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Black-Hole Weirdness

June 16, 2020

Black holes are just plain weird.

If you were to fall into a black hole a few times the mass of the Sun, for example, your body would be stretched, squeezed, and pulled apart atom by atom. So it seems logical that if you fell into an especially heavy black hole — one that’s billions of times the Sun’s mass — the effects would be even more dire. But that’s not the case. Instead, you could cross into the black hole and never even know it. As long as you stayed away from the center of the black hole, you’d get along just fine.

That’s because a black hole gets less dense as it gets heavier. A black hole that’s twice as massive as the Sun would contain eight times the volume of a black hole equal to the Sun’s mass. That makes the heavier black hole just one-quarter as dense.

And as the mass reaches jumbo numbers, the density drops dramatically. A black hole a hundred million times the Sun’s mass would be less dense than water. And at ten billion times the Sun’s mass, it would be less dense than air.

And as the black hole’s volume increases, its surface gravity goes down. So the tidal gravity of a super-jumbo black hole would be less than that of Earth.

Keep in mind, though, that a black hole is still a black hole. Anything that crosses its event horizon — the boundary between the black hole and the rest of the universe — could never come back out. It would be trapped forever — inside a black hole.

More about black holes tomorrow.

Script by Damond Benningfield

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