Physics:Cosmic catastrophe
The cosmic catastrophe is a thought experiment in which the sun were to instantaneously disappear. The question is what would then happen to the earth and the other planets orbiting the sun. According to Isaac Newton's classical theory of gravity, the planets would immediately cease to move in circular motion, and inertia would make them start traveling in a straight line.
Albert Einstein saw a deficiency in Newton's theory. The finiteness of the speed of light would mean that it would take a certain amount of time before the darkness from the sun's absence would reach the orbiting planet. Therefore, why would the planet instantaneously start traveling in a straight line before the arrival of information that the sun's disappearance has occurred?
The cosmic catastrophe thought experiment led Einstein to the invention of the General Theory of Relativity and the creation of the concept of spacetime. Spacetime allowed Einstein to fix the deficiency in Newton's theory. In Einstein's spacetime model, the disappearance of the sun would create gravitational waves in the spacetime. The gravitational waves travel at the speed of light, and an orbiting planet would not react to the sun's disappearance until after the gravitational wave has reached it. Only then, the planet would start to travel in a straight line.
External links
- The elegant Universe, part 1 of a 3 part Nova mini-series (see details under the "transcript" tab). Based on a book of the same title by Brian Greene.
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