- #1
bluemoonKY
- 131
- 16
I just watched the first part of Brian Greene's television program on PBS The Elegant Universe. In The Elegant Universe, the narrator shows a model of the solar system, and the narrator says that according to Newtonian theory, if the sun disappeared, the Earth's trajectory around the sun would change instantly. The narrator says that Einstein realized that nothing can travel faster than the speed of light. Therefore, the force of gravity cannot travel faster than the speed of light. It showed the model of the solar system again. It said that Einstein realized that if the sun disappeared, the sun's gravitational pull would keep acting upon the Earth until the sun's rays of light no longer reached earth. According to the narrator, Einstein realized that the sun's gravitational pull would keep acting upon the Earth until the sun's rays no longer reached Earth because gravity does not travel faster than the speed of light. To me, this is circular reasoning. Why did Einstein know that if the Sun disappeared, the Sun's gravitational pull would keep the Earth in orbit until the rays of light no longer reached Earth? Because gravity does not travel faster than the speed of light. How did Einstein know that gravity does not travel faster than the speed of light? Because Einstein knew that if the Sun disappeared, the Earth would stay in orbit around the sun until the Sun's rays of light no longer reached Earth.
Is there any explanation for how Einstein knew the speed of gravity that is not circular? If so, what is the explanation?
Is there any explanation for how Einstein knew the speed of gravity that is not circular? If so, what is the explanation?