- #1

A. Turner

- 3

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While I understand the significance of natural units, I am wondering why, in SI units, we are able to assign μ0 an exact value. The speed of light is experimentally determined in m/s, and given the relationship derived from Maxwell's equations, we know that c^2 = 1/√(ε0μ0). Thus by assigning μ0 an exact value of 4π*10^-7 in SI units, we are also defining the value of ε0. Thus we have defined the proportionality of charge to force in SI units -- which should be an experimentally derived value. So where am I going wrong here?

It must be that we are not actually 'choosing' the value of μ0. But then how is it exact in SI?

Thanks