Wikipedia:Reference desk/Archives/Science/2009 August 10

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August 10

Alice

Arg, this is driving me crazy. In Australia, isn't there some animal, or something to do with animals, that the term "alice" is applied to? Any help is appreciated. Thx. --207.206.137.204 (talk) 01:47, 10 August 2009 (UTC)

I'm not from Australia, but googling turned up a lot of Australian slang sites that all related "Alice" to Alice Springs, Northern Territory. There was also Alice the Pig. I wish I could have found more for you. I'm sure some of our Australian editors will be by shortly to assist. 152.16.59.102 (talk) 02:13, 10 August 2009 (UTC)

I've got that too , I'm fairly certain it's a nickname for the spiny euchidna (they call them alices), curiously there is absolutely nothing to prove this. Did you know that the platypus is austrlias only poisonous mammal?83.100.250.79 (talk) 02:23, 10 August 2009 (UTC)

@83.100: Considering how rare venomous mammals are, that's not much of a surprise, is it? --Scray (talk) 03:46, 10 August 2009 (UTC)

Subtle recommendation to use the term venomous by Scray noted -- "poisonous" refers to organisms that affect their predator upon consumption (or heterotroph, more specifically), whereas "venomous" more precisely refers to those organisms that envenomate other organisms without the need for consumption. I don't think the spur is a "last-licks" on the part of the male platypus to "get" the guy that eats him. DRosenbach ^{(Talk | Contribs)} 14:14, 10 August 2009 (UTC)

Thanks for highlighting that - it's an important distinction. --Scray (talk) 01:54, 12 August 2009 (UTC)

I'm Australian and I've never heard of Alice as a nickname for an animal. It is definitely used to refer to Alice Springs and perhaps sometimes as a nickname for a place like it, a dry remote town, of which there are a lot of in the outback. Vespine (talk) 03:24, 10 August 2009 (UTC)

You also have lice in Australia but you don't say "a lice" you would say a louse. Graeme Bartlett (talk) 21:48, 10 August 2009 (UTC)

You could however say all lice which would sound the same. Googlemeister (talk) 13:17, 11 August 2009 (UTC)

There is a koala called Alice in something called Animal Crossing.She is named for Alice Springs, about the only thing abbreviated to "Alice" here. - KoolerStill (talk) 20:17, 11 August 2009 (UTC)

Total Perspective Vortex IRL

Has an effect comparable to that of the Total Perspective Vortex from The Restaurant at the End of the Universe been observed e.g. in astronomy students? If so, how is it treated? NeonMerlin 02:52, 10 August 2009 (UTC)

Well there certainly haven't been any proven cases of "brain annihilation!" All facetiousness and humor aside, the controversial concept of Depressive realism is probably the closest concept. As for Astronomy students, they are probably some of the most grounded people, if only because they tend to form tigh-knit groups since they are often so few. Besides, our understanding of astronomy isn't nearly as wide-reaching as everything. ;) ~ Amory (user • talk • contribs) 03:09, 10 August 2009 (UTC)

Evolution and Paganism

I've heard that the theory of evolution has pagan origins in Babylon, 2000 years before Christ. Is that true?

Bowei Huang (talk) 04:04, 10 August 2009 (UTC)

No. No, it is not. Algebraist 04:15, 10 August 2009 (UTC)

And even if it were, scientific theories are to be judged on the veracity or falsehood of their predictions, not on their origins. —Preceding unsigned comment added by 81.11.170.162 (talk) 06:03, 10 August 2009 (UTC)

It wouldn't surprise me if that was true, to some limited extent - coming up with the concept of animals adapting over time to fit their surroundings is not an immense leap of intellect. Some pagans quite easily could have seen, say, a green insect living in grasslands and a similar-looking but brown insect in a nearby forest. From there it's not too hard to suggest that perhaps those two animals "evolved" to fit their surroundings. However, having said that it's far from being the "origin" of the theory of evolution - for one, there are very limited records from that far in the past, so the chances of any reasonable scientific thought surviving to be verified in the present day are very slim indeed. So yes - ideas that were perhaps related to evolution quite possibly were thought of that long ago, but it's unlikely that any evidence remains, and even if so it's unlikely if any of it was used in the formulation of the modern theory. ~ mazca ^talk 07:58, 10 August 2009 (UTC)

It is possibe that there were early theories of evolution, just as there were early theories of cosmology and early atomic theories. However, today's theories in these fields do not "have their origins" in the earlier theories. Today's theories in all three fields originated independently of the earlier theories. This is not true for all scientific theories: for instance, medicine, agronomy, and chemistry (and their theories) can be traced more or less continuously back to antiquity, even though the modern theories in these fields bear little relationship to those in antiquity. -Arch dude (talk) 12:11, 10 August 2009 (UTC)

I would have thought the the notion of breeding to develop characteristics (e.g. domesticating dogs etc) are likely to be old enough for this to be plausibly dating 2000BC. However on "pagan origins in Babylon, 2000 years before Christ" I think you may have misheard someone talking about the Biblical creation narratives which certainly derive in parts (order from chaos etc) from their Babylonian predecessors (or so we are taught in school). --BozMo talk 12:25, 10 August 2009 (UTC)

I think the OP is really asking whether the hypothesis of evolution was around back then - and I think it's extremely likely that it was. However, turning a hypothesis into a theory (in the scientific meaning of the term) is a more formal process - and that was certainly not done back in those early times. Merely having an idea that fortuitously turns out to be right doesn't qualify you as the inventor of a theory. It's only when observations, experiments and careful testing are performed and can exclude other possible causes that a hypothesis can be labelled as a theory in the scientific meaning of that word. There is no evidence that I could find that the Babylonians did that (and it's very unlikely that they would - the 'scientific method' is really only a couple of hundred years old). SteveBaker (talk) 12:51, 10 August 2009 (UTC)

People have understood the practical implications of evolution for thousands of years, even if they didn't have an understanding of molecular genetics. Basic concepts of breeding have existed for 10,000 years. People have long understood that one can control which traits are passed on through offspring to create slow changes in a population. There is no fundemental difference between traits that are encouraged by deliberate human intervention versus traits that are encouraged by adaptation to a changing environment. The only significant barrier to the modern theory of evolution is only the time scales involved. Once you detatch yourself for the need for the earth to only be 6000 years old, and are willing to accept an earth that is billions of years old, then the rest of it falls into place pretty easily. --Jayron32 18:20, 10 August 2009 (UTC)

Yet I don't think anyone before the 19th ct. made that connection. The principles of selection-by-man were not extended to create the concept of selection-by-nature. Answering the original question - no, the scientific theory of natural selection is not known to have been inspired, directly or indirectly, by any non-Christian beliefs. On the other hand, there are many cases of stories about species developing from each other through some kind of mystical force or magic, or through the will of a deity (thus, not through evolution in the modern scientific sense of the word). One commonly occurring belief is that some or all animals are descended from humans who were transformed into animals for one reason or another (sometimes as punishment for some transgression, but in other cases they are regarded as ancestors worthy of veneration). The opposite direction of development is less common, but not unheard of. I think I recall that in the creation myth of a certain Australian aboriginal tribe, fish miraculously turned into lizards, lizards turned into some kind of mammals and the mammals turned into a humans. I can't find the reference though, and I can't find any mention of this elsewhere, so I might be wrong. I do, however, find sources saying that in a couple of tribes in Tibet and in South Africa, humans were said to originate from apes or monkeys. It's a nice illustration of the difference between religion and science - the claim can happen to be the same, the difference is in the explanations and the methods to reach it.--91.148.159.4 (talk) 21:38, 10 August 2009 (UTC)

Bowie, if you're interested for a careful, interesting historical account about the development of evolutionary theory—which has its origins long before Darwin, and indeed has interesting connections to ideas about society, morality, and religion!—check out the two-volume biography of Darwin by Janet Browne. It does not strive to convince you of anything you don't want to believe (you can keep the wool in your ears if you'd like), but it will give you a much deeper understanding of where these ideas came from. The truth of it is far more interesting (and potentially more scandalous!) than anything your conspiracy theories will have up their sleeves. --98.217.14.211 (talk) 00:10, 11 August 2009 (UTC)

It's fairly well established that the "ancient" Greek astronomers learned much from the (far more ancient) Babylonians about astronomy. So the ancient Babylonians were certainly trying out their powers of observation to help them make predictions, not just consulting sheep intestines.

In a long lifetime of science reading, I've never heard anyone make the remarkable claim that the Babylonians invented a theory of evolution -- but I can imagine such a speculative hypothesis arising in modern times, because I heard people like H.W. Armstrong baying at the moon on AM radio. Twang (talk) 06:39, 11 August 2009 (UTC)

What was this pagan origin of evolution that was in Babylon 2000 years before Christ? What was it?

I have read about this claim in the section "2. Evolution" in Chapter 3: The Wisdom of Man in the book Mind Siege: The Battle for Truth in the New Millenium by David Noebel and Timothy LaHaye.

Bowei Huang (talk) 01:08, 12 August 2009 (UTC)

I'd be interested in seeing Noebel's pamphlet "Communism, Hypnotism And The Beatles." I just *knew* those mop-tops were up to no good. Twang (talk) 07:45, 12 August 2009 (UTC)

I know it doesn't seem open-minded, but I would recommend you ignore anything David Noebel has to say about humanism or evolution. The claims that you've read and come to ask us about have been complete rubbish, and the author seems (in my opinion, not that of the RefDesk or Wikimedia) to be a liar.

Twang, you have listened to Imagine, right? AlmostReadytoFly (talk) 08:10, 12 August 2009 (UTC)

It's Lennon, not the Beatles per se. He did have an activist period, but was always a Hippie-style leftie, not a Comintern-style one. Only someone wildly right-wing can fail to see a difference between the two. --91.148.159.4 (talk) 22:52, 12 August 2009 (UTC)

The ideology might be different, but the bullshit is the same. 98.234.126.251 (talk) 02:55, 16 August 2009 (UTC)

<Sarcasm>Are you paraphrasing Lennon's views on religion?</sarcasm> Nil Einne (talk) 17:07, 16 August 2009 (UTC)

No, I'm characterizing his political views in general. By the way, who are you to claim that religion is nothing but "bullshit"? 98.234.126.251 (talk) 00:01, 17 August 2009 (UTC)

Anyone can claim it. Who are you to claim that Nil Einne shares the opinion attributed here to John Lennon? —Tamfang (talk) 16:37, 6 October 2009 (UTC)

I was taken aback recently at a dinner table when the subject of atheism was brought up and someone remarked "they started communism didn't they" -- and upon reading Atheism I believe it explains how that propaganda came about in Christian churches. Atheists have really nothing to do with communism, and atheism is not an organised religion - its "members" vary from capitalists to communists and beyond. Here we see evolution being attached to 'pagans' as if only non-believers or heathens believed in such things. On the contrary believing in evolution (which as far as I know is a fact) has nothing to do with religious affiliation - in fact there are many Christians who believe in evolution. Rfwoolf (talk) 23:33, 16 August 2009 (UTC)

I'm a Christian and I believe in evolution; in fact, I think I've stated my views on evolution vs. Genesis in an earlier post (and got attacked by RedAct for it, too). 98.234.126.251 (talk) 00:05, 17 August 2009 (UTC)

Relativistic Doppler effect-not theta_s?

I am trying to derive the formula

$f_{o}={\frac {f_{s}}{\gamma (1+{\frac {v\cos \theta _{o}}{c}})}}$

in Relativistic Doppler effect#Motion in an arbitrary direction. I used an equivalent of Lorentz transformation to transform the light cone for an observer, A, to the shape in a coordinate system for another observer, B. A point at the edge of the light cone for A in the coordinate system A, with an angle around t-axis in the x-y plane, starting from x-axis, $\theta _{s}$, is

${\frac {1+{\frac {v}{c}}\cos \theta _{s}}{\sqrt {1-{\frac {v^{2}}{c^{2}}}}}}$

times a distance from origin after transformation. (In Lorentz transformation and Relativistic Doppler effect, directions of v seems opposite, and this is in Relativistic Doppler effect way)

I think this is the rate of change in wavelength. Changing it to frequency,

${\frac {\sqrt {1-{\frac {v^{2}}{c^{2}}}}}{1+{\frac {v}{c}}\cos \theta _{s}}}$.

This is like the one at the beginning, but with $\theta _{s}$ instead of $\theta _{o}$. How can I derive the correct one? Like sushi (talk) 05:03, 10 August 2009 (UTC)

That formula can be obtained by combining the effect due to the movement of the source away from the observer (that's the same effect that gives you the non-relativistic doppler effect) with an extra gamma factor due to time dilation. The first effect gives you a factor

$factor_{1}={\frac {f_{s}}{(1+{\frac {v\cos \theta _{o}}{c}})}}$

and the second effect gives the factor

$factor_{2}={\frac {1}{\gamma }}$

It is as simple as that. Dauto (talk) 05:43, 10 August 2009 (UTC)

Alternatively, you can use the fact that ${\frac {\omega }{c}}$ and $\mathbf {k} \,$ form a 4-vector $K=({\frac {\omega }{c}},{\mathbf {k} })$ in the observer's reference frame and apply a Lorentz transformation to get $\omega '\,$ in the sources reference frame. Choosing the x-axis along the direction of the source motion, we have

${\frac {\omega '}{c}}=\gamma ({\frac {\omega }{c}}-{\frac {v}{c}}k_{1})$

But we also have $k_{1}=-kcos\theta _{o}\,$, where the minus sign is due to the fact that the source is assumed to be moving away from the observed while the light ray must be moving towards the observer (otherwise it would never be detected). Putting all that together with the simple formula $\omega =ck\,$ we get

${\frac {\omega '}{c}}=\gamma ({\frac {\omega }{c}}+{\frac {v}{c^{2}}}\omega cos\theta _{o})$

which yields the desired formula. Dauto (talk) 06:16, 10 August 2009 (UTC)

Thank you for quick answer. But why is it not $\theta _{s}$ but $\theta _{o}$? I do not understand the alternative explanation. And I hope you will answer in a way that guides me from what I supposed in the first post.

Like sushi (talk) 06:31, 10 August 2009 (UTC)

The angle comes about when you take the component of the source velocity along the line connecting source and observer. That velocity is measured from the point of view of the observer (from the source's point of view it is not moving at all, obviously) which means that $\theta _{o}\,$ is the correct angle. Dauto (talk) 06:52, 10 August 2009 (UTC)

Here's a nice simple way to derive the redshift without coordinates. At the end I'll introduce coordinates and get back the usual formula. I'll use "1+z" for the ratio of received wavelength to transmitted wavelength because it's just about the only standardized notation for redshift out there. Ignore the added 1 and just think of "1+z" as a single symbol.

Let x_s and v_s be the sender's spacetime location and four-velocity at the time of sending and let x_r and v_r be the receiver's location and velocity at the time of receiving. Let X = x_r − x_s be the separation between them. Note X is a lightlike vector because x_s and x_r are connected by a light signal.

The sender waits an interval dτ, measured on her wristwatch, and then sends a second signal (or a second wavefront of the same light beam, if you prefer). The receiver receives this after an interval (1+z)dτ, measured on his wristwatch. (This is the definition of the redshift 1+z.) These second sending and receiving events also have to be separated by a lightlike vector—that is,

$\left(X+v_{r}(1{+}z)\,d\tau -v_{s}\,d\tau \right)^{2}=0.$

It's now just a matter of solving this for 1+z. Multiply out the square to get

$X^{2}+2X\cdot \left(v_{r}(1{+}z)\,d\tau -v_{s}\,d\tau \right)+(\cdots )\,d\tau ^{2}=0.$

The first term disappears because X is lightlike and the third term is negligible because we're assuming dτ is small. Dividing what's left by 2 dτ and rearranging we get

$1{+}z={\frac {X\cdot v_{s}}{X\cdot v_{r}}},$

which is the coordinate-free redshift formula. I don't know why anyone would want to uglify it by introducing coordinates, but here goes. Let X = (Δt, Δx) and v_s = (γ_s, γ_sv_s) and v_r = (γ_r, γ_rv_r). Then we have

$1{+}z={\frac {\gamma _{s}\Delta t-\gamma _{s}\mathbf {v} _{s}\cdot \Delta \mathbf {x} }{\gamma _{r}\Delta t-\gamma _{r}\mathbf {v} _{r}\cdot \Delta \mathbf {x} }},\quad {\mbox{or}}\quad 1{+}z={\frac {\gamma _{s}(1-(\Delta \mathbf {x} /\Delta t)\cdot \mathbf {v} _{s})}{\gamma _{r}(1-(\Delta \mathbf {x} /\Delta t)\cdot \mathbf {v} _{r})}}.$

Now Δx/Δt is a vector with magnitude 1 (= c), so (Δx/Δt)·v gives the component of v along the path of the light, which I'll call v_||. Thus

$1{+}z={\frac {\gamma _{s}(1-v_{s\scriptscriptstyle ||})}{\gamma _{r}(1-v_{r\scriptscriptstyle ||})}},$

which I'll grant you is also pretty easy to remember, though you have to be careful about the signs. As I've defined it, v_|| is positive for motion in the same direction as the light. Usually people pick coordinates where the receiver is at rest, in which case $1{+}z=\gamma _{s}(1-v_{s\scriptscriptstyle ||})$. Then they introduce an angle θ instead of writing v_|| and you have to remember how the angle was defined and whether it's a sine or a cosine and whether it's added or subtracted along with everything else and it just becomes more and more confusing, so I'm going to stop here. Incidentally, the coordinate-free formula works in general relativity also if you suitably interpret X (it can't be a vector anymore because the light signal crosses a large region of spacetime where curvature can't be neglected). You can derive the gravitational redshift and cosmological redshift formulas from it by choosing different coordinates and background geometries. -- BenRG (talk) 10:44, 11 August 2009 (UTC)

Ring Singularities

In a rotating black hole there is supposed to be a ring singularity, and if you fall through it you go to a negative universe(universe with gravity repulsive). Is there space in the middle of a ring singularity? I imagine it to be no, and you fall through the ring singularity to the other side of the spacetime surface, and because the spacetime(or only time) is curved "downwards" from the original universe, the spacetime is curved "upwards" on the other side, so gravity is repulsive. I also imagine that the fields may travel through the spacetime surface so that the only thing different about the negative and the ordinary universes are the gravitational fields. The Successor of Physics 05:59, 10 August 2009 (UTC)

I've never heard of this "negative universe". I think you just end up in a new universe with the same laws of physics (in fact, if it is possible to travel between the two it would be reasonable to consider then parts of the same universe). I think you would come out of a white hole, but they aren't repulsive, they actually look identical to black holes to an outside observer (this is very counter-intuitive, but it is what the maths says). --Tango (talk) 11:43, 10 August 2009 (UTC)

There is a region of repulsive gravity through the ring singularity in the Kerr-Newman metric. That's not a "universe with gravity repulsive", though, it's just the equivalent of a negative-mass object in our universe. If you brought two ordinary objects through the ring singularity they would still attract each other. Probably that region of the solution doesn't have any physical significance. Don't make the mistake of thinking that attractive gravity is "downwards" curvature and repulsive gravity is "upwards". The curvature is intrinsic—there's no up and down. The difference between attractive and repulsive gravity is more like the difference between elliptical and hyperbolic space. You might be thinking of the "gravity well" or "rubber sheet" picture of Newtonian gravity, where a valley is attractive and a hill is repulsive. A lot of books confuse that with spacetime curvature. -- BenRG (talk) 20:54, 10 August 2009 (UTC)

On a tangent, it's kind of funny when people talk about or movies and tv shows show things going "through" a black hole into a new universe or back in time, etc. Fraser Cain on the Astronomy Cast podcast had a good line about this. He said it's like a frog looking up at a blender and wondering "If I jump inside the blender will I go to a new universe? Or looking at a trash compactor and wondering if you can go to a new dimension. Unfortunately, if you go into a black hole, you just end up being blended and compacted into the stuff that's in the singularity itself (whatever form of stuff that is). 63.95.36.13 (talk) 22:00, 10 August 2009 (UTC)

An idealised black hole is a connection to "another universe", although it is impossible to actually travel between them, even if you could avoid being ripped to pieces, the connection doesn't exist long enough for even light to traverse it. However, even that doesn't matter because real black holes aren't ideal, when a black hole forms from the collapse of a star (rather than existing forever) the connection never exists in the first place. It is best depicted using a Penrose diagram like this one. Roughly speaking space is horizontal and time is vertical with up being forward in time - only one dimension of space is shown, the other two are the same, though. Travelling at the speed of light corresponds to travelling along a 45 degree line, travelling slower than light means being closer to vertical than that, that is why you can't leave the black hole once you are in it, you would have to move along a line more than 45 degrees off vertical, which means travelling faster than light. The connection between the two universes is a single point, you can't get through it without ending up in the black hole. (Ignore the electrically charged/rotating version - that's just weird! That is where the ring shaped singularities come into it, though.) --Tango (talk) 00:20, 11 August 2009 (UTC)

Thanks!

The Successor of Physics 04:36, 11 August 2009 (UTC)

First major sport to get the Deep Blue treatment?

Interesting line of discussion, I think...

Which major sport will be the first to get the Deep Blue treatment -- i.e., someone creates a robot that can match (if not exceed) the best human athlete?

Now certain sports like target shooting could almost certainly already be "solved" if anyone bothered, although sporting clays would present some difficulty!

But restricting it to major sports, which do you think would be easiest to beat? Which would be the last to go down?

Personally, I think golf will be the first to fall because it lacks the collisions and speed of other sports. The range-finding and condition assessment would seem perfect for a computer.

As for the last sport to fall? I think it would probably be basketball - satisfying the dribbling requirements and keeping track of the ball in such a confined, cramped space would present all sorts of difficulties... and that'd be after you solved all the basic mobility challenges...

What says the mighty Science Desk?

218.25.32.210 (talk) 07:54, 10 August 2009 (UTC)

I think that this is beyond our wisdom (no offence, anyone), but first, do you mean with robots performing the physical side of things? If not, what do you propose instead? Human bodies controlled by computer? And do other board games like Go count as "sports"? If so, I'd guess we'll crack them all first. Of course, by "board game" I mean "discrete" game, in which the set of possible states is finite. Even relatively simple games like pool are principally continuous, with an infinite number of states, though one could probably discretize the table into squares at minimal loss of performance. --Leon (talk) 08:56, 10 August 2009 (UTC)

Beyond whose wisdom? Here's a video of my classmates' robot playing Shuffleboard. Clearly, computers no longer need to stick to nerdy games like "chess" and "Go" - soon robots will be lining up on cruise ship decks and hogging all the shuffleboards with their precise, calibrated technique! Nimur (talk) 16:12, 10 August 2009 (UTC)

I thought I explained it well enough, but I guess not. Fully autonomous robots competing shoulder to shoulder against humans. Go, however much its proponents made enjoy trumpeting its complexity, is quite clearly not a "major sport" - let's keep it on topic! 218.25.32.210 (talk) 09:23, 10 August 2009 (UTC)

In that case, I haven't a clue. And I'm not convinced that the question is very clear. For instance, are the robots allowed some sort of "telepathy", meaning invisible radio contact between them? The rules of sports don't specify that humans can't be telepathic, to my knowledge! Are we placing limits on size (mass and volume) of these machines? If not, couldn't quite simple robots pummel humans with ease, in sports like boxing? Are robots allowed wheels, or must they have legs, like humans? With wheels, I'd imagine we could engineer some very fast robots. --Leon (talk) 09:32, 10 August 2009 (UTC)

What are you defining as a major sport? You've already ruled out target shooting, which does seem an obvious choice.

The men's world record for discus is only 74.08 m, whereas clay pigeon traps can shoot up to 100m, according to our article. Hammer throw would also be a relatively easy problem to solve.

Isn't taregt shooting what a LOT of miltary robot development is about? OK Granted missle defence or 'Let's get Osama!' isn't quite the same thing... 62.56.124.134 (talk) 20:54, 16 August 2009 (UTC)

I understand getting humanoid robots to balance is a difficult problem, which suggests sports involving lots of balancing and moving around would be difficult (e.g. basketball as suggested, gymnastics). Swimming might be easier, with the possibility of very hydrodynamic designs. AlmostReadytoFly (talk) 09:55, 10 August 2009 (UTC)

Against topic drift, the gods themselves contend in vain. (Redlink?!) —Tamfang (talk) 04:51, 11 August 2009 (UTC)

OP back, now at home hence the different IP. Here, I'll throw out some guidelines for the sake of discussion.

Rule 1 Robot must have a body similar to a human - 2 legs, 2 arms, walk upright, similar articulation (elbows, knees, ankles), sensors in the "head", dimensions equivalent with professional athletes of the same sport -- weight is unrestricted in non-contact sports (golf, tennis, swimming), but must also be equivalent in contact sports (football, rugby, sumo)

Rule 2 Robots may not communicate with teammates in any fashion that a human could not - so no infrared, no wi-fi - only auditory / visual / gesture based communication

Rule 3 Robots are autonomous during competition, not remotely controlled.

Off the top of my head, let's confine it to the following sports: swimming, track & non-throwing field (pole vault, high jump, etc), wrestling, sumo, American football, world football, golf, tennis, badminton, basketball, baseball, ice hockey, volleyball, and cycling.

I think cycling is particularly interesting - the energy efficiency advantages would be offset as it'd have to balance itself on a bicycle and rely on cameras for depth perception and road surface interpretation... 213.146.164.143 (talk) 12:05, 10 August 2009 (UTC)

My kid used to have a radio-controlled toy motorcycle. It balances very easily without any clever software, cameras or anything else. Once a bike is moving fast enough, the balance is rather automatic. SteveBaker (talk) 14:22, 10 August 2009 (UTC)

I don't know what qualifies you to set up the rules. You asked a question - the answer doesn't necessarily conform to your guidelines! Actually, your 'rules' are incredibly stupid...why should (say) a robot soccer player have to look and speak like a human? We didn't require Deep Blue to use neurons to think with - why should a robot have to have things like arms and legs and communicate with it's teammates using crappy audio links? Do you require 'eyes' to be made with a gelatinous lens projecting the image on to a curved interior surface - instead of just using off-the-shelf cameras? Do we have to build our audio detectors using fluid-filled chambers with little hairs protruding into them instead of microphones? Drawing the line where you drew it is an entirely arbitary decision - and one that completely precludes us from researching a proper answer. What you are asking is really "When will the first fully humanoid robot be built?" and that's not at all the same question - and because the definition of 'fully humanoid' is an arbitary one too - we're not going to be able to answer that one if you nail down the preconditions so tightly. It's like asking "When will the first robot appear that's painted pink with little blue stripes?"...the answer can only be "Nobody knows until it happens". SteveBaker (talk) 12:39, 10 August 2009 (UTC)

Ping pong was the first physical sport to be attacked robotically...without a doubt. A guy called Russell Anderson built a fairly successful ping pong playing robot back in 1986 - he even wrote a book about it: [1]. There were robot ping-pong contests held all over the place back in the 1980's - research into the subject more or less fizzled out once it was realised that the problem was pretty much solved. There is currently quite a bit of interest in robot soccer - and (to 'level the playing field') "segway soccer" between humans and robots. Someone mentioned shooting - there are several robotic paintball guns out there that can out-shoot a human with ease...especially on moving targets...switching out the painball gun for a 'real' gun would be a little dangerous - and doesn't really prove anything. Robotic gliders have beaten the human glider endurance record. It would be completely trivial to build a robot that could beat a human on any track running event...in fact anything like the shot putt, discus, javalin, etc should be entirely trivial to win robotically. In case you insist that the robots use legs for running...let me point out that I can build a robot to beat people in the wheelchair track events at the para-olympics when legs are specifically not allowed in the rules! SteveBaker (talk) 12:39, 10 August 2009 (UTC)

Which glider record were you thinking of, Steve. This article

claims a team is still trying to reach a 142-mile robotic flight while the human record seem to be 2200 km by Steve Fossett. 75.41.110.200 (talk) 14:52, 10 August 2009 (UTC)

You might like Robot competition. Personally my favourite is the dance competition. How long till the judges say robots are more artistic, have better costumes, express the music than humans? Next they'll be competing in another athletic sport as in A.I. Artificial Intelligence... Dmcq (talk) 14:02, 10 August 2009 (UTC)

I would imagine that you could design a robotic pitcher for baseball where one of it's arms is essentially a cannon capable of shooting the ball at a speed too high for a human player to hit, say 300 mph. That would far surpass any human achievements in that part of the sport. Even if he strikes out every time he bats, it would still be a major net gain for the team, so you wouldn't even have to program that part. 65.121.141.34 (talk) 16:12, 10 August 2009 (UTC)

I suppose Pitch-o-mat 5000 was just a modified howitzer? Nimur (talk) 21:13, 10 August 2009 (UTC)

'Bacteriocidality' of penicillin

"β-lactam antibiotics work by inhibiting the formation of peptidoglycan cross-links in the bacterial cell wall. The β-lactam moiety (functional group) of penicillin binds to the enzyme (DD-transpeptidase) that links the peptidoglycan molecules in bacteria, which weakens the cell wall of the bacterium (in other words, the antibiotic causes cytolysis or death due to osmotic pressure). In addition, the build-up of peptidoglycan precursors triggers the activation of bacterial cell wall hydrolases and autolysins, which further digest the bacteria's existing peptidoglycan.

Are these cross-links continually constructed during the lifecycle of the bacteria -- otherwise, penicillin should be merely bacteriostatic? Or is the secondary effect the major (I assume it's not, as it's secondary). DRosenbach ^{(Talk | Contribs)} 14:04, 10 August 2009 (UTC)

The cross-linking doesn't have to be continuous - it just has to be necessary for both daughter cells on division. If both daughters die on division then any active colony will collapse, and therefore penicillin would be bacteriocidal (This bit is just a thought experiment - read on for a real answer). If I remember my microbiology lectures correctly, during growth the cell wall is actually continually synthesized "on the inside" (closest to the inner membrane) and broken down by autolysins on the outside. This is to allow for expansion (the newly synthesized cell wall can stretch as it is not yet cross-linked). As, at least under ideal lab conditions, bacteria are continually growing then yes, the cross links are pretty much continually constructed during the lifecycle. 84.12.138.49 (talk) 22:50, 10 August 2009 (UTC)

Tornandos and Hurricanes in US

I didn't hear of a lot of press about a lot of tornados out in the Midwest. Was this a milder year than average? Does that have anything to do with the milder temperatures we had out here on the East Coast? Will that affect how many hurricanes we can expect out here this season? --Reticuli88 (talk) 15:45, 10 August 2009 (UTC)

For the latter two questions, our understanding of weather is still primitive enough that we can't draw any firm conclusions about wildly disparate weather trends being linked. For example, our tornado article notes a correlation with the Southern Oscillation (El Nino), which is also cited as a rationale for this year's lower-activity hurricane forecast. However, we note that the tornado-SO correlation is weak and moreover ties to winter tornadoes -- which have not yet occurred. Finally, even if borne out, the research doesn't create a causative tie between tornadoes and hurricanes; they would be merely correlated at best. — Lomn 16:12, 10 August 2009 (UTC)

Going back to the former, our article on tornadoes of 2009 cites 1053 US tornadoes as of 31 July; our tornado climatology article notes that the US reports about 1200 tornadoes annually. I don't find this year to be an outlier in terms of low tornadic activity. — Lomn 16:15, 10 August 2009 (UTC)

(ec) Generally, the cause of hurricanes in the United States is elevated water temperatures in the eastern Atlantic ocean, spurning west-bound low pressure systems; while the cause of tornados are large pressure variations in the air masses that originated over the western part of North America and are moving eastbound. If these two effects are correlated, or causally linked, I am not aware of any research indicating so. As Lomn pointed out, we don't really have a good model of how global weather patterns interplay - so it's hard to say for sure. Nimur (talk) 16:17, 10 August 2009 (UTC)

Pedantic nit-pick: I assume you really meant spawning, not spurning? 87.81.230.195 (talk) 00:01, 11 August 2009 (UTC)

That we haven't heard much about tornadoes this year is mainly a matter of luck; the worst tornadoes have been staying away from population centers, so the death toll has been much lower. While this May was unusually quiet as far as tornadoes go, this summer has been unusually active in the Northeastern United States.

The formative ingredients for tornadoes and hurricanes are so different, it is really impossible to discuss any correlation between the two with our current understanding of meteorology/climatology. Landfalling hurricanes do tend to produce tornadoes in their outer rainbands, but whether or not a tropical cyclone hits land is also just a matter of luck.-RunningOnBrains^(talk) 17:00, 10 August 2009 (UTC)

Neodymium Chloride

Hello. Does neodymium chloride (NdCl) exist? Thanks in advance. --Mayfare (talk) 17:48, 10 August 2009 (UTC)

I don't see why not -- its oxidation states probably means it would form analogues to iron chloride. John Riemann Soong (talk) 17:55, 10 August 2009 (UTC)

Like this maybe Neodymium(III) chloride .83.100.250.79 (talk) 18:09, 10 August 2009 (UTC)

@ [2] ~£1/g 83.100.250.79 (talk) 18:13, 10 August 2009 (UTC)

Indeed, similarly to iron, neodymium tends to have a +2 or +3 oxidation state. That means one would expect to have chloride salts NdCl₂ and NdCl₃ but probably not NdCl. I don't see an article for any ones for any other truly ionic salts (except for the previously-noted Neodymium(III) chloride) or any +2 valence compounds in Category:Neodymium compounds. DMacks (talk) 18:15, 10 August 2009 (UTC)

(ec)Yes, I think it does. Those, by the way, are the first four hits on Google. ~ Amory (user • talk • contribs) 18:21, 10 August 2009 (UTC)

There's probably a 1:1 ratio NdCl, but that's a different story, and not the common chloride that you can get in a tin, the orginal question ask-er would have to ask about it if they specifically wanted to know. (feel free)83.100.250.79 (talk) 19:39, 10 August 2009 (UTC)

There is probably not a stable NdCl monochloride. It does not get a mention in my copy of Advanced Inorganic Chemistry. To get this you may have to look in the gas phase. Graeme Bartlett (talk) 08:49, 11 August 2009 (UTC)

The CRC handbook's table Physical Constants of Inorganic Compounds lists the following:

• NdCl₂, CAS # 25469-93-6, green hygroscopic solid, melting point 841 °C
• NdCl₃, CAS # 10024-93-8, violet hexagonal crystals, melting point 759 °C, boiling point 1600 °C, density 4.13 g cm⁻³
• NdCl₃·6H₂O, CAS # 13477-89-9, purple crystals, decomposes at 124 °C, density 2.3 g cm⁻³

A search of crystallography databases also lists NdCl_2.31 and Nd₁₄Cl₃₃.

Ben (talk) 09:29, 11 August 2009 (UTC)

spirit fire

What proof would an alcoholic beverage need to be before you can light it on fire with a match? would 80 proof be sufficient? I want something exciting for a party. Googlemeister (talk) 18:31, 10 August 2009 (UTC)

Definitely. Most spirits are around 80 proof and they all light no problem. Be careful, though - flames from burning alcohol can be almost invisible unless the room is quite dark and they can leave the container dangerously hot after the flames are out. --Tango (talk) 18:38, 10 August 2009 (UTC)

You might find Alcoholic proof interesting. Edison (talk) 18:55, 10 August 2009 (UTC)

I'd suggest using Bacardi 151 - afaik, it's sort of the standard for flaming shots and the like. It's shitty cheap enough and burns better than the 80% proof stuff. ~ Amory (user • talk • contribs) 19:01, 10 August 2009 (UTC)

I'd avoid that; it burns too well. And for god's sake don't confuse percentage with proof like that. Please see alcoholic proof. Matt Deres (talk) 19:13, 10 August 2009 (UTC)

Oops, thanks! ~ Amory (user • talk • contribs) 19:55, 10 August 2009 (UTC)

Bacardi-151 is good, but 190-proof Everclear is better. Alas, it's illegal in too many places now. Twang (talk) 06:48, 11 August 2009 (UTC)

You can get similar stuff in Russia, easy enough. 98.234.126.251 (talk) 03:00, 16 August 2009 (UTC)

(e/c) Be extremely careful when lighting alcohol. If you're planning on doing a flambé kind of thing, a few quick tips: keep the lid to the vessel in your hand at all times. If the fire gets out of hand, the lid will cut off the oxygen supply. Keep a fire extinguisher within arms reach. And this sounds obvious, but turn off your stove, especially if you're using a gas stove - in fact, take your pan off the heat altogether. Gas plus fire = well, you get the idea. Also, the vapours coming off the alcohol normally ignite first, so expect the flame to start before you'd think you should expect the flame to start. Our article suggests adding cinnamon to the dish; I can't vouch for that myself. Why not try an electric pickle instead? What, no article??? Matt Deres (talk) 19:11, 10 August 2009 (UTC)

Here's an exciting party trick (I saw it done with some high tequila content mix drink). Get some small shot glasses. Fill it up and light it up. Quickly (before it gets too hot) cover it with your hand's palm extinguishing the fire. As the flame is extinguished it consumes O2 reducing the pressure in the cup enough to make it stick to your palm. Visibly shake your hand up and down mixing your drink Hold back the urge to let people know wheather/that you have slighly burned your hand. Dare other people to do the same. Tease the ones that refuse. Rinse and repeat untill bored or drunk. Make sure you have an bucket with ice "for drinks" near by just in case. Have fun. Dauto (talk) 19:15, 10 August 2009 (UTC)

Partial-vacuum is also substantially due to cooling of the headspace vapor after the flame is out. Burning does chemically consume the O₂, but two thirds of the oxygen gas consumed by burning ethanol winds up as CO₂ gas, so not nearly the "gas loss" one might expect. On the other hand, dropping the temperature of a water-vapor/CO₂/atmosphere from flame temp to hand temp is a noticeable pressure difference. See also Fire cupping. DMacks (talk) 19:39, 10 August 2009 (UTC)

I need to reinforce one point for our OP. The light you get from burning alcohol is NOT spectacular. It's almost invisible except in a fairly dark room when there is a faint blue light. To get something impressive there needs to be something besides the alcohol that's being burned. SteveBaker (talk) 12:56, 11 August 2009 (UTC)

Orthodontic braces

I know someone who has braces who is about the mid 20's agewise. Does an adult need braces longer then a teen would to correct the same problem? Googlemeister (talk) 18:37, 10 August 2009 (UTC)

According to this and this, yes it does, although there are some discrepancies. I am not a dentist (IANAD, that's a new one) but I presume it has to do with the fact that as a teen, one's teeth are still moving into their "final" position and can thus be tampered with more easily. As an adult, the teeth are relatively set, and it's harder to move them without altering all the others. Many still consider it worthwhile because of the long-lasting changes it will likely have. At any rate, if you're considering getting them, you should speak with a dentist to get the full picture. ~ Amory (user • talk • contribs) 18:55, 10 August 2009 (UTC)

If I'm not mistaken, getting braces also has long-lasting consequences: you'll be wearing a retainer to sleep for the rest of your life if you want your teeth to be straight. I would like to be wrong on this. Vranak (talk) 20:41, 10 August 2009 (UTC)

Like most answers, it depends. It depends on what needs to be done. There are many types of malocclusions that can warrant the need for braces, and there are issues of minor tooth movement. Even with a full mouth case, there are various levels of severity, that would range from closing some spaces to correcting crossbites and exposing impacted canines. If it's just about closing some spaces, it shouldn't take any longer, but if it's something much more complex, it might take longer than 18 months...but then so might a child who presents with some very complex case. DRosenbach ^{(Talk | Contribs)} 21:15, 10 August 2009 (UTC)

Questions/suggestions for Fetch (game)

On a whim I was looking at Fetch (game) and noticed the article didn't address some questions I was curious about. (I also posted these question in the article's discussion page, but figured you folks would be more reliable for answers.) First, do all dog breeds like to play fetch instinctively, or are there certain breeds who don't have an inclination for the game without training? It's unlikely that newborn pups play fetch, so at what stage of development do dogs show an interest in the game? And is there a researched evolutionary reason for dogs learning to play fetch (eg maybe dogs have been trained for thousands of years to fetch prey for hunters so the trait is now ingrained)?

And on a related note, what species other than dogs like to play fetch? Will some species of cats or birds play fetch, and if so how much training does it require if any? Is falconry a related activity, for example?

Finally, if anybody has good sources for answers to these questions, I'd recommend appending them to the Fetch (game) article. It would be a nice addition. 63.95.36.13 (talk) 21:52, 10 August 2009 (UTC)

I know that retrievers are specificially bred to retrieve which is like fetch. I don't know much beyond that. Rckrone (talk) 22:28, 10 August 2009 (UTC)

I've had an Uncle and Aunt who had a cat that would play fetch, and I don't believe they had tried to teach that particular cat to play fetch. But I would expect this to be a rare behavior in cats. 131.191.87.100 (talk) 23:37, 10 August 2009 (UTC)

Of the two cats I've had, both have "fetched" toy mice without any training, although as is usually the case with cats they're only letting you play with them, and on their terms. Both these cats eventually figured out that if they chase after the mouse but don't bring it back, the loving human will eventually walk over to where they are and then re-throw the toy. That's not exactly fetch anymore, but they did figure out how to game the system in their favor! ~ Amory (user • talk • contribs) 00:57, 11 August 2009 (UTC)

I have two Giant Schnauzers who have never in their entire lives even looked after a ball when it was thrown, let alone gone to fetch it. They might fit under your idea of a dog who doesn't have an inclination for the game without training. However, they were both raised in a kennel where there weren't many balls to be fetched, so that may have something to do with it. They are also super couch potatoes...208.65.223.146 (talk) 03:04, 11 August 2009 (UTC)

Cats'll play with a laser-pen spot for a while too, then lose interest in that. (I don't have any dog data on the subject.)

Pangaea 2

I about 250 million years we will have second Pangaea. But which oneis most likely? Pangaea Ulitma, Amasia or NovoPangaea. What is a novopangaea?--69.229.108.245 (talk) 22:03, 10 August 2009 (UTC)

According to our Pangaea Ultima article, Novopangaea is just another name for that predicted configuration. As to whether this or Amasia is most likely, I doubt there is any way to tell. 250 million years is a very long way ahead to predict. Mikenorton (talk) 22:14, 10 August 2009 (UTC)

South Africa and Cape Horn

Do South Africa tip (Cape Town) and tip of South America snow every year at basin (not the mountain) but surface level like metro-los Angeles-orange-county type land? Idoubt Cape Town often gets land-level snow altugh it's winter can be bone-chilly. Cape horn is just bad-weather, since it's coastal island, it is unlikely too to have a fixate snow seansons.--69.229.108.245 (talk) 22:21, 10 August 2009 (UTC)

Cape Town, South Africa, is at 33 degrees south latitude. this the the same distance from the equator as the southern shore of the Mediteranian (straits of Gibraltar, Tangier, etc.) Snow is not likely. By contrast, Cape Horn, at 55.5 degrees south, is much further away from the equator and is famous for nasty winter weather. -Arch dude (talk) 23:02, 10 August 2009 (UTC)

(After looking as some more pages) Cape town's record low temperatures is -1 degree C, or 30 degrees F. and it's average lows are higher than those of Los Angeles, which is farther from the equator. Cape Horn is considerably farther from the equator than Kiska, in Alaska.

I'm 28 and in my lifetime we've never had snow at ground level in Cape Town. Cape Town is a coastal city with a Mediterranean climate and quite temperate weather. We regularly get hail a few times during winter yes, but never the slow-falling snow we see on TV! On the other hand we always have snow in the higher lying areas such as the upper slopes of Table Mountain and towns further inland. Ceres, Western Cape is always inundated with Capetonians driving out every year whenever the first snowfalls of the season are reported there. We go crazy for the stuff, we're just not used to it! Also, since you do mention South Africa in your heading, I must mention that we almost certainly get snow in the Highveld areas of the country (cities such as Johannesburg and Pretoria for example), which are 100's of km metres above sea level and very far inland. On an aside, the coldest place in South Africa (and thus also getting regular snow) is Sutherland, a very remote inland town in the Karoo desert most famous for hosting the Southern African Large Telescope, the largest optical telescope in the southern hemisphere. Zunaid 18:51, 11 August 2009 (UTC)

Whoa! "100's of km above sea level" is really high! Like, thermospheric, man! Can they park the ISS there for maintenance? --Scray (talk) 02:05, 12 August 2009 (UTC)

Oops! I meant metres of course... Zunaid 14:24, 12 August 2009 (UTC)