What's the Time?

What's the time?
It's got to be close to midnight.
My body's talking to me.
Says it's time for danger.
...........Mimi, in Rent

Time is one of the most difficult issues in physics. We all know that the past is pretty different from the future, and that the film run backward can usually be told from that running forward. Glasses fall off the table and break, but nobody has ever seen scattered bits of glass spontaneously assemble on the floor and then leap up to the table. The problem is that all the laws of physics that we know seem to be time symmetric. So how do we get time assymmetry from purely symmetric laws?

Sean Carroll blogs about a seminar he and co-authors gave at UC Santa Cruz: Why is the Past Different from the Future? The Origin of the Universe and the Arrow of Time. The discussion following the post brings in little guns and big, with the most illuminating points being made by Sean and John Baez.

There is no future
there is no past.
Got to make the moment last.
............Mimi again

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