Theoretical physicist Brian Greene stopped by The Late Show last night to help Stephen Colbert explain gravitational waves to the layperson. Turns out, they are ripples in the fabric of space time, and space time is like a giant trampoline, except it’s not made out of trampoline material. It’s made out of something the human mind cannot yet fully comprehend. So that’s fun! Greene also shares the computer-simulated sound of two black holes colliding. If that catastrophic event actually happened anywhere near Earth, it would obliterate our bodies instantaneously, but honestly, the sound itself is too cute.