According to Wickipedia, affine geometry does not have a metric notion of length and angle. I have a series of videos on geometry for quadrature which deal with what I think is affine geometry. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-RX_ZHDQkyGo.html
Good question! *Absolute* length is when you say I ran 10 kilometers today. *Relative* length is when you say I ran twice as far today compared to yesterday.
@@MathTheBeautiful How would you verify that your reference length is one unit long? Ans: you can't. So what is absolute length? I understand that "1 meter" is a practical definition. But in itself doesn't help in constructing a concept of length. Ask yourself "how long is a line". Ans 1: twice as long as half a line. I.e., a line can be used as a reference length. Call it a meter if you like, but the choice of it's length and name are arbitrary I.e., there are two magnitudes. One is geometric, the other is algebraic. Neither one is absolute.
