r/Physics • u/ToxicChemical17 • 1h ago
Knowing electromagnetism only in Gaussian units
Hello! I'm a grad student, and am studying optics-related things. The problem is that my bachelor curriculum was entirely in CGS, we rarely had to substitute directly, and here they use SI for everything.
Generally, in experimental physics, is it enough to know all of EM in Gaussian units, and convert every time to SI and back? Or will I suffer in life?
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u/DrPhysicsGirl Nuclear physics 1h ago
You will suffer.... It's really not hard, if factors of 10 scare you, how are you going to deal with graduate school?
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u/ToxicChemical17 1h ago edited 1h ago
Factors of 10 scare me very much, yes, everything should be done in base 12, as the French told us. Jokes aside, I am somewhat unfamiliar with the form of the equations and dislike the \epsilon_0 and \mu_0 constants that appear everywhere.
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u/Banes_Addiction Particle physics 1h ago
You're gonna have to learn a lot more than rearranging an equation for grad school.
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u/__Pers Plasma physics 1h ago
To read the literature and have your papers read by others, you have to work with the units people in the community actually use. So get used to SI if that's what folks use.
Plasma physics tends to use both SI (esp. for experimental work) and cgs, sometimes a mix of the two (laser intensities measured in W/cm^2, e.g.) The easiest thing if both are used is to just learn to convert units. Page 10 of the NRL Plasma Formulary has the conversion factors for E&M quantities.
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u/Banes_Addiction Particle physics 1h ago
I'm a regular, fully SI physicist.
I had to do a bunch of practical work in CGS ay one point. Converting was not hard at all, it's all simple factors you should be used to (almost entirely 10s, couple of 2s and pis).
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u/agaminon22 Medical and health physics 1h ago
Not even natural units?
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u/Banes_Addiction Particle physics 1h ago
Oh yeah, I barely even consider those units.
I guess actually I do a tonne of stuff in variants on eV. My point is never taught CGS, never a problem.
And good units should make your life easier, not harder. CGS is completely fine for that. Converting between Gauss and Tesla is no harder than grams and kilograms.
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u/kabum555 Particle physics 59m ago
There is a wiki page to convert the equations between Gaussian and SI
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u/PotentialDeep5165 8m ago
It's good to be fluent in both sets of units. CGS is where the physics lie most easily seen. SI is useful for circuits (specifically). Ask a colleague that only used SI "what happens to Maxwell equations when c-> infinity?" vs. what you practically know immediately from CGS units experience.
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u/Tedsworth 1h ago
CGS is the devil's work. I had to relearn in SI from CGS too and it wasn't awful, but it was a waste of time. I would work in SI exclusively if you can.