Oh, wow, oh, oh, whoa, oh, wow.

Oh, wow.

Oh, wow. Hello, you're listening to The Science of Everything podcast, episode 159,

Quantum Electro Dynamics Part 2. I'm your host, James Fodor. In this episode, we are continuing

quantum electrodynamics, as the name indicates, and we're picking up straight from where we left off

last time, so please do listen to that episode before we listen to this one.

Otherwise, it's not going to make very much sense. I will very briefly recap what we discussed then.

I talked about how quantum electrodynamics is the first of the quantum field theories,

and it's an attempt to generalize the Schroenger equation to applying to cases where

special relativity is important, so very like high velocities. And to do that, we need to make a

variety of, essentially modifications to the Schroenger equation to produce first, we talked about

the Klein-Gordon equation, and then I talked about the Dirac equation and the gamma matrices

and the complicated algebra that that introduces as we need to deal with electron spin.

I then talked about the S matrix and perturbation theory,

which is essentially a way that we are able to describe the

interactions between particles in quantum field theory, particularly like electrons and photons.

The Dirac equation describes the free propagation of electrons, and the Klein-Gordon equation,

or a modification of the Klein-Gorn equation describes the free propagation of photons.

But when we want to describe the interaction of both of those, we need to use the S-matrix and perturbation theory.

And there's a long series of complicated approximations that needs to be made there.

And we talked about Wix theorem and propagators.

We finished up just leading up to introducing the approximations that are needed to actually

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