# Specialy theory of relativity

a 30-year old female astronaut leaves her newborn child on Earth and goes on a round-trip voyage to a star that is 40light-years away in a spaceship travelling at 0.90c. what will be the ages of the astronaut and her son when she returns?

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The child is unaffected by the effects of travelling at high speed and thus will be 2x40/0.9 years old = 88.89=90 years old. I'm not well enough versed in relativistic effects to calculate the age of the astronaut.

Doc Al
Mentor
To find the age of the astronaut, use the time dilation formula. (She can be viewed as a moving clock.)

what would her son's age be then?..is it 80 years +(0.02)(40years)=80.8years??

it's how long it would take from the sons perspective for her to get there. That is simple. it takes light 40 years to get there and she is travelling 0.9 times the speed of light so it would, using simple speed/time/distance type workings 40/0.9 = 44.445 years to get there. Then she has to travel back so you double it giving 88.89.

makes sense:) thankyou