Black holes were first theorized in the 1790's when Albert Einstein and Pierre La Place used Newton's laws to suggest the idea of an "invisible star."
If you ever get into a situation where you enter a black hole, then this is what would happen...
At first you wouldn't feel anything, due to a free fall. Gravity would then take over accelerating your speed, your body would then begin to stretch and pull you apart into noting.
There are three different types of black holes and they are called Stellar, Super massive and Primordial.
Super massive are the largest known to man, Stellar are the most common and Primordial were formed during the big bang, making them the oldest known black holes out there.
Some things to look for when detecting a black hole...
- Moving gases
- Dispersing objects