Many popular accounts claim that gravity waves move at the speed of light. Now, I know 2 things: Special relativity says their speed cannot be greater than the speed of light in a vacuum. Gravity is a different fundamental force than the electromagnetic force. The same goes for their fields, which are what their respective waves perturb. Why, then, should gravitational waves be expected to behave like electromagnetic waves? We couldn't have based the speed-of-light assertion on empirical observation either, since we haven't had them in our laboratories until now. In fact, even now it doesn't appear that we have measured their speed. So, why are all these people saying gravity waves travel at the speed of light?