At what minimum speed, in , should you travel so that you feel that you are traveling faster than the speed of light? If you don't think this is possible, put -1 as your answer.
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Let x be the fraction of the speed of light you are traveling at. By the theory of relativity, time is dilated by a factor of 1 − x 2 1 . Thus, your apparent speed will be 1 − x 2 x c . The inequality then becomes 1 − x 2 x c > c , or 1 − x 2 x > 1 . This rearranges to x > 1 − x 2 → 2 x 2 > 1 → x > 2 2 . Your speed must therefore be 3 × 1 0 8 × 2 2 = 2 . 1 2 × 1 0 8 m / s .