The Meaning of Relativity / Four lectures delivered at Princeton University, May, 1921

by Albert Einstein

' and a diameter of this circle. Imagine, further, that we have given a large number of rigid rods, all equal to each other. We suppose these laid in series along the periphery and the diameter of the circle, at rest relatively to

'. If

is the number of these rods along the periphery,

the number along the diameter, then, if

' does not rotate relatively to