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Researchers have made some unexpected readings of mysterious particles called muons, which may make us reexamine the Standard Model in physics.

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[♪ INTRO].

The universe is vast, complex and awesome. Despite hundreds, if not thousands of years of scientific endeavour, there’s still so much we don’t know about it.

And that point was hit home this week with results out of Fermilab — a particle physics lab in the US state of Illinois.  . In their experiments, tiny subatomic particles called muons disobeyed the laws of physics as we know them. And if the results hold, the only logical explanation is that there are kinds of matter and energy out there that physicists either don’t fully understand or don’t yet know about.

The way physicists currently explain how the universe works is mostly through something called the Standard Model. This model explains three of the four fundamental forces of the universe — like how electricity works and why particles stick together to make atoms, and elements, and us. The only one it doesn’t cover is gravity… because, well, gravity doesn’t seem to matter to subatomic particles.

Besides, we have the whole theory of general relativity for that. The Standard Model also describes 17 building blocks — called fundamental particles — that make up everything. These include things like the quarks which make up protons and neutrons in the central nuclei of atoms, as well as even weirder things, like muons.

They’re essentially the heavier cousin of electrons — the small, negatively-charged particles that buzz around atoms. Now, the particles and forces described in the Standard Model have been pretty great at explaining what we see happening here on Earth and in the universe in general. But physicists keep seeing more and more stuff that doesn’t quite fit.  And that’s where this news comes in.  Fermilab researchers ran an experiment where they measured how muons wiggle while they’re spinning around inside a giant magnetic ring.

You see, muons have their own little magnetic fields. And that means when they move through the stronger magnetic field generated by the ring in the experiment, they wobble a bit, kind of like a top spinning on a table.  How fast they wobble depends on how strong the muon’s mini magnetic field is and what other particles or forces they’re interacting with. Which means they can give scientists an exciting glimpse into the subatomic world.

Now, the Standard Model provides an estimate for how fast they should wobble based on how muons interact with the particles and forces that we know about. But researchers noticed their muons were wobbling faster than that estimate. See, the wobble is measured by a unit called a g-factor, which gives the strength and orientation of the muon.

And the muons should have had a g-factor of 2.00233183620... but their actual one was 2.00233184122. That might seem like a pretty tiny difference. But, it’s almost enough to totally table-flip physics as we know it.  Particles simply shouldn’t deviate from predictions.

Not if the universe works how we think it does!  So even that teeny shift suggests there are other forces or particles out there that were able to influence the muons’ wiggling.  To put it another way, the scientists say there’s only a one in 40 thousand chance that this finding was a fluke. Now this isn’t the first time researchers have seen muons acting strangely. Using the same magnet, a team at Brookhaven National Laboratory in New York got a similar result back in 2001.

But physicists aren’t tossing out their textbooks quite yet.  That’s in part because the result was from just one “run” of the experiment, which only represents about 6% of that data the researchers are hoping to collect. The team plans on doing this test several more times over the next several years — and they may end up getting a different answer when they do. It’s also possible the theoretical Standard Model estimate both they and the Brookhaven team compared their measurements to was off.

That estimate requires such complex calculation and extrapolation of data that more than 130 scientists worked together to get it! In fact, just last week, researchers from Penn State announced a different prediction for the Standard Model value that took supercomputers hundreds of millions of CPU hours to calculate.  And their number is actually closer to the one seen in the Fermilab experiment! Still, there seems to be mounting evidence that there’s something fundamental to the universe not being captured by the Standard Model.

Some experts even think it’s time for a new theory — one that explains everything, including gravity. Though, to actually figure out what would look like, physicists will need even more precise measurements from the subatomic world — so they can be totally sure that discrepancies between reality and the current model actually exist. And that means the Standard model will likely stick around a little while longer.  [outro] Thanks for watching this episode of SciShow.

News! Before I go, I want to remind you that you only have a couple weeks left to get this month’s SciShow pin!  This month features mini-neptunes — which just might be the most common kind of planet in the universe.  You know, looking at that pin, I’m kind of disappointed we don’t have one in our solar system. They look so cool!

I guess that’s all the more reason to get one for your wardrobe! All you have to do is head to and search for SciShow Pin of the Month, or click on the merch link below. [♪ OUTRO].