[removed]

The Dirac equation (1928) is basically the relativistic version of the Schrödinger equation (1925). It still came with the same limits - interactions are not modeled well, you can only look how particles behave in external fields.

QFT is based on special relativity, it wouldn't work without it.

The question is about special relativity, not general relativity.

Klein-Gordon equation [1] (1926) is also important to mention when it comes to early days of relativistic quantum mechanics.

[1] https://en.wikipedia.org/wiki/Klein%E2%80%93Gordon_equation#History

De Broglie's matter wave theory in 1924 appears to start from special relativity.

He assumed matter had energy frequency relationship the same as photons, then calculated the apparent wavelength seen by a moving observer based on the Lorentz transformation.

So QM was actually based on relativity from the start.

I'm still amazed by the level of insight, inspiration and daring in going from Klein Gordon to Dirac.

"Hmmm. This naive way of introducing relativity into QM gives us an equation that doesn't appear to describe the electron. What if we made it four-dimension? Oh, and what if we interpret the negative energy solutions as particles, too? And what's this weird behavior of the thing under rotation? Let's call that spin".

It's even deeper than that. Dirac noticed that the Klein-Gordon equation didn't produce a positive-definite current density, ρ. There were thus issues with interpreting it as a probability. He postulated a new equation and required that is linear in ∂/∂t, unlike the K-G equation. This would result in the associated continuity equation (the one that would describe the continuous probability) describing an acceptable probability. This immediately lead to other conditions (namely, the equation has to be linear in ∇) due to Lorentz Covariance. He realized his equation had the form of:
i∂ψ/∂t = (-iα•∇+βm)ψ
What are α and β? The hisory goes as "he immediately understood those were 4×4 complex-entries hermitian spinors, with trace 0, determinant and eigenvalues ±1, and that they could be of higher dimension than 4×4 but then this dimension would need to be even"

He no joke deserved his Nobel Prize

[removed]

[deleted]

[removed]

Niels Bohr postulated his atomic theory (circular orbitals) in 1913 in order to describe the spectra of hydrogen. A few years later, Arnold Sommerfeld extended Bohrs Model by considering elliptical orbitals and relativistic effects, since the electron is moving with around 1% of the speed of light. With this extension, sommerfeld could explain for the very first time the finestructure of the hydrogen spectra. This agreenemt confirmed not only Bohrs atomic theory, but is also considered as the first experimental verification of einsteins special theory of relativity. Back then, it was only 10 years old and quite controverse

[removed]