system
Given the following post, respond as if you're commenting on Reddit:
human
If you could remove a golf ball sized portion from a black hole mass would it retain its mass or evaporate?

This is something I have been wondering recently... is there a minimum or maximum mass limit that is required for a black hole to form or to stay formed?
gpt
You seem to think a black hole is a blob of stuff. It's not.

In its own reference system, all the stuff in a black hole collapses *all the way in*; it becomes a mathematical point, zero-dimensional - the singularity. You cannot remove "a golf ball sized portion" of something that measures exactly ZERO meters across.

Or, if you think the black hole volume is the volume inside the event horizon, wrong again. Inside the event horizon there's just empty space, it's not a line drawn in sand. A spaceship could orbit inside the event horizon of a giant black hole, no problem. It just can't get out.

Now, from a reference system infinitely far away, the black hole does not appear to collapse, it appears to be frozen for eternity at the moment the event horizon was created. But you can't remove "golf ball size portions" from infinitely far away - once you get close enough, you enter the other reference system where the black hole is a true singularity.

However, if you do manage somehow to remove energy from the black hole, it becomes less massive and the event horizon shrinks. This happens all the time with the Hawking radiation that black holes naturally emit. But it's radiation, not golf ball sized chunks. The more energy you remove, the more it shrinks, but the Hawking radiation also becomes more intense.

Once the BH is small enough, the outbound radiation *really* picks up and the microscopic black hole becomes a very bright object, radiating mostly hard photons and other nasty stuff, becoming even smaller, radiating even faster. It's a vicious cycle which ends up in the black hole releasing all its final energy in a giant bang - something like a Star Wars sized nuclear weapon. You don't want to be anywhere near when it evaporates completely.

There are proposals to create interstellar drives using black holes, kept just small enough to radiate a lot, but not too small as to blow up. You could feed them any crap the starship finds in its way. It would convert all mass into energy - 100% efficiency. Just like an antimatter drive but without the inconvenience of having to manufacture lots of antimatter. You do have to make or capture a small black hole, thou'.