LogFAQs > #972939659

I read an interesting article the other day about the Schwarzchild radius, which allows us to calculate where the Event Horizon would be for any object in the universe, and by extension lets us calculate just how small anything would have to collapse to in order to form a black hole.

For Earth, if the entire mass of the planet were to collapse to less than about 8 millimeters radius, Earth would become a black hole. For the Sun I think it's about 1400 meters.

So taking that one step further, we know that there are black holes whose radius is millions of miles across, which suggests an absolutely insane size before they became black holes.