Alongside black holes and white holes, wormholes have held a position of wonder in real physics as well as science fiction.
A wormhole is a theoretical cosmic object that connects two different points in space and time. As per Einstein, wormholes could theoretically connect two different universes.
American physicist John Archibald Wheeler coined the term “wormhole” in 1957 in a paper co-authored by Charles Misner. Wormhole theory technically existed before then without the actual word being used. Hermann Weyl spoke of “one dimensional tubes” in 1928 when discussing what we now know as wormhole theory of matter.
General relativity does allow for wormholes although I have used the word theoretically as there is no observational evidence for them as of yet. Wormholes only exist in mathematical probability.
The best way a wormhole can be described is a 2D flat surface with a hole in it. Beyond the entrance of the hole sits a 3D cylindrical tube with another opening at the other end identical to the entrance.
The main difference between a wormhole and a black hole is that space and time change roles beyond the black hole’s event horizon, that is the area beyond which not even light can escape from its gravitational grasp.
Another way to think of a wormhole is drawing two circles on opposite ends of a piece of paper. The space and time between the holes represents the actual plane of the universe in its flat sense. Should the piece of paper be folded in half so the two points of the wormhole are touching, it demonstrates the entry and exit of the wormhole.
It’s absolutely impossible to squeeze everything on wormholes into a single post although different aspects and regions of spacetime they affect will come on later in the series.