but fruit flies like a banana
The arrow of time has been understood for 100 years says Lumo, except, apparently, in the Caltech Cosmology department. Forgetting that for a moment, is it understood by Motl?
I find him a bit hard to understand when he's in his rage against the heathens polemical mode, but he and I have been in this rodeo before, so I'm just going to say that he seems to utterly miss the point in his critique of Sean Carroll and colleagues. The problem Sean addresses, and the Lubos tries to sweep under the rug, is that of how a direction of time emerges from time symmetric laws of microphysics.
Boltzmann was perhaps the first to struggle with this, and his answer was the so-called H theorem. Loschmidt pointed out that his proof in fact assumed something equivalent to what he was trying to prove. Lubos discusses a more recent attempt by Weinberg to prove a quantum field theoretic version of the H theorem. I couldn't really follow hi…