system
Given the following post, respond as if you're commenting on Reddit:
human
Why does the wormhole theory exist at all?

When two of my friends were talking about wormholes and i told them there is no evidence at all for wormholes they started talking about how multiple scientists claim they do exist. We all proceeded to look it up and I was correct however I do not understand  where the theory even came from. Is the theory that  black holes are wormholes and if so how would something that simply has an unimaginable mass in a small space  make you transport to a different place in space. Also what made scientists think about such a theory was some anomaly in space observed that suggested the existence of them? Thank you for ur help! :)
gpt
Principally, the reason is this:

wormholes are allowed by a very naive presentation of our theory of gravitation, general relativity (GR). As solutions for GR, they have been thoroughly studied and have been found to result in bizzarre consequences, such as time travel.

It is now understood that these weird effects should not (and do not) happen and this class of exotic solutions (wormholes & co.) should be excluded in some way. During the study of this type of solutions however it was also found that to *produce* then you always need some initial conditions that are "pathological" or at least unrealistic. In particular it was determined that pathological solutions are generated only when you violate sets of conditions known in general as positivity conditions.

We understand positivity conditions are satisfied in our Universe and GR should be supplemented with them, so that pathologies (including wormholes) do not happen. It can also be verified independently that positivity probably cannot be violated. Therefore while everyone understands wormholes or time travel are impossible, it is interesting and relevant to GR to study why and how they are impossible.

Also, these pathological features might become possible/important in the quantum gravity regime, this is not to be excluded. But that's for another time.