Dirac on Theoretical Physics

Here's a video clip of Paul A.M. Dirac explaining how theoretical physicists worked -- or, at least, how HE worked:

 

He was British, and his full name was Paul Adrien Maurice Dirac. I'm surprised I still remember that.

The Schrodinger equation wasn't consistent with Einstein's special relativity. Among other things, it got the spin of the electron wrong. (In fact, Schrodinger didn't include spin at all.)

Dirac derived the relativistic Schrodinger equation, consistent with Einstein, and, miraculously, it correctly predicted the spin of the electron (within a few percent; quantum electrodynamics--the field theory of relativistic quantum mechanics--would do the rest). Here's what Dirac's equation looked like:

That's kind of messy, though the Wiki page explains it. Psi is the usual wave function of quantum mechanics, although in Dirac's theory it's a 4-dimensionl vector. (In Schrodinger it's just a regular function over all of space and time, what physicists call a "scalar.") But my generation, and the one before, and those following know it as:

It's just mathematically simpler. Moreover, now we set c=1 (the speed of light), and, for that matter, G=hbar=k=1, where G is Newton's gravitational constant, hbar is Planck's constant divided by 2*pi, and k is Boltzmann's constant. These constants simply set the scale of dimensions, and can always be added back if you're looking for real-world predictions.

{If you're said it will take you "an hour" (or whatever) to drive from home to you grandma's, you did the same thing with units, taking your velocity to be =1.}

I don't think I've ever solved the Dirac equation except for a free electron, as has every other graduate student in physics, but I once saw a PhD dissertation that solved it for the hydrogen atom. It was nontrivial.)

Anyway...when he was a young physicist in Europe, Dirac derived his equation from general considerations, a real tour-de-force of both quantum mechanics, special relativity and mathematics for its time. It was better than Schrodinger.

Dirac was a little weird, no doubt an advantage:

His colleagues in Cambridge jokingly defined a unit called a "dirac", which was one word per hour.

This likely contributed to his great success. Dirac put forth his equation in 1928, and by 1933 won the Nobel Prize in physics, along with Schrodinger. Dirac has just turned 32 years old.

Wiki:

"After having relocated to Florida to be near his elder daughter, Mary, Dirac spent his last fourteen years of both life and physics research at the University of Miami in Coral Gables, Florida, and Florida State University in Tallahassee, Florida."

Dirac did other notable work besides his relativistic wave equation, but nothing on its scale, and it's what he will forever be known for. 

So I found it really interesting to watch him talk about what made him tick.