science Q

A black hole has a boundary, known as the event horizon. This is the point where the escape velocity is more than the speed of light. The gravity is just strong enough to prevent even light from escaping. Because nothing can travel faster than light, everything else will get dragged back also.

We cannot see what is inside the event horiz on of a black hole because light from there can never reach us. Even if we could (manage to) send a robotic probe into the black hole, it could never communicate back to us. From the outside, you can't tell what is inside a black hole apart from its mass and the rotation.

We basically understand what happens outside the black hole as you approach its event horizon, that infamous point of no return. The event horizon is where the escape speed exceeds the speed of light: you’d have to be going faster than light (which is impossible for any bit of matter) to escape the black hole’s gravity.

Astronomers face an embarrassing conundrum:

They don’t know what 95% of the universe is made of. Atoms, which form everything we see around us, only account for a measly 5%. Over the past 80 years it has become clear that the substantial remainder is comprised of two shadowy entities – dark matter and dark energy.

The former, first discovered in 1933, acts as an invisible glue, binding galaxies and galaxy clusters together. Unveiled in 1998, the latter is pushing the universe’s expansion to ever greater speeds. Astronomers are closing in on the true identities of these unseen interlopers.