The new gravitational wave detector captures the potential signal early in time.

Two intriguing signals spotted in a small gravitational-wave detector could represent all kinds of exotic phenomena — from new physics to dark matter interacting with black holes to vibrations from near the beginning of the universe. But due to the novelty of the experiment, researchers are reluctant to claim any breakthrough.

Installations such as the Laser Interferometer Gravitational-Wave Observatory (LIGO) use gigantic laser-guided sensors to look for considerable ripples in the space tissue called gravitational waves. These come from the collisions of black holes and neutron stars out in the distant universe, which are events so powerful they shake space-time and send out surges with wavelengths measured in hundreds of miles.

Long before these massive observatories were built, scientists suspected that gravitational waves of such sizes existed because they knew that black holes and neutron stars should sometimes crash together, Michael Tobar, a physicist at the University of Western Australia in Perth, told Live Science.

But there aren't any well-understood sources for gravitational waves with shorter wavelengths of between a few feet and a few miles. Nonetheless, "in the universe, there are always things that are not expected," Tobar said.

Recent years have seen a push to build detectors that can search for these smaller gravitational waves, including one Tobar and his colleagues built. Their device consists of a disk made from crystal quartz 1 inch (3 centimeters) in diameter, with a resonant chamber that produces an electrical signal whenever it vibrates at specific frequencies.

Tobar compared the set-up to a bell or gong that sounds like an unusual step. "If a gravitational wave hit that, it would excite it," he said. The sound inside the crystal is then captured as an electromagnetic signal by electrical sensors.

The researchers placed their detector behind multiple radiation shields to protect it from background electromagnetic fields and cooled it to shallow temperatures to minimize thermal vibrations in the apparatus.

Throughout the 153 days of the experiment, the crystal sounded twice, each time for one or two seconds. The team's findings w

ere published in the August 12 issue of Physical Review Letters.

Scientists are now trying to determine what caused the outcomes. Charged particles known as cosmic rays circulating from space are one possible explanation, Tobar said. However, he added a previously unknown type of thermal fluctuation in the crystal, which should have been minimal due to the super-cold temperatures, could be another.

The researchers wrote in their paper, but there are also many exotic prospects, such as a type of dark matter known as an axion spinning around a black hole and giving off gravitational waves. Moreover, many explanations may require previously unknown physics beyond the standard model that describes nearly every subatomic particle and force in the universe, Tobar said.

Shortly after the Big Bang, cosmologists think the universe went through a period called inflation. As a result, it expanded exponentially; Francesco Muia, a theoretical physicist at the University of Cambridge in the U.K., was not involved in the work.

At the end of this era, the universe might have gone through a phase transition, sort of like water changing from a liquid to a gas state when it boils, he said. If this happened, the growth could have deposited large quantities of energy into the space-time tissue, generating gravitational waves that could be seen through this experiment, Muia said.

He doesn't think there is enough evidence yet to say what the events in the crystal were one way or another, but he is excited for this experiment and others like it coming online shortly.

Tobar agreed. "It would be nice if they were gravitational waves, but who knows," he said.

Now that the researchers have these detections under their belt, they can build more sensors like this one, he added. For example, suppose several devices see the same signal at the same time. In that case, it could potentially point to something out in the universe and help to rule out internal processes like thermal fluctuations inside the crystal.