Friar Bellows

Recently, two astronomers used an array of radio telescopes in the USA and Germany to measure the time delay of radio waves (in this case, from a quasar) as they pass by a massive body (in this case, Jupiter). They combined this measurement with earlier theoretical work to deduce that the speed of gravity is approximately the same as the speed of light. The press hailed it as yet another vindication of Einstein's general theory of relativity.

But not so fast, says Clifford Will, renowned expert on experimental tests of (general) relativity. He analyses the situation and concludes that "measurements of the propagation of radio waves past Jupiter do not directly constrain the propagation speed of the gravitational interaction." In other words, gravity is still waiting to have its speed directly measured by us.

It's pretty cool to see science at work.