A small, unassuming disc-shaped resonator, less than 2 centimeters across, is listening to the whispers of spacetime. This newly developed acoustic wave resonator, in its initial 153 days of operation, has detected two intriguing events. Researchers believe these events could potentially represent high-frequency gravitational waves, a phenomenon never before observed.
The first detection of gravitational waves, ripples in spacetime caused by the movement of massive objects like black holes and neutron stars, occurred in 2015 by the Laser Interferometer Gravitational-Wave Observatory (LIGO). However, these detected waves were low-frequency signals. Some astrophysicists theorize that high-frequency gravitational waves may also exist, originating from hypothetical entities like primordial black holes or dark matter clouds. The quest to find these elusive waves is now underway.
A team of researchers from the ARC Centre of Excellence for Dark Matter Particle Physics and the University of Western Australia constructed this miniature resonator to pursue this goal. The device consists of a quartz disc, conducting plates, and an amplifier, encased within multiple radiation shields and cooled to minimize noise interference.
High-frequency acoustic waves passing through the disc cause it to vibrate. These vibrations induce an electric charge within the quartz, which is then detected by the conducting plates. An amplifier boosts the faint signal, making it easier for researchers to analyze. The resonator registered two noteworthy signals on May 12, 2019, and November 27, 2019. The team’s findings were published in Physical Review Letters.
An artist’s depiction of two black holes about to collide.
“It’s exciting that this event has shown the new detector’s sensitivity and produced results, but we need to determine precisely what these results signify,” William Campbell, a physicist at the University of Western Australia and a co-author of the study, stated in a university press release.
Several possibilities could explain the high-frequency signal. A crucial aspect of this research involves meticulous investigation and ruling out alternative explanations. Besides gravitational waves, other potential sources include interference from other particles interacting with the detector, a nearby meteor, a technical issue within the detector itself, or, perhaps most intriguingly, high-mass dark matter candidates.
However, a significant challenge is the uncertainty surrounding the existence of high-frequency gravitational waves. Currently, they remain a theoretical concept. The search is akin to an ecologist hunting for thylacine footprints—seeking evidence of something that may not even exist.
“The question of whether high-frequency gravitational waves exist warrants investigation because their discovery would imply new physics,” explained Michael Tobar, a physicist at the University of Western Australia and a co-author of the paper, in an email to MaagX.com. “Similar to the discovery of high-energy photons from the cosmos, it would usher in a new era of astronomy.”
In the next phase of the experiment, the team plans to build a duplicate detector and a muon detector. The second detector will broaden the device’s frequency range and enable researchers to cross-correlate their findings, Tobar stated. If the next generation of detectors captures a similar signal, the implications could be profound.
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