Nathaniel

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I'm a post-doctoral researcher with a wide range of interests. My career is in complex systems science (or maybe cybernetics) and the origins of life, but I also have research interests in

the foundations of statistical mechanics and its relationship to information theory
Earth systems science
non-equilibrium thermodynamics in general

I'm also generally interested in the foundations of quantum mechanics and in black holes, though I wouldn't say I'm an expert on those things.

It's probably worth noting that despite the fact that my research is in physics-related areas, all my degrees are in other subjects. If I occasionally seem to start talking in an alien language, this is probably why.

	6,259 reputation	bio	website	nathanielvirgo.com	visits	member for	1 year, 7 months
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May 14	comment	From where (in space-time) does Hawking radiation originate? Thanks, this looks promising. It would seem to imply that from the distant observer's point of view, the photons would appear to come from the practically-infinitely-hot extended horizon, and thus should appear to have interacted very strongly with the infalling matter.
May 14	revised	What are the limitations of performing music in space? might need to re-tune a piano
May 14	comment	Bunsen Burners and the Sun It's worth clarifying the answer to part 2 of the original question: yes, they are two different phenomena. The sun's yellow light is the result of black-body radiation, whereas the blue of a bunsen flame is due to spectral lines. To see the difference, compare the spectrum in this post to a black body one.
May 14	answered	What are the limitations of performing music in space?
May 14	comment	What are the limitations of performing music in space? The bellows of a pipe organ would be quite difficult to operate, although they're typically electric these days.
May 14	comment	What are the limitations of performing music in space? It might be quite difficult to play a double bass, just in terms of the logistics of holding on to it without gravity to brace it against the floor.
May 14	revised	From where (in space-time) does Hawking radiation originate? explained why pjcamp's answer is not a complete one. (It's getting a lot of upvotes.)
May 14	revised	From where (in space-time) does Hawking radiation originate? does the energy-time uncertainty play a role?
May 14	awarded	Nice Question
May 14	comment	Our Universe Can't be Looped? @Qmechanic please see my comment above. I agree that this is mostly a duplicate of that question, but one subtle and non-obvious difference is that the other question asks about a situation in which there is curvature, so it can only be answered with GR, whereas (I think) this one can be answered using SR alone. I don't know whether I'll have time to post such an answer, but would you consider re-opening it if I did?
May 14	comment	Our Universe Can't be Looped? @nonagon in a non-wraparound universe, all frames are equal. But, I think, in a wrap around universe they are not, because there is one frame in which the universe has a maximum size, and it's smaller in all other frames. Unfortunately it's hard to explain this without the aid of a diagram, and this question has been closed, which means I can't post one. (And unfortunately the "duplicate" question is actually different enough to this one that such a diagram would make no sense as an answer to that question.)
May 13	comment	Our Universe Can't be Looped? Personally, I think the resolution is that creating a "looped" universe in this way necessarily creates a preferred frame of reference that breaks the symmetry. One twin sees a lorenz-contracted universe that's smaller than the one the other twin sees. If I get time I'll write that up as an answer.
May 13	comment	Our Universe Can't be Looped? @zhermes no, it doesn't need curvature, at least if it only "loops" in one dimension. It's analogous to rolling a piece of paper into a tube - you don't need to stretch it.
May 13	comment	Our Universe Can't be Looped? @Manishearth why do you say that? It's not what happens in our (probably) non-wrap-around universe. I think this is a good question - at least, the answer doesn't seem trivial.
May 13	comment	From where (in space-time) does Hawking radiation originate? @pjcamp I've resurrected this rather old question. I do understand that the "piling up" is only from the point of view of a distant observer, and I understand why an infalling observer doesn't observe Hawking radiation. However, the question is about what an outside observer will see. I have substantially updated the question, which should make it clearer.
May 13	comment	Does a guitar sound different in zero (or micro) gravity? It's worth noting that a frequency change of one part in $5\times 10^4$ is about $\log2\left( \frac{5\times 10^4+1}{5\times 10^4} \right) \approx 2.9\times 10^{-5}$ octaves, or less than one 2500th of a semitone - quite a bit too small to be detected by the human ear.
May 13	revised	From where (in space-time) does Hawking radiation originate? added pjcamp's fourth option to the list
May 13	comment	From where (in space-time) does Hawking radiation originate? Why would someone downvote this? If it's unclear, tell me where so I can clarify; if it's obvious, please post an answer; if I've made a mistake somewhere then please post an answer, as I really want to know this. I can't really think of any other possible reason.
May 12	revised	From where (in space-time) does Hawking radiation originate? heavily edited; made the Penrose diagrams more prominent and removed some old stuff; changed title
May 12	comment	From where (in space-time) does Hawking radiation originate? @RonMaimon after thinking about this some more, I've realised I'm still confused. I've added some diagrams to the question, which should help to show why I can't come up with a satisfying mental picture from your answer.