“Spin” is a fundamental quality of elementary particles like the electron, which evokes images of a tiny sphere spinning rapidly on its own axis, like a planet in a shrunken solar system.
Only it isn’t. It can’t. On the one hand, electrons are not balls of matter, but points that are described by probability mathematics.
However, physics philosopher Charles T. Sebens of the California Institute of Technology argues that such a particle-based approach to one of physics’ most accurate theories could mislead us.
By framing the foundations of matter primarily in terms of fields, certain quirks and paradoxes that arise from a particle-centric view melt away.
“Philosophers are drawn to problems that have been unsolved for a very long time,” says seven.
“In quantum mechanics, we have ways to predict the results of experiments that work very well for electrons and explain spin, but important fundamental questions remain unanswered: Why do these methods work and what happens inside an atom?”
For nearly a century, physicists have wrestled with the results of experiments that suggest the smallest bits of reality don’t look or behave like objects in our daily lives.
Spin is one of those qualities. Like a spinning cue ball colliding with the inside wall of a pool table, it carries angular momentum and affects the direction of a moving particle. However, unlike a cue ball, a particle’s spin can never speed up or slow down – it’s always limited to a certain value.
To make the fundamental nature of matter even harder to understand, consider the fact that an electron is so small that it effectively lacks volume. If it were large enough to have volume, the negative charge spread across that space would push on itself, tearing the electron apart.
Even if we were benevolent and allowed the electron, as a particle, to have the largest radius that experiments would allow, its rotation would exceed the speed of light – something that may or may not be a deal-breaker on this scale, but it is sufficient for many physicists to dismiss the talk of rotating electrons.
One way to make the carpet of fundamental physics a little easier to map is to describe points of matter as actions embedded in the fabric of a field, and then interpret those actions as particles.
quantum field theory (QFT) successfully does this by weaving together aspects of Einstein’s special theory of relativity, classical field theory and the particle propositions of quantum physics.
It’s not a contested theory, but there’s still debate as to whether these fields are fundamental—exist even if the flares passing through them were to go silent—or whether particles are the key players that carry vital information and fields are just a convenience are script.
To us it may seem like a trivial distinction. But for philosophers like Sebens, the implications are worth exploring.
As he explained in a 2019 article in aeon Magazine: “Sometimes advances in physics first require a backup to reexamine, reinterpret, and revise the theories we already have.”
This revisit of quantum field theory emphasizes several significant advantages in prioritizing fields in physics over a particle-first approach, including a model that reimagines electrons in ways that could give us better insights into their behavior .
“In an atom, the electron is often represented as a cloud that shows where the electron might be, but I think the electron is actually physically distributed throughout that cloud,” Sebens said says.
By having an electron physically distributed over a field and not confined to one point, it could actually spin in ways that are less mathematical constructs and more a physical description.
While it still wouldn’t be a tiny planet in a solar system, this rotating electron would at least be moving at a speed that doesn’t challenge any laws.
How this diffuse spread of negatively charged matter resists blasting itself is a question Sebens has no answer to. But by focusing on the field aspects of a propagated electron, he considers all solutions to make more sense than problems arising from particles of infinite confinement.
There is a quote that has become folklore in the halls of quantum theorists – “Shut up and calculate.“It has become synonymous with that aphantastic landscape of the quantum realm, where imagery and metaphor cannot compete with the uncanny precision of pure mathematics.
However, every once in a while it’s important to pause our calculations and challenge a few old assumptions — and maybe even reverse to a new perspective on the fundamentals of physics.
This paper was published in synthesis.
