How do gravitational waves work?
Through our understanding of general relativity, we know that gravity can make gravitational waves, ripples in the fabric of space-time. The realisation that gravitational waves exist came from a simplified form of general relativity, and Einstein didn’t know if the waves were real or just an artefact of the simplification process. It took several decades before physicists came to the firm conclusion that general relativity does support gravitational waves.
Pretty much anything in the universe doing anything at all makes gravitational waves.
All it takes is a little wiggling, which gravitational waves have in common with pretty much any other wave – if you wiggle around in water, you make water waves. If your voice box wiggles around, it makes sound waves. If you wiggle an electron, you make electromagnetic waves. To make a gravitational wave, all you need to do is make mass accelerate. These waves travel out from the source at the speed of light and are literal ripples in gravity. When a gravitational wave passes through you, you get stretched and squeezed as if you were a piece of putty.