For a trip that’s out of this universe, just cross the event horizon of a black hole. Nothing that passes through an event horizon can ever come back out, so we don’t really know what goes on inside a black hole. But we can be pretty sure that it’s like nothing else in the universe.

A black hole’s mass is concentrated in a single point, called a singularity. Its gravity is infinitely strong. But as the distance from the singularity increases, its grip weakens. Eventually, it reaches a point where the escape velocity equals the speed of light – the event horizon. Since nothing can travel faster than light, anything that falls through the horizon is trapped. It may be doomed to merge with the singularity.

So the event horizon acts like the “surface” of a black hole. But it’s not solid – there’s nothing to ram into. Instead, it’s more of a boundary between the black hole and anything outside it.

The distance between the singularity and the event horizon marks the size of the black hole. And as more stuff falls in, the black hole gets bigger. A black hole that’s 10 times the mass of the Sun spans about 35 miles. The supermassive black hole at the heart of the Milky Way spans 13 million miles. And the heaviest black holes yet seen are more than 40 times the size of the orbit of Neptune, the Sun’s outermost major planet – a wide entrance to an out-of-this-universe experience.

More about black holes tomorrow.

Script by Damond Benningfield