Time travel and the universe.

[Christopher]

I've read that concept before. The Temporal Protection Conjecture implies that any such wormhole would destabilize and collapse as soon as the two ends got close enough together that it would be possible to traverse it, then return to the first end and actually be at an earlier time.

Yeah, because of the divergent stress-energy tensor, basically a feedback loop that overloads the spacetime metric with runaway energy and collapses it. But I'm just using it as a hypothetical example to illustrate the question.