It's a place or places in the USA where they've invented a really beautiful simple experiment for gravity wave detection. It's so easy to understand yet so so deep.
Very roughly there are two parallel mirrors and two laser beams measuring the distance between them. When you eliminate all the "noise" eg seismic activity from data about their movements, and they're still not exactly aligned, there are gravity waves.
The point being that they're rippling through everything right now, if they're real. Because the Big Bang released one heck of a gravitational ripple.
Intuitively there must be gravity waves because we already see how spacetime can be warped to become a lens, for example. If it's that floppy then you can wave it like a sheet.
Have you ever been under a parachute where people rippled it? They used to do it at this club called Whirlygig in London. In like 1989. The dj was called Monkey Pilot :)