12-17-2012, 06:28 PM
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smoke gets in your eyes
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Join Date: Jun 2000
Location: Eastern TN
Posts: 20,851
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It was the idea that photons are affected by gravity and therefore must have mass that was debunked. I haven't been in a physics class in a few decades so I'm sure there is fresher thinking but this is what I found - Gravitational lens - Wikipedia, the free encyclopedia
One fellow put it in terms that make sense to even me -
Quote:
Even though a photon has a zero mass, it is still affected by gravity. In particular, we can see the effect of gravity on light in a phenomenon called "gravitational lensing," in which a massive object warps spacetime such that it bends light. Light passing through the gravitational lens can be bent such that the light takes multiple paths and we end up observing artifacts of this effect.
The first gravitational lens was discovered in 1979 even though Einstein predicted the effects of a gravitational lens in his general theory of relativity several decades earlier. In the case of the Twin Quasar, a galaxy between the star and ourselves acts as a gravitational lens and we end up with the observation of two identical objects in the sky.
Similarly, truly massive objects like black holes have escape velocities that exceed the speed of light. That is, their gravity is such that light cannot move away from the black hole's gravitational field.
What these examples illustrate is that photons, like everything else, follow the straightest possible path through spacetime, and when spacetime is warped or bent by massive objects, the photons adhere to this curvature. We often think of gravity affecting objects based on their mass, and since photons have 0 mass it seems counterintuitive to suggest that light is affected by gravity. There is still much to be learned about light and gravity, but for now we must conclude that light is affected by gravity, even if you consider conformity to spacetime curvature as "indirect" effect compared to, say, our gravitational attraction to the Earth.
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Sixto
87 300D
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