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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.

Making More Tracks

Age 16 to 18
Challenge Level

We know the coordinates of the rear wheel. We need to find the coordinates of the front wheel. To do this think about the instantaneous direction of travel of the rear wheel of the bike at any moment in time as it travels along its curve. How far away and in what direction is the front wheel located?

For the conjecturing, always relate back to the physical experience of riding a bike.