Dark Matter: A Final Effort to Decode the Universe’s Greatest Secrets
Underground, scientists are getting closer to one of modern science’s most elusive goals: dark matter. In underground laboratories in the United States and Italy, they have installed huge buckets of liquid xenon and placed highly sensitive detectors on them in the hope of detecting subatomic collisions that would reveal the presence of this elusive substance.
However, the researchers acknowledge that the current generation of detectors have reached their maximum effectiveness and warn that if they do not detect dark matter using such machines, they may have to reassess their understanding of the universe entirely.
“Dark matter makes up about 85% of all mass in the universe, but so far we haven’t been able to detect it, despite building increasingly powerful detectors,” said physics professor Shamkur Gag at University College London. “We are now approaching the limits of our detectors and if they don’t find dark matter in the next few years, we may have to accept that there is something wrong with the way we think about the universe and gravity.”
The search for dark matter began in the last century when astronomers discovered that galaxies seemed to be spinning too fast to remain stable. Observations indicated that its mass must be ten times greater than its visible content (stars, planets, dust clouds) or else it would disintegrate.
The missing matter that generates the extra gravity needed to hold galaxies together is called “dark matter.” Astronomers initially thought they could be stars too small or too faint to be seen from Earth or by other candidates, such as neutron stars. However, new generations of powerful telescopes have shown that these possibilities are not viable.
So scientists have gone from astronomical to incredibly small to explain the missing mass of the universe. They argue that large numbers of undiscovered particles form invisible halos around galaxies and increase their gravitational fields. These virtual particles are called weak, massive, and weakly interacting particles, and researchers have struggled to discover them for two decades.
These efforts included building detectors deep in the Earth where they would be shielded from subatomic particles, caused by cosmic rays hitting the upper atmosphere that constantly fall to Earth and lead to streams of false positive readings on their instruments.
“It was expected that the weak collide with the xenon nucleus and the resulting flash of light would be detected by the detector and thus reveal the presence of faint dark matter,” Gag said. “However, despite years of effort, we still have to see one flash like this. We need more sensitivity.”
Now, researchers are pinning their hopes on history’s most sensitive cowardly hunters. One of them, built under the Gran Sasso Mountains in Italy, is known as XENONnT. The other, Lux Zeppelin, was built at a former gold mine in South Dakota. Both devices were packed with several tons of xenon, much more than any previous device had, and this would increase the chances of a weak core hitting.
“Both devices are currently in run-down tests and those tests will be completed in a few months,” said Gag, a Lux-Zeplin team member. “We may find that we’re detecting dark matter during this time, which would be very good news. Otherwise, both devices will work.” “Basically, the more xenon we have in our devices and the longer our detectors are on, the higher the chances of collisions and dark matter revealing their presence.”
However, it is now accepted that there is a possibility that this will not happen and that dark matter is still a long way off. As Mariangela Lisante, a physicist at Princeton University in New Jersey, reported in the journal Sciences Recently: “The weak hypothesis will face its correct calculations once the new generation detectors are operational.”
If Lux-Zeplin and XENONnT don’t find the weak, the two teams of scientists will have one last chance to use current technology to find them, and join forces to create an extremely wide detector containing tens of tons of xenon. It is a rare and expensive gas to isolate. And it will work for several years.
And if this detector of last resort fails to find dark matter, scientists will be at a loss. Making their instruments more sensitive would flood them with signals emitted by another type of subatomic particle, the neutrino, which rains billions of dollars on Earth every second. Other approaches must be taken.
“It could be that when we’re looking for the weak, we’re looking for our keys under the lamppost,” Gag added. “Dark matter could be much stranger than we’ve assumed until now. It could be made up of tiny black holes. Or it could be made of something a million times lighter than weak and would be very difficult to detect. Therefore, we have to be more sophisticated in our attempts to detect.” “
Such efforts to find a form of matter that hardly interacts with natural matter may seem superfluous. But without the gravitational pervasive influence of dark matter, galaxies, stars, and planets would not have held together in the early universe, and life as we know it would not have evolved. Therefore, scientists continue their efforts to discover its true nature.
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