The idea of time travel exists in human imagination for centuries. HG Wells and `Time Machine’ is popular science fiction reading. Travel to the future or the past is also riddled with puzzles and paradoxes. Can you travel to the past and change your present? The human stories one could build using these are quite mind boggling. There are various solutions to those paradoxes, and very convenient interpretations. But as said correctly, if there is no law against the travel, then it will happen. A very interesting take by Sean Carroll on time travel using a worm hole exists posted on you tube.
However what is interesting is that in quantum gravity, the question we are trying to answer is `whether time exists at all?’. Time is really a nuisance parameter in formulations of quantum gravity, and searching for it and making a meaningful connections to our familiar ever flowing time takes most of `our time’. If you ask me I would rather take the `ever sheltering’ blue sky as my convenient time, or maybe the tree next door as the new time. The cosmic time we take for granted, ever flowing, unidirectional, if Einstein’s theory is correct began at the big bang and will end at the big crunch. Even though it is infinite for our purposes, it has a beginning and an end. Maybe it is not different from the tree next door, so why not make the tree the clock if it makes the computations more easier. Tree Time travel will therefore also be much easier?
For the curious I am finally trying to find time to read the most recent original ideas on time by Julian Barbour. When I talked to him recently at a conference in Madrid he told me that his originality was facilitated by the fact that he worked as a translator of scientific papers, and never had to conform to a regular scientists’ job!
nonperturbativegravity 