Is Light Affected by Gravity?

This was the question of the day yesterday and I didn't know the answer to it, I could only guess.  My thought was that since light has no mass, and gravity is caused by objects with mass bending space-time, then no, light wouldn't be affected by gravity.  However, I kind of recalled reading something somewhere that said light WAS affected by gravity, so I decided to look into it this morning and this is what I found:

• Light does not have a "rest mass" because it cannot be brought to rest (light always moves at the speed of light), but it is affected by gravity and may even have a teensy weensy bit of its own mass but not to any degree that it really matters.  Some scientists at the University of California, Santa Barbara answer the question of light and mass on this page. 

• Now that we've just said that light/photons don't have rest mass because they don't ever rest, it turns out you can do some equation balancing that shows that because photons have energy, they also have mass.  Does this make sense?

• Ultimately, the important thing is that we know that light is affected by gravity because we've seen it happen.  Whether the photon has mass or not, it is definitely being affected by gravity. 

• Things with mass warp spacetime, so I guess since light travels in spacetime, it follows that it would be affected by that warping also?

• And this guy just kind of brings it all together really well in this video.

• And now, just to mess all this up in your head, listen to the RadioLab episode, "Speed".  It's a great show in general but the segment on light is really crazy.  After you've listened to that (but not before), check out the behind-the-scenes page on RadioLab.com for more info on the whole speed of light thing.  Amazing!