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A spiropath is a sequence of connected line segments end to end taking different directions. The same spiropath is iterated. When does it cycle and when does it go on indefinitely?

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Which Twin Is Older?

A simplified account of special relativity and the twins paradox.

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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?

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!