**Problem : **
A spacecraft travels at
0.99*c*
to a star
3.787×10^{13}
kilometers away. How long will a
roundtrip to this star take from the point of view of someone on the earth?

**Problem : **
With reference to the previous problem, how long will the roundtrip take for someone in the spaceship,
according to someone measuring from the earth?

**Problem : **
Now in the reference frame of someone in the
spaceship, what is the time taken for the roundtrip
as observed by a passenger, and by someone on earth (ignoring the times when the spaceship is accelerating
or decelerating).

**Problem : **
If one person stays on earth and one person travels to the distant star, who will age more during the trip and
by what amount?

**Problem : **
Twin A floats freely in outer space. Twin B flies past in a spaceship at speed
*v*
_{0}
. Just as they pass each
other they both start timers at
*t* = 0
. At the instant of passing B also turns on his engines so as to
decelerate at
*g*
. This causes B to slow down and eventually to stop and accelerate back towards A so that
when the twins pass each other again B is traveling at speed
*v*
_{0}
again. If they compare their clocks, who
is younger?