In 1975, Stephen Hawking lost his bet against the physicist Kip Thorne, denying him that Cygnus-1, an X-ray source, was a black hole. The payment was a one-year subscription to the erotic magazine Penthouse. Now, in just three minutes, he explains what a black hole is in the video that tops this post.
Remember that you can create subtitles for the video, but in any case here you can read the translation:
The wormhole is a solution to Einstein's equations, but a solution that most likely does not exist in nature. It is a tunnel to hyperspace that connects one part of the universe with another. The walls inside the tunnel attract each other and, if you tried to travel through it, you would die crushed.
Physicists work hard trying to figure out what needs to be done to travel through a wormhole without it collapsing. The conclusion is that you have to have something inside that repels the gravitational force of the walls, to prevent them from collapsing.
To achieve this, what was inside the wormhole must have negative energy. First you have to get rid of all the energy present in the tunnel until there is nothing left, except the vacuum. And then you have to keep drawing energy, as if it were a debt to the bank.
These regions of space have an energy debt with the rest of the universe. However, it seems that there are physical laws that prevent you from borrowing a lot of energy when there is no more energy in the bank. The rest of the universe does not let you take out more.
All the calculations and physical laws we have done strongly suggest that it is not possible to draw enough negative energy from the wormhole to prevent it from imploding. Despite this, physicists do not have consistent evidence that this is always the case.
Why can't we show that wormholes always collapse? Well, maybe because they don't always do it. We do not know.