# What is the reason gravitational waves propagate at speed of light? [duplicate]

I know Maxwell equation shows that it is the electric and magnetic properties of empty space which is why speed of light is constant, but what about gravitational waves? I have visited many answers but so far none seems satisfactory to me. Can we prove that gravitational wave is also a constant?

This is because gravitational waves are massless. Special relativity states that massless matter moves at $$c$$ in vacuum.