A spacecraft traveling at 99 percent the speed of light toward Alpha Centauri would cross 4.3 light-years in what feels like months to its crew, while decades tick by on Earth. That asymmetry is not ...

James is a published author with multiple pop-history and science books to his name. He specializes in history, space, strange science, and anything out of the ordinary.View full profile James is a ...

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Since the universe contains a finite amount of energy, reaching light speed is impossible for anything made of matter.