:Similar to polar diameter, the Earth only has one geometric property pertaining to speed, but that geometric property is a 4-vector ( the Earth's 4-velocity ), not a scalar.
12.
How " real " is a measurement of Earth's diameter from a frame approaching in the direction of the axis at 86.6 % of lightspeed and measuring the polar diameter to be 4000 miles?
13.
There is no self-contradiction with the Earth having an infinite number of different relative polar diameters, because there are obviously an infinite number of different 4-velocities that have nothing to do with the Earth.
14.
I'll call that 4-vector Earth's " polar 4-vector " and define it as being a 4-vector whose magnitude is the proper ( rest ) polar diameter, and whose direction in the Earth's rest frame points from the south pole to the north pole.
15.
:Completely analogous to the Earth's relative speed, there is a scalar that I'll call " relative polar diameter ", that's not a geometric property of the Earth per se, but rather a geometric relationship between the Earth and a 4-velocity that has nothing to do with the Earth.
