Paradoxes of the theory of relativity
The Clock Paradox
Should Bubba and Buffie be jealous that Wolfie and Hildie are getting old slower? Not at all. After all, Wolfie and Hilda are not enjoying the extra time. Their thoughts, their days, everything is going slower for them. They don't experience any extra time.
In fact, when you think of it, Wolfie and Hildie see a clock belonging to Buffy and Bubba going too slow compared with their clock. After all, they see themselves as stationary and Buffie and Bubba moving past them on a (very large) space ship. So they see Buffie and Bubba getting old slower than they are.
Each one sees the other's clock as moving slower than their own! This is known as time dilation; time on a moving space ship is observed to be stretched out. Once again, this is not a problem with bad clocks. This is the nature of time itself! How can this happen? The paradox is resolved when we consider how the comparison is done.
When Buffie and Bubba watch Wolfie and Hildie's clock, they do it by watching one clock on the space ship as it passes two clocks in two places on the moon. When Wolfie and Hildie do the comparison, they watch one moon clock as it goes past two separate clocks on their space ship.
It turns out that since the two pairs of observers can't agree on simultaneity, they have set their clocks incorrectly (relative to one another, in some sense) when they moved them into place for the comparisons. In any event, there is no paradox since the same clocks are not being used in the two measurements.
