What is quantum mechanics trying to tell us?

Classical physics didn’t need any disclaimers. The physics that was born with Isaac Newton and governed until the early 20th century seemed straightforward: matter was like little billiard balls. Accelerates or decelerates when exposed to forces. None of this needs any special explanations attached. Details can get messy, but there was nothing weird about it.

Then quantum mechanics came along, and it all got weird pretty quickly.

Quantum mechanics is the physics of atomic scale phenomena, and it is the most successful theory we have ever developed. So why are there thousands of competing interpretations of the theory? Why does quantum mechanics need an explanation at all?

Basically, what are you trying to tell us?

state affairs

There are many quirks in quantum physics – many ways in which it differs from the classical view of the world of well-known particles with properties that can be perfectly described. The weirdness you focus on tends to be your preferred interpretation.

But the strangeness that stood out the most, and which shaped most interpretations, is the nature of the “superposition” and analogy in Quantum mechanics.

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Everything in physics comes down to describing what we call a state. In classical physics, the state of a particle was only its position and momentum. (Momentum is related to velocity.) Position and velocity can be known as accurately as your equipment will allow. Importantly, the condition was never related to taking a measurement – you never had to look at the particle. But quantum mechanics forces us to think about the state in a completely different way.

In quantum physics, a state represents the possible outcomes of measurements. Imagine you have a particle in a box, and the box has two accessible chambers. Before the measurement is made, the quantum state is in a “superposition,” with one term for a particle in the first chamber and another term for a particle in the second chamber. Both terms exist simultaneously in the quantum state. The superposition is said to “collapse” only after the measurement has been made, and the condition has only one term – the term that corresponds to seeing the particle in the first chamber or second chamber.

What does quantum mechanics mean?

So what is going on here? How can a particle be in two places at the same time? This is also like asking if particles have properties of their own. Why should making a measurement change anything? And what is the exact measurement? Do you need someone to take a measurement, or can you say that any interaction at all with the rest of the world is a measurement?

These kinds of questions have generated library value for so-called quantum explanations. Some of them are trying to preserve the classical worldview by finding a way to reduce the role of measurement and preserve the reality of the quantum state. Here “truth” means that the state describes the world itself without reference to us. At the extreme end of this is the “many-worlds interpretation”, which makes every possibility in a quantum state a parallel universe that will materialize when a quantum event – a measurement – occurs.

This kind of explanation is wrong for me. My reasons for saying this are simple.

When the inventors of quantum mechanics broke with classical physics in the first few decades of the twentieth century, they were doing the best of what creative physicists do. They were finding new ways to predict the outcome of experiments by creatively constructing ancient physics while expanding it in ways that embraced new behaviors seen in the lab. This took them in a direction where measurement began to play a major role in describing physics as a whole. Time and time again, quantum mechanics has shown that at the heart of many of its strangers lies the role of a person who acts in the world to obtain information. This to me is the central lesson that quantum mechanics is trying to teach us: that we participate, in a way, in describing the science we do.

Now to be clear, I’m not arguing that “the observer affects the observed”, or that physics needs a place for some sort of cosmic mind, or that consciousness reaches into the machine and changes things. There are more subtle and interesting ways to hear what quantum mechanics is trying to tell us. This is one of the reasons I find so much to like about the named explanation QBism.

What matters is trying to look at the heart of the issue. After all, after all is said and done, what does quantum mechanics refer to? The answer is that it refers to us. It’s trying to tell us what it means to be a subject embedded in the universe, to do this amazing thing called science. To me, this is just as exciting as a story about the “God’s Eye” view of the universe.