Wrong, But That's Alright

Writing at Backreaction, physicist Sabine Hossenfelder points out an important feature of the discipline called "quantum mechanics." It is, she says, wrong.

Given that Dr. Hossenfelder is a theoretical physicist, this could seem counterproductive to her work. But as she explains, what ails quantum mechanics ails every scientific worldview so far created by human beings. Classical Newtonian mechanics, for example, is "wrong" because it does not correctly describe the behavior of very very small or very very fast objects. But if you decide you want to become a champion at billiards, immersing yourself in Newtonian physics would be a good step to take.

Quantum mechanics, Dr. Hossenfelder says, assigns quantum properties to the particles that make up the atoms that make up things. "Quantum properties" in this case means the attributes that are held by matter's most basic building blocks, such as (in some cases) being both and neither a wave nor a particle until a measurement is taken -- and then becoming either a wave or a particle depending on what is being measured for.

But the interactions between quantum particles also have quantum properties, and the realm of science that tries to probe and explain this phenomenon is called "quantum field theory." It's necessary because basic old quantum mechanics doesn't involve the extra level of weirdness added when the particle interactions come into play. Like Newtonian physics can't explain the very small and very fast, quantum mechanics can't explain what happens when this "second quantization" occurs.

It's sort of a matter of frames of reference, although those are my words rather than Dr. Hossenfelder's. Within the frame of reference of everyday activity and normal-sized objects, Newton's your guy. As mentioned before, the very small and very fast require a call to the bullpen for Einstein. But to account for the strangeness added when the interactions between the very very small are considered, you have to bring in Paul Dirac and company.

Even though it's wrong, there are a lot of occasions when quantum mechanics proves very useful for explaining some of the things going on in the universe. Dr. Hossenfelder paraphrases a statistician named George Box, who said, "All models are wrong, but some are useful." Wisdom, it would seem, would come in knowing which models are useful in which situations, and when they might need to be laid aside for others.