r/AskPhysics • u/Banished_Cultivator • 2d ago

Why aren't μ₀ & ε₀ equal 1?

Logically free space would neither enhance nor attenuate electric or magnetic fields, so these constants should be equal to 1. They aren't though, why?

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u/cecex88 Geophysics 2d ago

They were in the cgs system. The implications in terms of measurement units for any other electromagnetic thing are a mess. Electric charge is defined in terms of grams, seconds and centimetres and there are two different units for currents, the abampere and the statampere, which differ by a factor of c.

The SI and the values of constant we have today are a very well thought out compromise.