Dear night workers and people with vision!
A black hole is a cosmic object whose gravity is so great that not even light can escape from it. It is therefore completely black and attracts everything around it.
Only if a rocket is accelerated to sufficiently high speeds can it leave the earth, otherwise it will fall back to it. It is similar with light in a black hole: despite its speed of 300,000 km/s, it cannot overcome the gravity of the black hole.
By definition, we cannot see black holes directly, but they reveal their existence through the enormous gravitational forces in their surroundings. So we know with almost certainty that there is a black hole at the center of our Milky Way that is 4.3 million times the mass of the Sun. “Almost certainly” means that any explanation that avoids the existence of a black hole would require physics even more exotic than the black hole assumption.
In the context of Einstein's general theory of relativity, black holes are "infinities" in the space-time structure, and in principle they offer the possibility of connecting different areas (temporal and spatial) of the universe via a tunnel - so-called wormholes, through which time travel is then possible would be. Unfortunately - or thank God (?) - this is only a theoretical possibility, especially since such wormholes are unstable and would first have to be stabilized using exotic matter. So while black holes are very real objects in the cosmos, time travel is more something for science fiction.
Prof. Matthias Steinmetz
Scientific director of the Leibniz Institute for Astrophysics Potsdam (AIP) and professor of astrophysics at the University of Potsdam. His research interests include cosmology, the formation of galaxies and the structure of our Milky Way.
