320 Pre-class Exercise #1

Here's a tricky twist on the conventional twin paradox:

Bilbo and Bob are at rest relative to each other and are exactly the same age (according to the conventional synchronization of clocks in a single reference frame), but they are separated by a large distance.  At the precise instant that Bob turns 21 years old, he observes Bubba passing him at constant high speed, with uniform motion along the line connecting Bob to Bilbo.  Meanwhile, at the same exact instant in time, Bubba turns 21 years old.

1. When Bubba passes Bilbo some time later, is Bubba older, younger, or the same age as Bilbo?  Explain.  As with the conventional twin paradox, be sure to discuss the apparent symmetry of the views from each frame.

2. Does this mean that Bubba ages faster/slower in his frame than Bilbo and Bob in theirs?  If not, explain how Bubba's age can differ from Bilbo's while not differing from Bob's.