Wikipedia:Reference desk/Archives/Science/2010 July 22

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July 22[edit]

Lily Flower Identification[edit]

I was wondering if anybody could help me identify this lily flower. It has six petals that are pink with purple spots towards the center of the flower. The stamens are full of brownish-yellow pollen and there is a large, yellow, three-lobed projection in the very middle. Here is a link to a photograph I took of this lily: Lily Flower. I took this photo on a property in Northern Wisconsin and I am assuming that this lily is not native to the area. I have looked online and in a flower identification book, but have had no luck. If anyone could help identify it, that would be great! Thanks! Stripey the crab (talk) 01:54, 22 July 2010 (UTC)

Telling the difference between free fall and micro-gravity[edit]

I am locked in a room with no windows in a future space ship. I am experiencing complete weightlessness. Is there a way for me to find out if I'm orbiting a planet in free-fall or if I'm actually between galaxies in micro-gravity? Looking for multiple methods if they exist.--mboverload@ 03:05, 22 July 2010 (UTC)

Einstein says no: Equivalence principle#The Einstein equivalence principle. TenOfAllTrades(talk) 03:10, 22 July 2010 (UTC)
If you were in orbit there would be tidal forces between two masses that are different distances from the center of the planet. These forces would be small but probably measurable. anonymous6494 03:16, 22 July 2010 (UTC)
I agree with TenOfAllTrades. As a side issue, in between galaxies you are in an environment of genuine weightlessness - weight is mass times local acceleration due to gravity, and local acceleration is close to zero. An astronaut orbiting the Earth, or a swimmer diving off a tower, or a trainee astronaut in a reduced gravity aircraft all claim to be weightless but of course they are not weightless because local gravity is significantly greater than zero. The reason they believe they are weightless is because the ground reaction force acting between them and their surroundings is zero.
So the original question could be re-worded to ask whether it is possible to distinguish between situations where the local acceleration due to gravity is close to zero, and where the ground reaction force is zero. Without being able to make a long-term observation of motion relative to the stars I don't believe it is possible to distinguish between these two situations. Dolphin (t) 05:32, 22 July 2010 (UTC)
While ToaT and Dolphin51 are I believe correct, note that the Principle of equivalence assumes that measurements are only made at one point (which is what "local" implies). If measurements are made at two points, even if (say) only a foot apart, there are sometimes ways of distinguishing between gravitational and accelerational effects. (talk) 07:28, 22 July 2010 (UTC)
Tidal Forces
Take a look at the diagram showing two objects (your hands should do the trick) orbitting a big big blue planet (acceleration acting on the planet is not shown). The black arrows show acceleration due to gravity, The red arrows show the components of the acceleration toward the planet acting between the two objects (which a little bit of geometry shows is inversely proportional to the distance to the planet). If you feel more force pulling your hands together than you'd expect due to their usual mutual gravitational attraction, you're in orbit. David Carron (talk) 11:47, 22 July 2010 (UTC)
(Assuming I can remember my physics correctly...) A gyroscope will keep pointing in the same direction, relative to the rest of the universe. This can be used to tell if your spaceship is rotating. Accelerometers placed on the inside and outside edge of this rotation will indicate if the the ship is rotating around a point inside the ship, or an external point. In free movement, the centre-of-rotation will be the centre-of-mass. If you know where the centre-of-mass is you can tell if you are in orbit. If not, then a ship in orbit will tend to become tidally locked. During this process the ship's centre-of-rotation will move from outside the ship to the centre of the planet. Once the centre-of-rotation moves outside the ship, you can deduce that you are in orbit. A gradual movement of the centre-of-rotation is due to either tidal-locking or conservation of angular momentum due to objects inside the ship moving to, or away from, the centre-of-rotation, which will move the centre-of-rotation. CS Miller (talk) 11:39, 22 July 2010 (UTC)
Thinking about it more, until the ship is tidally locked, the reported acceleration will always have a component towards the centre of the planet, and thus will change over the course of each orbit (thanks David Carron, but the accelerometers are top and bottom, not front and back as in his diagram). So this can be used to deduce that you are in an orbit, without waiting for tidal locking to start. CS Miller (talk) 12:08, 22 July 2010 (UTC)
To expand slightly on my point, Einstein's statement of the equivalence principle (as described in the link I provided) does acknowledge that it only applies 'locally', and that the experiment needs to be 'small' with respect to variations in the ambient gravity field. That is, it doesn't work if your apparatus is sufficiently large and sufficiently sensitive to detect tidal effects across the length of your laboratory. Within the framework of the equivalence principle, I would argue that the rotation of the laboratory and the (eventual) establishment of a tidal lock constitutes such a 'non-local' experiment for our purposes. TenOfAllTrades(talk) 13:02, 22 July 2010 (UTC)
A gyroscope doesn't help at all, any more than noticing the local gravity inside a spinning spaceship would help. The circular motion of an orbit can be combined with any desired degree of rotation. --Tardis (talk) 14:53, 22 July 2010 (UTC)
Inertial navigation using gyroscopes is used for Apollo and the space shuttle. Gyroscopes are also used in the orbiting Hubble Space Telescope and its Rate Gyro Assembly can be seen here.Cuddlyable3 (talk) 15:18, 22 July 2010 (UTC)

What do blind people see?[edit]

I closed my eyes the other day and paid close attention to the little colors and whatnot and it got me thinking: if I had no eyes, what would I see? Does someone without eyes see black like when I close my eyes? Or do they not "see" anything, as in their minds just don't have a visual perception? I know it's hard to explain to someone who can see, but what is it like? (talk) 05:57, 22 July 2010 (UTC)

I believe it varies from one person to another. Of course if you had no eyes, you would not see anything, by definition. However, you might be interested to read up on closed-eye hallucination.--Shantavira|feed me 07:27, 22 July 2010 (UTC)
I get around 100000 Google hits on "What do blind people see?" A popular question! You may also be interested in Blind spot (vision). I once thought about using it to make an April Fool's joke claiming lots of people around the world were going blind for unknown reasons or a crazy reason like death rays from SN 1987A. The idea was to make a demonstration of the blind spot and claim it was just the start of gradually losing the whole field of view. However, I decided it was too cruel. PrimeHunter (talk) 14:29, 22 July 2010 (UTC)

Nothing. "Color" and "black" have no meaning to a person who is blind from birth. Cuddlyable3 (talk) 15:02, 22 July 2010 (UTC)

There has been a lot of research on this. My recollection from cog sci classes ages ago is that people born without sight generally don't have much of a concept of seeing at all and don't generally have a fully-developed visual cortex. People who become blind later in life—even after infancy—generally have a fully-developed visual cortex and describe their sight as black or white or gray or things of that nature. But this is a sketchy memory. "What made them blind" is important here, as well—people who are blind for defects in the eye probably have a different sense of it than those who are blind from defects in the brain. --Mr.98 (talk) 15:46, 22 July 2010 (UTC)
Ray Charles, who went blind when very young, said that he would dream about his mother's face. ←Baseball Bugs What's up, Doc? carrots→ 16:55, 22 July 2010 (UTC)
The colors and whatnot that you see when you close your eyes are discussed in our Phosphene article, and its "Electrical stimulation" section discusses electrically induced phosphenes in blind people. They weren't blind since birth. Seems like an easy question would be whether blind people see ordinary "pressure phosphenes" but I don't know. Comet Tuttle (talk) 16:31, 22 July 2010 (UTC)
I think it's also important to define what kind of blindness it is. I think if you are blind due the failure for reception of the visual signal (eye damage, optic nerve damage), it's going to be very different if there is damage in a perception portion of the brain (visual cortices). For the former I think it might be "black" with phosphenes, but for the latter I'll bet the person does not even realize that they are "missing" something. -- Sjschen (talk) 17:55, 22 July 2010 (UTC)

I suffer from an as yet undiagnosed ailment where I go blind for a few hours every few days, besides being incredibly painful, it is interesting to note that I do not see anything during these periods, not black, not white, not darkness, not light, not red like one sees when you close your eyes and look at a light. I see nothing. I just wish my doctor would get off her arse and cure me.


If my consciousness is not the product of my immortal soul, but only an illusion created by the electric impulses in my neurons, could other electric impulses - for example, in a computer network - also create the illusion of consciousness?--Quest09 (talk) 10:09, 22 July 2010 (UTC)

Have a look at Artificial consciousness. It might not have to be be an illusion. Zain Ebrahim (talk) 11:10, 22 July 2010 (UTC)
Yes - but it might take a very large and complex device to actually exhibit it. The human brain has 1011 neurons and 1015 connections between them. A typical PC has only 106 or 107 transistors in the CPU - and the number of interconnections isn't much more than that. Worse still, a neuron is a more powerful computing element than a transistor - which almost certainly packs in another order of magnitude or so. So there are many more orders of magnitude of growth needed before we're really close to having a powerful enough computer to start considering whether it might be possible to endow it with a consciousness. Even if we succeeded in building a computer that said "I think, therefore I am" spontaneously and without us explicitly programming it to do that, people would likely refuse to believe it. Certainly computers can create the illusion of consciousness...and many researchers believe that our "consciousness" is also just an illusion. I have no way to convince myself that you are conscious and not just simulating that state. We certainly don't have a test for consciousness - nor even a particularly good definition of the word - and there is wide disagreement about whether (for example) a dog or a chimpanzee could be considered "conscious". I think most people would say that a bacterium isn't conscious - some would certainly argue that a housefly isn't conscious...but where exactly on the scale does this turn on? SteveBaker (talk) 22:00, 22 July 2010 (UTC)
"Illusion" is not a very good word to use here, and it doesn't add anything to the question. You could just as well have asked, "If my consciousness is not the product of my immortal soul, but only created by the electric impulses in my neurons, could other electric impulses - for example, in a computer network - also create consciousness?" Using the word illusion implies that there is something that the electrical impulses are an illusion of. Looie496 (talk) 23:10, 22 July 2010 (UTC)

Spider Identification Please[edit]

I live near Vancouver, British Columbia.

I have taken many pictures of this spider I captured.

Can you identify which spider this is?

I found (and killed - was too scared to attempt capture) bigger spiders than this, so I am wondering if this spider can grow bigger?

I have taken a very high resolution of the picture. It is 3.6 MB. So you can download and zoom in.

I have more pictures if required for different angles.

Better Picture Spider.JPG

Spider Picture 1.JPG

--33rogers (talk) 10:26, 22 July 2010 (UTC)

Those pics are too blurry to see much of anything. You might post some better ones or perhaps look through here to see if you see your bug. --Sean 15:28, 22 July 2010 (UTC)
Still, I'd geuss either the Wolf spider (Lycosidae) or the Giant house spider (Tegenaria duellica). --The High Fin Sperm Whale 20:04, 22 July 2010 (UTC)


Why do qualia exist? -- (talk) 12:42, 22 July 2010 (UTC)

Not a very well-formed question. Do you mean, why do they exist rather than not exist? Or do you mean, why have we (and probably other creatures) evolved sense systems that operate the way they do? Depending how you define qualia, you'd get different answers for the latter (in some definitions it seems rather peculiarly human, in some it is just a term that applies to anything that 'experiences', probably even machines). For the former, there are no good answers, because it is not a particularly good question. --Mr.98 (talk) 13:12, 22 July 2010 (UTC)
Actually it is an excellent question to which Wikipedia cannot offer a better answer than the article on Qualia. Cuddlyable3 (talk) 14:57, 22 July 2010 (UTC)
No, it's bad question because it is exceptionally vague about what it is asking. It would need to be clarified for us to even presume to point him in the right direction. Asking why things exist when they don't have to exist is not a good question either, in my opinion—it presumes a lot of unstated things, wrapped in a wooly tissue of metaphysics. --Mr.98 (talk) 15:51, 22 July 2010 (UTC)
Our Hard problem of consciousness article specifies those exact four words as one of the formulations of the hard problem of consciousness. As the article states, the problem is unsolved. Comet Tuttle (talk) 18:30, 22 July 2010 (UTC)
Without qualia (I prefer just to call them "qualities" though) it would be hard to tell a ripe tomato from an unripe tomato. You couldn't even tell after you bit into one, because texture and flavor are qualities just as color is. You also would have a hard time detecting injury, since pain is a quality. Examples can be multiplied indefinitely. Looie496 (talk) 22:56, 22 July 2010 (UTC)
That's completely missing the point. Qualia are the subjective experience of these things. The question above can be rephrased, "why is there subjective experience?".
It's not really answerable on a scientific level, because science is about what you can prove publicly, and as Steve notes abovesomewhere, you can't prove to the public that you even do have subjective experience.
Nevertheless I think it's a genuine question, because you (or, at least, I) do have subjective experience, even without being able to prove it intersubjectively. It's just nonsense to talk about it being an "illusion", as illusions themselves are subjective experiences. --Trovatore (talk) 01:39, 23 July 2010 (UTC)
What is the difference between the subjective experience of a quality, and a quality simpliciter? Can there be such a thing as a quality that is not subjectively experienced? Looie496 (talk) 04:14, 23 July 2010 (UTC)
Sorry, I'm really not following. My point is that, a machine, for example, can tell a ripe tomato from an unripe one, without having any subjective experience of ripeness, or indeed of anything at all. --Trovatore (talk) 06:37, 23 July 2010 (UTC)
That's not a valid argument. It's as if I said that the value of hemoglobin is to carry oxygen in the blood, and you said I was wrong because it is possible to design a machine that transports oxygen in the blood without using hemoglobin. Qualities have value for recognizing things -- the fact that machines might recognize things without using qualities is beside the point. Looie496 (talk) 17:38, 23 July 2010 (UTC)
Well, you can put it that way, I guess. But I still think that no answer from usefulness is ever going to answer why the qualia are experienced subjectively. I'm taking it, possibly incorrectly, that you're arguing evolutionary adaptation or something. But what's not clear is why such adaptive mechanisms wouldn't just have resulted in p-zombies, with all the neurological correlates of qualia but no actual qualia themselves. --Trovatore (talk) 18:49, 23 July 2010 (UTC)
Well, we don't know what the neural correlates of qualities are (many people think we do, but they're wrong), and we don't know what the neural correlates of subjective experience are, so it's very difficult to say what would happen if you had one without the other, or if that is even possible. I agree with you that it's not clear why such mechanisms wouldn't have resulted in p-zombies, but given our level of ignorance of how the mechanisms work, I don't think it is reasonable to demand clarity at this point. Looie496 (talk) 20:44, 23 July 2010 (UTC)
An engineer's answer to Looie496's question might be: Sure; we talk about how red something is; but we don't talk about how middle ultraviolet something is, because we don't have visual receptors that happen to be able to sense that light frequency, and our UV sensing machines simply translate the middle-ultraviolet light into frequencies that we can see. But that's one quale (ugh, this word is awkward) which must exist, but which is not being subjectively experienced by any currently living creature. (If someone now cites a creature that can directly visually sense middle-ultraviolet light, then, first, you're a smartass, and second, pretend I said "extreme ultraviolet" or whatever is just out of range of all current life forms.) Comet Tuttle (talk) 17:11, 23 July 2010 (UTC)
Qualities don't correspond to sensory receptors. We don't, for example, have a class of sensory receptors for the color yellow. Even the qualities red, blue, and green don't actually match up with the so-called red, blue, and green receptors. We don't actually have a good understanding of how qualities are implemented by the brain, even at a practical level. Looie496 (talk) 17:38, 23 July 2010 (UTC)


I had a mouse that used to eat fingernails. When I held her in my hand she would immediately go to the end of my finger and start nibbling the nails, and if I cut a bit off and gave it to her she would gleefully take it and eat it. Why? What is in my fingernails she would like? —Preceding unsigned comment added by Can u read my poker face (talkcontribs) 13:19, 22 July 2010 (UTC)

Fingernails are made of Keratin. Mice and all rodents also like to gnaw - since their teeth constantly grow and need to be worn down. (talk) 14:53, 22 July 2010 (UTC)
Is protein deficiency likely? (talk) 03:21, 23 July 2010 (UTC)

Negative energy?[edit]

Our article Dirac sea says this:

Here the negative solution is antimatter, discovered by Carl Anderson as the positron.

Whereas I was under the impression that the positron had a positive mass, and a positive energy (as positron would appear to confirm). Then, is the formula is identical for the positron not the same as it is for the electron? If we took E=-mc2, would we not arrive at a negative energy? Thanks, Grandiose (me, talk, contribs) 13:27, 22 July 2010 (UTC)

The positron has negative mass and there is mutual annihilation when it meets an electron. Cuddlyable3 (talk) 14:53, 22 July 2010 (UTC)
I don't believe that's correct. As noted at our exotic matter article, virtually every modern physicist suspects that antimatter has positive mass and should be affected by gravity just like normal matter and bubble chamber experiments are often cited as evidence that antiparticles have the same inertial mass as their normal counterparts. — Lomn 14:57, 22 July 2010 (UTC)
(edit conflict) That may not be right - the antiproton has the same magnitude of mass as the electron, and opposite charge. They do indeed annilate one another: this can be interpreted 2 ways:
The mass is negative - simplifying mass balance equations eg Electron–positron annihilation the 'reactants' have net mass 0
The mass is positive - but the object is labelled an 'antiparticle'
There's a reason for this - if the mass were negative an positron would be repelled by normal gravity assuming Newton's law of universal gravitation and similar are functions of 'vector mass' and not of 'absolute mass' ie |M| - see Gravitational interaction of antimatter - there may be an ongoing debate. (talk) 15:03, 22 July 2010 (UTC)
All standard model particles have zero or positive mass. Some of them have "anti" in their names, but that doesn't mean much; "antiness" is not a property of particles. The gravitational behavior of many particles hasn't been experimentally tested, that's true. But the photon is its own antiparticle, as are the gluons that account for most of the mass of the proton and neutron. If antiparticles fell up then these particles would have to fall both up and down. Those experiments have been done, and they all fall down.
There is no such thing as "antimatter", exactly. There is a symmetry of nature that requires that fields/particles come in matched pairs with the same mass and spin and opposite values of all of their internal charges. There's a convention (inconsistently applied) of naming these particles "X" and "anti-X" for some X, but it doesn't matter which one gets the anti prefix. There's also no rule that these field pairs "annihilate" with each other. Because they have opposite charges, interactions of the form X + anti-X → Y + anti-Y are always possible as long as Y's mass is less than X's, because the charges on both sides add to zero. In particular, X + anti-X → 2γ is always legal (where γ is the photon). But this is just a special case of the general rules for interactions in quantum field theory. There's no point in speculating about why annihilation happens. It happens for the same reason everything else happens, whatever that is. -- BenRG (talk) 20:07, 22 July 2010 (UTC)
The argument given in Gravitational_interaction_of_antimatter#The_E.3Dmc.C2.B2_argument (for not using antimatter mass as negative) seems quite convincing to me.. (though perhaps it is less convincing if one is using E2=m2c4..etc. (talk) 23:12, 22 July 2010 (UTC)
That article is a disaster. Please ignore it entirely. This Usenet Physics FAQ entry is far superior. Somebody should rewrite the Wikipedia article from scratch based on the FAQ entry and other accurate sources. I hope it won't have to be me. -- BenRG (talk) 04:30, 23 July 2010 (UTC)
That's actually not true. Acceleration due to gravity does not depend on the mass of the object under consideration (as demonstrated by Galileo) and that is true regardless of the sign of that mass. The m in F=ma cancels with the m in F=GMm/r2, so the sign doesn't matter. An apple with a mass of -100g would still fall from the tree and hit Newton on the head. On the other hand, if the Earth had negative mass then it would repel everything (either of negative or positive mass). --Tango (talk) 22:41, 22 July 2010 (UTC)
Thanks for mentioning the sign cancelling when calculating acceleration - however if antimatter was negative mass an matter/antimatter gravitational interaction would result in the antimatter being attracted, but the normal matter repulsed - at least on simple analysis - I imagine this is one of the reasons why the Gravitational_interaction_of_antimatter#The_antimatter_gravity_debate has been well covered by various scientists and thinkers. (talk) 23:12, 22 July 2010 (UTC)
To answer the question - I recommend you read the linked essay from the article Dirac sea - it may actually help explain (or at least give context to) all this 'sweeping under the carpet' to do with negative mass and gravity and signs (hopefully). (talk) 15:19, 22 July 2010 (UTC)
Electrons that we observe have positive mass and negative charge. Positrons that we observe have positive mass and positive charge. The Dirac Sea is a way of interpreting the universe such that the natural (but unobservable) state of electrons is to have negative mass and positrons are an illusion created by the absence of electrons. The Dirac Sea conceives of the universe as being filled with an infinite number of negative mass energy "electrons". Sometimes, something comes along to kick one of these electrons out of the sea, across the mass gap, and into a state of positive energy. This positive mass electron then behaves as the electrons we know in ordinary life. In being excited, it leaves behind a hole in the sea. According to the Dirac Sea interpretation, a hole in the sea acts as though it has positive mass and the opposite charge as the electron that was excited. In other words, the hole acts as though it is positron, even though in the Dirac Sea model there are no such real particles as positrons. This interpretation of reality is rather counter-intuitive. It has some appeal because it resolves certain problems in understanding relativistic quantum mechanics. However, I would emphasize that the observable manifestations of the Dirac Sea are essentially identical to the traditional understanding of physics. In other words, it is mostly a way of interpreting reality (and giving different labels to the same phenomena), but it doesn't change the basic observations. Dragons flight (talk) 15:49, 22 July 2010 (UTC)
The problem with the infamous "E = m c2" equation is that "E" is vague. In fact, this subtle but essential clarification is the most important part of that equation. Invariant mass or rest energy is important to understand. So whether you need to add or subtract the quantity "m c2" depends on what you are actually doing. In the article linked, the explanation is a bit hazy, but I don't think it's suitable to assume that the negative sign on the square-root of the full equation is sufficient theoretical justification for the existence of negative mass. That's just a spurious root - it's tantamount to solving a quadratic-equation and obtaining both a valid and an invalid solution. Spurious roots can also used (invalidly) to prove that 1 = 0. They more often represent an incorrect assumption or a misuse of basic algebra, rather than any fundamental physical effect. Here's an article, Spurious Roots in the Algebraic Dirac Equation, that explores physical consequences of actual spurious roots of the Hamiltonian. Nimur (talk) 20:00, 22 July 2010 (UTC)

speeding up the cell cycle[edit]

I would like my human lung cancer cells to be encouraged to do mitosis while on my slide. What are some common techniques I can use? If it makes the cell skip some cell cycle checks it's OK -- as long as it doesn't cause any major nondisjunction events or make the cells kill themselves afterwards. Is mitosis inhibited at room temperature? John Riemann Soong (talk) 16:03, 22 July 2010 (UTC)

Just a quick point: if they're human lung cancer cells, haven't they already missed out some cell cycle checks? Regards, --—Cyclonenim | Chat  16:12, 22 July 2010 (UTC)
Or they could have some oncogenes, or suppressed p53. I don't really know -- I am just given them to work with. I think I catch a lot of cells with no (or a non-obvious) nucleus -- I thought they were apoptotic at first, but apparently a lot of them are just in prophase. But prophase takes waaaayyyy too long. (My time frame for observation is 3-6 hours.)
I suppose I could have them express fluorescent proteins (connected to cell cycle events) so I know which cells to look for or observe, but it might be a few months before I can do that. John Riemann Soong (talk) 16:18, 22 July 2010 (UTC)
Btw, when I incubate these cells at 37C in the presence of nanorods, I often see a few of them inside the nucleus (confirmed by focal plane checks). The only way this could have happened I see, is that the nucleus was dissolved during the incubation process and then reformed around some of the gold particles. Incubation takes 2.5 to 4 hours (usually ~3). Is it the temperature? John Riemann Soong (talk) 16:21, 22 July 2010 (UTC)
Why would the cells' nuclei dissolve during incubation at 37C? As I'm sure you're aware, that's body temperature and you don't catch nuclei dissolving in our bodies during cell division. I don't know why the gold particles are getting inside the nucleus, but I doubt it's because of the temperature. I can't really visualise how nuclei form during cell division very clearly. Do they form similar to the cells themselves and form from the division itself, or do the cells divide and then form new nuclei once separated? Either way, can't see why temperature would make gold nanorods appear in the nuclei.
On a less spectulative note, can't you just use a sort of rotation system with the cells you need to use? You mentioned that a lot of them were in prophase, but presumably not all of them. Can you just select the cells that are already undergoing mitosis/about to undergo mitosis and use those? Then, when you need more, go back and select the ones that have recently matured enough to undergo mitosis? Regards, --—Cyclonenim | Chat  17:20, 22 July 2010 (UTC)
The nucleus dissolves during prophase, doesn't it? Also, mu group is more chemical and microengineering than biological, so keeping track of lung cancer cell cycles would be rather new to them. But, it may be something I might do once I get back to my home institution. I meant to ask whether room temperature inhibits the onset or completion of prophase. John Riemann Soong (talk) 17:28, 22 July 2010 (UTC)
Speeding up the cell cycle is probably not what you want. You might be interested in cell synchronization. The easiest method would be to remove the serum (which contains all those tasty growth factors that cancer cells really love) by growing the cells in serum-free media for about 24 hours, which should arrest many/most of them in G1, then adding back serum-containing media to kick them back into growth phase. You might not necessarily have them exactly timed, but you'd probably be able to bias the population so that many of them would divide during the hours that you're observing them. --- Medical geneticist (talk) 19:03, 22 July 2010 (UTC)
Wow, thanks. And it can be pulled off within 1-2 days. (Important since my current research stint ends in 2 weeks.) Hmmm. Now to figure out how long the S and G2 phases of my particular strain of lung cancer cells are.. John Riemann Soong (talk) 23:36, 22 July 2010 (UTC)

Conservation laws and FTU[edit]

I have read that there were thought experiments with the constants to refute the concept of the fine-tuned universe, but what about the conservation laws? From what I know, if, say, the conservation of baryon number is violated, then the matter would become unstable and decays. Or if the conservation of linear momentum is violated, then, as the article suggests, the center of mass of any system of objects will always continue with the different velocity (which would yield quite harmful effects as I think). Looks quite strange for the randomly formed universe. Twilightchill t 18:43, 22 July 2010 (UTC)

Is there a question? My understanding is that this only applies to constants that seem totally arbitrary. i.e. those that either don't (seem to) have a reason for them, or a way to calculate them from other things. Ariel. (talk) 03:05, 23 July 2010 (UTC)
That is can conservation laws serve as an evidence of fine-tuned universe? Twilightchill t 03:51, 23 July 2010 (UTC)
Not necessarily. If all of the universe originated in a singularity which contained all of the mass/energy of the entire universe (the Big Bang), then the conservation laws are simply a consequence of the unequal spreading out of matter and energy following the Big Bang. The fine-tuned universe is simple a specific interpretation of the Anthropic principle. The fine-tuned universe theory is simply the Strong Antropic Principle taken to its strongest end. Its merely a tautology which states that the Universe is being observed by life, so the Universe must have properties which allow life to exist, else it would not be observed. In other words, since we exist, the properties of the Universe must allow us to exist; and a Universe with different properties would not allow us to exist. The idea that the Universe must be "fine tuned" for life isn't really required. The universe could have had any set of properties, many Universes could have existed which did not produce life. That is ultimately irrelevent, as there are perfectly valid and workable hypothesis which allow for infinite time. Given infinite time, all possible universes can come into existance, even those that have life. No need for fine tuning. Multiple universes can exist sequentially, or even simultaneously. For the extreme view on this, see Many-worlds interpretation, which holds that there are an infinite number of universes existing simultaneously. We live in those which allow life. Please note, however, that none of this actually precludes the existance (or non-existance) of God. Its perfectly safe to believe in God and also to study and understand His Creation... Just learn to accept Creation as it exists, not as you wish it to exist. --Jayron32 04:08, 23 July 2010 (UTC)
A small correction: what you wrote does not apply to the many-worlds interpretation, but rather to the Multiverse idea. Ariel. (talk) 06:33, 23 July 2010 (UTC)


I looked at our article, but it was a bit short, so my question is, at what point would a person experience redout? Is it something that is rapid, or sustained? Would a -3g maneuver cause redout if it only lasted 15 seconds? Googlemeister (talk) 18:45, 22 July 2010 (UTC)

Here's a fun demo some web-searching turned up: Classroom demonstrations in aerospace physiology (1963). Build your own red-out simulator! I'm having a hard time finding exact numbers, but the higher the G-force, the shorter the exposure-time needed to cause redout or blackout. Nimur (talk) 19:09, 22 July 2010 (UTC)
That's a redoubtable simulator. Cuddlyable3 (talk) 21:35, 22 July 2010 (UTC)
Well, I had thought a merry go round could be used as a redout simulator by securing a person with their head at the outside edge and their feet closer to the center, but according to my calculations, -3g could only be achieved by having a 5m radius merry go round spinning at 23 rpm, which is probably not too realistic. Also, an interesting byproduct would be that while my head is at -3g, my feet would be at -1g. Googlemeister (talk) 13:48, 23 July 2010 (UTC)

Fall of the ant[edit]

Why does a small creature like ant does not die by falling ? Is it simply because of air-resistance ?  Jon Ascton  (talk) 18:50, 22 July 2010 (UTC)

I suspect gravity plays a part; ie small insects weight a lot less so don't hit the ground as hard when they fall. (talk) 19:19, 22 July 2010 (UTC)
It's a consequence of the square-cube law. The amount of mass that is supported by (aerodynamic drag on) each unit of surface area of the falling ant is quite small, resulting in a very low terminal velocity. As well, the overall mass that must be decelerated on impact is quite tiny, even in proportion to the size of the creature's legs. TenOfAllTrades(talk) 19:33, 22 July 2010 (UTC)
(ec) :Yes, air resistance. In the simplest possible approximation, the air resistance (drag) force is proportional to the body surface area, that is, to linear size squared; whereas the gravity force is proportional to the body mass, that is, to the body linear size to the third power. The larger is the animal, the higher velocity it takes for the drag to balance the gravity pull. As a result, terminal velocity is roughly proportional to square root of the linear size. --Dr Dima (talk) 19:36, 22 July 2010 (UTC)
It's also a strength effect: if you approximate the ant as a cylinder (of fixed aspect ratio) hitting the ground end-on, then the kinetic energy to dissipate is proportional to the mass of the cylinder, but the compressive strength of the cylinder is proportional to its cross-sectional area. So even at the same speed (same KE/mass) a smaller cylinder will fare better. Consider that a cinder block may obviously be broken by being dropped from even a moderate height, but that it would be much harder to break the pieces again in the same fashion. --Tardis (talk) 19:55, 22 July 2010 (UTC)
Consider a spherical cow... Googlemeister (talk) 20:16, 22 July 2010 (UTC)
Does having an exoskeleton have anything to do with as well ? (talk) 23:39, 22 July 2010 (UTC)
Doesn't help the tortoise, does it? Or actually it may. When an eagle drops a tortoise on the rocks, the tortoise may survive the initial impact; but an animal of similar size but lacking a shell probably wouldn't. This is hearsay though; I never saw this actually happen. --Dr Dima (talk) 00:28, 23 July 2010 (UTC)
Seen it done with seagulls and clams on wet sand. Dropped from about 40-50 feet up, the clams shell cracks enough for the gull to get into it. --Jayron32 01:47, 23 July 2010 (UTC)
See the second paragraph of Bearded Vulture, Dima. Those with bald domes may want to avoid walking around hatless, courting the fate of Aeschylus (although it has apparently been decided to excise all mention of that legend from our article on the guy). Deor (talk) 11:28, 23 July 2010 (UTC)
That is false, a smal structure can take more force compared to its wight but this is compensated by shorter deacceleration distance.
The energy that can be absorbed by a spring is proportional to its mass. I think it is the air resistance that is the differnce.Gr8xoz (talk) 13:07, 23 July 2010 (UTC)


Why can't humans consume raw meat without getting sick while most other carnivorous (or in our case omnivorous) animals can eat it without getting sick? The Raptor Let's talk/My mistakes; I mean, er, contributions 23:46, 22 July 2010 (UTC)

Humans can consume raw meat – think of sushi or steak tartare. Physchim62 (talk) 00:30, 23 July 2010 (UTC)
We only get sick if we keep the meat around long enough to rot. Other meat-eating animals either eat meat while it is fresh or else have digestive systems that are capable of handling the bacteria and toxins in partially rotted meat. Looie496 (talk) 00:33, 23 July 2010 (UTC)
There is a surprisingly wide range of digestive capabilities - even across mammals. There are a whole range of things (like partially rotted raw meat) that true carnivores can eat - and things like grapes and chocolate that humans can eat that are fairly poisonous to many carnivores. SteveBaker (talk) 01:22, 23 July 2010 (UTC)
And then there is the issue of parasites, even when the meat is fresh. Trichinella species, for example, can infect both humans and carnivores, but only humans seem to care :) --Dr Dima (talk) 01:25, 23 July 2010 (UTC)
One of the theories I've heard is that the human appendix is the leftovers from a time when people did consume all their meat raw. When we started cooking meat, which presumably had a lot of advantages over leaving it raw, and stopped eating raw meat, the theory is that the appendix no longer was necessary and now plays a very minor role in the human digestive system. Note that some cultures still eat meat raw (not saying exclusively) - I believe that some Inuits eat raw seal. Falconusp t c
An additional note: You might get sick from eating raw meat because you're not used to it (or more specifically, your gut bacteria aren't used to it). In much the same way strict vegans often get sick if they go back to eating meat (at least the first few times), humans used to cooked meat may get sick if they eat raw meat. It's not an indication that they are incapable of processing it though, your gut flora just need time to adapt. —ShadowRanger (talk|stalk) 04:03, 23 July 2010 (UTC)
I'm surprised that nobody mentioned Salmonella, which can infect raw meat but can also appear in cooked meat. ~AH1(TCU) 23:23, 23 July 2010 (UTC)