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Gravity Probe B

Testing Einstein's Universe

Special & General Relativity Questions and Answers

Because of general relativity, do stars age at the same rate inside and at the surface?

No they do not, at least not exactly, by an amount that depends on:

 T = --------------------
                   2   1/2
       ( 1 - 2GM/rc   )

The differential effect between the core and surface is very small, but because the surface is at a higher gravitational field than the core, its rate of time passage is slightly less. But the difference is so slight that it would not have any affect on the overall evolution of the star. Also, the evolution of a star is determined by the speed of the fastest nuclear process, not what is happening on the surface at some 'retarded' time.

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All answers are provided by Dr. Sten Odenwald (Raytheon STX) for the NASA Astronomy Cafe, part of the NASA Education and Public Outreach program.