God and Quantum Mechanics, Part 1 – Einstein

“*If I were not a physicist, I would probably be a musician*.” – Albert Einstein*

(NOTE – A lot of the history here I have adapted from comments by Leonard Susskind in his Stanford Lecture #9 on Quantum Mechanics (2008) on YouTube.)

The name “Einstein” is German for “one stone” or “a stone”. No one talks about that often, probably because it doesn’t matter. The only sense in which I can relate it to Einstein the man is in the sense of Peter being the “rock” of the Christian church. Almost everything we think about physics today has something to do with Einstein’s work, even his errors.

You’ve probably heard the joke about the narcissist who believed the only mistake he ever made was that once he thought he’d made a mistake but hadn’t. That sort of happened to Einstein with the cosmological constant. Also, his battles with other physicists over the question of the fundamental nature of quantum mechanics, though futile, undoubtedly gave an impetus to those pursuing related lines of thinking that led to groundbreaking ideas that are very much alive today. I’m thinking primarily of Hugh Everett’s many worlds and David Bohm’s pilot waves but there are others.

We relate Einstein mainly to his theories of relativity, which are massive cornerstone works. We often forget that he can be considered the father of quantum theory also. Even though he spent the second half of his life resisting its implications, he was the first to understand those implications. In his 1905 paper on the photoelectric effect, he clearly concluded that light was made of quantized particles, now called photons, and understood and stated that this, along with earlier discoveries, meant that nature is fundamentally not deterministic but probabilistic. He then moved on to relativity, and it took 18 years for the rest of physics to catch up with this understanding.

Physicists were glad for the power of quantum theory to explain previously unexplainable phenomena, but most were still waiting for the “true” wave theory to be discovered so they could stop having to think about those pesky unpredictable photons. It was Arthur Compton’s discovery in 1923 of the effect bearing his name that put paid to that. He showed that the scattering of light by charged particles followed the mechanics of particle interactions, not waves. The evidence was really no stronger than that in Einstein’s 1905 paper, but it seems people were now psychologically prepared to accept it. Three years later with Heisenberg, Schrodinger, and a little after, Dirac, quantum mechanics was put on a solid mathematical foundation that has never been shaken since.

Quantum mechanics is a correct theory for the unassailable reason that it works. It works in a way that is deeper than classical mechanics because it explains things that classical mechanics can’t explain, and we can derive classical theory from quantum theory but not the other way around. Is it the final word? No one can say for sure, but it’s pretty robust.

So, the two cornerstones of modern physics, relativity and quantum mechanics, both trace their origins back to the rock, Einstein.

Why was quantum mechanics so problematic for Einstein? “Probably” because it’s probabilistic, which means it doesn’t actually say anything definite about nature. Since it is the most fundamental theory available to us, other theories can be derived from it and not the other way around, anyone who studies quantum mechanics is eventually disturbed by this.

To see what this means think about one of the simplest possible probabilistic physical experiments, flipping a coin. If you flip it once, you have a 50-50 chance of getting heads and the same chance of getting tails. You have no way of predicting which one (without cheating). Okay, that’s too simple. Now flip that coin 1,000 times. Now the odds say you will get approximately 500 of each, but not exactly. Getting exactly 500 of each is rather unlikely.

Now suppose you and 1,000 of your friends (you’re a popular person) each flip a coin 1,000 times. The odds now say that almost all of you will get approximately 500 heads and 500 tails. Now there will likely be some strange outliers. A few of you may get exactly 500 of each. A few will almost certainly get a whole lot more of one than the other. How many of you how many more? No way to tell exactly.

Would anyone get 1,000 all heads or all tails? It’s not likely, but it’s not impossible. In fact, going back to just your flipping the coin, there is no reason in the world you couldn’t flip 1,000 heads in a row the first time you try. What about all 1,000 of you flipping all heads? What? That’s impossible. Well…no, it isn’t. Just very very unlikely, and you would be very very surprised if that happened. So surprised that you would be certain the coins were rigged, and you would probably be right.

You see the problem?

Quantum mechanics says that every cause and effect is fundamentally like flipping coins or rolling dice. The coins and the dice are definitely loaded, and the results are predictable with a high degree of probability, but still, nothing is certain.

When scientists and engineers design sophisticated equipment like rockets to Mars or your electric toothbrush, they, we, and everyone else would like to be sure the rocket isn’t going to take three turns around the moon then give up on Mars and land in Peoria, and your toothbrush isn’t going to suddenly turn into a small handheld appliance version of Cujo. These things are very unlikely (you can add about a thousand “very’s” to that), but there’s a sense that at some level we want to know that things actually happen as expected – that cause and effect are linked together dependably except for human error. If in addition to human error there is also a hardwired random nature to outcomes, it’s unsettling.

Maybe the fact that Einstein so quickly understood the implications of quantum theory is why he, ahead of everyone else, developed an almost religious quest to undermine it. He failed. It’s the best description of nature that we have, even though it doesn’t describe nature itself at all; it just gives good guesses.

The guesses are very good. Rockets do get to Mars, and toothbrushes do their job peacefully. We don’t have to worry on a day-to-day basis. I think that in his efforts Einstein represented all of us. He understood how important science has become in our lives. We depend on it to be right. Maybe part of his purpose came from not wanting to let us down, even if the odds are incredibly small of that happening.

So where do I get the title of this series? I haven’t mentioned God at all. More to come….

Hugh Moffatt

Watertown, Massachusetts

March 11, 2022

*“If I were not a musician, I would probably be a physicist.” – Hugh Moffatt