Fifth Force of Nature May Have Been Discovered by Physicists

May 26, 2016 | Joanne Kennell

Artist rendition of tritium
Photo credit: Robert Couse-Baker/flickr (CC BY 2.0)

We might have to rethink how the universe works.

Our current understanding of the universe is that it is controlled by four fundamental forces: gravity, electromagnetic, and strong and weak nuclear forces. However, a study conducted by physicists in Hungary might have found evidence of a fifth force of nature. If verified, it would mean we need to rethink our understanding of how the universe works.

Now, you may be wondering what each of the fundamental forces does. Here’s a quick summary.

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Gravity is what holds the moon, planets, sun, stars, and galaxies together in the universe in their orbits. When considering massive objects, such as galaxies, gravity appears to be the most powerful force. However, when you apply gravity to the atomic level, it has little effect because the masses of subatomic particles are so small. At this level, it’s actually downgraded to the weakest force.

The electromagnetic force states that opposite charges attract, while like charges repel, and at subatomic levels, particles exert electromagnetic forces on each other. For example, positively charged protons hold negatively charged electrons in orbit around a nucleus — aka an atom. But electromagnetism can’t explain how the nucleus holds itself together.

Since a nucleus of an atom is made of positively charged protons and neutral neutrons, electromagnetism tells us that protons should repel each other and the nucleus should fly apart. This is where the nuclear forces come in. The force holding the nucleus together is called the strong force.

But one other nuclear phenomenon had to be explained: radioactive decay. This occurs when a neutron decays into a proton, anti-neutrino, and electron, where the electron and antineutrino are ejected from the nucleus. This decay and emission is caused by the weak force.

Now, back to this mysterious fifth force. Evidence of this force was spotted last year when a team from the Hungarian Academy of Science reported that they fired protons at lithium-7 creating unstable beryllium-8, which then decayed into pairs of electrons and positrons.

"According to the standard model, physicists should see that the number of observed pairs drops as the angle separating the trajectory of the electron and positron increases," Edwin Cartlidge wrote for Nature.

However, that’s not what the team saw. At roughly 140 degrees, the number of these pairs actually jumped, creating a little bump before dropping off again. This “bump” might be evidence of a brand new super-light boson that is only 34 times heavier than an electron, according to lead author A.J. Krasznahorkay and his team.

"We are very confident about our experimental results," Krasznahorkay told Nature, explaining that the chance of this bump being an anomaly is around 1 in 200 billion.

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Surprisingly, this paper was overlooked until a team in the US published their own analysis of the data last month. The US team, led by Jonathan Feng from the University of California, Irvine, calculated that the new boson could be carrying a fifth fundamental force.

The paper still has to be peer-reviewed, but it was uploaded to arXiv.org so researchers can conduct follow-up tests to either verify or disprove the Hungarian discovery.

Although this is not the first time researchers have claimed to detect a fifth force, the search has really heated up over the years, according to ScienceAlert. In fact, many scientists think there might be a particle out there called a “dark photon,” which could carry a new force that would explain dark matter — the invisible substance that makes up a large percent of the universe’s mass.

For now, the physics community remains pretty skeptical about the claims, but in a year’s time there should be more data to analyze, which will hopefully let us know if we need to start rethinking how the universe works.

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