Seems to be the first time this was confirmed via direct experimental observation of the orbitals:

  “This idea that relativity is important in heavy elements has been around since the 1970s,” said Lai-Sheng Wang, a professor of chemistry at Brown and the study’s corresponding author. “But we show direct spectroscopic evidence that what we learned in high school about chemical bonding isn’t true in heavy elements."

Yes: the article says "since the 70s"

The Dirac equation which is the equation for describing the wavelike behavior of electrons. It predicted the existence of antimatter and particle spin.

You start with the Schrödinger equation, add relativity to get the Klein-Gordon equation which is a mess because it's second order in time involving negative probabilities, if you in ways "take the square root" of it you get the Dirac equation.

Relativity has been part of the understanding of electrons since 1928.

https://en.wikipedia.org/wiki/Dirac_equation

There's even a Wikipedia page for it https://en.wikipedia.org/wiki/Relativistic_quantum_chemistry

Gold electrons at inner orbits travel at a large fraction of the speed of light, which is why gold isn't a silver color. That is really neat.

I don’t get it, someone explain? Doesn’t everything get color from relativistic effects?