Hacker News new | ask | show | jobs
by oh_my_goodness 1520 days ago
Here's a concrete example of entropy with just two macro-states, 'broken' and 'unbroken'. If it becomes unclear or unconvincing, can you point out where that happens? It's intended to be ELI5, clear enough to discuss coherently.

Question: Why is it when I drop a vase it smashes into a million pieces; however when I then drop the million pieces it does not form a vase?

Answer: Stop! Don't drop any more expensive vases. Start with these simpler systems that do repair themselves sometimes when you drop them.

Take a coin and align it so the 'heads' side faces up. 'Heads' means 'unbroken'. (The reason for that will become clearer as we do more experiments.) Now drop the coin on the floor. How often is the 'heads' side still facing up? Now if you drop it again, how often does it 'repair' itself so that the 'heads' side is up? (Really do this.)

Try the experiment with 2 coins. Align them all heads-up, drop them, then see if your pattern is 'broken'. ('Broken' means not-all-heads-up.) Drop the 'broken' coins again. How often do they 'repair' themselves? ('Repaired' means all heads-up.) ( Don't think about it! Don't solve for it! Do it! )

Try again with 5 coins. How often does a 5-coin system 'break' when you drop it? How often does a broken 5-coin system 'repair itself' when you drop it again?

How about 10 coins? How often does a broken pattern of 10 mixed heads/tails repair itself to all heads when you drop it again? Sometimes it does, but you'll have to be very lucky or patient to see it happen.

I think from here you can probably see (part of) the answer to your question about the vase. The word people use for this kind of thing is 'entropy'. With enough coins, the 'broken' state is much more probable than the 'repaired' state. The log of a probability is called 'entropy.'

https://www.quora.com/Why-is-it-when-I-drop-a-vase-it-smashe...