Quote Originally Posted by hitmandonny View Post
We would double at the same time. The sapce would appear the same and everything you would try to measure would be twice as big. Therefore the unit remains the same or equivalent, as I said algebra.
x=y
2x=2y
Metres and millimetres are measured using the speed of light and time, a metre being roughly one three hundred millionth of a light-second (the distance light travels in a second.) Both time and the speed of light would be unaffected if everything doubled in size, so a milli/metre would still be the same size it was previoulsy.