Bloggy Bits

Musings on the State of Space and Time and Travel therein

Apr 27, 2011   [permalink]

This is cool. Thanks to C.S. Miller for posting this link on my wall: "Spacetime has No Time Dimension" --New Theory Claims that Time is Not the 4th Dimension.

So, if time t is basically a parameterization (if I'm grasping this right), that is, turning "time" into a separate variable not tied to any specific dimension, and space just has a sequence of states (an idea familiar to any computer scientist) in four dimensions, then the speed of time need not be a constant - the fact that sometimes "time flies" and seems to go faster or slower than others might be a real phenomenon. :)

In other words, think of a chess game. Each move of a piece puts the (two dimensional) board into a different state, and a game is a sequence of states of the board, but how long the players take between each move isn't necessarily the same -- the sun could move barely a smidge in the sky or days could go by. We measure time, for example, by counting the number of oscillations of a cesium atom -- 9192631770 of them and we call it a "second." But perhaps one could, in effect, take a nap between one oscillation and another.

If that's the case, then I wonder if the impossibility of "faster than light" travel might not take on a quite different meaning. State changes seem to happen in relationship to each other -- all cesium atoms seem to oscillate the same number of times as each other when we measure them, so they're tied together, as are changes in other particles. But perhaps some undiscovered property of the now-not-time 4th dimension, or some interesting property of dark matter or dark energy, might alter that -- perhaps cesium atoms far away from here don't oscillate in tandem with the ones around here, or perhaps there's a way to move what appear greater distances in our 3D space via the 4th D, or to slow down the relative rate of state changes. (I do wonder what interesting properties dark matter/energy might have.)

The other question then is whether the state changes that might put the universe back into the same configuration as a prior state would count as time travel. In other words, if on a chess board you move your rook one square to the left, your opponent moves their queen one square forward, you move your rook one square to the right, your opponent moves their queen one square backward, the board, after four moves, is in the same configuration ("state") as it was four moves prior. (That's just the simplest way to get the board back to the same state following the rules of the game, but one could imagine other ways -- including picking up all the pieces and just resetting them into a configuration they used to be, like setting up the pieces for a chess puzzle.)

Is that not a sort of time travel? Isn't what we envision as "time travel" really just the state of the (local) universe returning to the same state as it was before? From which one could make different moves. Putting all the particles in the (local) universe back how they were previously (except for one's own brain, so you have memories of the events, assuming memory is encoded as the states of particles in your brain) would be like the movie Groundhog Day: The pieces get set back up the same, again and again, except for the ones in Bill Murray's head (his memories). Sounds like it'd be hard -- a lot of pieces to set up -- but.......! :)

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