So we know that gravity bends light. So what? It is just proof that gravity exisists, and that light probably has some sort of mass. What is gravity?
PS, without my work, you may have not had that super Hubble picture you posted.
So we can use General Relativity to calculate exactly how far it bends. We can also use it to calculate exactly how clocks slow down in gravitational wells, and how quickly elliptical orbits precess, and how rapidly binary pulsars spiral towards each other because of energy lost to gravitational radiation. Believe it or not, that last one is by far the most precisely measured of all the quantities.
It is just proof that gravity exisists, and that light probably has some sort of mass.
But it doesn't have any mass; we know that from completely independent measurements. But even so, if light had a tiny mass (actually, no mass is necessary even in this classical picture; but I leave it for the sake of argument) and gravity were a Newton-style inverse square law like electromagnetism, light rays would indeed bend, but the bending would be a factor of two smaller than is observed.
What is gravity?
It's the curvature of spacetime.
PS, without my work, you may have not had that super Hubble picture you posted.
And I thank you for it. But I suppose you still think me an ingrate for disagreeing with you.
Until the discovery of the missing mass of the universe, I too thought that light had a small amount of mass, due to the gravitational effects we can measure.
The presence of missing mass, (AKA dark matter)explains that what we were measuring was the gravitational effects of the matter that the light waves are traveling through, and it also goes a long way in describing what gravity is.
Consider that dark matter which comprises upwards of 90% or more of the total mass of the universe occupies what we have always classified as empty space. This means we and everything in the universe is moving through that dark matter. Gravity becomes differential inertia.
But this also raises a whole host of other unknowns, just like every other answer we have found.