If we place x'=x-vt, it is clear that a point at rest in the system k must
have a system of values x', y, z, independent of time.
xi = (x-vt) / sqrt(1-v^2/c^2)
xi = x' * beta where beta = 1/sqrt(1-v^2/c^2)
He [Einstein] wrote the lowercase greek letter Xi instead of x', -- Sylvia
Ref , Jan 1st, 2013
What a way to begin a new year - change Einstein's notation and then change
Poor sick sad Sylvia the psychopathic bigot.
-- This message is brought to you from the keyboard of
Lord Androcles, Zeroth Earl of Medway.
When I get my O.B.E. I'll be an earlobe.