111–120 of 144 posts
Countdown to a sci-fi movie where this idea is only half understood and the "proof of concept" device opens a portal to hell, where we meet the real Maxwell's demon... Now that I've typed this, I want to see it happen.
Do the wrong transform in, say, a Hilbert space and something quite horrible may come after you.
The second law of thermodynamics isn't really a fundamental physical law, but rather a promise based on statistics that says "disorder will increase or stay constant in a closed physical system". That said, it's entirely possible for entropy to spontaneously decrease in a closed system, the probability of this happening is just astronomically small for typical macroscopic systems. Example: If you have a system consis…
aren't people (and all living organisms) the quintessential example of a local decrease in entropy that results in greater overall entropy? we are highly ordered groupings of matter but we're really great at churning about the matter and energy around us and we eventually decompose too.
Yes, but that's not what the person you replied to was saying. They were pointing out that there can be a global, absolute decrease in entropy, it's just statistically very unlikely.
The second law of thermodynamics isn't really a fundamental physical law, but rather a promise based on statistics that says "disorder will increase or stay constant in a closed physical system". That said, it's entirely possible for entropy to spontaneously decrease in a closed system, the probability of this happening is just astronomically small for typical macroscopic systems. Example: If you have a system consis…
The second law of thermodynamics isn't really a fundamental physical law, but rather a promise based on statistics that says "disorder will increase or stay constant in a closed physical system". That said, it's entirely possible for entropy to spontaneously decrease in a closed system, the probability of this happening is just astronomically small for typical macroscopic systems. Example: If you have a system consis…
Doesn't evaporative cooling work against the second law somehow? There is a system with some average temperature, and spontaneously enough entropy is created to cause some of the liquid to reach boiling temperature and leave the system, which decreases the average temperature of the liquid.
Mass and energy is leaving, thus the average temp decreases but so does the particle count.
So this article does the Maxwell Demon some injustice. There is a key point about the demon that when he is 'sorting' the particles into two bulbs or rooms, that the gate he is working on is frictionless. In this way, you can can see that there is no energy entering the system, yet the entropy is decreasing. Now, this is where things get interesting to me (please correct me if I'm wrong here). What the demon is addin…
Exactly. Maxwell's Demon is a magical construct. In reality, any active device that sorts molecules into high and low energy bins would take power to run, and would generate more heat (or other entropy) than it removed by doing the sorting.
Earlier quoted context omitted.
The second law of thermodynamics is as fundamental as the uncertainty principle: The former is a result from markov chains and information theory, the latter is a result from fourier analysis of conjugate variables. What would you consider a "fundamental physical law"?
Nature is under no obligation to comply with mathematical analysis.
Earlier quoted context omitted.
This is very true, and is the case with many 'laws'. Another example is with centre of masses: Take a hollow sphere, clearly the c.o.m. should be in the very middle, yet an object placed inside has not force whatsoever on it so it isn't attracted to the c.o.m. and the idea breaks down (NB objects outside are attracted predictably). This is because this idea is purely a tool to make calculations of large groups of par…
I don't think that's true. An object would be attracted to the inner surface of the sphere because that's where the mass actually is. The shape you're describing doesn't have a center of mass the way we traditionally think of it.
Earlier quoted context omitted.
I don't think that's true. An object would be attracted to the inner surface of the sphere because that's where the mass actually is. The shape you're describing doesn't have a center of mass the way we traditionally think of it.
An object inside the hollow sphere would in fact be attracted to each individual mass-ful particle on the surface of the hollow sphere. But (assuming uniform density on the sphere) the net effect is 0 (it feels no gravitational attraction whatsoever). The best way to prove this is to compute the gravitational force between your object and any arbitrary particle on the surface, then do the integration over all the par…
Earlier quoted context omitted.
Shut off the flow of energy and the cold would catch up to us a long time before the second law of thermodynamics. (our frozen, desiccated corpses would probably retain their organization longer under such conditions)
I'm no physicist, but isn't the cold a result of the second law? Or is the second law a consequence of the dissipation of heat? Also, is thermodynamic entropy applicable to organized matter?