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Which Twin Is Older?

A simplified account of special relativity and the twins paradox.


In a snooker game the brown ball was on the lip of the pocket but it could not be hit directly as the black ball was in the way. How could it be potted by playing the white ball off a cushion?


Draw three equal line segments in a unit circle to divide the circle into four parts of equal area.

Scale Invariance

Age 16 to 18
Challenge Level

Peter Townsend succesfully solved this fascinating problem, providing us with one of the best solutions we've ever recieved. Awesome!