An experiment in the UK failed to find evidence of a particle that would explain most of the mass of the universe. But the search is not over.
When cosmologists observe the way the universe expands, they find that modern theories of matter cannot explain much of the energy of the universe. They call the unknown energy 'dark energy', and theorists have tried to explain it by offering undetected particles and corresponding fields. The experiments failed to find evidence of such particles, but this is not necessarily a bad thing in physics.
"We have not ruled out everything," Claire Barage, an associate professor of physics and astronomy at the University of Nottingham in the UK and one of the study's authors, told Gizmodo. "There is still a parameter window that is perhaps more interesting."
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Physicists understand the forces between ordinary matter in the universe, like electromagnetic force, as fields (where you determine in the field how strongly you feel the force) with the corresponding particles (you can understand the interactions between two particles of matter such as the exchange of force particles). So, some dark energy theories suggest that this is a new kind of force too weak to be observed on Earth with a corresponding particle; these proposed particles have names such as chameleon or simteron. Recent computational evidence shows that the theory of chameleons, so called, since their properties depend on the environment in which they exist, is a viable theory of dark energy. Researchers working in the UK have previously suggested that, if these forces existed, they could be detected using a special type of experiment similar to the release of two Galileo balls from the top of the slope.
tower in Pisa. Researchers placed an alloy ball sized almond attached to a stick so it could move around in an extreme vacuum chamber. They then pumped and captured a pulse of cold rubidium atoms, then released the trap. Using a discovery scheme called atomic interferometry, based on brilliantly specially rotated lasers on atoms, researchers measure how atoms move toward an aluminum ball held in different positions, looking for the slightest difference in acceleration from theoretical expectations.
The experiment found that if there were chameleon or symmetron particles, their effects were too slight to be measured by this setting, according to a document published in Physical Review Letters. This kind of null result is important – it tells theorists and experimenters to look elsewhere for a dark explaining energy particle.
These results confirm a similar set of paper results for 2017 by a team of scientists here in the United States, albeit with a slightly different detection pattern. This document "is of very high quality and confirms our earlier boundaries," Holger Mueller, head of efforts for 2017 at UC Berkeley, who did not participate in the new study, told Gizmodo in an email. "They use similar but not identical techniques, so this is a significant reinforcement of the experimental data. I would like to fully share that this was a theoretical article by Burrage, Copeland and Hinds, "three of the scholars on this new book," which inspired us to look at chameleons. "
And it's important to keep looking. These experiments leave room for some repetitions of the chameleons, Burrage told Gizmodo. It's now a matter of increasing the sensitivity of those experiments.