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Gravity Probe B

Testing Einstein's Universe

Special & General Relativity Questions and Answers

Does light travel at the same speed back and forth along a straight line?

The Michaelson-Morley experiment showed that the propagation of light in any inertial reference frame is completely isotropic. There is no difference in its velocity with respect to its direction of motion.


Return to the Special & General Relativity Questions and Answers page.

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