Researchers at Stockholm University recently made a significant discovery about water using advanced x-ray lasers. They found a hidden “critical point” in water that appears when it is deeply supercooled, specifically around -63 °C and 1000 atmospheres. This finding, shared in the journal Science, could help explain why water behaves so differently compared to other liquids.
Water is vital for life, yet it has unusual properties. For example, most liquids become denser as they cool, but water is most dense at 4 °C. This is why ice floats on water and why colder water sits below warmer water in lakes and oceans. When water cools below 4 °C, it starts to expand again. If it goes below 0 °C, it continues to expand, a behavior not seen in most other substances.
To investigate these behaviors, scientists used super-fast x-ray pulses from lasers in South Korea. Anders Nilsson, a Professor of Chemical Physics at Stockholm University, explained, “We could observe how water transitioned from liquid to solid before freezing. For years, there have been theories about a critical point in water, and now we’ve confirmed its existence.”
At low temperatures and high pressures, water can exist in two different liquid forms. These forms can merge at the critical point, creating a highly unstable condition where water switches rapidly between the two states. This volatility is crucial for understanding the unique characteristics of water.
Interestingly, researchers observed that molecular motion slows down as water approaches this critical point. Robin Tyburski, another researcher, noted, “It feels like once you enter this state, you can’t escape, similar to a black hole.” This insight opens up new avenues for research into the unusual dynamics of water.
The breakthrough took decades, and many researchers have long sought to understand this critical point. Aigerim Karina, a postdoc at Stockholm University, shared her excitement about using amorphous ice to reach this critical region, emphasizing its potential for future discoveries.
This finding also raises questions about life itself. Fivos Perakis, an associate professor, remarked on the uniqueness of supercritical water at ambient conditions, pondering if this is just a coincidence or if there’s something deeper to learn.
The study addresses long-standing mysteries about water’s properties, a topic that has puzzled scientists for over a century. Anders Nilsson highlighted that understanding this critical point can help clarify water’s role in various processes, from climate change to biological functions.
This important research reflects a collaborative effort among various institutions, including Stockholm University, POSTECH University, and the Max Planck Society. As researchers continue their exploration, the implications of this discovery will likely resonate across multiple scientific fields.
For those interested in diving deeper, you can read the full study here.
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