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View Full Version : Gravitational Redshifts: Main Sequence vs. Giants



Fraser
2010-Nov-27, 09:20 PM
One of the consequences of Einsteins theories of relativity is that everything will be affected by gravitational potentials, regardless of their mass. The effect of this is observed in experiments demonstrating the potential for gravity to bend light. But a more subtle realization is that light escaping such a gravitational well must lose energy, and [...]

More... (http://www.universetoday.com/80353/gravitational-redshifts-main-sequence-vs-giants/)

Atlas shrugged
2010-Nov-27, 09:35 PM
I always wondered how we could accurately measure the redshift of a star sufficiently far enough away that it would be effected by other stars along the way and the light we see by the time it arrives at Earth has been subjected to the gravity of many other objects before reaching us.

Hornblower
2010-Nov-27, 11:21 PM
I always wondered how we could accurately measure the redshift of a star sufficiently far enough away that it would be effected by other stars along the way and the light we see by the time it arrives at Earth has been subjected to the gravity of many other objects before reaching us.If the light from a background star grazes a foreground star, I would expect it to be deflected slightly but not appreciably redshifted or blueshifted. We can envision it as gaining some energy on the way into the gravitational well and losing it on the way out, thus ending up much as it was before encountering the foreground star.

Atlas shrugged
2010-Nov-28, 09:53 PM
If the light was slowed down from the gravity along the way , then that would affect its color without having to do with it's originating star.

Jerry
2010-Nov-29, 12:53 AM
Make no mistake: This is another failure of a test of General Relativity. It could be, as the authors speculate, there is a competing and perfectly offsetting effect (not likely). It could also be that there is less precision in the measurements than the authors had hoped for. But it is wrong to say 'relativity has passed every test'.

Atlas shrugged
2010-Nov-30, 09:43 PM
This would also cause the redshift to increase the farther away the originating star, the more gravitational pull it has passed before arriving.