Spearthrower wrote:
Jus fixin' teh kaos, boss...
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Blip wrote:I'm hoping for some help from one or more of the physicists here.
Some of you know that I'm doing a course on astrophysics with Oxford ContEd. I don't have a maths or physics background, but the course is designed to be accessible to a wide range of people, and so it is. Mostly.
However, I've come across something which I don't understand and with which our tutor's answer hasn't really helped me. Looking at results from Hubble, it seems that the most distant, i.e. oldest galaxies 'look strange – smaller, irregular, lacking clearly defined shapes.'
Nearer, i.e. more recent galactic views show more ordered galaxies; as that site explains '[c]loser in, we see numerous galaxy interactions and collisions as galaxies come together and merge, growing in the process. And nearer still, we see versions of the large, stately galaxies we know today. '
Help! How does this square with the entropy of the universe increasing?
hackenslash wrote:
As for the deck of cards thing, in reality, an ordered deck has only slightly lower entropy than a shuffled one. Such a system has greater entropy if the deck is scattered around the room. The reason for this is that, because it requires work to put the deck in order, entropy has been brought lower locally at the expense of an increase in entropy less locally, because energy has been expended in ordering it, and is thus unavailable for performing work.
romansh wrote:[Assuming the same "work" goes into ordering and shuffling?
newolder wrote:Shuffling in the dark is easy; sorting into suit order needs the energy of illumination.
But we've already flogged this dead horse earlier in the topic and agreed that card pack order has little, if any, connection to entropy.
newolder wrote:Shuffling in the dark is easy; sorting into suit order needs the energy of illumination.
But we've already flogged this dead horse earlier in the topic and agreed that card pack order has little, if any, connection to entropy.
Spearthrower wrote: so in that metaphor, the ordered deck has the higher (maximal?) entropy, there is no other way for it to move from that state. Basically, it's the glass of ice and the glass of water metaphor.
romansh wrote:
A pack of cards in of itself has an entropy whether sorted or random.
romansh wrote:A system of a pack of cards and a shuffler or sorter also have an entropy. The sorter can do work and sort the cards and the system's entropy will increase. Or the shuffler can do work and shuffle the cards and the system's entropy will increase. We could argue, possibly quite accurately, that it takes more work to sort. But then the shuffler can continue shuffling until the same amount of work was done.
romansh wrote:In what way will the entropy of the cards be lower for the sorted pack?
Spearthrower wrote:
Ask it another way: what's the energy gradient inherent in the system of a deck of cards? Where's the disequilibrium?
Cito di Pense wrote:
And your point would be? It's already been mentioned that each sorting of the deck is equally probable. You're stuck on the notion that there is only one sorting that is 'ordered' according to the definitions of suit and rank, and that's completely arbitrary. Every other sorting of the deck is just a permutation of the order. To render it in the "balls and urns" formalism, there are 52 urns containing one ball each and no empty urns. The balls are distinguishable but the urns are not, unless the urns are labeled. In physical systems, energy levels are populated or they are not.
hackenslash wrote:Exactly right. As noted by Styer in the paper I quoted, disorder is a metaphor for entropy. Indeed, the deck of cards is a metaphor for a metaphor. It's a metametaphor.
Evolving wrote:Blip, intrepid pilot of light aircraft and wrangler with alligators.
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