Key takeaways

  • Scientists at Fermilab conducted the Muon g-2 experiment, achieving results that suggest we might discover a fifth fundamental force, challenging the current Standard Model of particle physics.
  • The Standard Model explains how particles and forces interact, but it has limitations, especially with complex phenomena like dark matter and quantum mechanics. This experiment hints at gaps in our understanding.
  • The experiment measured the magnetic moment of muons with double the precision of previous attempts. A muon behaves like a tiny magnet, and the measurements didn’t match the predictions of the Standard Model.
  • The discrepancy between the experimental data and the Standard Model’s predictions suggests that there might be an unknown particle influencing the results, possibly indicating a fifth force.
  • The Muon g-2 experiment will continue for three more years, with researchers expecting even more precise measurements. This ongoing research could lead to groundbreaking new physics, expanding our understanding of the universe.

When pushing science to its boundaries, you often want an experiment to provide one of two results. First, you want to see a favorable result—something that verifies your models and assumptions and says, “Yes, what we thought we understood? We do, indeed, grasp it.” Second, you want to see an outcome that validates our lack of knowledge.

Fermilab researchers conducted an experiment known as Muon g-2 (pronounced “muon g minus two”). They recently revealed that they have successfully replicated their results with double the precision. So, what was the outcome? Oh, nothing much… just the possibility that we’re going to discover a fifth, previously undiscovered basic force that contradicts the entire Standard Model of particle physics.

That sounds like a huge deal, and it is. It’s understandable if this seems unclear. Let’s step back a little.

We’ll start with the Standard Model, which serves as a model for almost everything. As far as we know, everything in existence is made up of fundamental particles and governed by fundamental forces. There are four known fundamental forces in nature: electromagnetism, the strong nuclear force, the weak nuclear force, and gravity. The Standard Model describes how all of the basic particles and forces interact (with the exception of gravity, which is in its own bucket). It has been able to anticipate and explain a wide range of scientific occurrences.

However, the Standard Model is also imperfect. Researchers have been finding holes in the concept, particularly as we’ve begun to investigate more sophisticated physics, such as dark matter, what happens within black holes, and how quantum mechanics works. That doesn’t imply it’s awful, incorrect, or worthless. It just cannot express everything. And as we’ve been able to conduct increasingly complicated tests, we’ve seen an increasing number of events that the Standard Model cannot explain.

This takes us to the Muon G-2 experiment. The experiment, which had been planned for many years, attempted to obtain extremely accurate measurements of the behavior of something known as a muon’s magnetic moment. A magnetic moment functions as a very small magnet within a particle, controlling how it travels through a magnetic field. And a muon is just a very large electron.

Researchers sent a stream of muons through a superconducting magnetic storage ring, where they spun about 1,000 times at nearly the speed of light. The ring was packed with detectors that allowed researchers to get highly exact measurements of the muons’ magnetic moments, which they could then compare to the Standard Model’s predictions.

When they compared the predictions, they discovered that they did not match the experimental data. While this experiment has yet to explain why the two numbers differ, the fact that prediction and actuality create two distinct results suggests one thing: we’re missing something. And if we miss anything in an experiment based on the Standard Model’s predictions, then follows that the Standard Model is also missing something.

“If the measurements don’t match the prediction, it could indicate the presence of an unknown particle in the loops—which could, for example, be the carrier of a fifth force,” particle physicist Jon Butterworth told The Guardian.

More data on this experiment will be collected over the next three years because it is currently ongoing. And the team anticipates the next round of research to produce a reading even more exact than this one, just as this current finding is twice as precise as the first.

However, based on what they have previously discovered, hypotheses are emerging. The team believes that this might be a previously unknown basic force, bringing our total to five and revealing a whole new understanding of the underlying physics of our world.

If they are correct, this isn’t simply a novel finding. It would be completely new science.

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