If you enjoy watching videos on the internet, you've likely already witnessed the phenomenon known as
supercooling. Basically, the process involves taking ultra-pure water and putting it into a clean, smooth container that lacks any structural defects. If the conditions are right, when you attempt to freeze such water by dropping its temperature below 32 degrees Fahrenheit (0 degrees Celsius), it surprisingly will remain in a liquid state.
This is because in order for ice to form, it needs a foundation upon which to grow, called a
nucleation site. Typically, ice first forms around dust particles or rough spots on a container's surface. But if there is no nucleation site from which the ice can spread out, the water will continue to drop in temperature while remaining in liquid form. Then, when you add a nucleation site to the supercooled water — by either introducing an imperfection or vigorously shaking the container — the chilled liquid will solidify into ice almost spontaneously.
If disturbed, water chilled below its freezing point (called supercooled water) can quickly and dramatically turn to ice.
European Synchrotron Radiation Facility
It's this odd behavior of supercooled water that researchers are now hoping to exploit in order to help them search for the
elusive substance known as dark matter, which accounts for roughly 85 percent of the universe's overall mass, yet only weakly interacts with normal matter.
According to new research presented on April 14 at a
meeting of the American Physical Society (APS) in Denver, Colorado, scientists have shown — for the first time — that supercooled water does not need a macroscopic nucleation site to suddenly turn to ice. Instead, the researchers found that introducing subatomic particles, namely neutrons, can also cause supercooled water to rapidly freeze.
"We managed to discover a new property of supercooled water," said lead author Matthew Szydagis, a physicist at the University at Albany in New York, in a
press release. "To our great surprise, we found that some particles (neutrons) but not others (gamma rays) trigger freezing."
With these new results comes a tantalizing possibility: Astrophysicists may soon be able to use this new-found property of supercooled water to aid in their never-ending hunt for one of nature's biggest enigmas. "Not only do we have a new detector of fundamental particles," Szydagis said, "but potentially of dark matter because neutrons are thought to emulate it."
Snowballs from dark matter
The researchers have dubbed the new detector the "snowball chamber," a name proposed by Szydagis' wife, linguist Kel Szydagis. The snowball chamber mirrors the names of other devices commonly used in particle physics. These include the
cloud chamber and the
bubble chamber, which use supersaturated vapor and superheated liquid, respectively, to track the movements of charged particles within a vessel.
The snowball chamber, seen in action in this slow-motion video, is filled with supercooled water that quickly freezes when a neutron creates a nucleation site. Since dark matter particles are thought to behave similar to neutrons (which also have no charge), researchers think the chamber could be used to search for the mysterious substance.
Joshua E. Martin
But because water within a snowball chamber does not spontaneously freeze when
charged particles like electrons disturb it, the study says the detector is "potentially ideal for dark matter searches seeking nuclear recoil alone."
Most experiments that attempt to directly detect dark matter rely on observing how the
nuclei of atoms recoil after they interact with dark matter particles — which are thought to continuously stream through the Earth in huge numbers. But one of the greatest challenges related to detecting dark matter is eliminating interference from other types of background particles, which tend to be charged and therefore scatter electrons. However, such charged particles don't seem to diminish the effectiveness of the snowball chamber.