Assertion: black hole | /r/HasAspect | an event horizon
Facets:
value: really
type: DEGREE
value: across
type: LOCATION
Source sentences:
text: So while a black hole has an event horizon that, once you get close enough, you can never escape, a white hole has an event horizon that you can never even get close to (and that is not even counting the burning that you would get when you try!).
text: But we're told all black holes have event horizons — the line you cannot cross or be forever lost inside the black hole — what gives?
text: Thus, a black hole with a mass equal to the sun has an event horizon 3 kilometers in radius (6 km in diameter).
text: A black hole with a mass equal to the Earth (0.000003 solar masses) would have an event horizon whose radius was 0.000009 km, or 9 millimeters, or the size of your average American 1¢ penny.
text: The black hole at the center of the Milky Way, for example, is estimated to have a mass equal to about 2,500,000 suns and have an event horizon many millions of kilometers across.
text: One question scientists hope to answer is whether black holes really have event horizons, as predicted by general relativity.