If a person lives on the average 100 years in his rest frame, how long does he live in the earth frame if he spends all his life in a spaceship going at 60% of the speed of light .

Explanation

Given ` t = 100 years `
` V = 60 / 100 d. C = 0.6 C . `
` Delta t = 1 / (sqrt 1- V^(2) / c^(2))`
`= 100 v / (sqrt 1 -(0.6)^(2) c^(2) / c^(2))`
`= 100y / 0.8 = 125 y` .