As a (former?) cosmologist, these closed loops aren’t a new concept as far as I recall (I’m pretty sure Matt Visser’s book Lorentzian Wormholes has a suggested solution in it). In fact I think there was some talk about this in relation to variable-speed-of-light (VSL) theories.
Time travel, of course, is intimately linked to the question of reversibility. Generally one of the arguments against time travel is the fact that macroscopic processes are fundamentally irreversible (due primarily to the ensemble behavior of probabilities). Hence time flows in one direction. But many quantum processes are reversible (that’s part of the “weirdness”).
The loop question adds the possibility that the universe is a closed loop and so the direction of time doesn’t matter. My problem is the fact that results from WMAP imply that the universe is Euclidean (or ‘flat’ in cosmologist parlance). To me that suggests that, if it is a closed loop, it’s a pretty big loop since it looks Euclidean from our 13.7 billion year perspective.
In addition, the results indicating the accelerating nature of the expansion seems as if it might pose a problem for this as well.
In short, I wouldn’t count on chatting with Newton any time soon.
As a (former?) cosmologist, these closed loops aren’t a new concept as far as I recall (I’m pretty sure Matt Visser’s book Lorentzian Wormholes has a suggested solution in it). In fact I think there was some talk about this in relation to variable-speed-of-light (VSL) theories.
Time travel, of course, is intimately linked to the question of reversibility. Generally one of the arguments against time travel is the fact that macroscopic processes are fundamentally irreversible (due primarily to the ensemble behavior of probabilities). Hence time flows in one direction. But many quantum processes are reversible (that’s part of the “weirdness”).
The loop question adds the possibility that the universe is a closed loop and so the direction of time doesn’t matter. My problem is the fact that results from WMAP imply that the universe is Euclidean (or ‘flat’ in cosmologist parlance). To me that suggests that, if it is a closed loop, it’s a pretty big loop since it looks Euclidean from our 13.7 billion year perspective.
In addition, the results indicating the accelerating nature of the expansion seems as if it might pose a problem for this as well.
In short, I wouldn’t count on chatting with Newton any time soon.