[jfoutz]

I recall some effort in moving from imperial measurement to metric. Reality itself does not care, but the math sure gets easier if you carefully select units.

Actually, another neat example is analog vs digital computation. your models can get very different answers. I recall some Mandelbrot guy talking about that.

[retzkek]

See Gaussian (cgs) units for an example, compare Coulomb's law in cgs and SI: https://en.wikipedia.org/wiki/Gaussian_units#Unit_of_charge