: what’s a closed timelike curve ?

Question

: what’s a closed timelike curve ?

In: Physics

Answer 1

It’s a path through spacetime which crosses back upon itself. These aren’t typically possible, but with a wormhole or other special topology it can be possible to conceptually construct a closed 4D curve which a photon could follow and cross back upon itself.

Constructing on in real life could enable certain time machine constructs, which we don’t see in reality.