- author, Gush blah
- roll, BBC News
All the forces we experience every day can be reduced to just four categories: gravity, electromagnetism, the strong nuclear force, and the weak nuclear force.
These four fundamental forces control how all objects and particles in the universe interact with each other.
The discoveries were made at a US particle accelerator facility called Fermilab.
They built on findings announced in 2021, in which the Fermilab team first hinted at the possibility of a fifth force of nature.
Since then, the research team has collected more data and reduced the uncertainty in their measurements by a factor of two, according to Brendan Casey, senior scientist at Fermilab.
“We’re really exploring new areas. We’re defining (measurements) with better precision than ever before.”
In an experiment called “g minus two (g-2)”, the researchers accelerated subatomic particles called muons around a 15-meter-diameter ring, spinning at nearly 1,000 times the speed of light.
The researchers discovered that these particles may behave in a way that cannot be explained by the current theory, called the Standard Model, due to the influence of a “new force” of nature.
While the evidence is strong, the Fermilab team has yet to come up with definitive proof.
They were hoping to get it now, but the Standard Model’s uncertainty about how much muons oscillate has increased due to developments in theoretical physics.
In essence, it is as if the goalposts of experimental physicists were moved.
The researchers believe they will have the data they need and that the theoretical uncertainty will diminish enough within two years for them to reach their goal.
However, a competing team at the Large Hadron Collider (LHC) in Europe hopes to get to those results first.
Scientist Mitch Patel of Imperial College London is among the LHC physicists trying to discover flaws in the Standard Model.
He told BBC News that finding experimental results that contradict the Standard Model would be one of the greatest advances in physics.
“Measuring behavior that does not agree with the predictions of the Standard Model is the holy grail of particle physics. It would revolutionize our understanding, because the model has withstood all experimental tests for more than 50 years,” says the scientist.
Fermilab says its next set of results will be the “ultimate confrontation” between theory and experiment that could reveal new particles or forces.
So what is the Standard Model and why is it so important to get an experimental result that doesn’t fit your expectations?
Everything in the world around us is made of atoms – which in turn are made of smaller particles. These interact to create the four forces of nature: electricity and magnetism (electromagnetism), the two nuclear forces, and gravity.
Its behavior is predicted by the Standard Model, and it has predicted its behavior over the past 50 years perfectly, without a single error.
Muons are similar to the electrons that orbit atoms and are responsible for electric currents, but they are about 200 times larger.
In the experiment, they were made to oscillate using powerful superconducting magnets.
The results show that the muons are oscillating faster than expected by the Standard Model. Professor Graziano Venanzoni of the University of Liverpool, one of the lead researchers on the project, told BBC News that this could be caused by a new, unknown force.
“We think there might be another force, something we don’t know about now. It’s something different, we call it the ‘fifth force.’ It’s something different, something we don’t know yet, but it should be important, because it says something new about the universe,” they explain.
If confirmed, this would undoubtedly represent one of the greatest scientific developments in the last 100 years since Albert Einstein’s theories of relativity. This is because the fifth force and any associated particles are not part of the Standard Model of particle physics.
Researchers know there is what they describe as “beyond the Standard Model physics” out there, because current theory can’t explain many things astronomers observe in space.
This includes the fact that galaxies continue to accelerate after the Big Bang that created the universe, rather than the expansion slowing. Scientists say the acceleration is driven by an unknown force called dark energy.
Galaxies also spin faster than they should, according to our understanding of how much matter is in them. Researchers believe this is due to an invisible particle called dark matter, which again is not part of the Standard Model.
The results have been published in the Journal Physical Review Letters.
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