5 ms·

My first instinct would be that this is due to entropy rather than minimizing energy, but the article doesn't mention that hypothesis. Is it easy to rule this o

by tgb 7y ago

My first instinct would be that this is due to entropy rather than minimizing energy, but the article doesn't mention that hypothesis. Is it easy to rule this out?

ggus 7y ago
Isn't "minimizing energy" a definition for entropy? My idea is that, when shaking, all pieces try to move. Big pieces can only go upwards, while small pieces can go sideways (and take the space that was previously taken by a big piece). This ends up with the effect of big pieces floating to the top
- zentiggr 7y ago
  I use this to sort out favorite flavors and types of snack mixes all the time. Irritates my wife a little when I've eaten all of one type and left the rest.
- jjoonathan 7y ago
  > Isn't "minimizing energy" a definition for entropy? No. If you have a system with a well-defined energy/entropy exchange rate (temperature) you can use it to put entropy in units of energy, add it to your energy term, and model the combined system behavior on the basis of this "free energy." The free energy is not a fundamental quantity, though, and it doesn't define entropy. That's why the first two laws of thermodynamics are "Energy is Conserved" and "Entropy Increases," not "Free Energy decreases."
- amluto 7y ago
  > Isn't "minimizing energy" a definition for entropy? No. I’m not really sure how you’re trying to define entropy, but you’ll probably have quite a bit of difficulty with endothermic processes if you try to think about entropy like this. For example, if you sprinkle sodium acetate in water, the sodium acetate dissolves, and the solution absorbs heat in the process, thus increasing the energy of the system. In general, entropy increases but energy just moves around.
itronitron 7y ago
the Brazil nut effect results in less randomness in the system as larger items rise to the top and smaller ones descend
- pletnes 7y ago
  The system isn’t closed - you’re exchanging energy and entropy with the shaker.
- tgb 7y ago
  That makes sense, thanks for resolving it for me.
uoaei 7y ago
It's about maximizing density, which corresponds roughly to 1) minimizing energy by making the aggregate have as low of a center-of-gravity as possible, and 2) minimizing entropy of the arrangements of the components. Often energy and entropy minimization coincide quite closely but don't exactly share the same minimum nor optimization path.

by tgb 7y ago

My first instinct would be that this is due to entropy rather than minimizing energy, but the article doesn't mention that hypothesis. Is it easy to rule this out?

ggus 7y ago

Isn't "minimizing energy" a definition for entropy? My idea is that, when shaking, all pieces try to move. Big pieces can only go upwards, while small pieces can go sideways (and take the space that was previously taken by a big piece). This ends up with the effect of big pieces floating to the top

zentiggr 7y ago
I use this to sort out favorite flavors and types of snack mixes all the time. Irritates my wife a little when I've eaten all of one type and left the rest.
jjoonathan 7y ago
> Isn't "minimizing energy" a definition for entropy? No. If you have a system with a well-defined energy/entropy exchange rate (temperature) you can use it to put entropy in units of energy, add it to your energy term, and model the combined system behavior on the basis of this "free energy." The free energy is not a fundamental quantity, though, and it doesn't define entropy. That's why the first two laws of thermodynamics are "Energy is Conserved" and "Entropy Increases," not "Free Energy decreases."
amluto 7y ago
> Isn't "minimizing energy" a definition for entropy? No. I’m not really sure how you’re trying to define entropy, but you’ll probably have quite a bit of difficulty with endothermic processes if you try to think about entropy like this. For example, if you sprinkle sodium acetate in water, the sodium acetate dissolves, and the solution absorbs heat in the process, thus increasing the energy of the system. In general, entropy increases but energy just moves around.

itronitron 7y ago

the Brazil nut effect results in less randomness in the system as larger items rise to the top and smaller ones descend

pletnes 7y ago
The system isn’t closed - you’re exchanging energy and entropy with the shaker.
tgb 7y ago
That makes sense, thanks for resolving it for me.

uoaei 7y ago

It's about maximizing density, which corresponds roughly to 1) minimizing energy by making the aggregate have as low of a center-of-gravity as possible, and 2) minimizing entropy of the arrangements of the components. Often energy and entropy minimization coincide quite closely but don't exactly share the same minimum nor optimization path.