1. If the Michelson-Morley experiment were to be conducted with gravitational waves instead of light waves, would the results be any different? 2. Ought we to expect the existence of "gamma" gravitational waves and "radio" and "microwave," etc. gravitational waves? In principle, could there be a "gravitational microwave background?" 3. Corollary to #2: Ought we to expect gravitational waves to undergo Doppler effects? 4. Back when we thought light moves through an ether, we hypothesized (based on the nature of light) that the ether must be something akin to a really rigid glass. We no longer believe in the ether, but we do believe in a "spatio-temporal fabric" (tomayto/tomahto) through which gravitational waves move. Given the nature of gravitational waves, to what material substance would we compare the fabric of space-time? Glass? Rubber? Water?