12,662 reputation
23163
bio website nathanielvirgo.com
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visits member for 2 years, 9 months
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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.


23h
comment Sea surfer position displacement
@Renan oh, there's no need to delete your answer, it's not wrong! It's just that buoyancy is only one of the forces that contribute to balancing the gravity force, especially if you're on a smaller board. The other is hydrodynamic lift, which is similar to the aerodynamic lift provided by a wing. I imagine the fluid dynamics of this are somewhat complicated, but I've never looked into them in detail. (I'm only a surf beginner myself, but I've tried standing on a longboard while not moving and it does sink. This must be even more so for shortboards.)
1d
comment Sea surfer position displacement
Buoyancy isn't all that important for surfing. Unless it's a foam board (a very big, very buoyant design that's easy for beginners) a surfboard will sink if you try to stand on it in still water. Surfing works because of lift generated by moving along the water surface.
Jul
19
awarded  Good Question
Jul
19
revised Why did nuclear testing not result in nuclear winter?
multiple typos in the word "stratosphere"
Jul
19
comment What conditions do a bunch of atoms need to satisfy to have a temperature?
@ticster maybe, but it's very dependent on me finding time - I'd say don't hold your breath!
Jul
19
comment What conditions do a bunch of atoms need to satisfy to have a temperature?
Great question! I could write a great answer if I had time, but it would be an awful lot of work. The short short version is that a system really needs to be in equilibrium to have a temperature, and the two beams travelling in opposite directions are not in equilibrium, since you could certainly extract work from such a system. But that's an over-simplification, because there are lots of systems that have temperatures without being in equilibrium. (E.g.: a human being.) Disentangling that in a formal way is possible, but as I said, a lot of work.
Jul
18
awarded  Popular Question
Jul
18
awarded  Nice Question
Jul
18
comment Not-so-hot black shirt
Not a proper answer, but when looking at an image of myself taken with an IR camera I was surprised to find that my black fleece top appeared white. So that kind of synthetic material might be an example, although I wouldn't want to wear it on a hot day!
Jul
18
asked If there were fundamental forces weaker than gravity, would we know about it?
Jul
18
comment Do objects gain and lose heat at the same rate?
@alemi that's very dependent on the situation, e.g. the geometry of the object and its surroundings. Sometimes it does make a big difference. In engineering situations where people really care about heat flow rates, people go to a lot of effort to calculate the convective heat flux. Usually you can only do it by numerically simulating the air flow, and software packages to do this are a profitable business. I've used them in the past. In this case I would expect the sign of the temperature difference to have a measurable effect.
Jul
18
comment Do objects gain and lose heat at the same rate?
This is a good answer, but it would also be worth mentioning convection. A warm object in a cold fridge will heat up the air surrounding it, which will rise up to the top and draw in more cold air from the sides. This increases the rate of cooling. However, a cold object in a warm room will cool the air surrounding it. Cold air sinks rather than rising, so it will mostly just hang around the object and stay cold. So the rate constant will actually be different in the two cases as well.
Jul
18
comment Can you explain Fermat's Principle to me?
Please say which text book you are referring to. Always, always, always give your source when quoting, on this site or anywhere else.
Jul
18
revised Can you explain Fermat's Principle to me?
added 10 characters in body
Jul
11
comment Should a radiation-filled Universe be scale invariant?
I'm not 100% sure of my reasoning here, but if the universe is filled with radiation then doesn't that radiation have to have a particular temperature? If so then the Planck formula gives it a characteristic wavelength, which breaks the scale symmetry. I don't know but I would assume the Friedmann equation is based on radiation at equilibrium at some temperature (which is constant over space but not time for an expanding universe).
Jul
11
comment Why do almost all nuclear reactions release energy?
I don't understand how an endothermic process can consist of exothermic steps. Obviously there can be some exothermic steps, but they have to be outweighed by other ones that are endothermic, because energy is a state function. Right? (I don't know anything about nuclear processes, but thermodynamically what you said sounds odd, unless I didn't understand it correctly.)
Jul
9
revised Is there an upper limit to a rocket's size/payload?
added 34 characters in body
Jul
9
comment Is there an upper limit to a rocket's size/payload?
@Jason I've added the missing explanation to my answer.
Jul
9
comment Is there an upper limit to a rocket's size/payload?
@KyleKanos I've fixed the answer so that it explains the issue with gravitational acceleration properly, and also explains why Asad's answer to the linked question is wrong (and yours is right).
Jul
9
revised Is there an upper limit to a rocket's size/payload?
added 1712 characters in body