Read something interesting the other day (over at this site).
If you throw a stone in a pond, the wave travels at a certain speed. If you make a sound in the water, the "wave" travels much, much faster than the wave generated by the stone.
The reason is that the wave created by the stone is a transverse wave; the energy is being passed along at right angles to the direction of the wave, so you get that up and down motion in the wave.
Sound is a compression wave (longitudinal), so the energy is passed along in the direction of the wave, hence it's much faster and more efficient.
What if gravity and light were the same way?
We know how fast light travels (about 300,000Km per second). We used to think gravity didn't have a speed, it was instantaneous. We have now been able to measure gravity, so it does take time, just not very much. They estimate that gravity "waves" travel about 20 billion times faster than the speed of light.
So imagine this if you will: The vacuum of space is actually filled with particles called neutrinos. What if neutrino's were the medium in which these waves travel? Gravity would be a "compression" wave, hence it travels much faster, and light would be a transverse wave, so it's not only much slower, but it would resolve the issue that light is both a particle and a wave that science has been struggling with for a hundred years.
Just a theory right now, but seems to fit a lot of facts, and doesn't "not fit" anything we can find yet.