The emu-cgs ( or " electromagnetic cgs " ) units are one of several systems of electromagnetic units within the centimetre gram second system of units; others include esu-cgs, Gaussian units, and Lorentz Heaviside units.
12.
Can anyone tell me where / when c was first used as the symbol for the speed of light ( or for an equivalent like Maxwell's ratio of the electrostatic to electromagnetic unit, which has the dimension of length / time )?
13.
In the old " electromagnetic ( emu ) " system of equations defined in the late 1800s, " k " m was chosen to be a pure number, 2, distance was measured in centimetres, force was measured in the cgs unit dyne, and the currents defined by this equation were measured in the " electromagnetic unit ( emu ) of current " ( also called the " abampere " ).
14.
The discovery of this relationship started in 1855, when Wilhelm Eduard Weber and Rudolf Kohlrausch determined that there was a quantity related to electricity and magnetism, " the ratio of the absolute electromagnetic unit of charge to the absolute electrostatic unit of charge " ( in modern language, the value 1 / \ sqrt { \ mu _ 0 \ varepsilon _ 0 } ), and determined that it should have units of velocity.
15.
There are lots of logical problems with these claims ( essentially, they are impossible to measure because there is no reference unit to compare against ), which I tried to explain to him on the above Talk page, but ultimately the objection from Wikipedia's standpoint is that he is unable to provide sources, hence the above claims are original research . ( There are, of course, references to the contrary, but he claims to understand electromagnetic units better than the referenced sources, e . g . better than Jackson, author of the canonical graduate textbook " Classical Electrodynamics ", or otherwise he redefines " vacuum " in a nonstandard circular way to claim that the references are irrelevant .)
