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Gnengi
2012-Nov-25, 10:31 AM
Is the amount by which light is bent by gravity proportional to the wavelength (eg. energy) of the light, since more energy means more implied mass (due to E=mc^2)?

Just asking this because light bending in high gravitational fields may be due to the space (and time) being bent due to gravity (or to be precise; the other way round), therefore when light travels in a straight line as it would normally, it appears to bend because the straightness of the space is being distorted by the gravitational field. If that were correct, it would mean that the energy (wavelength) of the light has nothing or little to do with the amount bent.

Which is correct? Or is it a combination of the two?

Thanks,
Gnengi.

caveman1917
2012-Nov-25, 12:16 PM
It doesn't depend on its energy, it is bent by the gravitational field of another body, not itself. Say the amount of bending light has that goes close to the sun depends on the mass/energy of the sun, not its own. At least in so far as you can take the photon's mass/energy to be insignificant, which you can. It's akin to that objects fall down at the same speed (well acceleration really) irrespective of their own mass.

trinitree88
2012-Nov-25, 03:58 PM
Is the amount by which light is bent by gravity proportional to the wavelength (eg. energy) of the light, since more energy means more implied mass (due to E=mc^2)?

Just asking this because light bending in high gravitational fields may be due to the space (and time) being bent due to gravity (or to be precise; the other way round), therefore when light travels in a straight line as it would normally, it appears to bend because the straightness of the space is being distorted by the gravitational field. If that were correct, it would mean that the energy (wavelength) of the light has nothing or little to do with the amount bent.

Which is correct? Or is it a combination of the two?

Thanks,
Gnengi.

Gnengi. There's another way of looking at it,too. When Galileo dropped the large and small balls off the tower of Pisa, the larger mass had the larger gravitational force due to it's mass, but an exactly equally large inertial mass (F=ma), so it's acceleration, independent of air resistance was exactly the same as the small one. So if you considered two photons of different energy as being converted to mass by Einstein's E=mc2, then the same thing would apply for the principle of equivalence to be true...(known true to ~ 8 sig figs). pete

edit: now for the trinity of equivalence to be true, changing the ambient neutrino sea gradient ought also to cause bending of the light path.