This is the answer to problem 3.2.8.

Return to relativity

For the figure lets say that the velocity of ship B with respect to planet A is (1/2)c after departure in the +x direction and the speed of ship C with respect to planet A is (1/2)c after departure in the -x direction. There are triplets one of which is on planet A, one of which is on ship B and one of which is on ship C. The departure happened on their 30th birthday. After departure they remain in states of constant velocity forever.

**a.** According to the standard of simultaneity for the one on planet A, show that the ages of the siblings on A's 35th birthday are 34.3 years old.

**b. **How fast is ship B moving with respect to ship C?

**c.** According to the standard of simultaneity for the one on ship C how old are the siblings when C is 34.3 years old?

**d.** According to the standard of simultaneity for the one on ship B how old are the siblings when B is 34.3 years old?

a.

**b.**

**c.**

d.