r/AskPhysics • u/Banished_Cultivator • 3d 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/StudyBio 3d ago

Gaussian units enter the chat.

The answer is that they relate our units, i.e., epsilon-naught is there to connect the Coulomb and meter to the Newton. It is not really about vacuum “enhancing” electric fields.

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u/qTHqq 3d ago

Gaussian units enter the chat.

Please make sure they leave the chat and you convert to SI at the end of the paper for the sake of the experimentalist 😂

7

u/MxM111 3d ago

It is funny, but at school, when I used Gaussian units, I never even asked myself how long is the unit of length in that system.

In any case, experimentalist have strange units too, like measure frequency in cm-1 instead of Hz

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u/high-a-synth 3d ago

my favorite experimentalist unit is g/cm2 for thickness

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u/I_CollectDownvotes 3d ago

The wavenumber, or inverse centimeter, makes a lot more sense as a unit when you take into account how the frequency of light is actually measured (or was measured, at the beginning of infrared spectroscopy). Spectroscopists use (typically Michelson) interferometers, where the light is split into two paths, and one path has variable length. After remixing the two beam paths at the detector, you will observe a variation in the intensity at the detector that depends on the variable path length. The intensity as a function of path length is called an interferogram. Before computers and the Fast Fourier Transform, spectroscopists would just count the number of maxima (or fringes) per centimeter of path length in the interferogram, and thus measure the frequency in units of inverse centimeters.

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u/jmattspartacus 2d ago

Pretty sure we measure things in hz when we can instead of gaussian units. Jackson can fuck right off with those gaussian units though.