Question: what are black holes and what are they made of?

Alexander Burke answered on 8 Mar 2018:

A black hole is an area in space time (somewhere in the universe) where nothing, not even light, can escape the immense gravity of the black hole. Theory suggests (called the no hair theorem) that black holes only have two properties; how heavy and how fast they can spin. Black holes also have a thing called an “event horizon”. This event horizon is almost like a “one-way door” where you can pass through it and can never return. Lastly, black holes are incredibly heavy – a black hole the size of a golf ball would weigh the same as earth. Now, the first question was easy to answer… the second question is, a quite simply (in my opinion), the hardest question (so far!) to answer. In short: no one knows what a black hole is made out of. In saying this, I’m going to give you my best guess on what they’re made of. Black holes are NOT made up of anything physical. Black holes are not made out of stone, or planets or of star stuff. Black holes are made up of “Vacuum space and time”… this being, they are not so much a physical being but more an extreme warping at a place in our universe. I would be curious what the other engineers views are on this because this is an extremely difficult question to answer… for that you get a point. Good work (Y). A