Scientists Just Found a Hidden Critical Point in Water Right Before It Freezes
NEWS | 31 March 2026
As water gets colder, its behavior becomes increasingly weird from a physics perspective, and researchers looking for explanations have found something new: a previously hidden 'critical point' that emerges in supercooled water that doesn't freeze. Through a variety of pressure and temperature tricks, scientists can keep water in a liquid form well below the standard freezing point. Previous studies have theorized that at this special stage, water separates into two distinct phases – both a high-density liquid and a low-density liquid. In this new study, an international team of researchers has obtained more direct evidence of this liquid-liquid state, as well as a critical point beyond which water shifts into a single but volatile state in terms of its molecular structure. Getting any kind of proper look at these water states has proven difficult, because they exist right on the boundary of water freezing and turning into ice. It's been described as a "no man's land" in terms of trying to get proper measurements. "What was special was that we were able to X-ray unimaginably fast before the ice froze and could observe how the liquid-liquid transition vanishes and a new critical state emerges," says chemical physicist Anders Nilsson, from Stockholm University in Sweden. "For decades there has been speculations and different theories to explain these remarkable properties and one theory has been the existence of a critical point. Now we have found that such a point exists." Rapid heating (via infrared lasers) and super-quick snapshots (via X-ray) were crucial to the experiments carried out here. Ice engineered by the researchers was pushed through the liquid-liquid state, across the critical point, and into the fluctuating state, all while observations were made on the tiniest timescales. While the precise critical point remains to be found, this study narrows the boundaries significantly. The researchers think it's around the -63 °C (-81.4 °F) and 1000-atmosphere mark, which will help with further investigations. What's more, the critical point seems similar to a black hole. As water gets closer to it, the system dynamics of the liquid slow down, and structure changes take much longer. This makes it impossible for the liquid to avoid the transition. These discoveries may seem esoteric and of interest only to physicists, but they actually advance our understanding of how water works (and why it can behave so oddly) at a fundamental level. It has implications for almost everything that water is involved in on our planet and beyond, which is a lot. "Researchers studying the physics of water can now settle on the model that water has a critical point in the supercooled regime," says Nilsson. "The next stage is to find the implications of these findings on water's importance in physical, chemical, biological, geological, and climate-related processes." You only need to look at ice cubes to see the weirdness of water. When matter cools, it usually shrinks and becomes denser – but not with water, which is why ice cubes float near the top of a glass rather than sinking to the bottom. Related: Hot, Black Ice Might Be Responsible For Neptune's Wild Magnetism A variety of other strange properties exist in water beyond its most common states, including the two-in-one liquid behavior analyzed here. This is another step forward, but there are lots of questions still to answer. Something else that separates water from other liquids is that it's essential to life, as far as we know. That's a direction the researchers want to continue to explore. "I find it very exciting that water is the only supercritical liquid at ambient conditions where life exists and we also know there is no life without water," says chemical physicist Fivos Perakis, from Stockholm University. "Is this a pure coincidence or is there some essential knowledge for us to gain in the future?" The research has been published in Science.
Author: David Nield.
Source