6 ms·
The more mass, the more gravity. The more gravity, the larger the escape velocity. But there's a maximum speed in the universe, the speed of light. If a body
by 29athrowaway 2y ago
The more mass, the more gravity.
The more gravity, the larger the escape velocity.
But there's a maximum speed in the universe, the speed of light.
If a body has so much mass that the escape velocity is higher than the speed of light, you got a black hole.
- jmdeon 2y agoBut escape velocity refers to objects with mass, which light is without. Really its more about bending spacetime so much that light among all else gets trapped in a well of it.
- 29athrowaway 2y agoI was trying to come up with a 1700s-like explanation.
- mathgradthrow 2y agoescape velocity does not explicitly refer to an object with mass. One of the earliest observations about gravity is that the acceleration that results is independent of the mass of the falling object. This is why it is called escape velocity instead of escape momentum.
- moi2388 2y agoTechnically that’s not certain yet, we just know it’s very small. There are still experiments setting upper bounds. Technically..
- DoctorOetker 2y agolight has no rest mass, and how often have you seen a photon at rest?
- LorenPechtel 2y agoLight is subject to escape velocity the same as matter is. A black hole is just as black in a Newtonian universe as an Einsteinian one. Without an understanding of the warping of spacetime he had no idea of the truly one-way nature of a black hole, but he was right about light not being able to make it out. It's an approximation but a pretty good one.
- Maxatar 2y agoThe escape velocity is a nice pedagogical argument but it's completely incorrect and almost trivial to see why. You certainly don't need to actually be moving at an escape velocity in order to move against the gravitational field of an object. Heck even on Earth it's not like rocket ships actually reach the escape velocity of Earth which is 11 km/s, they travel at less than half of that speed, let alone airplanes or helicopters which don't travel anywhere close to it. An object that is able to sustain even 1 millimeter per year will be able to move arbitrarily far away from Earth, or Jupiter, or the Sun. Black holes don't trap light because of escape velocity, and the fact that the Schwarzschild radius happens to be similar to a body's escape velocity is because both of them use the same fundamental principle in their derivation, not because the Schwarzschild radius is derived from the escape velocity.
- lkdfjlkdfjlg 2y agoRight. In general relativity the fact that you can't escape a black hole isn't about velocity, it's about geometry. There's literally, physically, no path out.
- BirAdam 2y agoBut that is due to extreme curvature on account of the body’s mass. I think that John Michell was on the right path to discovering black holes, but the sciences known to him and his time weren’t sufficient for him to complete the thought.
- mathgradthrow 2y agothese two concepts are distinguishable, since velocity ends up being about geometry.
- lkdfjlkdfjlg 2y agoWord salad.
- jameshart 2y ago> it's not like rocket ships actually reach the escape velocity of Earth Not sure what definition you’re using for ‘rocket ships’ - but obviously rockets that operate in earth and cislunar orbits don’t need to reach earth escape velocity. But interplanetary probes surely have to exceed the escape velocity, right? Edit: ohhhh I think I see what you mean: you don’t have exceed escape velocity at earth’s surface. Sure. You can go to a higher altitude where escape velocity is lower and just exceed that.