Wormholes are a sci-fi trope that everybody has heard of, a swirly (often blue-colored) tube that lets the protagonist jump between large distances or to other worlds. Of course, wormholes of this type are pure fiction and do not exist in our universe, but that does not mean that the phenomenon itself is not real.
Holes in 4-dimensional space-time
Wormholes are quite simply put holes in the 4-dimensional fabric of space-time that allows objects to cross between two points in no time at all. You could compare this to an ant walking on a sheet of paper. To get to the bottom it would have to walk towards the edge and then back, but If we punch a hole through the paper then it can move to the other side at much faster speeds.
Now, while this may sound very similar to the movie versions of wormholes, there are some important caveats that distinguish the two, most of which are based on Einstein’s theory of relativity, which predicts the existence of these phenomena.
Could wormholes really exist in the Universe?
First off, they would be incredibly rare as gravity would force them to collapse mere fractions of a second after they open. An effect that can only be counteracted by means of negative energy, which counteracts gravity and allows the tube to stay open. The depiction of wormholes is perhaps best done by the new Dune movie, where one of the large ships shows a different planet through an opening in its center. Things that move close to it get swallowed and spat out on the other side, where they continue their travel like nothing happened.
Of course in order to travel through the object has to be smaller than the wormhole, which is the next big difference between the movie and reality-based phenomenon. In our world wormholes might in fact be all around us, opening and closing constantly but never growing beyond the size of a few atoms. Larger and more stable wormholes might exist as remnants from the Big Bang, where tiny amounts of negative energy fell into such wormholes and stabilized them. Then as the universe expanded, the wormholes moved apart with it.
The last big difference between real and fake wormholes is that it is not possible to direct them, or at least not possible for us. Many shows use the balloon analogy to describe wormholes, saying that we live on its surface and that we can jump through the center. The biggest caveat here is that our universe is four-dimensional, so we can’t know the way in which the wormhole points!
All in all, these phenomena are more fiction than fact at this point, but so were black holes for the first 50 years of their existence are suggested. So it is very possible that one day, perhaps in the near future, someone finds evidence of their existence.