• How do you measure moving time? Is this a crazy question? Recall that we had to be careful about measuring moving length (the eraser across the blackboard), where we had to be very sure to mark the positions of the two ends at the same time. What about reading the time from two clocks which have inertial relative motion?
• If light is spherical waves and the length shrinks along the line of relative motion of two observers, what can compensate to keep the waves spherical for all observers?
• What is the path of a beam of light which goes vertically up and down in the rest system as seen by a horizontally relatively moving observer? Caution: it isn't a parabola.
• If a relativistic car zooms through a garage which it's too long to fit into at rest, the car contracts to fit inside the garage, if only for a brief time. How would the driver of the car view the length of the garage? This is called the "Garage Paradox."

Revised October 13, 1997.