Testing whether gravity bends light

[Drops of Fire]

The experiment Einstein proposed that supposedly proved successful kind of confuses me. If you can prove a beam of light bends when near the sun, how can we prove that from Earth with a picture because by the time we're able to see it to take a picture, the light has already gone passed the sun and reached Earth and any effect it would've had on it would be gone by then. At that point, all the light would appear to be bent everywhere about the about the same despite whether or not some of it passed the sun to get here, right?

 

[Janus]

The trick is that as the light passes the Sun and bends it leaves the Sun's vicinity along a different line than what it came from. when that light reaches us, we see the object that produced the light in a different position than we would have if the Sun had not bent it's path. By comparing the apparent positions of stars next to the Sun during an eclipse as compared to their normal relative positions, we can tell if they seem to shift position when their light skims the Sun on the way to us.

Here's an image that illustrates this:

http://astrobob.areavoices.com/astrobob/images/1919_light_bending_Jose_Wudka_1.jpg

 

[HallsofIvy]

In a nutshell, the idea was to observe the (apparent) distance between two stars when the light from each passed close to the sun and when it didn't.