Possible Duplicate:
The speed of gravity
It takes a long time for a radio signal to travel to the planet Mars.
What if we made a special type of radio that could detect small changes in gravity from a fall away object. For example, a satellite in orbit around Earth. That satellite had a device that allowed it to make small changes in it's gravity field. The detector orbiting Mars could detect these changes, and convert it into a communications signal.
Would these two devices be able to communicate with each other instantly using gravity? There by providing a real-time communications link between Earth and Mars?
