Relative Motion and the Twin Paradox
Date: Around 1993
Why does one twin age more slowly in the famous "twins paradox"?
Well, That is the whole point of the paradox! From the point of
view of the twin who is in the space ship, that is exactly what happens.
However, everything breaks down if the twin in the space ship decides to slow
down, turn around, and come back and visit his twin back on earth. During
that deceleration and turning phase, he suddenly sees his twin on earth get
older and older and older, while he does not age much at all. Actually,
motion in our universe really is not all that relative. Position is relative,
and different positions in our universe have different average velocities of
all the matter in that area (the velocity of the Hubble expansion), so if you
think about the physical universe, relativity seems a little less than
Click here to return to the Physics Archives
Update: June 2012