The study, published in Science Advances in 2023, builds on earlier work by physicist Kostya Trachenko and colleagues showing that liquid viscosity is tied directly to fundamental physical constants. That finding established a lower limit for how “runny” liquids can be. The newer research extended the idea into biology, asking whether the same physical rules that shape the cosmos may also quietly determine whether cells can function.

Why Liquid Flow Matters for Life

Life depends on movement at microscopic scales. Nutrients must travel through cells, proteins need to fold correctly, and molecules constantly diffuse through watery environments. All of this relies on viscosity, the property that determines how easily a liquid flows.

According to the researchers, the Universe appears to operate within a surprisingly narrow “bio-friendly” window where viscosity and diffusion remain suitable for life. If the constants governing physics shifted by only a few percent, liquids essential to biology could become dramatically thicker or thinner.

“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 team says the consequences would extend far beyond drinking water or oceans. Human blood, cellular fluids, and the chemistry that powers life all rely on carefully balanced flow properties.

“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.” Professor of Physics Kostya Trachenko said.

A New Twist on Cosmic Fine-Tuning

Physicists have long debated why the Universe’s constants appear finely tuned. Tiny differences in values such as the electron charge or the strength of fundamental forces could prevent stars from forming heavy elements needed for planets and life.

What makes this research unusual is that it shifts the discussion from stars and galaxies down to the level of living cells. Previous fine-tuning arguments often focused on nuclear reactions inside stars. This work argues that even if stars and heavy elements still formed, life might remain impossible if liquids could not flow properly inside organisms.

That introduces a second layer of fine-tuning. The constants not only appear compatible with a universe full of matter, but also with biological systems that depend on delicate liquid dynamics.

The researchers even suggest that multiple stages of tuning may have occurred. In the paper, Trachenko compares the possibility to biological evolution, where traits emerge independently over time. The idea remains speculative, but it raises the possibility that nature may favor stable physical structures in ways scientists do not yet fully understand.

Later Research Expanded the Idea

Since the original publication, scientists have continued exploring how viscosity, diffusion, and fluid behavior connect to fundamental physics. Follow-up theoretical work reviewed how liquid motion inside cells may place additional limits on the values of physical constants, especially in systems involving biochemical “machines” such as molecular motors.

Other researchers have also examined how viscosity itself may arise from deeper physical laws. A 2023 analysis highlighted growing evidence that liquid viscosity may be linked to universal physical limits rather than simply being a property measured in laboratories.

Together, these studies are helping reshape an old scientific mystery. Instead of viewing the constants of nature only through the lens of cosmology and particle physics, scientists are increasingly asking whether the conditions needed for flowing liquids and functioning cells should also be part of the equation.

Could Physics and Biology Be More Connected Than We Thought?

The idea remains highly theoretical, and many physicists would caution that there is still no accepted explanation for why the constants of nature have their observed values. But the research opens an unexpected path for thinking about one of science’s biggest questions.

For decades, the mystery of fundamental constants was mostly explored through black holes, stars, and subatomic particles. This work suggests the answer may also involve something much closer to everyday life: the simple ability of liquids to flow through living cells.

A new study led by researchers at the University of Michigan suggests the comet was born in conditions far colder than those that shaped our own solar system. The findings come from an analysis of the comet’s unusual water composition, which revealed extraordinarily high levels of deuterium, a heavier form of hydrogen.

The research was published in the journal Nature Astronomy and received support from NASA, the U.S. National Science Foundation and Chile’s National Research and Development Agency.

“Our new observations show that the conditions that led to the formation of our solar system are much different from how planetary systems evolved in different parts of our galaxy,” said Luis Salazar Manzano, lead author of the study and a doctoral student in the U-M Department of Astronomy.

Alien Comet Contains Unusual “Heavy Water”

Water molecules are made up of two hydrogen atoms and one oxygen atom, giving water its familiar H₂O formula. In ordinary water, hydrogen atoms contain only a proton. But some forms of water contain deuterium, an isotope of hydrogen that includes both a proton and a neutron.

Researchers discovered that 3I/ATLAS contains an exceptionally high amount of this deuterium-rich water. While small amounts of heavy water exist on Earth and in comets within our solar system, the levels found in 3I/ATLAS were dramatically higher.

“The amount of deuterium with respect to ordinary hydrogen in water is higher than anything we’ve seen before in other planetary systems and planetary comets,” Salazar Manzano said.

According to the researchers, the deuterium ratio in the comet was about 30 times higher than what has been measured in comets from our solar system and roughly 40 times higher than the ratio found in Earth’s oceans.

Clues About a Frozen Birthplace

Scientists use deuterium levels as a kind of chemical fingerprint that reveals the conditions present when celestial objects formed. By comparing these ratios with those found closer to home, researchers can infer what kind of environment produced the comet.

The team concluded that 3I/ATLAS likely formed in a much colder region with lower radiation levels than the environment that created the planets and comets in our solar system.

“This is proof that whatever the conditions were that led to the creation of our solar system are not ubiquitous throughout space,” said Teresa Paneque-Carreño, co-leader of the study and assistant professor of astronomy at U-M. “That may sound obvious, but it’s one of those things that you need to prove.”

How Scientists Studied 3I/ATLAS

The researchers said the study was only possible because astronomers detected 3I/ATLAS early enough for detailed follow-up observations.

After the discovery, Salazar Manzano and collaborators secured observing time at the MDM Observatory in Arizona, where they detected some of the first signs of gas emissions from the comet (MDM stands for Michigan, Dartmouth and the Massachusetts Institute of Technology, the observatory’s original partners).

Salazar Manzano then teamed up with Paneque-Carreño, who brought expertise using the Atacama Large Millimeter/submillimeter Array, or ALMA, in Chile. ALMA’s instruments are sensitive enough to distinguish deuterated water from ordinary water, allowing the team to precisely measure the ratio between the two.

The researchers say this marks the first time scientists have successfully performed this type of water analysis on an interstellar object.

“Being at the University of Michigan and having access to these facilities was the key to making this work possible,” Salazar Manzano said. “We were part of a team that was very talented and very experienced in multiple areas, all of us complemented each other and that’s what allowed us to analyze and interpret these data sets.”

More Interstellar Visitors Could Be Found

The study also demonstrates that astronomers may soon be able to chemically analyze additional interstellar objects to better understand how planetary systems form across the galaxy.

So far, scientists have identified only three known interstellar objects entering our solar system, but researchers expect that number to rise as more advanced observatories begin searching the skies.

Paneque-Carreño emphasized that preserving dark night skies will be essential for spotting these faint visitors.

“We need to be taking care of our night skies and keeping them clear and dark so we can detect these tiny and faint objects,” she said.

Additional support for the research came from the Michigan Society of Fellows and the Heising-Simons Foundation. ALMA is operated through a partnership involving the European Southern Observatory, the NSF and Japan’s National Institutes of Nature Sciences in cooperation with the Republic of Chile.

The new research, led by Cardiff University, examined version 4.0 of LIGO-Virgo-KAGRA’s Gravitational-Wave Transient Catalog (GWTC4), which contains 153 reliable detections of merging black holes.

Researchers focused on whether the largest black holes in the catalog could be “second-generation” objects. In this scenario, black holes formed from dying stars collide with each other, then merge again in dense stellar environments where stars are packed up to a million times more tightly than around our Sun.

The findings, published in Nature Astronomy, suggest the most massive black holes detected through gravitational waves belong to a separate class with a very different history from smaller black holes.

Gravitational Waves Reveal Two Black Hole Populations

“Gravitational-wave astronomy is now doing more than counting black hole mergers,” explains lead author Dr. Fabio Antonini from Cardiff University’s School of Physics and Astronomy.

“It is starting to reveal how black holes grow, where they grow, and what that tells us about the lives and deaths of massive stars. This is exciting because we can use the information to test our understanding of how stars and clusters evolve in the Universe.”

By analyzing the gravitational-wave signals, the team identified two distinct groups:

• a lower-mass population consistent with ordinary stellar collapse
• a higher-mass population whose spins appear exactly like those expected from hierarchical mergers in dense star clusters

Researchers say the spin behavior of the heavier black holes was especially revealing.

“What surprised us most was how clearly the high-mass black holes stand out as a separate population,” recalls co-author Dr. Isobel Romero-Shaw, Ernest Rutherford Fellow at Cardiff University.

“Unlike the lower-mass systems we analyzed, which were generally slowly-spinning, the higher-mass systems are consistent with having more rapid spins, oriented in seemingly random directions. This is the exact signature you would expect if black holes were repeatedly merging in dense star clusters.

“That makes the cluster origin much more compelling than it was with earlier catalogs.”

Evidence for the Black Hole “Mass Gap”

The study also strengthens evidence for a mysterious “mass gap” predicted by astrophysicists for decades. According to this theory, stars above a certain size should explode so violently that they are destroyed completely instead of collapsing into black holes.

This would create a forbidden range where black holes formed directly from stars should not exist.

The researchers identified this transition in black holes with masses around 45 times greater than the Sun.

Dr. Antonini said: “In our study we find evidence for the long-predicted pair-instability mass gap — a range of masses where stars are not expected to leave behind black holes at all. Gravitational-wave detectors have successfully found black holes that appear to sit in or near that gap, which we identify at around 45 solar masses.

“So, the key question now is are these black holes telling us that our models of stellar evolution are wrong, or are they being made in another way?

“The biggest black holes in the current sample seem to be telling us about cluster dynamics, not just stellar evolution.

“Above about 45 solar masses the spin distribution changes in a way that is hard to explain with normal stellar binaries alone but is naturally explained if these black holes have already been through earlier mergers in dense clusters.”

Black Holes Could Help Scientists Study Nuclear Physics

The researchers say the discoveries may eventually help scientists investigate processes deep inside massive stars.

The team used the transition near the mass gap to study an important nuclear reaction linked to helium burning in stellar cores.

“In the future, gravitational-wave data may help scientists study nuclear physics, because the mass limit set by pair instability depends on the nuclear reactions taking place in the cores of massive stars,” added co-author Dr. Fani Dosopoulou, a research associate at Cardiff University.