A physicist at Queen Mary University of London argues that the constants of nature may be tuned for more than stars and planets. They may also decide whether liquids such as water and blood can flow well enough to keep living cells working.

The idea comes from Prof. Kostya Trachenko and colleagues. Their study appeared in Science Advances in 2023, according to recent reports. The work is theoretical, not an experiment, and the findings have been circulating again in news coverage this year.

Life depends on fluids moving at tiny scales: nutrients reaching cells, waste leaving them, and molecules diffusing through water. All of that depends on viscosity, a liquid’s resistance to flow. Trachenko’s group had shown in a 2020 Science Advances paper that fundamental constants, including the Planck constant and the proton-to-electron mass ratio, set a lower limit on how runny any liquid can be.

The new argument takes that further. If those constants were slightly different, the researchers say, liquids could become too thick or too thin for cells. “If water were as viscous as tar, life would not exist in its current form or not exist at all,” Trachenko said, as quoted by ANI. For blood, he said the “viscosity of our blood would become too thick or too thin for body functioning.”

That adds a second test to the familiar fine-tuning puzzle. Earlier arguments focused on constants that let stars forge the heavy elements planets need. The Queen Mary work suggests a universe could make those ingredients and still have liquids unsuited to life. “Understanding how water flows in a cup turns out to be closely related to the grand challenge,” Trachenko said, according to ANI.

The group’s follow-up, published in The European Physical Journal E in January 2025, found that the viscosity of blood is surprisingly close, on a fundamental scale, to a value derived from basic constants.

There are limits. The precise range of constants life could tolerate is uncertain, and life elsewhere might use liquids other than water. Why the constants have their observed values has no accepted explanation, and Trachenko’s suggestion that constants could somehow evolve, like biological traits, is speculative.