Time travel? Alternate universes? Hebrew U. professor explains black holes

The Jerusalem Post spoke to Hebrew University Prof. Prof. Tsvi Piran to better understand black holes.

A simulated image of a black hole. (photo credit: Wikimedia Commons)
A simulated image of a black hole.
(photo credit: Wikimedia Commons)
Black holes have long fascinated Hollywood – from Superman to Star Wars.
On Tuesday, three scientists won the 2020 Nobel Prize for Physics for their discoveries about black holes. But what is a black hole?
The Jerusalem Post spoke to Hebrew University of Jerusalem Prof. Tsvi Piran to better understand. Answers have been edited for clarity and conciseness.
What is a black hole?
It’s a region in space that acts like a trap. You can get in, but nothing can get out – even light, which is why it is called a black hole. We cannot see inside. We cannot see it directly.
So how do we know they exist?
The only way we know the black hole exists is because it has enormous gravitational pull and this enormous gravitational pull influences matter around it.
Why are Black Holes important?
First of all, the concept that such a thing exists – something that nothing can get out of – is a unique phenomenon. Now we seem used to it. But 20 or 30 years ago, most scientists did not believe that such an object existed. This was a new object that was predicted theoretically by Roger Penrose and others and later was discovered by observation. The discovery was very hard, because you cannot see it directly, but only indirectly.
Also, while we don’t fully understand them, certain features that are inside black holes probably hold the key to some very exciting developments in physics.
Like what? What could we learn from black holes?
One of the biggest open questions, and this was raised by Roger Penrose, who won the Nobel Prize, is what is at the center of a black hole? Penrose’s work shows that in our current understanding of physics, we cannot tell what the fate is of someone or something who falls into a black hole. We don’t know what happens – but we think we can find out.
Today, in physics, one of the biggest problems is the merging between two great pillars of physics: one is Einstein’s Theory of Relativity and second one is Quantum Theory, which are sort of inconsistent with each other. The big hope is that through understanding what happens at the center of black holes – and understanding black holes in general – we will be able to merge these two theories.
That is why black holes are exciting and interesting to physicists.
Why are they so excited for Hollywood?
There are speculations – and they are probably wrong – that if you fall into a black hole then you fall from the black hole to other universes or into another part of the universe. These speculations are interesting and exciting. Such speculations are also related to the idea that black holes hold within them the secrets of building time machines – like in the movie Interstellar.
But black holes are in outer space - has anyone ever fallen in one?
We never got even close to a black hole. We know they are there, but to get to them you have to leave Earth and travel quite far. So, no, no one has ever fallen into a black hole, but we have observed matter that is falling into them.
What’s next?
Who knows? We might discover that it is a good idea to jump into a black hole because it may provide you a way to travel back in time. So, that’s the next big thing – figuring that out. I am not sure it will happen soon, but it is the ultimate goal.