>>11968719A: the past.
the past always has greater energy than the present, or future, because entropy.
therefore, on a long enough timeline (and if time travel is real, you have virtually infinite time for a civilization to advance)
Eventually, your civilization reaches the heat death of the universe, and so travels back in time to the beginning on the universe, when it is still young.
And now repeat that a few trillion, or quadrillion times (because with time travel, you can do this, and if you can, that means it has already happened an uncountable amount of times)
Eventually, you siphon ALL of the energy FROM the big bang, to power your civilization.
and by "Eventually", I of course mean "Instantaneously" because that's how time travel works.
So, if time travel was possible, the universe would cease to exist at the literal moment of it's beginning.
Q.E.D. time travel doesn't exist, because the universe exists.
