Ah, c'mon, Dan, no response to this? PLEASE PLEASE I enjoy reading your responses. And if ever there were a highly inflexible, NON-bended straight line, Southhack's given you one. Now, some will say it's a cruel sport. It's too easy. It's like hunting elephant in a zoo. But I say: Go for it!
A while back I decided that Southack is a "science troll", purposely throwing monkeywrenches into scientific discussions. No one could be as obtuse as he seems to be, especially since he throws just enough science into a post to show that he *does* know some (like his allusion to diffraction above), and ought to know better than he pretends. Furthermore, he has a track record of being able to recognize when he's fighting a losing battle on one point and he chooses that moment to fling another spitball into the discussion, drawing the discussion in another direction.
He also has the troll's habit of declaring victory after getting nailed, which he knows just infuriates/frustrates most of his sparring partners.
He enjoys rankling us science-types, no more, no less, and he does it by making preposterous statements that cause people to scramble to correct him.
So rather than argue with him ad infinitum, I find it useful to just hammer a few of his posts into the ground in each thread to ensure that people see that they needn't take him seriously -- after that it's a waste of time to bother with his every subsequent attempt to keep trolling, his credibility is already gone, and his followup posts thus speak for themselves.
But since you insist...
Light distorts slightly going past the edge of something (like a thumb held out, although the effect is very slight and hard to see unless you artificially enhance it) not because of gravity (it's easy to prove that the amount of gravity generated by your thumb is so tiny that it can't possibly explain the phenomenon) but because of diffraction, which is an effect caused by the wave nature of light. The "waves of light" curve slightly as they pass near an "obstacle" in the same way that ocean waves curve a bit around the edge of a jetty, although given the speed and wavelength of light, the amount of "spread" is slight (but noticeable).
So again, Southack is playing the fool when he implies that diffraction is caused by "gravity" and "gravitons" and that there's any connection to the "speed" of gravity.
Nonsense.
What I said was that Gravity easily bends Light (e.g. thumb experiment, Black Holes, etc.), but that Light did not appreciably bend Gravity.
I also said that one would be more inclined to attribute such a discrepancy (i.e. one bends the other but not vice-versa) to a large difference between the two, such as a large difference in their speed.