Scientists have known for years that water behaves weirdly.
Other liquids like alcohol and oil grow heavier as they’re compressed. But water becomes lighter — ice cubes float in a glass of water, after all. Other fluids grow denser as they cool. But, oddly, water is most dense at around 39 degrees Fahrenheit, or before it freezes.
Now scientists in Sweden have learned that water’s counterintuitive behavior stems from its uncanny ability to exist in two liquid states. Writing in the journal Science, they explained how sophisticated sensors helped them shed light on mysteries that researchers have spent more than a century trying to unravel.
They hope their work could eventually explain how water helped spark the creation of life.
“Water behaves very strangely compare to other liquids. We should be very grateful for it. Otherwise we probably wouldn’t exist,” Anders Nilsson, a study co-author and professor of chemical physics at Stockholm University, told Seeker. “Life couldn’t live without those properties because the bottom of the ocean would have frozen during the ice ages.”
Using mile-long, X-ray lasers in Japan and South Korea, Nilsson and his team were able to watch water molecules in millisecond-long clips as they transformed under increasingly colder temperatures.
It’s important to understand that ice freezes at 32 degrees Fahrenheit only when it contains impurities. Absolutely pure water, on the other hand, might not freeze despite sitting for years in subzero temperatures. In 2011, scientists discovered that water can remain a liquid until around minus 55 degrees Fahrenheit.
“Most people think water freezes at zero degrees Celsius but that is because you have crap in it,” said Nilsson.