Wikipedia:Reference desk/Archives/Science/2008 March 15

= March 15 =

Quantum Physics II

 * How does a wave have a charge (like an electron)?
 * How does light (a wave-particle) and an electron (also a wave-particle) have differing masses if they are both particle-waves?
 * How does a wave have mass at all?

Zrs 12 (talk) 03:39, 15 March 2008 (UTC)


 * Mass and energy are equivalent. Anything with energy has mass. An electromagnetic wave does have charge, but positive and negative mixed together so that the result is neutral. Light is a traveling wave, confined to moving at light speed, whereas an electron is a wave packet, something like a standing wave, and therefore can travel at other speeds.


 * But the 'why' questions dig at the limits of what we know of the universe. — kwami (talk) 03:54, 15 March 2008 (UTC)


 * Yes I know $$E=mc^2\,\!$$, so why does the electron have a mass and photons not have a mass? They both contain energy, no? Zrs 12 (talk) 04:00, 15 March 2008 (UTC)


 * A photon has zero rest mass, not zero mass. 'Zero rest mass' is a fiction, another way of saying that it can't be at rest. The mass of a photon is its energy. — kwami (talk) 04:07, 15 March 2008 (UTC)


 * The concept of relativistic mass have gone out of use, kwami, rest mass is just an obsolete term for mass. Narayanese (talk) 09:41, 15 March 2008 (UTC)


 * Electrons aren't waves. They are electrons. They have wave-like properties, they exhibit wave-like behavior (in some circumstances). But they are not "waves" per se. (When you lose track of the metaphor and the thing-itself then you're heading into the territory of confusion.) --98.217.18.109 (talk) 14:59, 15 March 2008 (UTC)


 * According to | this resource electrons are particle waves. Is UC Berkeley wrong or am I missing something?  Furthermore photons are also wave-particles (photons).  What am I missing? Zrs 12 (talk) 20:01, 15 March 2008 (UTC)


 * That's a theoretical claim which has not been demonstrated. — kwami (talk) 19:56, 15 March 2008 (UTC)


 * Well, don't confuse one professor's lecture at UC Berkeley with UC Berkeley the institution! I haven't the time to figure out where in that hour-long lecture the claim comes up but if I were his teaching fellow (and I have been a teaching fellow in similar classes), I would probably be explaining to my students the basics of the Copenhagen interpretation in response. Electrons are electrons. When we understand them with macroscopic metaphors our understandings will be in part imperfect. It is important to remember this. We can model their behavior like a wave in some situations, and we can model their behavior like a particle in others. (Wave-particle duality). But they are neither waves nor particles. They are electrons. They act like both waves and particles. See Complementarity (physics). There are, of course, other interpretations of QM, but frankly I find Copenhagen to be the most intuitively straightforward once you grasp it, as a non-scientist. It makes your questions unnecessary and removes the confusion of worrying too much about what it would mean for a wave to have a charge—the wave doesn't have the charge, the wave is just another function of what an electron is, just as the charge is part of that. An electric charge is just a fundamental property of the subatomic entity.
 * If you wanted to point me to the specific time in the lecture I'd be happy to take a look at it. My bet is that the professor is just trying to convey to the non-scientist students that electrons are like both waves and particles. Again, I think a more thorough explanation—if I were doing it, anyway—would be to separate out the epistemology of the electron (what we can know about it, how we can know it) from the ontology of the electron (what the electron really is), which is more in the style of Copenhagen, and in my non-scientist opinion, easier for non-scientists to grasp (personally I think scientists have very little clue what's easier for a non-scientist to grasp or how non-scientists learn, but that's just my own observation, being someone who has long been on the borders between science and the humanities). Regarding it as a "particle wave" is fine shorthand for remembering it has both properties but again, it's a metaphor, it's in a human language, it will have limitations. --98.217.18.109 (talk) 20:19, 15 March 2008 (UTC)


 * From 10:42 to about 16:30 he talks about electron waves orbiting the nucleus. This part is what I was talking about. Zrs 12 (talk) 22:21, 15 March 2008 (UTC)

can we produce 50,000 units of electricity from solar energy
Hi, I want to know wheather i can produce near to 50,000 units of electricity from concentrated type solar panels. I live in a tropical country with ample sun light. Please give me the precice amount of stream needed and the time it needs to be converted into stream.I would also like to know about the suitable dynamo needed with price margine.please help me this is my last resort and this is not an homework question.(e-mail removed to avoid abuse)--Manoj man1990 (talk) 06:21, 15 March 2008 (UTC)


 * Find out the amount of units of electricity you can get from a single solar panel in your country and work out how many you would need to get 50,000 units. Better still contact a solar panel supplier and ask them.


 * What do you mean by stream? is this about a water generation method?
 * 87.102.21.171 (talk) 10:54, 15 March 2008 (UTC)


 * What unit? Saying "50000 units of electricity" is like saying there is 1000 units between New York and London. Doesn't say anything at all about the actual distance - the unit could be nanometers or parsecs for all we know! -- Aeluwas (talk) 11:27, 15 March 2008 (UTC)


 * I think the OP is referring to a solar thermal concentrator using steam as the heat transfer fluid. There are some links in solar thermal energy that may be of use. If by 'units' you mean watts, then the answer is yes, systems delivering tens of MW have been built. If by 'units' you mean kWh per year, then the answer is still yes, since 50,000 kWh per year is not that much. --Heron (talk) 11:38, 15 March 2008 (UTC)


 * Stream is a common (but usually incorrect, depending on language) synonym for "electricity" in many languages. For example, my own native language Dutch has "stroom". User:Krator (t c) 15:12, 15 March 2008 (UTC)


 * While anon could be more clear, when it comes to household/consumer electricity, Units of electricity nearly always means kWh. This is in most English speaking countries that I'm aware of including the UK, NZ, Malaysia and apparently the US as well. Household bills and electricity providers will often talk about units rather then kWh although I presume it is defined somewhere in the small print for legal purposes Nil Einne (talk) 15:38, 15 March 2008 (UTC)


 * But OP can't mean kWh, because "produce near to 50,000 kWh of electricity from concentrated type solar panels" would be meaningless. 50,000 kWh in how much time? --Heron (talk) 18:23, 15 March 2008 (UTC)


 * Unless they say otherwise, I'd assume they mean to produce 50,000 kW per hour. Of course, since solar power only works when the Sun's out, the next question would be how much beyond 50,000 kW must be generated at peak production to allow for it to be stored so 50,000 kW can be drawn continuously.  This assumes that a continuous power supply is needed.  For some tasks, like pumping water into a water tower, I suppose it's fine to only operate the machinery when the Sun is shining. StuRat (talk) 18:13, 16 March 2008 (UTC)


 * Check out -- this may be of some help, although all associated info is in Canadian dollars and presupposes you want to buy the solar panels commercially available in Canada. -- Vance.mcpherson (talk) 21:27, 17 March 2008 (UTC)

Observes & speed of light
I may have asked this question before, but if I did, I probably didn't understand the answer as it has been bothering me still.

An observer is in a train travelling at 10 m/s on a double track in space. Another train passes on the second track, travelling at 10 m/s as well. Through the side window, the observer sees that train as if it were moving at 20 m/s, causing a certain amount of motion blur etc.

Then, the train starts travelling at 160,000,000 m/s (or: slightly more than half the speed of light), and another train passes at 160,000,000 m/s. What does the observer see? User:Krator (t c) 15:23, 15 March 2008 (UTC)


 * I'm a bit confused as to how many trains there are and what you are describing. If one train is going 10 m/s then it can't be passed by another train going the same speed, unless you mean 10 m/s relative to the other train. Also, are talking about trains accelerating (from 20 m/s to 160,000,00 m/s) or moving at constant velocities? Because that changes how it is handled with relativity and etc.; acceleration is much more complicated than constant speeds. In other words, I think you need to clarify a bit of what you are asking. In any case, if what you are asking is will at anytime one observer see a train passing him at the speed of light, then no, he won't—he'll see the speed as being slower, one way or another (the amount of space passed in a given amount of time will never mean their velocity is c or greater—either the time will be measured differently or the amount of space will be measured differently, depending on how you look at it). --98.217.18.109 (talk) 16:16, 15 March 2008 (UTC)
 * If an outside observer would see the two trains as moving in opposite directions, both at 1.6m/s, then an observer in one of the trains would observe the other as moving at about 2.49m/s. See velocity-addition formula. Algebraist 17:58, 15 March 2008 (UTC)


 * The OP means that the other train is travelling in the opposite direction. His problem is that if both trains are travelling at more than half C then surely the velocity of one train observed form the other will be more than C?   The answer is that no it won't.  Velocities do not add linearly, so in this equation where u and v are the velocities of the trains and w is the velocity of one observed from the other;


 * $$w \approx u+v\,\!$$


 * is only approximately true when u and v are small compared to C. The correct formula for adding velocities under special relativity is;


 * $$w = \frac{u+v}{(1+\frac{uv\,\!}{C^2})}$$


 * From which it can be seen that w can never be more than C. The best it can do is equaal C if either u or v are C also.  Sp in ni  ng  Spark  17:58, 15 March 2008 (UTC)


 * Two trains passing each other at 160 Mm/s will look the same, from the perspective of someone riding one train, as a train at rest being passed by a train going at about 249 Mm/s (all speeds measured with respect to the track). But neither case will look at all like a sped up version of the 10 m/s case. It will look more like this. High-speed physics isn't at all like a faster version of low-speed physics. Fundamentally the reason you can't "add velocities" is that the space of velocities is hyperbolic. When you're dealing with small relative speeds, you're dealing with a small part of the space that's approximately flat, so you can pretend it's exactly flat and use vectors. When you're dealing with large relative speeds this doesn't work any more. Hyperbolic geometry is unfamiliar, but there's a close analogy with spherical geometries like the surface of the Earth. When you're only mapping a small part of the Earth you can pretend it's flat, but you can't make a flat map of a large part of the Earth without distortion. It's the same with velocities. The usual meters-per-second velocities measured with respect to a "reference frame" are actually the Klein model of hyperbolic space, which is a kind of map projection. That article unfortunately has no pictures, but the Poincaré disk model is similar and has some pretty pictures. See also Escher's Circle Limit woodcuts. All of the like-colored shapes in those pictures are the same size; they just look different because of the projection. If you scale the Klein disk so that it has a radius of c, and say that O is the center of the disk, P and Q are points 160 Mm/s from the center in opposite directions, and R is a point 249 Mm/s from the center, then the real distance between P and Q (in the hyperbolic space) is the same as the distance between O and R. That's why those two cases of the passing-train problem are the same. They look different on the map, but that's because it's distorted near the edges. There's nothing deep about the "velocity addition formula"; it's just a side effect of the traditional use of the Klein projection, which is just a historical accident. -- BenRG (talk) 19:30, 16 March 2008 (UTC)
 * I'll munch on this answer for the coming month. Thanks! :) I've only done so much physics, but I think I'll be able to understand the above with the help of some physicist friends. User:Krator (t c) 22:42, 16 March 2008 (UTC)

Kinetic energy and related matters
Hi. This is not homework. So, an apple with a mass of 100 grams dropped from the height of one metre, negligizing air resistance, releases approximately one joule of energy? However, at what downward speed is the apple travelling at by the time it hits the ground? What about from a height of 10 metres? I know acceleration of gravity is just under 10 m/s, but how to calculate the velocity the object is travelling at by the time it hits the ground? If an object is thrown upwards, and say is is travelling at 40 m/s, will it be travelling at 30 m/s upwards after one second, and 20m/s after 2 seconds? Will it start to fall down after 4s, or is acceleration more complicated than that? Say is starts falling down, it will be travelling at 10 m/s after one second, but what about after 2 seconds, will it be travelling at 20m/s? How can we calculate based on height? Also, how does one joule compare to the equivalent of one kg of force? Does the density of the impacted surface usually affect the amount of energy released, such as in asteroid impact simulation given by LPL Arizona? If an object weiging 1 kg is travelling forward without downward interference from gravity, such as pendulum or rolling, and air resistance and friction is negligible, and travelling at 10 m/s, how many joules of kenetic energy? What about 1 kg at 20m/s? Is this calculation linear or exponential? If a (hypopthetical) bullet (average) was shot directly upwards, how high would it reach? If it was shot downwards from the altitude of 1 km from the ground, would it speed up by then because of acceleration or slow down because of air resistance? If you and a ball were falling out of the sky at the same altitude and the same velocity, say at 100m/s, can you safely catch the ball? If an object were to explode upon impact, caused by the impact alone and not some inner explosive force such as a grenade, so it's not a bomb, would the released energy be the same as if they didn't explode? If two bullets hit each other exactly head-on, with exactly the same mass and exactly the same speed, and were travelling exactly horizontal, and they have exactly the same volume and exactly the same density, and air currents and resistance were negligiable, what would happen? If a gamma-ray photon and a radio-wave photon hit each other head on, and didn't miss, would the resulting annilated matter, if any, travel more in the direction the gamma ray was travelling because higher energy, or is it impossible because different wavelengths? Can black holes implode? Have I asked this before? Thanks. ~ A H  1 (TCU) 15:32, 15 March 2008 (UTC)


 * An apple with a mass of 100 grams dropped from the height of one metre, negligizing air resistance, releases approximately one joule of energy?
 * Correct.


 * However, at what downward speed is the apple travelling at by the time it hits the ground? What about from a height of 10 metres? I know acceleration of gravity is just under 10 m/s, but how to calculate the velocity the object is travelling at by the time it hits the ground?
 * It's 10 m/(s^2). velocity=acceleration*time, distance=time^2*acceleration/2. You know acceleration and distance. Solve for time, then velocity.


 * If an object is thrown upwards, and say is is travelling at 40 m/s, will it be travelling at 30 m/s upwards after one second, and 20m/s after 2 seconds? Will it start to fall down after 4s, or is acceleration more complicated than that? Say is starts falling down, it will be travelling at 10 m/s after one second, but what about after 2 seconds, will it be travelling at 20m/s?
 * That is all correct.


 * How can we calculate based on height?
 * If you're talking about calculating speed from hight, you already asked that.


 * Also, how does one joule compare to the equivalent of one kg of force?
 * I assume you mean the weight of a kg, which is about 10N. It's one-tenth of a meter times as much. That is, pushing with a force of 10N over a tenth of a meter uses one J. This is what happens when you mix units.


 * Does the density of the impacted surface usually affect the amount of energy released, such as in asteroid impact simulation given by LPL Arizona?
 * No, assuming mass, rather than volume, is constant, but it does affect the way in which it is released.


 * If an object weiging 1 kg is travelling forward without downward interference from gravity, such as pendulum or rolling, and air resistance and friction is negligible, and travelling at 10 m/s, how many joules of kenetic energy? What about 1 kg at 20m/s? Is this calculation linear or exponential?
 * Kinetic energy=mass*velocity^2. It is neither linear nor exponential.


 * If a (hypopthetical) bullet (average) was shot directly upwards, how high would it reach?
 * I don't know the speed of the average bullet, or the effects of air-resistance, but if you know the former and ignore the latter, distance=time^2*acceleration/2. Air resistance would be far from negligible.


 * If it was shot downwards from the altitude of 1 km from the ground, would it speed up by then because of acceleration or slow down because of air resistance?
 * Terminal velocity for a bullet is much slower than what speed it's fired at. It would slow down, and approach terminal velocity.


 * If you and a ball were falling out of the sky at the same altitude and the same velocity, say at 100m/s, can you safely catch the ball?
 * Air resistance would make a much larger difference for the ball, then for you, but if you ignore that, you'd both be in free fall and the ball would seem to hover, making it both safe (insomuch as falling out of the sky is safe), and extremely easy.


 * If an object were to explode upon impact, caused by the impact alone and not some inner explosive force such as a grenade, so it's not a bomb, would the released energy be the same as if they didn't explode?
 * The energy remains constant. Unless there's some way it's storing the energy, the amount released will be the same. Whether or not it explodes will make a difference in how the energy is released, and thus its destructive power.


 * If two bullets hit each other exactly head-on, with exactly the same mass and exactly the same speed, and were travelling exactly horizontal, and they have exactly the same volume and exactly the same density, and air currents and resistance were negligiable, what would happen?
 * They'd either bounce off of each other or fuse. I've seen a picture of two bullets that collided in midair and fused, so I know that one's possible. The other is probably also possible. I'd say it depends on the bullet.


 * If a gamma-ray photon and a radio-wave photon hit each other head on, and didn't miss, would the resulting annilated matter, if any, travel more in the direction the gamma ray was travelling because higher energy, or is it impossible because different wavelengths?
 * From some point of reference, they're the same wavelength. I think they can annihilate each other, but I don't know if they have to. If they do, momentum will be conserved, so the resulting matter/antimatter or whatever gets released will be moving more in the direction of the gamma ray.


 * Can black holes implode?
 * They're as imploded as it gets. If our current physics are wrong, and they can implode more, there'd be no way to tell, as no information about the internal structure can leave the event horizon. — DanielLC 18:02, 15 March 2008 (UTC)


 * AH1, are you taking the piss?  Sp in ni ng  Spark  18:09, 15 March 2008 (UTC)


 * What?!? This? *confusion*. ~ A H  1 (TCU) 18:48, 15 March 2008 (UTC)


 * Never new that was Hiberno-English. Amazing what you learn on Wikipedia!  Sp in ni ng  Spark  19:08, 15 March 2008 (UTC)


 * It may be more common in Ireland, but it's plenty common in south England. Algebraist 20:56, 15 March 2008 (UTC)


 * And in New Zealand, too. Not an expression to use when your among Americans, who are likely to interpret it as a golden shower. StuRat (talk) 18:04, 16 March 2008 (UTC)


 * You never know your luck, though (if that's the sort of thing you like). You might have randomised yourself into the path of a fellow ... er, urinee, and if you don't put it out there, you might miss a "golden" opportunity.   --  JackofOz (talk) 18:35, 16 March 2008 (UTC)


 * Hi. By the way, great answer to my question. However, what did you mean by asking if I am taking the piss?! I still don't get it, so before I list some ridiculous possibilities, can you explain what you meant originally by this so I can solve this mystery that has been plauging me for the past 90,000 seconds? Thanks. ~ A H  1 (TCU) 19:32, 16 March 2008 (UTC)


 * It means something like "Are you teasing us ?". In the context of this post I would guess they think you may be asking so many question just to annoy us.  You might want to ask fewer questions at a time, to avoid this type of reaction. StuRat (talk) 22:47, 16 March 2008 (UTC)


 * The best American translation for "taking the piss" is "pulling (my) leg", I think. &mdash;Tamfang (talk) 22:23, 19 March 2008 (UTC)

Effect of carbon dioxide on photosynthesis
Hi all have a question I couldn't find the answer to. I know that the carbon dioxide concentration in air is usually about 0.035% but plants can benefit from much higher concentrations, up to 0.5% I believe. If the concentration is increased further I have heard it has a detrimental effect on photosynthesis causing the stomata to close. My question is why does a large concentration of carbon dioxide in the air cause the stomata to close? Surely they would benefit from the carbon dioxide. Any help would be much appreiciated. —Preceding unsigned comment added by 172.201.120.93 (talk) 15:45, 15 March 2008 (UTC)


 * This is a very complicated problem; see, for example, abstract of this paper. I am afraid there is no simple answer to this one. Sorry. --Dr Dima (talk) 16:08, 15 March 2008 (UTC)

Wikimania - is it an academic conference?
Is Wikimania considered an academic conference? Are publications presented there published in peer reviewed outlets? --Piotr Konieczny aka Prokonsul Piotrus 16:22, 15 March 2008 (UTC)


 * Not routinely, though some presenters will be academics who also choose to publish their work in academic journals. Dragons flight (talk) 16:26, 15 March 2008 (UTC)

Metabolism and conservation of energy
For people or creatures that have a fast metabolism, where is the additional energy they consume going? (Mostly I care about people, but one would think that general principles would be the same across species.) I know certain studies have found that people who fidget generally are skinnier, so maybe some of it is mechanical energy that is used in gross motion. Besides that it seems like you would either need to be passing improperly digested food or translating that energy into heat somewhere. But do people with high metabolisms really have higher body temperatures? (Or have dilated surface blood vessels so that they give off heat more quickly, or something like that?) Any insight into this would be welcome. Thanks! Mangostar (talk) 17:51, 15 March 2008 (UTC) (I just noticed I wasn't that precise. I understand that technically someone who fidgets more and is skinny because of it doesn't really have a faster "metabolism". Still, my general question is the same. I guess there are three categories that I'm seeing initially--dissipation of energy through motion, poor digestion (seems implausible), and various internal processes/metabolism that would generate heat... Mangostar (talk) 17:57, 15 March 2008 (UTC))


 * I could be thinking about this the wrong way myself, but I don't think there's such a thing as dissipation of energy through fidgeting per se... I think that has to be heat dissipation as well. Say you're moving your foot from side to side... when you start a leftward stroke, you're turning your body's chemical energy into kinetic energy (and heat, because of the inefficiency of muscles).  But then you have to decelerate your foot (if you want to keep it), so you're turning that kinetic energy into... heat, as far as I can figure.  It could be a bit of air motion, but it doesn't seem like that would account for much.  So unless the air motion is more important than I'm guessing, then it does seem like people with faster metabolisms must have higher body temperature.  But I'm not a physicist; I'm probably mixed up somewhere here.  --Allen (talk) 20:48, 15 March 2008 (UTC)
 * As for the dissipation thing I just meant that there immediately you are creating mechanical energy. Obviously that is somehow transformed into mechanical energy in the air around you as well as heat in the air and in your muscles etc. I just meant to distinguish that from heat that is generated from chemical reactions in your body. Mangostar (talk) 22:45, 15 March 2008 (UTC)
 * Mangostar's original thought is on the right track - conservation of energy. Basically, the energy expended plus the energy stored by an organism must be equal to the energy ingested.  In practice, estimating those quantities is difficult; for instance, the energy expended will include both mechanical energy and heat energy (as Amcbride noted, life here on earth has not yet developed muscles that can work in reverse by converting kinetic energy into chemical energy).  As a general principle, if an organism uses more energy, it must consume more energy, so the short answer to your question is that people who have faster "metabolisms" must eat more food, but it's really more complicated than that.  And I don't know about the body temperature thing, but it looks like the article Warm-blooded has some good info on that topic.  --Bmk (talk) 20:58, 15 March 2008 (UTC)
 * I guess my big question here is, are people who are naturally skinny normally just hotter than people who are naturally fat (assuming they eat the same amount of food and move the same amount)? To the extent it's true that some people are "naturally" thin in that their bodies are just extremely inefficient at energy (i.e. fat) storage, where is all that energy going? Mangostar (talk) 22:45, 15 March 2008 (UTC)
 * I'm not sure if that has anything to do with your question but when I eat cheese or fatty meat I sweat. So does my brother. People sometimes ask me if there is something wrong so maybe it is not that common. I don't know. 200.127.59.151 (talk) 01:19, 16 March 2008 (UTC)


 * I don't know the answer, but I would like to add that this is a really good question.


 * It's well known that different people have higher and lower metabolic rates. People with lower metabolic rates are in a sense "more efficient" at utilizing their food, in that they waste less of the energy derived from their food and therefore either need less of it or put on weight faster.  There's also the terribly unfair result that if you're overweight, and go on a diet and eat less food, your body decides that you're "starving" it, and decreases its metabolic rate further, nullifying your efforts.


 * But Mangostar is absolutely right: that energy has to go somewhere. And it pretty much has to be released as waste heat -- that's generally the end result of any energy-transfer process.


 * I'm not aware that people with higher metabolisms have higher temperatures, but if we think about it, that couldn't be the answer anyway; if the excess energy just went into heating you up, you'd get hotter and hotter until you incinerated. So the heat has to be lost to the environment.  (Now, it's true, given a constant ambient temperature, hotter objects lose heat to the environment faster, but I can't see a difference of a degree or two in human body temperature making much of a difference here.)


 * Perhaps people with a higher metabolic rate breathe faster, and thus lose more heat in the warmed air they exhale. —Steve Summit (talk) 15:09, 16 March 2008 (UTC)


 * This is just ignorant speculation, but maybe we are looking at this from the wrong way around. Thinner people have less fat to provide insulation, and hence it seems likely that they will dissipate internal heat more rapidly.  Maybe skinny people need to burn energy more rapidly than the rest of us simply to maintain the same body temperature.  Dragons flight (talk) 17:19, 16 March 2008 (UTC)


 * I had a grandmother who must have had a migh metabolic rate, because she was a "ball of energy". She would vaccuum every day, go to the grocery store every day, etc.  I imagine she burnt the energy as heat which was dissipated as she rapidly moved around the home, to the store, etc.  A person in motion should transfer heat to the air more quickly than one who stays still.  If they sweat then evaporative cooling will lower the temp, so there the energy is also going into vaporized water, just like a flame under a pot of boiling water. StuRat (talk) 17:56, 16 March 2008 (UTC)

Skeleton
Hi All. I came across this skeleton at the Middle Head Fortifications in Mosman, New South Wales. Does anyone know what this could be. Cheers. --User:Adam.J.W.C. (talk) (talk) 23:36, 15 March 2008 (UTC)


 * It might be a bat, though that little "hand" would have to be a foot of that were the case. Has more teeth than most species of bat, I reckon. --98.217.18.109 (talk) 00:17, 16 March 2008 (UTC)
 * Apart from the head, I though the rest of it looked quite human, I suspected that it could be a bat due to the fact that there is some kind of black colored skin or something wrapped around the skeleton. The only animal that I have come across in abundance in that area are hairs and rabbits. Cheers. --User:Adam.J.W.C. (talk) (talk) 00:31, 16 March 2008 (UTC)
 * The forelimb is absolutely not bat-like. It would be easier if there was a better view of the head. Check that. Rather, the front teeth on the bottom jaw (which is pointing straight down) look rather rodent-like. But that's a bit of a guess. -- Flyguy649 talk 01:31, 16 March 2008 (UTC)
 * It might not be a forelimb. Imagine it is a hind limb. It's not unlikely that the skeleton is jumbled up. I thought it looked rather rodent like, but I've never seen rodents with long arms like that. However bat legs can be quite long. (I am no mammal expert, though.) --98.217.18.109 (talk) 04:10, 16 March 2008 (UTC)

I guess one should not discount any one of a small number of Australian animals that have the general appearance of rodents - bandicoots, possums, gliders, potoroos etc., and with which we are not familiar in the skeletal state. Definitely not a bat with a 'hand' like that. Richard Avery (talk) 08:31, 16 March 2008 (UTC)


 * Possum is a real possibility. Bandicoot, potoroo, no way. Glider, can't tell, not enough to compare with. You can google things like "Possum skull" and see if it looks anything like the skull show there, it's an easy way for ruling things out (doesn't always rule things in, though). The more I look at it, the more I think the top jaw is broken—it is lacking symmetry with the bottom one and would have a tremendous underbite as is. --98.217.8.46 (talk) 15:44, 16 March 2008 (UTC)

The Great Gazoo ? :-) StuRat (talk) 17:36, 16 March 2008 (UTC)

The lower incisors tempt one to say it's a rodent, but there is no diastema (dentistry). This question was posted in various places, and I think the most clueful reply is at Talk:Rat. William Avery (talk) 19:21, 16 March 2008 (UTC)


 * I'm pretty sure its a sugar glider Petaurus breviceps, might be another species. I tell by the broad hands (all four much the same) with parallel fingers bunched into fists. I recognise the anatomy from removing them from water tanks through the bottom 25mm tap hole. This is why you must always cover the overflow pipe with netting. Polypipe Wrangler (talk) 23:27, 16 March 2008 (UTC)


 * Mmmm... I don't know. The skull doesn't look right. Compare with this skeleton of a sugar glider (from one of my favorite stores—The Bone Room in Berkeley). The body type looks right though—maybe some other species of glider? --98.217.8.46 (talk) 04:17, 17 March 2008 (UTC)


 * Have a look at this possum skull and see what you think, especially the lower jaw dentition. Richard Avery (talk) 08:34, 17 March 2008 (UTC)


 * That looks extremely plausible. --Captain Ref Desk (talk) 14:35, 17 March 2008 (UTC)


 * Just asking, but can a foetus develop a skeleton? -- Zachary crimsonwolf  14:24, 20 March 2008 (UTC)


 * Ever see a newborn without bones? —Tamfang (talk) 17:15, 2 April 2008 (UTC)