# Special & General Relativity Questions and Answers

## What fraction of the perihelion advance of Mercury is due to special relativistic effects?

Special relativity does not enter into the calculation and contributes nothing. Here are the contributions for Mercury:

Total precession...................5599.74 +/- 0.41 arc seconds/century ........................................................................ General precession.................5025.64 +/- 0.50 Other planet perturbation.......... 531.54 +/- 0.68 G. relativity + Solar oblatness.... 42.56 +/- 0.94 .......................................................................The total measured precession is 5599.74 arc seconds per century and consists of the three contributions listed. General precession is the gradual rotation of the celestial coordinate frame due to purely Newtonian effects, similar to the precession of the Earth's spin axis. The only 'relativity' in the calculation is General relativity having to do with the curvature of space-time in the vicinity of Mercury's orbit, which has nothing to do with special relativity.

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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.