1. does gravity red--shift light?

Does gravity redshift light? So if a light comes from a strong gravitational field is it redshifted or blueshifted?

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Wow.

-- Jeff, in Minneapolis

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Yes gravity does redshift light if the source of the light lies in a gravitational field. There's a few ways to visualize this. It takes energy for the light to climb out of the gravity well, so as the light looses energy it's wavelength becomes longer and the light becomes redshifted.

4. conversely ... if you are in the well the light coming in will be blueshifted.

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Yep pretty much.

6. But there is no net change for light that passes through (into and out of) an area of strong gravity, as it is shifted one direction on its way in and is shifted the other direction by the same amount on its way out.

7. Thanks and again appologies ...

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How does GFRST compare in (order of) magnitude with Doppler Effect RST?

9. gospelmidi, I suggest that you spell out what GFRST means, and then provide a specific situation for your question, and do this in a new thread please.

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Hyperphysics, a very useful website, has a good take on the experiment by Rebka-Pound, using a Mossbauer detector to measure the photon energy loss, over a short vertical ascent....SEE:

http://hyperphysics.phy-astr.gsu.edu...iv/gratim.html

pete

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The Mössbauer effect in relativity studies with high precision measurement of energy of the gamma ray has made a direct demonstration of the gravitational red-shift. The change in the energy of a quantum of electromagnetic radiation as it moves through a gravitational field.
It is considered as a relativistic Doppler effect from the thermal motion. Also it is viewed as a direct demonstration of the relativistic time widening: the slowing down of the clock in a moving coordinate system.

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