What Is Matter?

What Is Matter? February 26, 2012

Learn in a couple minutes:

I ran this by a padawan physicist (i.e., a physics graduate student) and here was his verdict on the accuracy:

It’s cute and amusing, but accurate. There are two caveats I’d add though. Pauli exclusion principle prohibits two electrons from being in the same state, or two muons from being in the same state, but an electron and muon can be in the same state. So electrons (and matter made up of electrons) ‘take up’ space in the respect that they prohibit other electrons from entering it, but matter made of a different species of particle would not be prohibited from entering the space ‘taken up’ by electronic matter. It’s not too important a point though, since matter in the real world is made up of electrons and atomic nuclei.

The other is that the Pauli exclusion principle applies to different species of particles called fermions, with intrinsic angular momentum with half-integers of the reduced Planck constant, but it does not apply to bosons, with integer spin. (Photons and the Higgs are examples of bosons.) So photons don’t take up space, and neither does light, in any regard.

So I don’t know whether light/radiation qualifies as matter, and I think in the past it was considered something different than matter. I guess it depends on who you ask. But this is probably because ‘matter’ isn’t really a technical term with a specific definition in physics.

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