16,610 reputation
44678
bio website nathanielvirgo.com
location
age
visits member for 3 years, 9 months
seen 23 mins ago

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.


Feb
11
comment Why aren't there any clear planets/ stars?
It's a good question, and neither the question nor the correct answer have anything whatsoever to do with the linked "why is water clear?" question. The actual answer is that even things like water or hydrogen gas, which are clear in small quantities, are no longer clear if you scale them up to the size of a planet. I hope someone has the time to write up a good answer explaining this.
Feb
7
comment Sun in front of horizon after sunset; mirage or reflection?
I suspect that it's a reflection - I think the atmosphere is bending the light such that you can't see the Sun directly, but you can see the rays that have been bent by the atmosphere and then reflected off the sea. But I'm not at all sure about this. +1, it's a good question.
Feb
7
revised Random musing, is $\langle\psi^*|\psi\rangle$ = $\langle\psi^*|I|\psi\rangle$, where I is the identity operator a legit operator?
deleted 17 characters in body; edited title
Feb
5
comment What is the interpretatation of individual contributions to the Shannon entropy?
Oh sorry. The first was just a Wikipedia link. Yes, the point is that paper makes the Rényi entropy feel like a physically and informationally meaningful thing, whereas to me the Tsallis seems like a mysterious equation that comes from nowhere. (But if you know an interpretation I'd like to hear it.)
Feb
5
comment What is the interpretatation of individual contributions to the Shannon entropy?
it's not just a related quantity, it's a more general one that includes yours, but anyway. Yes I meant to post two links. The second is an interpretation of the Renti entropy. I don't know a good interpretation of the Tsallis entropy, it always seemed a bit arbitrary to me.
Feb
5
comment What is the interpretatation of individual contributions to the Shannon entropy?
@NikolajK your other thing seems related to the Rényi entropy. I do know a nice interpretation of the Rényi entropy, though its exact relation to your formula would need some thought.
Feb
5
comment What is the interpretatation of individual contributions to the Shannon entropy?
@NikolajK it's not so much "I don't know an interpretation" (although I don't) as "here's a reason why you wouldn't expect there to be an interpretation."
Feb
5
answered What is the interpretatation of individual contributions to the Shannon entropy?
Feb
3
comment What does a long strip of explosive sound like when detonated?
Probably quite a bit like a roll of thunder, which is essentially the same thing.
Feb
2
comment Unmixing of gases: What is the relevant temperature for my Entropy?
@mart typically the heat bath is just the atmosphere or water surrounding the thing that's doing the unmixing. Known practical practical methods for unmixing macroscopic quantities of fluids are so far from the theoretical maximum efficiency that the temperature of the heat bath makes no difference to the energy they need. The point is just that in priciple, if you had access to a heat bath at a lower temperature than the system, then in principle you could design a Maxwell's demon type thing to take advantage of it and unmix more efficiently.
Jan
31
answered Is $ds^2$ just a number or is it actually a quantity squared?
Jan
28
comment Confusion in understanding the concept of beats
You might find the diagrams and explanation at en.wikipedia.org/wiki/Beat_(acoustics) helpful.
Jan
27
comment Is there a thermodynamic limit on how efficiently you can solve a Rubik's cube?
...so if you have an inexhaustible supply of initially solved dummy cubes then you can indefinitely solve cubes by transferring their scrabledness into the dummy cubes - but with one dummy cube you can't solve more than one other cube.
Jan
27
comment Is there a thermodynamic limit on how efficiently you can solve a Rubik's cube?
@CJDennis that's a good idea, and it took me a while to see why it can't work. Let's say you've solved the cube and now you want to offload the 'waste' information about its initial state into the dummy cube. If the dummy cube is in a known state (e.g. already solved), you can just 'swap' the information in memory with the dummy cube's state, clearing the memory. But if you (the machine's designer) don't know the dummy cube's state then this doesn't work; there's $2^{65}$ bits of unknown information in memory, and another $2^{65}$ bits in the dummy cube - it can't all compress into the cube.
Jan
26
comment Lagrangian mechanics and initial conditions vs boundary conditions
More reasonable for what? They are different types of problem and each has its uses.
Jan
25
revised Bra-ket of products
edited tags
Jan
25
comment Is the work-energy theorem valid for only particles or rigid bodies as well?
@Gerard work is being done, but just not on the block. Instead it's being done on the atoms that make up your hand and the block, and it is indeed increasing their kinetic energy, which you feel as heat.
Jan
23
answered Why hasn't an exact solution to the Navier-Stokes equations been found?
Jan
23
comment Is there a thermodynamic limit on how efficiently you can solve a Rubik's cube?
@MarkEichenlaub I think your comment is right; another way to look at it is that the link you seek is exactly Landauer's principle. It says that although information need not be preserved on the macroscopic level, we can't erase macroscopic information without increasing the number of microscopic states. This is essentially because of what you say in your comment: at any given time the total state of the system can be partitioned into $\text{macrostate}\otimes\text{microstate}$, so by Liouville's theorem you can't decrease the first without increasing the second.
Jan
23
comment Is there a thermodynamic limit on how efficiently you can solve a Rubik's cube?
@MarkEichenlaub it looks like the discussion resolved the rest of your questions - is that right?