UNITED STATES, Oct 21: Imagine a universe where stars still shine, planets still form and water exists, but liquids are so thick that living cells can barely function. Even with the chemical ingredients for life, the conditions might make living organisms impossible.
According to ScienceDaily, Scientists have uncovered a remarkable connection between the fundamental laws of physics and the ability of life to exist. Their findings suggest that even relatively small changes to some of the universe's most basic physical constants could dramatically alter how liquids flow, potentially preventing essential biological processes from taking place.
The discovery, detailed in a study published in Science Advances, came from physicist Kostya Trachenko at Queen Mary University of London. His theoretical analysis identified an additional constraint on the values of fundamental physical constants: They must permit liquids to move in ways that support life within and between cells.
The work raises a profound question about the universe. Why do the fundamental laws of nature have values that appear so well suited to the existence of life?
- The Fundamental Constants That Shape Our Universe -
Fundamental physical constants are numbers that govern how the universe operates. Examples include the mass and electric charge of an electron and the Planck constant, which plays a central role in quantum mechanics, the branch of physics that describes matter and energy at extremely small scales.
These quantities are generally considered universal and unchanging over time. Their values influence everything from the behaviour of atoms and chemical bonds to the nuclear reactions that power stars and produce elements essential for life, as per ScienceDaily.
Despite their importance, scientists still do not know why these constants have the particular values we observe.
An important clue emerged in 2020, when Trachenko and his colleagues demonstrated that fundamental physical constants place a lower limit on the viscosity of liquids.
Viscosity describes how strongly a fluid resists flowing. Water has relatively low viscosity and pours easily, while honey and tar are much more viscous and move slowly. The researchers showed that there is a fundamental limit to how freely a fluid can flow, with that limit ultimately connected to the basic constants of nature.
The 2023 study took this connection much further by examining its implications for biology.
- Why Tiny Changes to Physics Could Make Life Impossible -
Every living cell depends on the movement of molecules. Nutrients must reach the places where they are needed, waste products must be transported away, and countless chemical reactions must occur in a liquid environment.
Another important process is diffusion, the natural spreading of particles through a fluid. Diffusion helps molecules move around cells and enables many of the chemical interactions required for life.
If the viscosity of those fluids changed too much, these processes could become severely disrupted. Liquids that were too thick might prevent vital materials from moving efficiently, while excessively low viscosity could also interfere with the controlled flow necessary for biological functions.
Trachenko explained the surprising connection, saying, "Understanding how water flows in a cup turns out to be closely related to the grand challenge to figure out fundamental constants. Life processes in and between living cells require motion and it is viscosity that sets the properties of this motion. If fundamental constants change, viscosity would change too, impacting life as we know it. For example, if water were as viscous as tar, life would not exist in its current form or not exist at all. This applies beyond water, so all life forms using the liquid state to function would be affected."
The implications extend beyond water. Although all known life depends on water, hypothetical organisms elsewhere in the universe might rely on different liquids. The same fundamental physical constraints would still influence how those liquids behave.
Trachenko suggested that the range of constants compatible with cellular life could be surprisingly narrow.
"Any change in fundamental constants, including an increase or decrease, would be equally bad news for flow and for liquid-based life. We expect the window to be quite narrow: for example, viscosity of our blood would become too thick or too thin for body functioning with only a few per cent change of some fundamental constants such as the Planck constant or electron charge," as per the ScienceDaily website.
These predictions come from theoretical models rather than experiments in which scientists actually changed fundamental constants. The precise limits that different forms of life could tolerate remain uncertain.
- A Cosmic Mystery Billions of Years in the Making -
What makes the findings especially intriguing is that the same fundamental constants that influence liquid flow also govern the nuclear reactions responsible for creating heavy elements inside stars.
Long before the first living cells appeared, stars were producing elements such as carbon and oxygen that would eventually become essential components of living organisms.
Physicists have long investigated whether the constants governing these nuclear processes must fall within certain ranges for complex matter to exist. But the ability to create life's chemical ingredients does not necessarily guarantee that life can function.
Trachenko's analysis showed that some physical properties governing liquid flow could change without disrupting the combinations of constants needed to produce heavy nuclei in stars.
In other words, a hypothetical universe might still produce the elements necessary for life while having liquids so viscous that cellular processes could not operate.
That means the conditions needed to support life may involve more than the ability to form stars, planets, and complex chemistry. The physical properties of liquids could impose additional requirements on the universe's fundamental constants.
- Follow-Up Research Reveals a Surprising Connection to Blood -
The investigation continued beyond the original discovery.
According to the ScienceDaily website, in a follow-up study published in January 2025 in The European Physical Journal E, Trachenko and colleagues examined how fundamental physical constants influence more complicated biological fluids, particularly blood.
Unlike water, blood is a complex mixture containing plasma, red blood cells, platelets, and other components. Its viscosity depends not only on molecular properties but also on how these components interact.
For example, red blood cells can form clusters that increase resistance to flow. As the blood moves faster, those clusters can break apart, allowing it to flow more easily. This behaviour makes blood considerably more complicated than a simple liquid.
The researchers found something unexpected. Despite the enormous complexity of blood and the relatively large size of red blood cells, its viscosity remains surprisingly close, on a fundamental physical scale, to a theoretical value derived from basic physical constants.
They proposed that interactions between closely spaced blood cells may help explain this connection. Even though red blood cells are vastly larger than atoms, the forces acting where their surfaces approach one another involve distances small enough for molecular and quantum effects to matter.
The 2025 analysis also emphasised an important complication. Estimating which fundamental constants are compatible with life requires accounting for both the intrinsic properties of liquids, determined by fundamental physics, and the additional effects created by interactions among cells and molecules, reported ScienceDaily.
These findings offer a more detailed framework for investigating the connection between the universe's basic physical properties and the biological processes that depend on them.
- Could the Laws of Physics Have Evolved? -
The research also points toward an even deeper mystery: Why do the fundamental constants have values that allow so many different physical processes to work together?
One speculative possibility raised by Trachenko is that multiple forms of fine-tuning may be involved. The values that allow stars to manufacture heavy elements and those that permit liquids to support cellular life may represent separate requirements.
He suggested an intriguing analogy with biological evolution, in which different useful characteristics can emerge through separate processes.
Perhaps some broader evolutionary principle could help explain how nature arrives at combinations of physical properties capable of supporting stable structures and increasingly complex systems.
For now, this remains a conjecture. Scientists have not established that fundamental constants evolve through such a mechanism, nor have they determined why those constants possess their observed values.
Still, the connection between liquid flow and fundamental physics opens another way to investigate one of science's biggest unanswered questions.
Something as ordinary as water moving through a glass, or blood circulating through the body, may hold clues to why the universe has the physical properties that make life possible.