Normally people think of gravity as pulling on objects. You can instead think of it as pulling on the space those objects are in.

A black hole happens when there is enough gravity that space gets pulled inwards somewhere, at at least the speed of light.

Gravity falls off with distance, and the distance where space is being pulled inwards at exactly the speed of light is called the "event horizon".

It has this name because speed of light is the speed of causality: events that happen further in, are "over the horizon" for you, they cannot causally influence you.

▲

0x20cowboy 7 hours ago | parent [-]

> Normally people think of gravity as pulling on objects. You can instead think of it as pulling on the space those objects are in.

(Very uneducated person here) I’ve always wondered if large objects caused gravity, or if maybe large objects form in the places where there is a lot of gravity. This is probably elementary, but I’ve never looked in to it. Maybe today is the day!

	▲	lopsotronic 5 hours ago \| parent \| next [-]
		If you want to take a very large-scale - if poetic - view of things, you could also (very arguably) say something like "Mass is Fate". Mass represents a zone where probabilities want to be. The more that aggregate, the more they make other things want to glom on. With a high enough density, nothing that's nearby can glom to literally anywhere else, and there's your black hole. The Great Inevitable. In this space, there are no other possibilities. Very Demiurge-y.
	▲	ben_w 7 hours ago \| parent \| prev \| next [-]
		Dark matter is mysterious enough to be compatible with both at the same time, I think. (Is a collisionless gas really even an "object"?)
	▲	rcxdude 3 hours ago \| parent \| prev [-]
		I mean, it's kind of both: objects have gravity, which attract them together, which creates more gravity and larger objects. Stars are what happens when the rest of physics disagrees with this (and black holes are when gravity wins anyway).