Question: will a black hole ever come to earth?

Michael Schubert answered on 29 Nov 2023:

Black holes don’t really move about very much (more on this later), so it’s not likely that one would come to Earth. The nearest black hole we know about to Earth right now is 1,560 lightyears away, which is nearly nine quadrillion miles – much farther away than you ever have to worry about! (Black hole event horizons are usually very small, so they can’t “eat” anything that doesn’t get extremely close to them.) Even if our own sun became a black hole, it wouldn’t swallow the Earth; our planet would just keep orbiting around it the same way it does right now.

Although black holes don’t move around, the universe is constantly changing shape, and so things move about in it relative to one another. Think about drawing two dots on a piece of paper and then moving the paper about (and maybe even bending it). The two dots don’t move, but you can make them get closer to and farther away from each other. It’s possible that, one day, this constant change will bring a black hole close to Earth, but the chances of that are so low it’s hard to even calculate – and, although it could happen millions of years from now, it certainly isn’t likely to happen in our lifetimes!