It turns out that in order to answer that question, you need a little of quantum ... the history of chemistry," a 1978 paper on the topic explained. "It seems to be mainly a relativistic effect." ...

Finally, relativistic quantum processes can be studied in laboratory during laser-target interactions, where high-energy events like electron-positron pair productions occur in a plasma environment.

Besides quantum theory, general relativity is one of two pillars of modern physics – our working theory of gravity and of the very large, of planets, galaxies and the universe as a whole.

But to understand how things work in the real world, quantum mechanics must be combined with other elements of physics – principally, Albert Einstein’s special theory of relativity ...