The valley created by a black hole gets steeper and steeper as you approach it from a distance. It’s also why light can’t escape a black hole: the sides of the valley are so steep that light isn’t going fast enough to climb out. That’s why, when you get close enough to any massive object, including a black hole, you fall towards it. When objects come near, they fall into the valley. The more massive an object is, the more space is stretched and bent around it.Ī massive object creates a kind of valley in space. Matter and energy bend and stretch space. Stretching spaceĪlbert Einstein’s general theory of relativity tells us matter and energy have a curious effect on the universe. Incidentally, that’s why black holes are black: we can’t bounce light off a black hole the way we might bounce a torch light off a tree in the dark. That’s impressive, since light is the fastest thing known to science! The gravitational field of a black hole is so strong that even light can’t escape it. That’s why we build rockets: we have to travel very fast to break out of Earth’s gravity. A gravitational field is what keeps us stuck to Earth, and what keeps Earth revolving around the Sun.Īs a rule of thumb, the more massive an object is, the stronger its gravitational field.Įarth’s gravitational field makes it extremely difficult to get to space. Like planets and stars, black holes have gravitational fields around them.

What are black holes?Ī black hole is an extremely massive object that is typically formed when a dying star collapses in on itself. But, even leaving that small detail aside, attempting to travel into the past using a black hole might be the last thing you ever do.

But don’t expect to be heading back to visit the dinosaurs any time soon.Īt present, we don’t have spacecraft that could get us anywhere near a black hole. Black holes form natural time machines that allow travel to both the past and the future.

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