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bio website nathanielvirgo.com
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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.


3h
comment At what velocity does space no longer equal a vacuum?
@BenCrowell I'm not sure (it's a while since I read the book in question), but I think this particular thing is based on reality. It's basically just the point that once you're travelling near $c$, the odd H atom or dust particle here and there can no longer be neglected, because of the enormous kinetic energy involved in collisions with them. (I might be wrong though.)
Oct
19
answered How much entropy is produced in evaporating water due to irreversible evaporation towards equilibrium (humidity=100%)?
Oct
19
revised How to calculate magnitute of average acceleration?
edited tags
Oct
12
comment Is it possible to start fire using moonlight?
Well, the Moon's surface temperature during the day is about 123 celsius, which isn't hot enough to ignite paper or lighter fluid, so if we had to rely on black-body radiation from the Moon and pure optics then it would be impossible. But since as you say moonlight is reflected rather than re-emitted, it might be in-principle possible. I imagine you'd need a ridiculously large collection area though.
Oct
11
comment Why is $d$ generally not used instead of $r$ in Newton's derivation of force of gravitation?
I would guess it's because the most obvious application of Newton's law is to calculate the force on something orbiting a much heavier object in a roughly circular orbit. (E.g. planets around the Sun, or satellites around planets). In this case $r$ is the radius of the orbit.
Oct
10
comment Describe Ising model dynamics in stochastic differential equation or stochastic process
For the stochastic process approach, you might like to look into "Glauber dynamics". As for whether there's a meaningful way to approximate/summarise the dynamics as coupled differential equations, I don't know. It sounds hard.
Oct
7
comment Are all machines linearly scalable?
An even earlier influential discussion was Discourses and Mathematical Demonstrations Relating to Two New Sciences (Galileo, 1638). As I understand it from second-hand accounts, one of the two sciences was the relation between material strength and scaling, and the other was kinematics.
Oct
6
revised Rate of time progression
URL formatting issue (SE didn't like the em-dash character)
Oct
3
answered Unmixing of gases: What is the relevant temperature for my Entropy?
Oct
2
revised If I shout at the sky, will some molecules reach escape velocity?
descriptive title
Sep
30
awarded  Explainer
Sep
30
awarded  Yearling
Sep
29
awarded  Informed
Sep
28
comment Disequilibrium during infinitesimal steps of a thermodynamic reversible process & cause of maximum work to be achieved during reversible process?
... If there is no friction at all, the oscillations will take place for a very long time - but not forever, because the gas itself has some viscosity, and this will eventually turn the kinetic energy into heat. On the other hand if there's lots of friction the piston won't oscillate at all, but will just slowly move towards its equilibrium point. But in all of these cases the amount of heat generated will be the same. It has to be, because the final position of the piston is the same, so the energy difference between the initial and final states is the same. All that energy must become heat.
Sep
28
comment Disequilibrium during infinitesimal steps of a thermodynamic reversible process & cause of maximum work to be achieved during reversible process?
@user36790 actually it's due to a lack of friction. Imagine the system before you remove the first piece of lead. The pressure force balances the weight of all the lead shot. Now remove one piece - now the pressure is the same, but the weight is less, so the piston will start to move up. But this decreases the volume, and therefore the pressure force. Shortly the weight will be greater than the pressure force, so the piston will slow down and reverse its direction, compressing the gas again. These oscillations will continue until friction damps them, and this friction generates heat. ...
Sep
27
comment Is a chain REALLY only as strong as its weakest link
I've edited my answer - see the last paragraph.
Sep
27
revised Is a chain REALLY only as strong as its weakest link
added 723 characters in body
Sep
27
comment Is a chain REALLY only as strong as its weakest link
This isn't really a case of the thicker string being weaker, though, it's just a case of more force being applied to the stronger string than the weaker one.
Sep
27
comment Disequilibrium during infinitesimal steps of a thermodynamic reversible process & cause of maximum work to be achieved during reversible process?
...this means that the total energy change of the system is the same - the question then is how much of that energy went into heat, and how much went into work? In the case of the lead shot, most of it goes into work - when you remove a piece of shot, the piston lifts the rest of it against gravity, which is work. But it also jiggles the piston around a bit and makes some heat. When you remove a grain of sand, the amount of jiggling is much less and so even more of the energy goes into work. By the time you get to infinitesimal grains, there's no jiggling (and no heat generated) at all.
Sep
27
comment Disequilibrium during infinitesimal steps of a thermodynamic reversible process & cause of maximum work to be achieved during reversible process?
@user36790 after you've removed the 1000 pieces of lead shot, you've removed a total weight of $1000mg$. This has allowed the piston to expand, doing work. After you've removed the 100,000 grains of sand, you've removed a force of $100{,}000\times (m/100)\times g = 1000mg$, the same as for the lead shot. So although the total amount of heat generated by friction goes to zero as the size of the grains decreases, the total change in volume and force stay the same. (to be continued...)