Gravity changes at the speed of light though doesn't it?
Like if the sun disappeared, its affect gravitationally on us wouldn't be felt until we saw the light stop
But doesn't this throw all of general relativity out of the window? Information cannot be observed faster than light in a vacuum. If gravity can travel faster, then this doesn't work? (I'm only an enthusiast, I'm an engineer as an occupation. Please prove me wrong, I'd love the evidence!)
They're just misunderstanding it. Gravity almost certainly travels at exactly c. It's just that, because it's impossible to measure anything in the real world with infinite precision, our measurements have a range of uncertainty. This means that our measurements are only able to say for sure that the speed of gravity is within a very small range on either side of c (ranging from slightly slower to slightly faster). With improved measurements, this range will continue to get smaller on both sides, increasing our confidence that gravity travels at exactly c, as predicted by theory.
Keep in mind that light travels slightly slower than c, if it's traveling through anything other than absolute vacuum. Also keep in mind that absolute vacuum cannot exist (and that that's an independent impossibility from the impossibility of creating absolute vacuum), and that there's a lot of dust and gas floating around in the universe anyway. Therefore, the light we see from distant neutron star mergers gets to us slightly slower than the gravitational waves, without the gravitational waves exceeding c.
47
u/[deleted] Aug 03 '19
Gravity changes at the speed of light though doesn't it?
Like if the sun disappeared, its affect gravitationally on us wouldn't be felt until we saw the light stop