I don't know about anyone else but I'm pretty fascinating by black holes! I think that black holes are very interesting. They can be extremely large. For years I thought nothing compared in size to the star UY Scuti, which has a radius 1700 times larger than the sun. When I learned about the TON 618 black hole, I couldn't believe how much larger it was than UY Scuti. It feels like comparing the size of an atom to the size of a country.https://www.youtube.com/watch?v=FBchtofZJSM
But their potential size is definitely not the only thing interesting about black holes. As long something has mass, any thing and any person can become a black hole, just as long as it's condensed into a small enough size so ridiculously dense, that even light cannot escape its gravitational pull. This is almost unfathomable to really think about, but to give an example, the earth would have to be condensed down to the size of a penny in order to form a black hole.
Another thing that's pretty interesting to imagine is what would happen if a black hole were to suddenly form on our planet. Black holes basically swallow everything that has mass, just as long as they're close enough to it. So let's say Teddiursa figured out a way to condense a human into a space just 1 sextillionth times smaller than a grain of sand. This person would become so unbelievably dense that they would die, but their dead body would become a black hole.
If this were to happen, the black hole would basically eat away at everything in sight, swallowing the earth from the inside, but leaving the rest of it a scattered disc of hot rock. (At least this is what I believe the outcome would be based on a video I watched and one article I read).
But I'm no expert and I have a question for anyone who may know more than me about black holes. If a black hole can't feed off of anything, it simply evaporates, but it releases enough energy to destroy basically everything in sight (Energy it releases would be equal to many million or billion+ megatons of TNT, which depending on the size could be an unfathomable number of times more powerful than any nuclear weapon we ever detonated).
However, if a black hole does have matter to feed upon, it continues to grow while it swallows mass. Are these two different outcomes the result of different size black holes? Both outcomes would destroy the entire world (maybe unless the black hole is extremely small), but one vanishes and the other continues to grow. My assumption is that if a black hole is too small it won't be able to swallow mass easily. Would the black hole just evaporate if it's really really small, while the bigger one would grow and live on?