The inflationary version of the Big Bang theory has space-time expanding faster than light. Which is something worth thinking about.

What is gravity? If we knew that, then we'd have our theory of quantum gravity and the gods know what else. But we don't.

Gravity may very well operate in the 'extra dimensions' required by string theory. No one has ever spotted a graviton and they may never spot one. Is gravity simply the effect of mass/energy on space-time? We understand so much about this force, and yet it remains a very big mystery.

If gravity can't be modulated so that it operates as a signal, it could operate at speeds in excess of c. Without violating causality.