zlacker

>>qqqqqu+(OP)
The LIGO detector. I've never heard a logical explanation for it. If your explanation is that gravitational waves stretch and squash spacetime so light takes different amount of time to bounce from an emitter back to a measurer, then you don't have even a slight understanding of how it works. If your explanation doesn't involve higher spatial dimensions (not time) then you don't understand it. If you haven't even considered higher spatial dimensions when explaining LIGO then you shouldn't even try for the incorrect explanation above because you don't have any of the pieces of the puzzle.

>>steveb+2m
> If your explanation is that gravitational waves stretch and squash spacetime so light takes different amount of time to bounce from an emitter back to a measurer, then you don't have even a slight understanding of how it works.

Well, I'll bite. I'm a physicist and I understand LIGO. What's your alternative explanation?

>>knzhou+cm
I have no idea how it works, I don't have an explanation, I just know the one spouted by people doesn't make sense

>>steveb+Bm
Well, if you're uncomfortable with LIGO, you're in good company. Once a whole decade went by in physics where people couldn't agree if it would work in principle or not. And it is true that a lot of common explanations are bad (e.g. "it's just a ruler" is not complete by itself because "why doesn't the light get stretched too?"). Nonetheless, today we have a variety of independent explanations.

Maybe you'll find this paper helpful: https://aapt.scitation.org/doi/10.1119/1.18578

>>knzhou+Tm
Would you say it's accurate to say LIGO is a big interferometer measuring changes in lengths of the arms due to gravitational waves, with some extra analysis to figure why it still works even though the light waves get stretched? Or is OP correct that such an explanation means I "don't have even a slight understanding of how it works" and a correct explanation must "involve higher spatial dimensions (not time)?"

>>rrss+Ls
I'd say that's a perfectly fine explanation. And in fact the light does get stretched. For sufficiently low frequencies, that's fine because there's enough time for new (unstretched) light to enter and exit the apparatus. At higher frequencies this causes the sensitivity of LIGO to fall.

Part of the popular confusion around how LIGO works is the freedom in coordinates: there are different, perfectly good definitions of space and time you can use, and the explanation sounds different in each one. So people can get them mixed up. For example, my previous paragraph makes sense in "transverse traceless gauge", but not in others.

I'm not sure what GP was referring to with "higher spatial dimensions".