Wikipedia:Reference desk/Archives/Science/2012 March 18

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March 18

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Resolved

What chemical compound is produced when carbon monofluoride and thulium are combined, if any? 71.146.8.88 (talk) 01:45, 18 March 2012 (UTC)

I assume that a redox reaction will take place at high temperatures, to form carbon and trifluoridothulium. Plasmic Physics (talk) 02:13, 18 March 2012 (UTC)

Thulium can also from a carbide. At low temperatures graphene fluoride or your carbon monofluoride are quite unreactive. Graeme Bartlett (talk) 10:07, 18 March 2012 (UTC)

Thanks. 71.146.8.88 (talk) 18:43, 18 March 2012 (UTC)

Thanks. 71.146.8.88 (talk) 18:45, 18 March 2012 (UTC)

Physics. Adding vectors.

I am faced with this problem: we have a 200N (newton) force heading west. we have two 200N forces heading off 30 degrees, one in a NE direction one in a SE direction. The net force is equal to 200 newtons in a east direction. We need to find the missing force which will make the net force equal to 200N E. I have tried using trig to find the magnitude of the two 200N forces but still cant find the answer. Paradoxical 0^2 (talk) 02:11, 18 March 2012 (UTC)

First, ignore all those vectors you started with. Since you know the resultant vector, they don't matter. Now, break down the desired 200N vector in the NE direction to the components headed North and East, then subtract the resultant 200N vector headed East from the East component, to get the final amount you want headed East (it will actually be negative, meaning West). Then combine this West component with the North component to get the missing vector. If you show your work, we will check it for you. If my explanation doesn't make sense, please let me know. StuRat (talk) 02:22, 18 March 2012 (UTC)

(edit conflict)Since the NE and SE forces are symmetrical about the East-West axis, their North-South components cancel out. Use Pythagoras theory to calculate the East-West components of the NE and SE forces (treat their given values as their respective hypotineuses). Once you have them, it is simply a case of adding or substracting them from or to the West force, and calculating the difference with the net force. Remember to assign the correct sign to each direction (possitive/negative) to each cardinality. Plasmic Physics (talk) 02:24, 18 March 2012 (UTC)

Still don't understand,here is all the working out i have:

cos(45)*200N=105.064398N
(I believe this is the right way to get the adj side here)
so we have to have 105.064398+(-200N)+x=200N
this x≈294.936 N
this is clearly not right.
by the way the answer given is 53.6 N east

Paradoxical 0^2 (talk) 04:04, 18 March 2012 (UTC)

Your calculator is set to radians, not degrees. 200×cos(45°) = is 141.421356. However, I don't get the given answer. Perhaps I don't understand the problem. In your original post, does "The net force is equal to 200 newtons in a east direction" mean the net force of all 3 original vectors, or only the two vectors at 30 degree angles ? StuRat (talk) 04:11, 18 March 2012 (UTC)

that is the net force with the vector that we are trying to find, i belive that is called the resultant vectorParadoxical 0^2 (talk) 04:28, 18 March 2012 (UTC)

that is with all the vectors added up we are left with a 200N final vectorParadoxical 0^2 (talk) 04:30, 18 March 2012 (UTC)

including the vector we are trying to find Paradoxical 0^2 (talk) 04:32, 18 March 2012 (UTC)

Also, are those vectors 30 degrees above and below straight East ? If so, where does the 45 degree angle come in ? StuRat (talk) 04:11, 18 March 2012 (UTC)

whoops, but still the answer aint right Paradoxical 0^2 (talk) 04:37, 18 March 2012 (UTC)

http://content.jacplus.com.au/secure/ebooks/07314/0731408209/14/image_n/nt0030-y.gif here is the question — Preceding unsigned comment added by Paradoxical 0^2 (talk • contribs) 04:43, 18 March 2012 (UTC)

That requires an account to view it. Can you do a screen grab and upload it here ? I can help you if you don't know how. StuRat (talk) 04:46, 18 March 2012 (UTC)

How do you do that? — Preceding unsigned comment added by Paradoxical 0^2 (talk • contribs) 04:49, 18 March 2012 (UTC)

There are 4 steps:

1) Do the screen grab.

2) Save the image as a JPG (or PNG, GIF, PDF, or TIF).

3) Upload to Wikipedia.

4) Display it here.

Do you need help with all 4 steps ? StuRat (talk) 04:59, 18 March 2012 (UTC)

[1] Paradoxical 0^2 (talk) 05:00, 18 March 2012 (UTC)

I made it a link. It's rather blurry and there's no text. Can you zoom in on it before you do the screen grab and include any text ? (The text might be for a whole group of problems, not just this one.) StuRat (talk) 05:05, 18 March 2012 (UTC)

I understand the problem without needing to see a copy of what's printed in the book. The description of the problem in the first paragraph above seems to me like a perfectly reasonable description of the problem, and indeed has an answer of 53.6 N east. But your math is making three mistakes, only two of which have already been identified above:

• The problem says the angle involved is 30 degrees, but in your first equation, you're using 45 degrees.
• You need to calculate the cosine using degrees on your calculator, not radians.
• There are two vectors each contributing a force of 200 cos 30 N in the easterly direction, but your second equation only includes the easterly contribution of one of those two vectors. Red Act (talk) 05:44, 18 March 2012 (UTC)

Here's the answer:

Let North and East be positive.

X = 200 N (East) + 200 N (West) - 200 N (North-East) x cos(30°) - 200 N (South-East) x cos(30°)

X = 53.6 N (East)

Plasmic Physics (talk) 05:57, 18 March 2012 (UTC)

I don't understand how you can add 200 East and 200 West. Shouldn't they cancel each other out ? StuRat (talk) 06:01, 18 March 2012 (UTC)

No, because they have the opposite sign, and substracting a negative results in addition. It is a result of rearanging the original equation. Plasmic Physics (talk) 06:04, 18 March 2012 (UTC)

Thanks very much guys! sorry for being such a pain. Paradoxical 0^2 (talk) 06:10, 18 March 2012 (UTC)

Here it is with a force diagram. For some reason they omitted vector D, the one we are trying to find, from your diagram:

                      B
                  * 
              *  
A <-------+------->D
              *
                  * 
                      C

Resultant = east component of B + east component of C + D - A

200 = 200(cos(30°)) + 200(cos(30°)) + D - 200

400 = 200(cos(30°)) + 200(cos(30°)) + D

400 = 400(cos(30°)) + D

400 = 400(0.866) + D

400 = 346.4 + D

400 - 346.4 = D

53.6 = D. StuRat (talk) 06:16, 18 March 2012 (UTC)

Resolved

Always being able to feel your heart beating is not normal?

In primary school when taught about how to measure heart rate, I noted that I could actually always feel my heart beating. So, I never have to bother trying to find my pulse. I did realize at the time that this means that most people cannot (always) feel their own heart beating, but I didn't make too much out of this. No doctor has ever found a problem with my heart, and I am extremely fit. However, I've never heard of people who don't have heart disease who can always feel their heart beating. Count Iblis (talk) 02:50, 18 March 2012 (UTC)

I can't feel it, but can hear it when my blood pressure is high. StuRat (talk) 02:57, 18 March 2012 (UTC)

I also used to be able to hear it in one ear when holding my head in a certain position for several years. But that was after I suffered an injury to that ear. But just being able to feel it is actually very handy, I don't need heart rate monitors when exercising, I just need to look at my wach while running! Count Iblis (talk) 03:12, 18 March 2012 (UTC)

Have you tested this to check if your reckoning of your heart rate matches with the account of a pulse meter? SkyMachine ⁽⁺⁺⁾ 06:45, 18 March 2012 (UTC)

It really amazes me that anyone would not feel it. I mean, I feel each heartbeat at the heart, with a sensation that varies according to diastolic blood pressure; I feel it at the inside of my elbows, with a sensation that changes when systolic blood pressure goes over 140; I typically feel it in my toes, legs, hands, abdominal organs (hard to tell which is which though), and many other places. I would say that even the cerebral arteries have a noticeable pulse sensation, especially if my blood pressure gets up over 150 for some reason. And there's also a small degree of control over all the arteries also, though it's hard to tell how much is manipulation of blood pressure in general. (At one point, trying to experiment with or "improve" cerebral blood flow, I actually managed to give myself a painless but quite disturbing ocular migraine; I've generally discontinued that research... I actually suspect that the "emotion" of shame/embarrassment is mostly a sensation of vasoconstriction somewhere near Broca's area, and ensuing results) But an exception to all this is that for some reason the aorta seems devoid of sensation. Wnt (talk) 15:14, 18 March 2012 (UTC)

WNT, do/did you also feel it when your blood pressure is/was 120? My uncle can also feel every beat, but then he has extremely high blood pressure (220 sometimes even higher) due to a coarctation of the aorta. Count Iblis (talk) 23:16, 18 March 2012 (UTC)

Oh, absolutely. In fact, when my blood pressure used to go a bit low when dieting (I think it was a mild instance of orthostatic hypotension) it produced a very distinct and somewhat unpleasant sensation, like my heart had to "suck in blood", which as I understand actually does happen when pressure in the vena cava is low enough. Wnt (talk) 15:27, 19 March 2012 (UTC)

SkyMachine, yes, it is the same (within measurement error, I obviously get the average over, say, ten seconds instead of instanteneous values). When I'm exercising I typically run at such a speed that the heart rate is between 150 bpm and 160 bpm. I simply start running at a speed that feels right to me and only then do I check my heart rate. It is then almost always what it should be. My resting heart rate is around 40 bpm, a bit higher than that when I've done strenuous exercise the day before and the day before that. Occasionally, when I take longer breaks from exercising (I normally exercise 5 times per week, but every few weeks I'll have 3 days of no exercise at all), my heart rate sometimes drops to 37 bpm. Count Iblis (talk) 23:19, 18 March 2012 (UTC)

It's possible for an awareness of one's heartbeat to be a sign of any of a number of health problems, not just heart disease. Given that the question involves a specific individual, it would be a violation of the reference desk's "no medical advice" guideline for me to list the various possible diagnoses, or probably even to mention the article that I'm getting this information from. So ask your doctor as to whether it may be indicative of a health problem in your case. Red Act (talk) 01:47, 19 March 2012 (UTC)

Surely you jest. No doctor has ever asked me if I could feel my own heartbeat - I daresay I'll not receive any professional medical advice on that subject this side of the grave. Wnt (talk) 15:28, 19 March 2012 (UTC)

So what if no doctor has ever asked you if you could feel your own heartbeat? There are lots of symptoms that no doctor has ever asked you about, because there are lots of diseases that your doctors have never had a reason to suspect that you might have. Just because you have never had any indication of a health problem that might prompt your doctor to ask you if you could feel your own heartbeat, doesn't imply that the same is true of the OP. Red Act (talk) 16:27, 19 March 2012 (UTC)

Honestly I think that not being able to feel your own heartbeat sounds like the pathological condition. It seems obvious enough that direct sensation of the process gives useful feedback (e.g. when eating a little Epsom salt would be good). There are specific mechanisms to mediate the sensation. [2] So far as I know it is common for traditional meditation practices to focus on such sensation, and while health claims for them may be controversial, who calls such practices pathological? Wnt (talk) 21:19, 19 March 2012 (UTC)

Incidentally, are those of us who feel our heartbeats the only ones aware of skipped heartbeats, or do the others become aware of it only in that circumstance? Wnt (talk) 15:52, 19 March 2012 (UTC)

Moving your hand in front of your closed eyes in a pitch-dark room

I noted that I can actually "see" something moving in my field of vision when I do this, even though it should be impossible to see anything at all. Is this caused by the brain always taking into account the way body parts move in front of the field of vision when processing visual information? I can imagine that the algorithm used by the brain is not perfect and if there is nothing to see at all, you could be seeing an artifact of the algorithm... Count Iblis (talk) 03:29, 18 March 2012 (UTC)

I doubt if your room is really pitch black. Likely some starlight, etc., filters in through the windows, even on moonless nights. This isn't enough light for you to actually see, but is enough for what you describe. To have a room really be completely dark would require no windows, and seals around all the doors. StuRat (talk) 04:42, 18 March 2012 (UTC)

I'm going to agree with StuRat, considering that as few as nine photons will cause your brain to register having seen something. Someguy1221 (talk) 04:54, 18 March 2012 (UTC)

Nine photons and/or or a really, really shallow wave of light. --134.255.75.71 (talk) 07:29, 18 March 2012 (UTC)

To test this you should repeat the same scenario but get someone else to move their hands in front of your closed eyes and see if you can still determine when they are moving as opposed to being at rest. SkyMachine ⁽⁺⁺⁾ 07:43, 18 March 2012 (UTC)

And you may still be able to detect this without vision, by feeling the draft, hearing the movement or sensing the changed electrostatic environment. Even blocking the ambient noise can be detected. Graeme Bartlett (talk) 09:28, 18 March 2012 (UTC)

You can control for these variables if you put some thought into it. The question is how is the mind percieving the movement? Is it outside sensory data that is being recieved, or is the mind constructing the sense of a hand moving because it already knows the hand is moving. The mind might just be predicting where the hand might be in the absense of confirming sensory data from the eyes. SkyMachine ⁽⁺⁺⁾ 09:39, 18 March 2012 (UTC)

Not only that, it's ridiculously easy to control for! Insider the dark house, find a door with a window in it (making the rooms on either side "pitch black" by covering any other sources of light into the rooms) and have someone on the other side either do the movement quietly or not move at all when you tell them loudly through the door. Your eye can be right against the window, they can stand back but move their hand close by the window when they hear your muffled request to do so. (or they can do nothing and see if you read a false positive). Tell them what you think, and within short order they'll tell you if you're getting it right. --80.99.254.208 (talk) 12:56, 18 March 2012 (UTC)

I used to do a bit of caving. When the all the lights are turned out in a cave, you can see nothing at all, absolutely nothing but blackness, except mayber a bit of retained vision. Alansplodge (talk) 22:39, 18 March 2012 (UTC)

I've noticed too that I can sort of vaguely sense my hand in a totally dark room. And I can assure you it was totally dark. The human eye does have an extremly weak response to infrared. So I tried an experiment with a black painted roughly forearm sized piece of metal warm to 35 C. Results were inconclusive though - I could feel the warmth on my skin if I brought it within 200-300 mm of my face. There is another possibility: Most people know that the eye has 2 kinds of light sensor - the rods and cones. Rods and cones produce the conscous perception of light. But there is a third kind of sensor in the eye - modified ganglion cells. Mammals have these for sychnonising the body circadian rythm to the night-day cycle. Not a lot is known about these sensors. Maybe these respond to infrared as well as visible light, and maybe there is some crosstalk into the conscious perception, as adjacent ganglion cells process the output of the rods and cones. Ratbone124.178.47.224 (talk) 13:19, 18 March 2012 (UTC)

To really get all scientific, their response should be random, and not influenced by whether you got it right before. They can memorize 10 responses beforehand, for example, after flipping coins to see what they'll do. Or they can do more than 15 if they have something they can feel (a baille sheet?) taped to the wall that tells them their response). The weaker your ability to see them, the more tests you need to establish statistical confidence. --80.99.254.208 (talk) 12:54, 18 March 2012 (UTC)

also I should mention that a hidden assumption is that a person is very good at being at the other side, like a game where they're trying to be stealthy. I think as hunters (hide and seek etc) we are very good at being stealthy and have fun doing so in a game context. So all they would do is quietly slowly move their hand in front of the window or not, and otherwise not 'give away their position'. --80.99.254.208 (talk) 13:12, 18 March 2012 (UTC)

• To interpret this I should ask a related question: how common is it for people to start dreaming when in the dark? I used to do work in darkroom where it was inappropriate to use a safe light for what could be over an hour, and it was absolutely routine for me to see/imagine all sorts of things despite concentrating on the task at hand. For me these were 1) blue and occasionally yellow wave patterns 2) rarely, a photorealistic "rehash" of recent unfamiliar visual stimuli - for example, if playing cards for the first time in a year the patterns would then show up during the same day 3) faint, ghostly, indistinct, mostly blue dream images of all varieties. This third type is relevant here - when moving a hand in front of my face, I might see something like that, though then again, the hand might not stay where it was supposed to be, or it might segue into monsters and maidens. Is that the way it works for other people? Wnt (talk) 15:25, 18 March 2012 (UTC)

I second the caving story, underground, you can not see your hand waving in front of your face even with your eyes OPEN. I think "expectation" would play a large part in this. I've waled through my house a few times when it has been very dark and a couple of times I'll get a really impending feeling that i'm about to walk into something or bump into something and when I eventually get the light on, I'll realise that the chair I thought was there was actually moved, or I wasn't in exactly the spot I thought I was. Vespine (talk) 23:31, 18 March 2012 (UTC)

I just repeated this experiment in a completely dark room with eyes closed with also one hand covering my eyes and with the other I wave in the field of vision. I can vaguely see something moving, it doesn't make any difference whether or not the other hand is covering my eyes. It seems to me that somehow information from the part of the brain involved in motor control influences the part involved in vision... Count Iblis (talk) 23:29, 18 March 2012 (UTC)

Maybe these Grid cells have something to do with it. SkyMachine ⁽⁺⁺⁾ 07:31, 19 March 2012 (UTC)

Interesting! Note also that what I'm sensing is more a sense of motion without seeing much. It is very similar to trying to spot a very faint object, say M51 using 8 by 40 binos. Where I live there is quite some light polution and M51 is a threshold object for my 8 by 40 bino. Only when conditions are optimal can you spot it in your peripheral vision when moving your binos up and down a bit. You then get the sense that there is something there, but you don't actually see it. For objects that are a bit brighter like M33 you see it in the peripheral vision without having to move the binos up and down, and then you do actually see something. Count Iblis (talk) 14:51, 19 March 2012 (UTC)

Oh, and just a final thought, In order to rule out this being just a result of proprioception or blind tracking of the hand by the eye, you can hold some hand sized implement to extend your reach so that the implement is being waved before your eyes but your hand is not in your "field of vision," and if you still detect motion it would lean toward an interpretation of subtle sensory detection. SkyMachine ⁽⁺⁺⁾ 11:21, 20 March 2012 (UTC)

I would like to comment that it's very difficult to get into a room with absolutely zero photons, even if you got drastic, covered all the windows with thick blackout curtains, and lined the walls with lead. Even if we constrain ourselves to only counting photons with energies that are unambigously within the visible spectrum, it's still very hard to get into a room with absolutely zero visible photons. As has been pointed out, the human eye can detect a very tiny number of photons; but there are constraints on the minimum number of photons are necessary to form an image. "Pitch black" is a weakly defined term, but it shouldn't be construed as "zero visible light." In very dark rooms, your eye, like an artificial imaging sensor, will be limited by photon noise, and in the extremum case of detecting a single photon, seeing the motion of your hand is physically indistinguishable from seeing "not the motion of your hand." Nimur (talk) 18:17, 19 March 2012 (UTC)

I'm quite surprised that no one has linked to blindsight yet. Maybe not directly related, but it's still a very poorly understood phenomenon. Try this little test; you may surprise yourself. -RunningOnBrains^(talk) 02:03, 21 March 2012 (UTC)

Correct me if I am wrong. Rods are black and white eye sensors that deal with low light. Cones are the colour ones that need higher light. The minimum sensitivty for a rod is the same as that of a candle 14 miles away.--Canoe1967 (talk) 09:09, 23 March 2012 (UTC)

Tiger cognition

Hi I would like to learn more about tiger cognition. I read the article on elephant cognition, and I want to know the same type of information, but for tigers (brain size/mass/structure, use of tools, language, self-awareness, etc). The Tiger article itself doesn't address these either. Any help is appreciated. Thanks.--99.179.20.157 (talk) 03:31, 18 March 2012 (UTC)

One interesting measure of their intelligence is that they only attack from the back, when their prey is the most helpless. They do this by recognizing the face of the animal they are attacking (not each particular face, just that it is a face). We know this because people in tiger-infested areas of India have learned to wear face-masks on the backs of their heads, which protects them from attacks. So apparently tigers aren't smart enough to distinguish a real face from a cheap plastic mask. StuRat (talk) 04:39, 18 March 2012 (UTC)

Er, citation needed? AndyTheGrump (talk) 04:59, 18 March 2012 (UTC)

Not sure why you don't believe me, but sure, here you go: [3]. StuRat (talk) 05:09, 18 March 2012 (UTC)

They're not fooled. They just see how silly the mask looks, and feel really, really sad for you. Someguy1221 (talk) 05:21, 18 March 2012 (UTC)

Or maybe they can't attack because they are doubled over laughing. StuRat (talk) 05:43, 18 March 2012 (UTC)

Alright, having actually looked into this now, there is precious little research done on tiger cognition specifically. You may have far more luck asking about cat cognition in general. If I had more time at the moment I'd actually look into that and give you a real answer. Someguy1221 (talk) 05:47, 18 March 2012 (UTC)

OK, that sounds reasonable. Cats have been given the mirror test, and are smart enough to figure out that their reflection is an illusion, and ignore it thereafter. However, they aren't smart enough to figure out that they are seeing an image of themselves, so apparently lack of concept of "self", which also implies an inability to empathize with others/see things from another POV. StuRat (talk) 05:55, 18 March 2012 (UTC)

I'm not sure that a solitary predator has any need to 'empathize with others'. See Ludwig Wittgenstein, and his comments about lions speaking (though come to think of it, lions, as social animals, may have more of a need for empathy than tigers...) AndyTheGrump (talk) 06:23, 18 March 2012 (UTC)

It could be helpful for a tiger. For example, knowing that the villagers of the person they are about to kill will get very upset and come after the tiger with guns might be a good thing to understand. Or, on a more basic level, knowing that the prey animal will run towards the pack when threatened might enable them to figure out that they need to position themselves between it and the pack before they pounce. If you're unable to think about what others are thinking, this type of reasoning becomes more difficult. We could eventually get to game theory, where we also consider other's reactions to our actions, based on their actions, based on our actions, etc. StuRat (talk) 06:34, 18 March 2012 (UTC)

The issue here is that you're conflating "knowing what others are thinking" with "observing repeated actions." A tiger can observe that prey generally try to reach the herd for safety without necessarily understanding "the prey thinks it will be safer in the herd." That's what makes it so difficult to understand animal cognition. As another example, a crow that has learned cars are really good at cracking nuts open doesn't know anything about what the driver of the car is thinking. — The Hand That Feeds You:^Bite 14:39, 21 March 2012 (UTC)

Agreed, except that you said "reach the heard for safety". The tiger wouldn't know why the prey does this, just would note that it does run to the herd. If it did know why, the advantage would be the ability to predict how the prey might behave without having several failed hunts first. StuRat (talk) 23:27, 21 March 2012 (UTC)

which branch of statistics

which branch of statistics (or other science, but I assume with the tools of modern statistics) deals with which religion is most likely to be true.

(Obviously 'we can't know for sure' 100.000...%, a hundred sigmas, as an almighty Taco could have fabricated all the evidence, implicating some nonexistent God) — Preceding unsigned comment added by 149.200.102.16 (talk) 14:57, 18 March 2012 (UTC)

I'm not sure what the origin of the story is (maybe they know on Humanities) but there's an old story about the Emperor of a faraway land, who had never been seen by the people. [4] Desiring to make a statue of him, they needed to find the length of his nose, so a vote was held, and the results were averaged to get a figure. (Hmmm, maybe it should have been a median... [5] ;) That's all statistics can do for religion. One can find deep philosophical truths, but striking an average of the responses has nothing to do with it. Wnt (talk) 16:08, 18 March 2012 (UTC)

For what it's worth, Feynman retells that story in Surely You're Joking, Mr. Feynman!, without giving a source. -- BenRG (talk) 19:57, 18 March 2012 (UTC)

Religion is a matter of faith, and is entirely unconnected with how likely it is to be true. Science cannot help with questions of religion, if it could they would no longer be questions of faith and no longer a matter of religion. SpinningSpark 17:23, 18 March 2012 (UTC)

Obviously religions make a lot of factual statements that can be tested. Christianity says that someone named Yeshua lived in Judea at a certain time and did various things, some of them witnessed by a large number of people. Buddhism says that desire is the cause of suffering. These are statements that can be tested against available evidence. The fact that some people will ignore the results is beside the point. -- BenRG (talk) 19:57, 18 March 2012 (UTC)

You can't quantify uncertainty in precise numerical terms except in very limited circumstances. If you're measuring the average of a numerical property (like nose length) across a population, and you have an accurate list of the members of that population and the ability to compel anyone you choose to submit to the measurement, you can pick a random sample and calculate a degree of confidence in your estimate of the mean. In any vaguer circumstance, you get much vaguer results. When the thing you're trying to test is a vague statement about a historical event and the evidence is whatever historical documents happened to survive, you can't come close to attaching a numeric confidence level to your conclusions. -- BenRG (talk) 19:57, 18 March 2012 (UTC)

Perhaps it's the branch known as "Figures don't lie, but liars do figure." ←Baseball Bugs ^{What's up, Doc?} carrots→ 20:36, 18 March 2012 (UTC)

I imagine more recent religions are designed to match what science tells us about the world a bit more than ancient religions. Have the crystal vibration nuts adapted their "religion" to string theory yet ? StuRat (talk) 02:20, 19 March 2012 (UTC)

Maybe somewhat, but even the newer religions contain testable hypotheses that contradict scientific evidence, in part due to science having progressed since the religion was created. As an example, the Book of Mormon has been around for less than 200 years, but its account of the origins of native Americans conflicts with genetic analysis that has been possible since around the late 1990s; see Genetics and the Book of Mormon. As an even more recent example, Scientology has only been around since the early 1950's, but Scientology's chronology of the universe, which includes events that supposedly took place as long ago as 7 x 10⁸⁵ years ago, conflicts with the actual age of the universe (about 13.7 x 10⁹ years), which has only really been accurately known since the first accurate measurement of the Hubble constant, in 1958. Red Act (talk) 04:35, 19 March 2012 (UTC)

Your last statement is too generous to Scientology. The early estimates of the Hubble constant were inaccurate, but only by a factor of six or so. Similarly, we had estimates for the age of the Earth and the age of the oldest stars that were roughly several billions of years well before Scientology was invented. Anything proposed to occur more than ~10×10¹⁰ years ago would have been clearly inconsistent with Science even in 1950s. Dragons flight (talk) 05:04, 19 March 2012 (UTC)

Yeah, I was already thinking of rewriting the last sentence of my post above, since it doesn't adequately reflect the state of physical cosmology at the time of Scientology's creation. At the time of Scientology's creation in the early 1950's, it wasn't even really clear yet that the universe hadn't been around forever. The derivation of the Friedmann equations and Hubble's law, and Hubble's observation thereof, all took place in the 1920's. But there was an alternative Steady State theory that had just come out in 1948, that allowed for a static universe. Indeed, the term "Big Bang" was coined as a pejorative term in 1949 by a Steady State theorist. It wasn't really until some observations in the 1960s, especially the discovery of the cosmic microwave background radiation in 1965, that the Big Bang theory emerged as the clear winner among the two competing theories. So Scientology's use of a set of times far older than the actual age of the universe by itself didn't really clearly contradict science yet in the 1950s. Red Act (talk) 07:26, 19 March 2012 (UTC)

To be clear, no religion can be proved bogus in this way, because religion can be interpreted differently.* For example, a religion could define a "year" as changing in length in proportion to the age of the Universe (i.e. a logarithmic scale). This is entirely reasonable since otherwise in the first nanosecond of the universe objects could move all the way from one end of the universe to the other in a second. In our modern time it makes 1/15,000,000,000 difference in the length of one year to the next, which nobody would notice. Religion can only be scientifically disproved when it comes out and starts telling scientists what they should be seeing, i.e. making testable predictions. As long as they stay in their own domain, they are invulnerable. Wnt (talk) 02:49, 22 March 2012 (UTC)

* Whether Scientology is a religion, or merely a way of doing quack psychiatry without a license, is another question...

Surely anyone hoping that statistics can help to justify religion needs to look at Lies, damned lies, and statistics, "particularly the use of statistics to bolster weak arguments". HiLo48 (talk) 18:32, 19 March 2012 (UTC)

Thomas Bayes a theologian, invented Baysian statistics. Graeme Bartlett (talk) 08:59, 21 March 2012 (UTC)

why does the chain make a 'triangle' shape between front (pedal) gear, back (wheel) gear, and this arm, on high-quality bikes?

Resolved

on a high-quality bike like this: http://www.bike-trend.com/wp-content/uploads/2009/06/gt-force-carbon-pro-2009.jpg why does the chain not go directly between the forward and after gears, both above and below - instead, below an arm makes it form a triangle (in case it isn't clear what I'm saying I drew the triangle here in red: http://imgur.com/cFFIH.jpg -- the green is what I would expect instead of the red triangle. To get the green, you would just reflect the top half the chain makes going from back gear to front pedal, reflected horizontally so it looks the same below (result: http://imgur.com/xf083 )....soo...why the triangle? --79.122.101.84 (talk) 18:36, 18 March 2012 (UTC)

The gear assembly hanging down is the derailleur, which is there to move the chain back and forth between the different gear ratios on the wheel hub.--Aspro (talk) 18:48, 18 March 2012 (UTC)

As always, one can usually consult a Wikipedia article on this very subject and we do indeed have one: Derailleur gears.--Aspro (talk) 18:52, 18 March 2012 (UTC)

The question is, why such a large triangle? The last picture I ended up drawing looks fixed-gear; obviously you would need different amounts of chain to connect different sized gears. But the picture I showed seems to show that the angle (the angle of the triangle corner that is closest to the right/front of the bike) is much larger than necessary. Does this have some benefit? 79.122.101.84 (talk) 19:00, 18 March 2012 (UTC)

The gears have all the same tooth pitch but different 'diameters' . With many gears, one not only has the problem of needing the angle of the chain to be kept as near perpendicular to the wheel hub axial but also take up the slack as it moves to smaller diameter gears. A slack chain is liable to jump off the sprockets. The more slack to be taken up the longer the derailleur arm.--Aspro (talk) 19:13, 18 March 2012 (UTC)

Even good bikes (like mine) with internal hub gearing often have a "derailleur", or at least the cage. The idea here is to take up the extra slack the chain develops as it slowly wears out, so it won't slip or jump of. --Stephan Schulz (talk) 23:57, 18 March 2012 (UTC)

Why such a large triangle? we have an article section for that Fifelfoo (talk) 03:06, 19 March 2012 (UTC)

Hey, thanks! The article was too technical for me to digest when you first linked it, but linking the section, I think I understand. It wasn't what I expected. (I expected an answer that would show that for some reason it's better for the chain to come up at closer to vertical as it makes it's way up the back gear and toward the front pedal: hence a larger triangle gets it closer to that. (it's taken up at an angle closer to vertical, not completely horizontal). Alternately, I thought the angle might have fed the chain better due to some other consideratio, like this design is more immune to a twig etc getting stuck in there, I don't know exactly. Anyway thanks for clearing it up! It seems the answer is almost 100% just about the "slack" that is represented by the amount of chain that's needed to connect the two smallest and the two largest possible gears. We can mark this resolved. --80.99.254.208 (talk) 09:29, 19 March 2012 (UTC)

Quite so. As the article mentions, if you have two rings in front (unlike the bike in your picture, which has three), there is less "slack" that needs to be handled, and so the "derailleur" does not need to be as big (compare).--Itinerant1 (talk) 23:53, 19 March 2012 (UTC)

Gynandromorphs and intersex

can we call a gynandromorph a "partial intersexed creature" ?. thanks. 109.64.44.20 (talk) 18:42, 18 March 2012 (UTC)

See Intersex#"True_hermaphroditism". Note, however, that there is a certain amount of room for play in these definitions; conceivably, I can picture a case of something/someone who is a gynandromorph in the sense that, oh, the Y chromosome was lost in the skin of his left hand, so that tissue is XO female, but I wouldn't call him an intersex. Wnt (talk) 19:20, 18 March 2012 (UTC)

looking for a book in microscopy

i need a book that shows authorized real and pure (UN-edited) Photographs of atoms (via scanning tunneling microscope for example) and even such photos ("captures") of molecules. if the book contains photographs of cells, proteins and all other "family members", than it will be blessed. much thanks guys. 109.64.44.20 (talk) 18:56, 18 March 2012 (UTC)

Are you looking for a textbook on scientific microscopy, or for a coffee-table book with attractive microphotographs? 87.113.82.247 (talk) 19:08, 18 March 2012 (UTC)

By "authorized" do you mean "public domain" or "copyleft", etc., or something else? You might try PubMed Central and/or ArXiv for papers instead of looking for a whole book... Wnt (talk) 19:46, 18 March 2012 (UTC)

Here's an arXiv paper with STM pictures of graphene, with focus on the individual carbon atoms (pages 10-12). Any general biology book will have plenty of photos of cells, but photos of individual proteins will be a lot harder to find though - in fact, I don't think any exist, since proteins have a complex non-cystalline 3D structure which can't be scanned with current microscopes (strictly speaking, none of the pictures are photographs, since light is far too imprecise to take images on the scale of individual atoms. Scanning tunnelling microscopes work by basically moving a very fine needle over the object being imaged, using the movement of electrons from the molecule to the needle to work out the structure of the molecule). Hope this helps. Smurrayinchester 21:39, 18 March 2012 (UTC)

Ah, here's a paper in Nature which seems to have STM images of proteins. Here's an atomic force microscopy image of part of a protein too (I know AFM can indirectly measure proteins, but I didn't realise it could make direct images too). Smurrayinchester 21:46, 18 March 2012 (UTC)

Hi. i am the asker, well, indeed, i need a "coffe-table" book. in "authorized" i mean that the author worked very hard to legally put the content in his book... :) will download the articels right now. thanks! 81.218.145.251 (talk) 17:47, 19 March 2012 (UTC)

It sounds like you might be after something like this which has images showing both extremes of scale and everything in between (power of ten style). Oh actually, this looks even more what like what you want. SmartSE (talk) 22:09, 19 March 2012 (UTC)

Pentacene also has an image (bigger here) of it from an atomic force microscope which I think is/was one the best atomic images so far. SmartSE (talk) 22:14, 19 March 2012 (UTC)