Several of the tools that enabled one of the most significant scientific triumphs of the twentieth century – the detection of gravitational waves – are now being used to the long-running quest for dark matter.
Dark matter, which is thought to account for approximately 85 percent of all matter in the Universe, has never been directly seen and so remains one of the most puzzling riddles in contemporary physics to this day.
Scientists believe that existing gravitational wave technology has the actual ability to finally uncover the alien material and even determine what it is comprised of, thanks to the incredibly sensitive detectors that have already been demonstrated through multiple exceptional discoveries.
Researchers from Cardiff University’s Gravity Exploration Institute have taken the first step toward this goal in a paper published recently in Nature. They used tools known as laser interferometers to search for a new type of dark matter, which was discovered for the first time.
At least until quite recently, the general consensus was that dark matter was made up of heavy elementary particles.
Despite a slew of efforts, these have not been identified, and scientists are now looking to alternate theories to explain what is known about dark matter.
New research suggests that dark matter is actually a scalar field, which would appear to behave as invisible waves bouncing around galaxies, including our own Milky Way, according to one theory.
“We discovered that our sensors, which were originally built to detect gravitational waves, might be used to seek for this new type of dark matter,” said Professor Hartmut Grote of Cardiff University’s Gravity Exploration Institute, who was the driving force behind the investigation.
During the operation of a laser interferometer, two beams of light are bounced between mirrors before colliding with an optical detector. Researchers can determine how out of sync the beams of light are with one another, which is a proxy for any disruption the beams meet, using this information to make extremely accurate measurements.
The Laser Interferometer Gravitational-Wave Observatory (LIGO) is comprised of two interferometers located in the United States, each with two 4 km long arms arranged in the shape of a “L.” These interferometers were used to detect gravitational waves for the first time in 2015 and have since been used numerous times.
The UK/German GEO 600 detector in Germany, where Grote worked as the lead scientist from 2009 to 2017, is another highly sensitive interferometer that was used to develop much of the technology that is now used to detect gravitational waves. Grote was the lead scientist on this detector from 2009 to 2017.
The GE0600 detector was employed in this investigation for the first time to explicitly hunt for dark matter, which was a world first.
According to lead investigator Sander Vermeulen, who is also from Cardiff University’s Gravity Exploration Institute, “Scalar field dark matter waves would pass right through the Earth and our instruments, but in the process of doing so, they would cause objects such as mirrors to vibrate ever so slightly.”
In sensors such as GEO600 or the LIGO detectors, the vibrations of mirrors would affect the beams of light in a certain way characteristic of dark matter, which is something we should be able to detect depending on the exact features of that dark matter.
Despite the fact that dark matter has never been physically observed, scientists believe it exists as a result of the gravitational effect it has on objects all around the universe. Examples include the possibility that a vast amount of invisible matter could explain why galaxies spin in the way they do and how they came to be in the first place.
Despite the fact that the team was unable to detect any form of dark matter in this new study, they claim that they are making significant first steps toward introducing this technology to dark matter searches and that they have already made significant progress in terms of narrowing down certain parameters for future studies.
“I was startled at how sensitive an instrument may be for hunting dark matter when it was originally designed for a completely different purpose,” Professor Grote continued.
According to Vermeulen, “we have absolutely ruled out several ideas that claim dark matter has particular features, so future searchers will have a better understanding of what to look for.”
According to the researchers, “We feel that these new techniques have the actual potential to uncover Dark Matter” at a later date.