I am studying electromagnetism and have encountered the Heaviside-Lorentz unit and Gaussian unit. In these unit systems, the constant $c$ keeps occurring. For example, the Maxwell equations are of this form. enter image description here

So, I think in these unit systems, $c$ is some nontrivial constant other than $1$. However upon reading the Wikipedia about natural units, it states that the Heaviside-Lorentz unit and the Gaussian unit are natural units and $c=1$. So I am confused. Why does $c$ keep occuring in the two units if $c$ is jus equal to $1$? Could anyone please explain?

https://en.wikipedia.org/wiki/Natural_units#Electromagnetism_units : This is the link to the Wikipedia about natural units that I read.

  • $\begingroup$ It doesn't say they are natural units. $\endgroup$ – secavara Feb 16 '18 at 15:27
  • $\begingroup$ It says. "There are two main natural units for electromagnetism." $\endgroup$ – Keith Feb 16 '18 at 15:34
  • $\begingroup$ Oh that's poorly written. They become natural if you take $c=1$. $\endgroup$ – secavara Feb 16 '18 at 15:48
  • $\begingroup$ So, that means I can take $c$ not to be $1$? So, in the above Maxwell equations, $c$ is not $1$ and therefore not omitted? $\endgroup$ – Keith Feb 16 '18 at 16:05
  • 1
    $\begingroup$ Yes, unless you are specified to work in natural units, you are expected to keep the $c$'s in these electromagnetic unit systems. For a complete description of unit systems you can check the appendix in Jackson's book, Classical Electrodynamics, 3ed. $\endgroup$ – secavara Feb 16 '18 at 16:09

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