Scientists have identified a surprising connection between the fundamental laws of physics and the conditions required for life. Their findings suggest that relatively small changes to some of the universe’s fundamental physical constants could dramatically alter fluid behavior and prevent essential biological processes from occurring.

This theoretical work by physicist Kostya Trachenko of Queen Mary University of London identifies additional constraints on the values of fundamental physical constants. For life to exist, fluids must be able to move within and between cells in ways that sustain biological functions.

The findings raise a profound question: why do the laws of nature have values that appear so well suited to the existence of life?

Fundamental constants that shape the universe

Fundamental physical constants are numerical values that govern how the universe works. Examples include the mass and charge of the electron and Planck’s constant, which plays a central role in quantum mechanics—the branch of physics that describes matter and energy at very small scales.

These quantities are generally considered universal and unchanging over time. Their values influence everything from the behavior of atoms and chemical bonds to the nuclear reactions that power stars and create elements essential to life.

Despite their importance, scientists still do not know why these constants have the particular values observed in our universe.

An important clue emerged in 2020, when Trachenko and colleagues showed that fundamental physical constants set a lower limit on the viscosity of liquids.

Viscosity describes how strongly a fluid resists flow. Water has relatively low viscosity and is easy to pour, while honey and tar are much thicker and move more slowly. The researchers found that there is a fundamental limit to how freely fluids can flow, and that this limit is ultimately connected to the constants of nature.

A 2023 study further explored the biological implications of this relationship.

Why small changes in 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 removed, and countless chemical reactions must take place in a liquid environment.

Diffusion is another essential process. It is the natural spreading of particles through a fluid and helps molecules move through cells, enabling many of the chemical interactions required for life.

Major changes in fluid viscosity could disrupt these processes. A liquid that is too thick may prevent important substances from moving efficiently, while a liquid that is too thin may fail to provide the controlled flow required for biological functions.

Trachenko described the relationship this way:

“It turns out that understanding how water flows in a glass is closely related to the grand challenge of uncovering its fundamental constants. Life processes within and between living cells require movement, and viscosity determines the properties of this motion. As fundamental constants change, viscosity changes beyond what we know. For example, if water were as viscous as tar, life would not exist in its current form or at all.”

The implications extend beyond water. Although all known life depends on water, hypothetical life elsewhere in the universe might depend on other liquids. The same fundamental physical constraints would still influence how those liquids behave.

Trachenko suggested that the range of fundamental constants compatible with cellular life may be surprisingly narrow.

“Any change in the fundamental constants, including increases or decreases, would be bad news for flow and fluid-based life forms alike. We expect the range to be very narrow. For example, a few percent change in some fundamental constants, such as Planck’s constant or electron charge, would make the viscosity of blood too thick or too thin for bodily functions.”

These predictions come from theoretical models rather than experiments in which scientists directly change fundamental constants. The precise limits that different forms of life could tolerate remain uncertain.

How the laws of physics connect stars, elements and life

The relationship between fundamental constants and liquid flow is especially significant because the same constants also govern the nuclear reactions that produce heavy elements inside stars.

Stars created elements such as carbon and oxygen long before the first living cells appeared. Those elements later became essential components of living organisms.

Physicists have long studied whether the constants governing stellar nuclear reactions must fall within particular ranges for complex matter to exist. However, producing the chemical ingredients of life does not necessarily guarantee that life can function.

Trachenko’s analysis showed that some physical properties governing liquid flow can change without disrupting the combination of constants needed to produce heavy nuclei in stars.

In a hypothetical universe, the elements necessary for life could therefore be produced even if the available liquid were so viscous that cellular processes could not operate.

This suggests that the conditions required for life involve more than the ability to form stars, planets and complex chemistry. The physical properties of liquids may impose additional constraints on the fundamental constants of the universe.

What blood reveals about fundamental physics

The investigation continued beyond the initial findings.

In a follow-up study published in January 2025 in European Physical Journal E, Trachenko and colleagues examined how fundamental physical constants affect more complex body 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 the properties of individual molecules but also on how these components interact.

For example, red blood cells can form clusters that increase resistance to flow. When blood moves faster, those clusters break apart, allowing the blood to flow more easily. This makes blood considerably more complex than a simple liquid.

The researchers found something unexpected. Despite the complexity of blood and the relatively large size of red blood cells, its viscosity on fundamental physical scales remains surprisingly close to theoretical values derived from fundamental physical constants.

They proposed that interactions between closely packed blood cells may help explain this relationship. Although red blood cells are much 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 highlighted important complexities. Estimating which fundamental constants are compatible with life requires consideration of both the intrinsic properties of fluids, determined by fundamental physics, and the additional effects produced by interactions between cells and molecules.

Together, these findings provide a more detailed framework for investigating how the physical properties of the universe influence the biological processes that depend on fluid movement.

Could the laws of physics have evolved?

The research also points to a deeper mystery: why do 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 the values that allow liquids to support cellular life could represent separate requirements.

He suggested an interesting parallel with biological evolution, in which different useful properties can emerge through separate processes.

Perhaps broader evolutionary principles could help explain how nature arrives at combinations of stable structures and physical properties capable of supporting increasingly complex systems.

For now, this remains speculation. Scientists have not established that fundamental constants evolve through such mechanisms, nor have they explained why the constants have their observed values.

Still, the connection between liquid flow and fundamental physics offers another way to investigate one of science’s biggest unanswered questions.

Something as ordinary as water flowing through a glass or blood circulating through the body may contain clues about why the universe has the physical properties that make life possible.