You realize that gravity must follow the same path as light, right? i.e. curved.
And thus gravity could not be escaping a black hole?
And that, gravity-isn't-bending-space, is provable?
Gravity is observed to travel at the speed of light, so between two arbitrary points A and B it travels the same *distance*. Subdivide the path in two, make that midpoint B and it must also travel the same distance to that midway point. Subdivide it to the limit case of distance tends to zero and prove its the same *path*, not just the same distances...
So gravity is following the same path as light. Since you've observed gravitational lensing, you also know lights path is curved, so gravity's path is also curved.
If light cannot escape a black hole, neither can gravity, because they follow the same path, everything travelling magic number 'speed of light' follows that same path.... curved.
And gravity isn't bending space, because gravity's *strength* depends on it's relative *location*, if it bent space, its *location* would depend on its *strength*, ... circular logic, .... so you can see why gravity isn't the cause of the bent space.
I assume this is all common knowledge?
That "light-years" thing, (assuming light travels in a straight line and at constant speed, neither of which is true), kinda always bugs me.
Light doesn't travel in a straight line, gravity doesn't travel in a straight line, when light hits you, it does not carry the information of the curved path it has followed, and you perceive it as if it was a straight path. You have nothing to compare it with, nothing, not even the path of gravity. You perceive light as if it travels in a straight line based on its short distance approximate behaviour, and you project that onto light that's come across a universe as if it travelled in a straight line.
It is impossible for light to be travelling in a straight line, of course, any non-zero bend in space means the light would travel in a loop and wrap back on itself, and you've already observed gravitational lensing, so you already know its non-zero bend!
The universe is finite.... everything loops back to the same place eventually, even light. You treat it as if the bending is tiny, and can be ignored, but that's just how you perceive it, because you think light travels in a straight line. Yet you can literally see the edge of the observable universe....it's not tiny bending!
Lights path is not straight.
Light and matter, they're the same thing, affected the same way. You compare light to matter and get the constant limit case for speed... of course you do: The scale of matter is from its motion, the speed of light is from its motion, they're moving over the same field, so of course if you compare one to the other you get a constant! Both are affected the same way by the same field.
i.e. the speed is not constant, you just perceive it that way.
Obvious question: how would you define a straight line in that system? You can no longer use light to define the straight line, because you know it is following a curve and cannot detect that curve! You will always perceive it as if it is straight.
Well, obviously, a force travelling infinitely fast has zero time to be affected by any bending, so you should 'hypothesize' such a force, attempt to model such a system.