time travel might not be possible, or we should have at least seen

送交者: silxirt 于 2013-01-04, 22:53:54:

回答: in my view, if there is time travel, 由 pgss 于 2013-01-04, 21:19:12:

time travelers.

All those attempts are to explain how to prevent violation of the basic laws IF time travel is possible.