Einstein’s beef with quantum physics, explained | Jim Al-Khalili for Big Think

• Einstein is celebrated for giving us the special theory of relativity. The fact that nothing goes faster than light, time is the fourth dimension, but he didn't come up with the equations. That was the interpretation, the narrative of the equations, and it's the same with any other theory in physics.

With quantum mechanics, it's different. We have the equations of quantum mechanics, but we can't agree on what that equation means. Schrodinger's equation being the most famous one, we can crank the handle and produce numbers from the equation, but the narrative, the story, the explanation is still something that we are arguing about. And that bugs me.

By the end of the 19th century, it was already known that we needed some new physics to explain mysterious phenomena - X-rays - like radio activity, that energy seemed to be coming out of nowhere, to understand the behavior or the structure of the atom. And so when quantum mechanics came along, it wasn't because physicists were sitting, scratching their heads thinking, "There must be some deeper understanding of the nature of reality. I know, let's come up with quantum mechanics." It was forced on physicists because of experimental results that were inexplicable.

It's a fuzzy, probabilistic world. Things are never behaving in one way for certain; atoms can have two energies at the same time, electrons can be in two places at the same time, particles aren't discreet, little lumps; they can sometimes behave like spread-out waves of probability. It's really down at a level far beyond anything that we can visualize or imagine.

If we think about everyday objects, a tennis ball, for example, subject to the laws of Newtonian mechanics; you drop down, orders of magnitude, down to a millimeter, down to a micrometer, down to the scale of individual cells or bacteria. Ultimately, when you get down to something like a billionth of a meter, then you start to encounter the fuzziness of the quantum world.

The founding fathers of quantum mechanics in the 1920s, people like the Danish Physicist, Niels Bohr, Werner Heisenberg, Wolfgang Pauli - and they realized they could make predictions for the results of measurements, but you only make the connection with the real world if you look. So that's how they got away with not needing a narrative, the 'shut up and calculate interpretation.' More correctly, it's known as the 'Copenhagen narrative.'

But now, many physicists, including myself, argue that it's not a narrative at all; it's a bury your head in the sand approach. Einstein was very unhappy about this, by the way; he said, "No, look, the job of physics is to know and understand how the world is, not just to make predictions about the results of experiments and that sort of operationalist view. Well, fine, that's useful but that doesn't give us real understanding." That's why we still need a narrative.

The knowledge of quantum mechanics together with Einstein's theories of relativity really gave us the modern world. We wouldn't have developed an understanding of materials and how they conduct electricity, so we wouldn't have understood semiconductors; we wouldn't have developed silicon chips; therefore, we wouldn't have computers. I wouldn't be talking here in this medium today were it not for our quantum understanding.

But there are aspects of the quantum world that are more mysterious. Quantum entanglement, for example, the idea that let's say, two electrons that are separated in space can nevertheless somehow behave in a coordinated way. There are speculative ideas about whether space itself is connected together via quantum entanglement.

We don't all need to be experts in quantum mechanics; not even the smartest quantum physicists knows how stuff goes on inside their smartphone. But we are going to be developing ideas like quantum cryptography, quantum computing, quantum sensors - these are ideas and technologies that are going to affect us in our daily lives, so we do need to have enough of an appreciation of the science simply to know what to trust, who to trust. As we peel back layers of t...