May the Forces Be With You

Yeah, I’m a day late.

When you write articles on specific days of the week you can’t fight the calendar. And this year 4 May landed on a Tuesday. Nobody likes to read about a holiday, no matter how fourced, after it happens. I could have posted this episode on Monday, but I knew I needed to promote the blue tits as quickly as possible when I saw they were already hatching. So you’re forced to read this one on Cinco de Mayo.

In a way, though, it’s fitting to explore today’s topic on the fifth.

Although not quite as ubiquitous as another recent topic, the layers of the planet, you might have learned in school that all the natural forces we experience in the universe can be divvied into four distinct classifications: gravity, electromagnetism, the strong force, and the weak force.

Gravity you know well. Toss an apple in the air and it comes back toward the massive Earth. All entities of mass or energy are attracted to each other; that’s gravity. Electromagnetism you also experience all the time. It’s a physical interaction between charged particles, carried by electric or magnetic fields. Electromagnetism is responsible for radiation, including light, in addition to batteries and magnets.

The strong and weak forces might be a little less familiar. They are also known as the strong and weak nuclear forces, which goes a long way to explaining what they do. The strong force is responsible for keeping atomic nuclei together, as it’s an attractive force between protons and neutrons. The weak force is a bit more complicated, but it’s essentially the reason that radioactive decay occurs.

For many moons, these four forces have comprised the standard model of natural interactions.

If you read the article on the new inner inner layer of the core of the planet, you probably know where this story wants to go.

Last month, the physics world erupted in apoplectic hysteria after the results of an experiment hit the wire. Cambridge University professor Ben Allanach reacted, “My Spidey sense is tingling and telling me that this is going to be real. I have been looking all my career for forces and particles beyond what we know already, and this is it. This is the moment that I have been waiting for and I’m not getting a lot of sleep because I’m too excited.”

The moment he waited for came from the Fermi National Accelerator Laboratory (Fermilab) in Batavia, Illinois. There, scientists studied muons, a sub-atomic, fundamental particle. A separate group of scientists from Hungary and California had noted “puzzling anomalies in their experimental data” in relation to muons. They discovered that muons “wobble” at a rate that differs from what the standard model predicts they should when they are subjected to a magnetic field.

The claim that a set of data does not conform to the standard model is big news and requires a lot of repeated testing to confirm the results. For something of this magnitude, the big labs of the world are required. Fermilab devised a set of experiments to test the data rigorously.

The Muon g-2 experiment actually did not provide any conclusive evidence about the muon wobbling. Why then were physicists so titillated? Scientists like to be really sure about discoveries. Experiments need to be repeatable on a mass scale, especially when the subject in question is of such large importance. The Fermilab results weren’t conclusive, but they were really positive. They advanced the claim to “4.1 sigma.” That’s jargon for, essentially, the probability that the claim is correct based on experiments (standard deviation, for those of you who love the maths). 4.1 sigma means there is only a 1 in 40,000 chance that the statistical data are a fluke.

Sounds like pretty good odds, which is why Allanach and theoretical physicists around the globe were losing sleep. But 1 in 40,000 is not good enough to close the door. In order to ordain a proper discovery, scientists need to hit the threshold of 5 sigma, which correlates to a 1 in 3.5 million chance of something being a coincidence.

In other words, it’s extraordinarily likely that we have discovered a new force, but experiments need to get us to a much greater level of certainty before we can add it to the textbooks.

Why does the wobble of a muon mean the discovery of a new force? Mostly because none of the standard interaction forces can cause the change detected in muons.

So what is the new force? Spoiler let-down alert: no one knows. It might be related to undiscovered subatomic particles. Tim Tait, one of the co-authors of the revolutionary paper on the topic, stated the new force seems to act a lot like electromagnetism, but “interacts only with electrons and neutrons – and at an extremely limited range.”

Even though the nature of the force is still a mystery, it could have enormous ramifications across the physics universe. It could explain the expansion of the universe, which has to date been attributed to dark energy, a purely theoretical substance. It could be the key to a Grand Unified Theory, often called the “Holy Grail of Physics,” which might bring together large-scale cosmologies, such as relativity, and the nano-sized realities of quantum mechanics.

It could also simply just be a fifth force that we had never noticed.

If you’ve read this far, you get the final payoff and we circle all the way to the opening.

It’s fitting that I’m a day after May the Fourth Be With You. We had four forces and now we likely have five, so the fifth of May is a proper spot to celebrate.

Some of the possible names for the new force include “flavour force” and “third family hyperforce.” Something referencing Baby Yoda might be more appropriate. Is there a Star Wars character who breaks the fourth wall?

May the road rise to meet you and may all the forces be at your back!