Black holes aren't the cosmic vacuum cleaners they are rumored to be, but could you still fall into one? What would happen to you? The answer to that question depends on whom you ask (thanks to quantum gravity).
Time Slows So Much That You Never Reach the Black Hole
As you approach a black hole, you do not notice a change in time as you experience it, but from an outsider’s perspective, time appears to slow down and eventually crawl to a stop for you. General relativity explains that an object in the presence of a strong gravitational field will pass time more slowly, a process known as time dilation, and an effect that increases the closer you get to the black hole. If you’ve seen the movie Interstellar, you probably remember the scene where two brave explorers spend only a matter of minutes on the surface of a planet near the black hole while the astronaut who stays on the ship experiences 40 years passing.
You would notice the effect indirectly, however, because you would see everything that ever fell into the black hole before you also slowly approaching the point of no return (called the “event horizon”) below you but never quite making it there.
So who is right? This discrepancy, and whose reality is ultimately correct, is a highly contested area of current physics research.
The trouble lies in reconciling quantum mechanics, which describes our universe on the very small spatial scales like those of atoms, with general relativity, which describes our universe in the presence of massive objects. While both of these theories work well on their own, a unifying explanation that combines the two, often called quantum gravity, remains elusive. Black holes provide a rare environment where these two regimes meet: an incredible amount of mass packed into a very, very small space.
One thing we would both agree on, however, is that you’d never make it back out again to tell your story. Just as time marches only forward for us while space is static, the opposite would become your reality. Time would stand still, but you would be unable to get off the train bringing you further and further towards the massive black beast.
Until next time, this is Dr. Sabrina Stierwalt with Everyday Einstein’s Quick and Dirty Tips for helping you make sense of science. You can become a fan of Everyday Einstein on Facebook or follow me on Twitter, where I’m @QDTeinstein. If you have a question that you’d like to see on a future episode, send me an email at firstname.lastname@example.org.