### Comment:
Huh, never thought about gravity needing a medium to travel through. I dunno, I always thought of gravity as the medium for everything else ya know?

### REPLY:
Spacetime itself is a medium. I was interested by the LIGO result when the detector caught two black holes merging. The signal didn’t slow down at all as it passed through the Earth’s core. What I’d like to find out is how to get gravity to exhibit the properties of a surface wave.

### END.