Space.

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…time of 2.2us but found - lifetime is dilated to 49.2us Implications of time dilation and length contraction for space travel *Travellers will age more slowly to stationary observer *Time dilation - possible to travel to stars in one lifetime oHowever travelling at 0.999c - take 4.47 yrs to reach closest star; on return it will be 200 yrs later on earth *If speeds can be reached in excess of c (300c) possible to travel into past