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Gravity Probe B

Testing Einstein's Universe

Special & General Relativity Questions and Answers

Has it been experimentally proven that the speed of light is the fastest?

Yes. So far as electromagnetic and gravitational fields are concerned, all observations both of direct phenomena, and based on indirect mathematical deduction, place the speed of light as the maximum speed limit. These include both timing experiments and the fundamental basis for quantum electrodynamics which is the modern theory of electromagnetism which is accurate to ten decimal places.

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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.