You may have seen some headlines this week about the discovery of a fifth fundamental force of nature. Maybe you even read a bit about it, but then probably quit reading, because... particle physics, quanta, bosons, force carriers...
Step away from the articles: We're here to help.
If you remember any of the physics you learned in school, it's possible you may remember that there are four fundamental forces of nature.
They are in no particular order gravity, electromagnetism, the weak nuclear force and the strong nuclear force.
Fifth? Am I supposed to know the other four?
Gravity is fairly easy to understand: any two things that have mass (atoms, people, planets, stars) are drawn towards each other. The bigger the mass the stronger the pull. Easy peasy.
Electromagnetism? Well that's simple, it's electricity and magnetism mashed up. Yes, but that doesn't really explain how it works. The Electromagnetic force explains how things that are electrically charged (positively or negatively) interact with each other. One of the big takeaways, a magnetic charge can create an electric charge, and vice versa. Those interactions are responsible for electric power generation which is kind of a big deal. Electromagnetism and how it pushes and pulls objects is responsible for the energy in things like batteries and magnets, but it also includes light, which is just waves of electromagnetic radiation.
The other two are the weak and the strong nuclear forces and while they're both stronger than gravity they only act in the tiny spaces between atoms, and the even smaller spaces where quantum physics starts making everything really weird.
The strong nuclear force in fact is the strongest of the four known forces and basically the glue that binds everything together. It is responsible for keeping protons and neutrons (which along with electrons make up atoms) stable and then allows those to bind into atomic nuclei. The weak force on the other hand is responsible for radioactive decay, the opposite of the strong force, it is what controls how things on a nuclear level fall apart. Oh and by the way it's responsible for fusion, and keeps our sun bright and warm.
That's what the four forces are, without getting too into the weeds on how these things work.
So what about a fifth force?
But, we do need to get into the weeds a bit, because we need to know what makes gravity or any of the other forces actually do their thing.
Does one body with mass, just magically start moving towards another massive thing? Nope, it's made possible by things called force carrier particles. Force carriers are the particles that carry information between things and tell them how to behave. Think of force carriers as little pocket constitutions for each of the four fundamental forces. They lay out not only all the rules for how to behave but also force the forces (ha) to act by those rules.
The force carriers for gravity are hypothetical things called gravitons, for electromagnetism they're the photons. For the weak nuclear force the carriers are called W and Z particles, and for the strong nuclear force, gluons. These force carries are all classified as examples of bosons.
But last year, a group of physicists at the Hungarian Academy of Sciences saw what the University of California at Irvine (UCI) physics department called "puzzling anomalies in their experimental data." The Hungarians weren't sure what the anomalies were but they pointed to the existence of a new kind of light particle. That's about as far as they got. They were unable to figure out if this new particle had mass, or if it was a new kind of boson with no mass, like a photon.
Unfortunately, to paraphrase Abraham Lincoln, the world "little noted nor long remembered" the Hungarian scientists' work.
Except for a team of physicists led by Jonathan Feng, UCI professor of physics and astronomy. Along with his team, Feng took a look at the Hungarians' work, pulled together a host of other similar experiments and decided that the Hungarians may in fact have found a new kind of force carrier boson.
"Sometimes," Feng says, "we also just call it the X boson, where X means unknown." If they're right, a new force carrier particle means there must be a new force, a fifth fundamental force.
The teams' work was just published in the journal Physical Review Letters. “If true, it’s revolutionary,” Feng said. “For decades, we’ve known of four fundamental forces...this discovery of a possible fifth force would completely change our understanding of the universe, with consequences for the unification of forces and dark matter.”
And no, we're not even going to get into dark matter at this point.
So where has this force been hiding? Feng says that it's simply been overlooked in the past. "Its interactions are very feeble," says Feng.
But he adds, "There are many experimental groups working in small labs around the world that can follow up the initial claims, now that they know where to look.”
So what does it do, and what does it mean?
This new force is very similar to the electromagnetism, but, according to Tim Tait who co-authored the "while the normal electric force acts on electrons and protons, this newfound boson interacts only with electrons and neutrons – and at an extremely limited range."
But more research is needed to determine exactly what THAT means when it comes to how the physical world works.
So, If this new force is confirmed, what would it do for our understanding of the world? Not even Feng knows yet. But there's no shortage of speculation. It could play a role in helping scientists find the Holy Grail of Physics, the Grand Unified Theory. This fifth force might help unify the effects of the electromagnetic, weak and strong nuclear forces, “manifestations," Feng says, "of one grander, more fundamental force.”
It's long been the dream of physicists to figure out if or how electromagnetism, and the strong and weak nuclear forces work together, and this new force could be a big piece of that that puzzle.
If we can prove the existence of this fifth force it might bring us one stop closer to making real sense of how our universe works.