Question

Alex and James are twin brothers, both 18 years old. James travelled to another planetary system with a super-fast spaceship moving at 0.6c = (3/5)c, promising to return to spend his 30th birthday on Earth, together with Alex who remained on Earth. Having learned about Special Relativity, they each think that they will be older than their siblings when they meet again!

a) What is the Twin Paradox? Why do they both think that they will be older than their sibling when they meet again?

b) Which of the two is correct? Why?

c) What will be Alex's age when they meet?

Answer 1

a) In experiment of twin paradox,one of the two twin siblins moves in space with high speed spaceship and another stay at on the earth. Each one thins they are moving relatively with respect to each other. Due to high speed time is dialated. So both of them thinks that they are older than other one.

b) Person at ground will be older than person in spaceship.

Alex is older than James. So Alex is correct.

c) time spend by alex in space is of (30-18) = 12 years.

Actual time for which James was in space is given as

So actual age of Alex

while James is of 30 years.