An astronaut who was $20$ years old left to explore the galaxy in $1980,$ on a spaceship travelling at$2\mathrm{.}5$x$10^8$m$/$s$.$ After $40$ years of travel, how old does he appear to be$?$ Please answer showing full steps with the formula

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This question is essentially asking about the effects of time dilation a phenomenon predicted by Ein... View the full answer