Dark energy, which scientists believe is responsible for the universe’s accelerated expansion, has never been actually observed or measured. Instead, scientists can only speculate about it based on its impact on visible space and matter.
Finding verifiable evidence of dark energy’s influence on distant objects — even the geometry of space itself — is a major target of NASA missions like the forthcoming Nancy Grace Roman Space Telescope. However, a team of cosmologists proposes in a recent report published on September 15 in the journal Physical Review D that scientists may not need to look further into the cosmos to make second-hand observations of dark energy – it could have been spotted right here on Earth.
The scientists claimed that indications of dark energy were discovered at the Gran Sasso National Laboratory in Italy during a dark matter detection experiment. According to a study headed by University of Cambridge academics and published in the journal Physical Review D in September 2021, some inexplicable results from the XENON1T experiment in Italy may have been generated by dark energy rather than the dark matter experiment meant to discover.
They devised a physical theory to describe the discoveries, which they believe were caused by dark energy particles created in a region of the Sun with strong magnetic fields, however more research is needed to corroborate this theory. According to the researchers, their research could pave the way for the quick identification of dark energy.
From little moons to gigantic galaxies, from ants to blue whales, everything we can see in the clouds and in our everyday world makes up less than 5% of the universe. The rest is gloomy. Dark matter, the unseen force that holds galaxies and the cosmic web together, accounts for around 27% of the total, while dark energy, which causes the universe to expand at a faster rate, accounts for 68 percent.
Dr. Sunny Vagnozzi of Cambridge’s Kavli Institute for Cosmology, the paper’s first author noted that they know a lot more about dark matter because its existence was recommended as early as the 1920s, while dark energy wasn’t revealed until 1998. Huge experiments like XENON1T are meant to directly discover dark matter by looking for indications of dark matter ‘hitting’ conventional matter, but dark energy is, even more, harder to identify.
Researchers search for gravitational interactions, or how gravity pushes objects about, to find dark energy. Dark energy’s gravitational influence is repulsive on the biggest scales, driving things apart from each other and speeding up the expansion of the Universe.
The XENON1T experiment revealed an unusual signal, or surplus, over the anticipated background around a year ago. Dr. Luca Visinelli, a scientist at Frascati National Laboratories in Italy and a co-author of the study, mentioned that these kinds of excesses are often flukes, but once in a while they can also lead to fundamental discoveries. The team looked into a scenario in which this indication could be due to dark energy rather than the dark matter that the experiment was intended to identify.
At the time, the most common belief was that the excess was a result of axions, which are hypothetical, extremely light particles created in the Sun. The number of axions necessary to describe the XENON1T signal, on the other hand, would radically affect the development of stars much heavier than the Sun, contradicting what we see.
Although we are still learning more about dark energy, most physics models for it predict the presence of a so-called fifth force. Anything that cannot be described by one of the four fundamental forces in the universe is commonly known as the outcome of an unknown fifth force.
We do know, though, that Einstein’s theory of gravity performs admirably in the local universe. As a result, any fifth force connected with dark energy is undesirable and must be ‘hidden’ or screened on small sizes, and can only act on the greatest scales where Einstein’s theory of gravity fails to describe the Universe’s acceleration. Many dark energy models include so-called screening systems that dynamically obscure the fifth force in order to disguise it.
Vagnozzi and his co-authors built a physical model that used chameleon screening, a form of the screening process, to demonstrate that dark energy substances created in the Sun’s strong magnetic fields may clarify the XENON1T excess.
Vagnozzi explained that their chameleon screening prevents the generation of dark energy particles in extremely dense objects, eliminating the issues associated with solar axions. According to him, it also allowed them to separate what occurs on the smallest scales, where density is incredibly low, from what occurs on the greatest scales when density is extraordinarily high.
The scientists utilized their model to demonstrate what would occur in the detector if the dark energy was created in the tachocline, a region of the Sun where the magnetic fields are especially powerful.
Their calculations show that dark matter detection experiments like XENON1T might potentially be utilized to detect dark energy. However, the original excess must be proven beyond a reasonable doubt. According to Visinelli, they need to be certain that this isn’t a one-time occurrence. If XENON1T detected anything, we’d anticipate excess in the following experiments, but this time with a much stronger signal.
If the excess was caused by dark energy, future upgrades to the XENON1T experiment, as well as related experiments like PandaX-xT and LUX-Zeplin, suggest that dark energy could be straightforwardly detected within the next couple of years.