfully explains the gravitational lensing in the Bullet Cluster, using this as its reference. Red Act (talk) 00:51, 17 June 2009 (UTC)[reply]
I would expect it to be at the high end of the audible range, based on intuition. How would you define the resonant frequency? Where is the energy applied? Edison (talk) 02:22, 17 June 2009 (UTC)[reply]
A fingertip is a structure of the human body that is constructed of many different tissues. There is no uniform answer to you question. Medical ultrasonography only covers part. There are many other imaging techniques that rely on various resonance frequencies. Most of those do not consider Skin. 68.208.122.33 (talk) 05:29, 17 June 2009 (UTC)[reply]
Resting a finger lightly on a loudspeaker cone delivering bass tones may give an impression that the finger resonates slightly at some frequency. However the fingertips are so like rubber that any resonance would be so heavilydamped as to be probably undetectable. Cuddlyable3 (talk) 08:13, 17 June 2009 (UTC)[reply]
Why does so little of the energy become sound when objects strike each other?
Sound power says that a jackhammer is only 1W of sound power. You make 2 orders of magnitude more than that just standing still. What is the efficiency ratio? (Joules of kinetic energy dissipated to joules of sound (all frequencies) produced) Sagittarian Milky Way (talk) 02:05, 17 June 2009 (UTC)[reply]
If I attached the business end of a jackhammer to a flexible cone of plastic inside a properly designed sound enclosure, the sound output could be orders of magnitude higher. It is designed to break concrete, not to cause air vibrations. Edison (talk) 02:20, 17 June 2009 (UTC)[reply]
If you can find the watts of electrical power consumed by the compressor that feeds the jackhammer then you have its overall power ratio regarded as an unintended loadspeaker. Power is also released at supersonic frequencies and as heat. Cuddlyable3 (talk) 08:03, 17 June 2009 (UTC)[reply]
Maximum possible impact of one person
Is there any theoretical upper limit on how much of humanity, or of the universe as a whole, one person can ultimately impact in one lifetime? Any lower limit? NeonMerlin01:52, 17 June 2009 (UTC)[reply]
If you're the guy who invented the self-replicating nanobots that end up malfunctioning and consuming first the entire planet for resources to increase their number, then spreading out from there, then 'lots'... ;) --Kurt Shaped Box (talk) 01:58, 17 June 2009 (UTC)[reply]
Well, if chaos theory says that the flapping of a butterfly's wing can change the course of a hurricane on the other side of the earth a year later then the amount of change that the least noticable, laziest couch-potato can make in a lifetime is WAY more than that! The theoretical upper limit is determined by the speed of light. If you live for 100 years - the theoretical limit of your influence during your lifetime is a sphere 200 light-years in diameter. But beyond your lifespan...there is no theoretical limit. I strongly suspect the upper and lower limits of influence are pretty similar. But a lot depends on what you mean by "impact". Genghis Khan had a pretty wide-spread influence - he's known for a lot of very specific influence. But the total number of atoms he rearranged as a result of his actions are pretty similar to the "influence" of anyone else. It's a matter of notability. SteveBaker (talk) 02:15, 17 June 2009 (UTC)[reply]
Taking "impact" literally, presuming a person massing 120kg (because they want to make as big an impact as possible), and travelling near light speed (for the above reason), they'd deliver an impact approaching (0.5 x mass x speed x speed) 5.4 EJ. That's quite an impact. --Polysylabic Pseudonym (talk) 07:44, 17 June 2009 (UTC)[reply]
What is the difference between an oil and a fluid?
I am an apprentice fitter & turner, 2nd year. I have just started to learn about hydraulic fitting, and my tradesman wants me to find out the difference between an oil and fluid. I have used google and yahoo, but can't find anything. Everyone seems to say they are the same thing, but they are not. So I want to know the difference. All I know so far is that a fluid is used to transmit power, whereas an oil is purely a lubricant. —Preceding unsigned comment added by Thenickoff (talk • contribs) 05:34, 17 June 2009 (UTC)[reply]
I have no particular technical training or knowledge, but in terms of hydraulics "hydraulic fluid" and "hydraulic oil" mean the same things - they even point to the same wikipedia page. Hydraulic fluid is generally made of mineral oil. More generally, see oil and fluid - outside the field of hydraulics these terms are very, very, very general. --Polysylabic Pseudonym (talk) 07:32, 17 June 2009 (UTC)[reply]
Oil is a fluid, so is water. Thus not all fluids are oil. You seem well aware of the application of oil in particular. There are many applications of fluids in general, including washing, irrigating, drinking, swimming, floating boats on, putting out fires, thermometers (mercury or alcohol - both are fluids), riot crowd control, eye/nose/ear drops, steam engines,... Hydraulic systems are not my field but the article Hydraulic fluid says it may or may not be an oil. Cuddlyable3 (talk) 07:33, 17 June 2009 (UTC)[reply]
Determining the Credibility of Research Journals
Until recently I was very naive about research journals, sort of blindly accepting their published results as being peer-reviewed and trustworthy, even if I'd never heard of the journal before. As a writer who is now frequently tasked with reporting on advances in cancer research, this is admittedly foolish. But then I came across Regulatory Toxicology and Pharmacology, and recognized the editor's name as a notorious one in his field, and later read that it receives funding from RJ Reynolds.
I'm aware of the more renowned journals, such as The Lancet, but the List of medical journals is extensive. I assume that over time, familiarity will breed the necessary discretion. Until then, are there methods of determining the credibility of research journals I haven't heard of? Wolfgangus (talk) 06:59, 17 June 2009 (UTC)[reply]
Your scepticism of journals funded by vested interests is evidence that you are no longer naive. In reports about a major research field such as cancer it would be wise to look for reliable, third-party, published sources similarly to the WP:RS guideline. Cuddlyable3 (talk) 07:14, 17 June 2009 (UTC)[reply]
On Wikipedia there is also WP:MEDRS and the reliable sources notice board, WP:RS/N. In real life, googling the journal and the editorial stuff may help. Looking for red flags is useful. And check Google Scholar to see how often and how widely a given paper has been cited. --Stephan Schulz (talk) 07:21, 17 June 2009 (UTC)[reply]
If the result of a study doesn't sound right, you will have to examine the methodology used and make your own conclusions (don't forget to also read the footnote containing any possible conflict of interests of the authors). For pharmacology this can be difficult and sometimes an error will be impossible to spot as it is not noted in the research (see: Retracted article on dopaminergic neurotoxicity of MDMA published in one of the big three journals (Nature, Lancet, Science)). --Mark PEA (talk) 09:20, 17 June 2009 (UTC)[reply]
OK- The guidelines in both WP:MEDRS and WP:RS seem sound, I can work with those. Google Scholar I hadn't given thought to, so I appreciate that as well. With regard to the reliable sources notice board here, that page is new to me as well. Does that concern only sources used on Wikipedia? It appears that way. (Oh and thanks so much for your time and assistance). Wolfgangus (talk) 09:39, 17 June 2009 (UTC)[reply]
Quarternary Structure
I've looked around for this on here. What exactly holds the quaternary structure of a protein together. All I could find on here was that the monomers are not normally covalently linked, then the article talked about many methods of determining the quarternary structure. Any help is much appreciated, thanks...Oh, and while I may currently be doing an assignment on proteins and enzymes, this is actually a personal interest question that has cropped up while doing it. —Preceding unsigned comment added by Alaphent (talk • contribs) 09:53, 17 June 2009 (UTC)[reply]
what stops hurricanes carrying on exponentially? if there is the energy for them to get to the size they do, why doesn't it carry on increasing? i am not a scientist at all, but i was thinking maybe it has something to do with friction, though i have no idea if this is relevant to air particles. is it to do with air pressure? as it moves into low pressure areas it kind of disperses?
cheers
~~ Ropata (talk) 03:36, 13 June 2009 (UTC)
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Please do your own homework.
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