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Special Theory of Relativity
Einstein published what is now one of the most famous scientific theories in 1905. The Special Theory of Relativity explained that energy and matter are the same (expressed in the equation E=mc2), and that the speed of light is constant, and that nothing can go faster than the speed of light. It also explained that odd things happen to objects moving closer and closer to the speed of light. For example, time slows down and the object appears shorter. One experiment used to test this had one ultra-accurate clock on a high-speed jet and another on the ground to test if time would slow in the jet. Just as Einstein’s theory predicted, time slowed (if only slightly) in the jet, which was only capable of traveling at a fraction of the speed of light.
Unfortunately, this means that science fiction space travel, such as in Star Wars, is not possible (at least in the scope of this theory), as a Star Wars hyperdrive propels a ship faster than the speed of light. However, in Orsen Scott Card’s Ender’s Game, the younger two Wiggin siblings leave Earth for a new planet as young adults and are still young when their older brother is dying of very old age.
General Theory of Relativity
Ten years after Einstein published his Special Theory of Relativity, the General Theory of Relativity was published. The General Theory of Relativity explains how gravity is the result of the curvature of the time-space continuum, caused by large objects dimpling the time-space continuum.
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This theory also explains how s phenomenon can be observed at different times. For example, because of a phenomenon known as gravitational lensing, scientists were able to observe a supernova occur four different times. This is because the star that went supernova was in a different galaxy, and the intense gravity of that galaxy bent the light, causing a gravitational lens to form. The light traveling around the lens takes different paths, each traveling over a different amount of time (Redd, Nola Taylor).