1st guy: The fundamental laws of physics are CPT invariant.
But we know that we need to handle the past differently than the future and
Bayesian inference proves this too.
2nd guy: But why is the future so different from the past?
Well, I can explain that if I assume initial conditions with low entropy.
But why would the initial state have low entropy?
Wait, I can explain that with some cosmological mumbo-jumbo.
1st guy: This just shows how stupid that 2nd guy is. We know that entropy always increases. This is a fact.
Therefore it follows that the entropy was lower at the beginning of the universe and all that mumbo-jumbo is not needed and just crazy.
3rd guy: Hey 1st guy - have you never heard of Loschmidt?
1st guy: Loschmidt's paradox only arises once someone adds the assumption that reconstructions of the entropy in the past are made by the same methods as predictions for the future.
3rd guy: I happen to have Mr. Loschmidt here, let's ask him about that ...
This is the nice and clean version of that dispute. Reality was of course a bit more ugly ... and I made up the ending.
3 comments:
If you assume time reversal invariance at the micro scale, my paradox always applies
-- Jo Jo L
Physics Stack Exchangeon Loschmidt
CIP,
yes I pointed to this answer, because (despite some poor wording) it says it best: L's paradox is not just the statement that an irreversible behavior cannot be derived from reversible fundamental laws.
It is the statement that the H-theorem fails in half of the (a priori) possible cases.
And it seemd clear to me that in this debate some people were not aware of that ...
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