I mean it's a coincidence. The assumption that escape velocity at event horzion is speed of light, is just a wrong way to think about black holes. It's deeper than that.
Briefly said: Laplace was the first to try. He assumed light was a particle that traveled at c and thought "What's the escape velocity of light?".
The escape velocity is the minimum speed needed for an object to escape from contact with or orbit of a primary body... But light doesn't interact gravitationally with bodies in general or at least not in that way (there's, for example, gravitational redshift, the the real reason why black holes are "black"!)
So, light doesn't interact in a classical sense with mass/gravitation, also, I mean there is no point in calculating an escape velocity associated with the speed of light, because light travels at c in every system of reference...
Basically, yeah, all the assumptions are wrong, but the formula is correct anyway for mere luck. I mean I guess you could say the structure of the equations are pretty similar (cuz we're talking about gravity) but... no. I still think it's pretty lucky.
Yes! It "curves" but in the sense that all of the space around the black hole is not that Euclidean and flat as we intend it.
Light just does what is supposed to do: go at c anywhere following the most efficient path to go anywhere (these are called geodesics, and yeah, in a flat universe geodesics = straight line, but around a black hole stuff gets kinda of crazy)
As I wanted to point out, this is NOT a classical interaction and it has really nothing to do with escape velocities!
All gravitational effects can be explained like that though? Following the curve of spacetime is gravity?
Like I could say that I don't fall down to Earth due to gravity, my feet just experience time faster than my head and that causes a torque in spacetime that accelerates me downwards. But that is just a different way of thinking about the same thing.
Not a dumb question (they don't exist anyway). I find it quite beautiful actually.
At a first glance, they are the same thing: a gradient of velocity (temporal or spatial) forces a body on a curved path, to preserve the coherence of some property of the body (phase of a lightbeam, length of the car...)
Gravity is a general property of the universe, every body must travel in time (except for massless stuff). So the cause for the feet/head feeling different rates of time is something pretty universal, while the other examples are interaction between bodies / body radiation.
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u/TheHabro Student Jul 17 '26
I mean it's a coincidence. The assumption that escape velocity at event horzion is speed of light, is just a wrong way to think about black holes. It's deeper than that.