the difference between -5 and 5 is 10
so people can make out in diffrent galaxies
because, 2 can go into 5 but if you had 5 and tried to put it into 2 it wouldn't work!
im not quite sure what you mean, but earth is located in the milky way galaxy.
I guess (stress the word guess) it has something to do with the composition of those galaxies and the phenomenon of refraction. Every chemical element refracts a certain colour in the rainbow...