Wednesday, January 15, 2014

Keeping time, time, time

Over at Maggie's Farm there's a link to an article on current thinking on the nature of time in physics.

The headliners are too eager to say "time is an illusion" or "time does not exist."

It is more accurate to say that there are descriptions (so far unverified, esp. models that involve string theory) that are independent of time. Claims that time can be an "emergent" quantity are not yet supported by examples. The "holographic dual" model (Maldacena's; read the article) maps processes on the boundary to events inside the volume in an interesting analog to classical EandM, but it remains to be verified, and that a model of it links quantum entanglement on the boundary to space-time structure within doesn't mean the model means anything.

Feynman famously wrote the equation that described all physics: "U=0". Of course the details of what goes into "U" are a bit more complicated, and not all of them are known. That's my take-away from the article: there are very interesting symmetries under study (physicists love symmetries), and as usual some are time-independent. Time as we know it is a perfectly fine coordinate when describing human life, but things get pretty weird at tiny time scales or huge energy densities at which "time" is harder to understand. (e.g. orbit a rotating black hole)

The thing about duals is that both representations are good, they just emphasize different aspects of the situation. Sort of like old familiar coordinate transformations--polar coordinates make studying rotations easier, but the old x/y/z description works too.

So no, time is not an illusion. But read the article anyway.

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