The strange history of the quantum world is too long for a single article, but it covers the period from 1905, when Einstein first published the solution to the photoelectric puzzle, to the 1960s, when a complete, well-tested, rigorous and insanely complex solution emerged. The quantum theory of the subatomic world has finally been revealed, it’s quite a story.

This quantum theory will provide its own complete and holistic revision of our understanding of light. In the quantum picture of the subatomic world, what we call the electromagnetic force is actually the product of countless microscopic interactions, the work of indivisible photons interacting in mysterious ways. It’s literally like a mystery. Quantum structure does not provide insight into how subatomic interactions actually occur. Instead it gives us a mathematical toolset for calculating predictions. While we can only answer questions about how photons actually work with a shrug, we at least have some predictive power that will help ease the pain of quantum uncertainty.

It is very difficult to do physics in quantum mechanics, that is, to make predictions using mathematical models to verify an experiment. This is because quantum rules are not ordinary rules, and in the subatomic realm all bets are off.

Interactions and processes at the subatomic level are not governed by the predictability and reliability of macroscopic processes. Everything makes sense in the macroscopic world (mainly because we have evolved to understand the world we live in). I can throw the ball to a kid so many times that his brain can quickly detect a reliable pattern: The ball leaves my hand, the ball follows an arc, the ball moves forward and eventually lands on the ground. Of course, there are differences depending on speed, angle and wind, but the basic essence of the ball thrown is always the same.

This is not the case in the quantum world, where perfect prediction is impossible and reliable assertions are lacking. On a subatomic scale, probabilities rule the day; It is impossible to say exactly what any particle will do at any given moment. And this lack of predictability and reliability first worried and then disgusted Einstein, who eventually left the quantum world behind and shook his head in regret at his colleagues’ flawed work. And so he continued his work, trying to find a unified approach to combining two known forces of nature, electromagnetism and gravity, into a structure that was decidedly non-quantum.

When two new forces (strong and weak nuclear forces, respectively) were first proposed to explain the inner workings of the atomic nucleus in the 1930s, this did not stop Einstein. Once electromagnetism and gravity were successfully combined, working with the new forces of nature would not require extra effort. Meanwhile, their quantum-inclined contemporaries happily embraced the new powers and eventually incorporated them into the quantum worldview and structure.

By the end of Einstein’s life, quantum mechanics could describe three forces of nature, whereas gravity was separate, and his theory of general relativity became a monument to his intelligence and creativity.