# How does the delay of pulsar signals prove that gravity travels at the speed of light?

In the Hulse-Taylor binary pulsar system, the orbit of the two neutron stars results in the warping of space time causing the pulses to arrive earlier and later because of the longer distance travelled when the pulse crosses the gravitational field. How does this prove that gravity moves at the speed of light?

This makes it extremely likely that gravitational waves are a thing. Of course, you couldn't have gravity waves if the speed of gravity were infinite. So, at first glance, it certainly seems to confirm that the speed of gravity is finite. Furthermore, the amount of energy radiated away with gravity waves is dependant on the speed of the wave. The theories relate the radiated power as proportional to $1\over v^5$, where $v$ is the speed of the wave. It turns out that if you make $v=c$, you get the exact amount of energy radiated away as what corresponds to the orbital decay of the system to within no more than $1\%$. So it would stand to reason that the speed of gravity is likely the speed of light.