# cgs Gauss' system of units

I had never seen this system until today, and I'm really confused. I've read the wikipedia article about it but I still don't know how to change between this and the international system. For example, studying emision of radiation of an electric dipole: $\wp$, one gets to an equation for the magnetic potential given, in Gauss' system, by:

$$A=\frac{1}{cr}\dot\wp$$

How could I change that? I don't know how to deal with all the $4\pi$ that appear over there, and how are $\mu$ and $\epsilon$ constants omitted.

Thanks

EDIT: From the table at that wiki article I can just change the $c^{-1}$ by $\mu_0/4\pi$, but given that gaussian system just changes a lot of constant by 1, I have doubts about that.

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– Mark Eichenlaub Mar 29 '13 at 17:26
@MarkEichenlaub Ok, generally, I understand where both systems come from, but I still have not clear how to change between systems. The only thing I could do is to go to the beginning and start deriving in both systems to see the differences. – MyUserIsThis Mar 29 '13 at 17:29
It's not really possible to safely translate formulae from one of the CGS systems to SI. However, you may use the table above to do the opposite. The former is impossible because SI is sort of redundant, it introduces both $\epsilon_0$ and $\mu_0$ so that $\epsilon_0 \mu_0 c^2=1$ but because there is an independent electric unit, Ampere, one covers CGSM and CGSE etc. simultaneously. But some of these constants $\epsilon_0,\mu_0$ get lost in any CGS, they're set to one, so there's no way to reliably guess where $\epsilon_0$ or $\mu_0$ should be restored when returning to SI. – Luboš Motl Mar 29 '13 at 18:42
And I've never seen $\wp$ used for anything outside of pure math. – Chris White Mar 29 '13 at 20:08
@LubošMotl Thanks, that's both relieving and it sucks. I will try to get used to cgs Gauss' system as I am seeing it is actually used. – MyUserIsThis Mar 29 '13 at 20:14