The simple explanation is that if one could enter and then exit a black hole, one could be connected to some other location in space-time in the universe (or even a parallel universe). That could mean travelling backwards in time. Two big problems.
First all the work done (all theoretical of course) shows that one cannot get through a black hole intact.
Second, there is a fundamental problem of causality. This has been the central plot element of several very popular movies. Back to the Future and Terminator series both play on the problem of causality. In BTTF, Marty's entry into the past almost causes his mother and father not to marry and him not to be born (remember that the picture of his family that he is carrying starts to disappear.) Of course, his entry into the past has a major effect on the present, when he returns. Similar issues with the Terminator movies. How can a person from the future affect the past, so the future changes and the person in the future no longer exists to change the past?
There has been serious experimental work done testing whether particles called tachyons exist (some observations hinted that the products of the collision of some subatomic particles may have been observed before the collision itself was observed.) However, there was nothing that came out of the experiments.
I don't think anyone ever came back from entering a black hole?
And if you can enter one and not exit it nobody knows what's in it?
Our imagination is @ its best.
Is it possible to go inside a black hole and survive?
by Gemma Lavender, 16 December 2014
Can you venture into a black hole and live to tell the tale?
"Most likely not. Black holes, whether they have the mass of one star or a million stars, have a very strong gravitational pull that increases enormously the closer you get to them.
This pull would create powerful tidal forces that would stretch you until they pulled you apart in a messy process called spaghettification. However, the more massive the black hole, the weaker its gravity – so for the biggest black holes in the universe the tidal forces might not be so great as to rip you apart. That is, at least not until you reach the singularity at the heart of one of these objects.
However, time will appear to slow down for you as seen from observers on the outside and once you are past the event horizon – the point of no return – there is no way that anything, not even light, can escape the black hole."
P.S. "Spaghettification" is the scientific (astrophysics) term; I didn't know that.
Theoretically, particle physicists could link different corners of the Universe.
"Teleportation and travelling forwards through time may be possible through wormholes, the bipolar black holes that link different regions of the universe. This is the conclusion drawn from a model created by Kyriakos Papadodimas of CERN and Rik van Breukelen of the University of Geneva. Instantaneous travel and travel into the future would become possible by travelling through a wormhole, and this completely free of the time dilation predicted by Einstein’s theory of relativity. It is, however, “a purely theoretical model that would only apply to an elementary particle, such as a photon”, adds van Breukelen.
With their model, the physicists have developed a new category of worm hole and describe – in theoretical terms – how information stored on a particle (e.g., using its electrical charge) could travel instantaneously to another part of space-time. “Wormholes are today still only theories”, says van Breukelen. “But, in principal, it would be possible to create an artificial black hole, by using a particle accelerator, for example, although it would have to be a billion kilometres long, the same distance the Earth travels around the sun in a year. So it’s an idea that’s theoretically possible, but also many millennia ahead of its time”.
Investigation into the phenomenon is advancing on two separate tracks: the Anti-de Sitter space (AdSn), based on a quantum theory of gravitation, and the conformal field theory (CFT), a model of elementary particles that treats them as excitations of the fields of fundamental forces.
This work remains abstract in nature. There’s still a long way to go before computers can simulate the behaviour of particles travelling through a worm hole. “That will require quantum computers, which may not see the light of day for another 15 years. Even then, we’re still talking simulations, but it beats waiting 2,000 years”, says van Breukelen."