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.
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 behavior of atoms and chemical bonds to the nuclear reactions that power stars and produce elements essential for life.
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:
"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 was 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."
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.
Source: ScienceDaily
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