Pyle, of a model of distorted space in the Solar System. It looks like we have two effects going on: each object’s velocity affects how it experiences gravity, and so do the changes that occur in gravitational fields. The Earth, for example, since it’s also moving, kind of “rides” over the ripples traveling through space, coming down in a different spot from where it was lifted up.
It's a stroke of brilliance to realize that Newton's laws require an instantaneous speed of gravity to such precision that if that were the only constraint, the speed of gravity must have been more than 20 billion times faster than the speed of light!īut in General Relativity, there's another piece to the puzzle that matters a great deal: the orbiting planet's velocity as it moves around the Sun.
The orbits of the planets were so well studied and so precisely recorded for so long (since the late 1500s!) that if gravity simply attracted the planets to the Sun's prior location at the speed of light, the planets' predicted locations would mismatch severely with where they actually were. It’s just that they’re landing side by side in such quick succession that they form a spot that moves faster than the speed of light, but really, it’s just an illusion.If that were the only difference between Einstein's theory of gravity and Newton's, we would have been able to instantly conclude that Einstein's theory was wrong. The individual particles coming out of my laser, the photons, are still travelling to the moon at the speed of light. “In truth, nothing here is really travelling faster than the speed of light. If you can flick that beam across the moon’s surface in less than a hundredth of a second, which is not hard to do, then that laser spot will actually move across the surface of the moon faster than the speed of light,” says the host on this Veritasium video. “There is a classic method where you shine a laser at the moon. Using a bit of geometry, however, isn’t there a way to make it go faster? This video below shows why you’d think it would work that way, but it actually wouldn’t.
In a vacuum, light goes close to 300,000 km/s (roughly 186,000 miles a second). We at Universe Today often hear theories purporting that Einstein is wrong, and perhaps one of the most common things cited is the speed limit for light used in his relativity theories.
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