• Question: Why if you are just outside of the horison of a black hole you are not pulled in but if you are just on the inside of a black-hole you are dommed to be sucked in, moreover how does time move from the horison to the center of the black hole?

    Asked by jabbathepizzahut to Ben, Ezzy, Mario, Sam on 21 Mar 2012.
    • Photo: Ben Smart

      Ben Smart answered on 21 Mar 2012:

      If you’re just outside the event-horizon of a black hole then you’ll still be pulled in towards the black hole, but you still have a chance of escape. Once you cross the event-horizon then you have no chance of escape, because the forces of gravity are just too strong. So strong in fact that not even light can escape (which is why the hole is called a black hole – no light comes out of it).

      As you get closer and closer to a black hole the force of gravity you experience gets stronger and stronger. The event-horizon of a black hole is the point where gravity becomes so strong that nothing, not even light, can escape.

      As for time, that gets more complicated 🙂 Time slows down for objects in gravitational fields. The stronger the gravitational field, the slower time passes for that object. As you moved closer and closer to the centre of the black hole, you wouldn’t be aware of time slowing down, you would continue to experience time passing at a normal rate. However you would be experiencing less time than if you had stayed away from the black hole. For example, say you have an identical twin the same age as you. You both start off far away from the black hole, and you twin stays there, but you move towards the event horizon and then go back to your twin. Your twin will now be much older than you, because time has passes slower for you (because you were closer to the black hole) than your twin.

      Inside a black hole you would still experience time passing at a normal rate, and so would only experience a fraction of a second of time before you reached the singularity in the centre of the black hole.

    • Photo: Elizabeth Pearson

      Elizabeth Pearson answered on 21 Mar 2012:

      The event horizon of a black hole is the point beyond with nothing, not even light, can escape as the pull of gravity is too strong. It just sinks straight in. If you are beyond this horizon though gravity still acts on you. You’re still being sucked in. But you can get away. The closer you are though, the more difficult to get away.

      From what we know of black holes it does affect time the closer you get. The stronger gravity is the slower time passes. If you were close to a black hole (in some special suit that meant you weren’t torn limb from limb) you’d feel like time was passing normally. If you came back even though you thought you’d been gone for 5 mins you’d find out that you’d been gone for 5 years!

      Inside a black hole though no one really know what happens. Due to time slowing down from the outside something falling into a black hole would look like it was taking an infinitly long time to reach the centre but for the thing inside the black hole time would be passing normally!

      Black holes are facinating, but they did always break my brain a little.