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Q & A: Are the speeds of light and gravity the same?

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Most recent answer: 09/05/2011
which one is the fast? (gravity or light)
- MAYANK (age 24)
Yes, they're the same as far as we can tell.   According to the theories of special and general relativity they should be equal.   The speed of light has been measured by many observers, the first was Roemer, a Danish astronomer who in 1676 noticed slight discrepancies in the eclipse times of the moons of Jupiter.  It's much more difficult to accurately measure the speed of gravity.  The best measurement, again using the planet Jupiter duration an occulation of a radio source, was performed in 2002.  It's a difficult  measurement with fairly large uncertainties but the speed was determined to be within 20% that of light.


(published on 09/05/2011)

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