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Q & A: speed of gravity

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Most recent answer: 09/13/2008
Q:
Does gravity act faster than the speed of light, and can this be measured?
- frank hearnshaw (age 69)
sheffield,s yorks,england
A:
Changes in gravity (e.g. when some stars spin around each other) propagate exactly at the speed of light. I can't think of any completely direct measurements, offhand. However, the rate of slowing down of the spin of certain pulsars fits theoretical predictions based on gravity waves very well. If the wave speed was something else, the predictions would be different. There are much deeper reasons for thinking the speed is the speed of light, but this is one concrete piece of evidence.

Mike W.

(published on 09/13/2008)

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