- 2026 Mar 11

- 2026 Mar 9

- 2026 Mar 6

- 2026 Mar 4

- 2026 Mar 2

2026 Mar 11

- Where Some See Strings, She Sees a Space-Time Made of Fractals

Q&A | VIEW ON WEBSITE

Where Some See Strings, She Sees a Space-Time Made of Fractals

By Charlie Wood

March 11, 2026

Pushed down to a certain scale, the laws of physics seem to fall apart. Astrid Eichhorn, a leader in an area of study called asymptotic safety, thinks we just need to push a little further.

Astrid Eichhorn, a physicist at Heidelberg University in Germany, is a leader in the field of asymptotic safety — a conservative theory of quantum gravity.

Konrad Gös for Quanta Magazine

Introduction

Astrid Eichhorn spends her days thinking about how the laws of physics change at the tiniest scales.

Imagine zooming in closer and closer to the device on which you’re reading this article. Its apparently smooth screen quickly dissolves into a jiggling lattice of molecules, which in turn resolve into clouds of electrons buzzing around atomic nuclei. You dive into a nucleus, and atoms disappear as you enter the domain of quarks. It is here, where protons loom as large as solar systems, that Eichhorn’s explorations begin.

Past this point, the fundamental forces themselves shift. Electromagnetism and the weak interaction intensify, while the strong force slackens. The changes happen in a fairly regular way, so physicists have a good sense of how they work … until they don’t.

When an atom appears as large as the observable universe, the established laws of physics can no longer tell you what happens between particles separated by an atom’s width. Gravity, a force that’s too weak to notice at the scale of atoms, grows strong in an erratic way. You’ve just crossed over into the “Planck” realm.

The apparent breakdown of particle physics at this scale has inspired some dramatic theories. Some physicists argue that this failure point in our understanding tells us that the universe is fundamentally composed not of particles, but of vibrating strings and membranes. Others argue that at these smallest scales, space and time themselves must dissolve into structures such as loops.

Eichhorn and her colleagues are pursuing a different possibility. In 1976, Steven Weinberg, a theorist who would eventually earn a Nobel Prize, pointed out that if you zoomed in far enough, you might reach a place where the rules of physics would stop changing. New realms would stop appearing; the intensities of the forces would stabilize; and gravity would turn out to make perfect sense after all.

Eichhorn, a physicist at Heidelberg University in Germany, has over the last decade become a leading theorist investigating this idea, called asymptotic safety. In particular, Eichhorn has emphasized the importance of taking into account the ways in which matter affects space-time, and vice versa. “She is the expert of gravity-matter systems in asymptotic safety,” said Alessia Platania, a physicist at the University of Copenhagen who has worked with Eichhorn.

The quantum fields in nature have ripples that balance in just the right way to stabilize the laws of physics at shorter scales, Eichhorn’s work has suggested.

Konrad Gös for Quanta Magazine

Over the last decade, Eichhorn has made significant strides toward showing that the quantum laws likely do stop changing around the Planck scale, just as Weinberg suspected. She has also connected Planck-scale physics with physics at scales that are easier to study — a famously challenging task for anyone working with a theory of gravity at the smallest levels. Quanta recently spoke with Eichhorn about these efforts. The interview has been condensed and edited for clarity.

What’s the big problem? If we treat gravity like the other forces at the smallest scales, what goes wrong?

So, the approach we use with most of the forces is called quantum field theory. It assumes the universe is full of quantum fields. Fields have ripples that manifest as pointlike particles. These particles move through a continuous space-time and interact via forces.

Ultimately the problem is that if we try to treat quantum gravity as a fluctuating quantum field in this most straightforward way, then this approach does not work.

Very roughly, for a well-understood force like electromagnetism, we need to consider fluctuations in the field at all scales. And these fluctuations never stop coming as you zoom in. They act like virtual particles with higher and higher energies. We know how to account for the effects of these high-energy virtual particles in our calculations: The intensity of the force changes, but that’s it.

But when you try to add gravity, which Albert Einstein linked with the structure of space-time, the fluctuations become problematic. At shorter distances, the higher-energy virtual particles interact in new and different ways. We can’t account for these ever-changing effects, so quantum field theory fails to predict what will happen at those tiny scales.

Physicists use the machinery of renormalization, which Eichhorn describes as a “mathematical microscope,” to calculate how the world changes as you zoom in and out.

Konrad Gös for Quanta Magazine

What do physicists think this failure of quantum field theory is telling us?

It tells us that something new happens as we zoom in. And I would say there are roughly three lines of thinking as to what that might be.

One is that maybe quantum field theory breaks down, full stop. The objects are not points, in the way that we think of elementary particles as points. Instead, they become stringy. That’s string theory.

To this day we call it the OMG plot. It was just so mind-blowing to us, that this idea really works out in a quantitative way.

Another is that we need to remove the assumption that space-time is continuous. I take my glass of water, and it looks continuous to me, but fundamentally it’s atomic. Maybe it’s the same with space-time. This is the idea spelled out in loop quantum gravity, or in causal sets.

Or you can say that fields and particles persist; space-time persists; and the new thing is that space-time takes on a structure that is, broadly speaking, like a fractal: The intensity of the forces, including gravity, stops changing, and you start seeing the same picture, the same rules for how particles talk to each other, over and over. That’s the idea I’m pursuing, asymptotic safety. If this self-similar realm exists, then the fluctuations of space-time, and of the other fields, would become stable enough for us to make predictions using good old-fashioned quantum field theory.

A fractal-like space-time sounds cool, but it also sounds pretty out there. Why is this a sensible thing to expect?

One reason is that symmetries are very common in many theories of nature. Space-time itself has symmetries, for instance. There are no special directions, no special places, and no special times. But we do have special scales: The world looks one way to humans, another way to bacteria, and yet another way to electrons. That’s peculiar. So I think it’s a natural assumption to say that at the fundamental level, maybe there are no special scales. Maybe there is a symmetry between scales, a scale symmetry.

Eichhorn also studies the ways in which asymptotic safety could be compatible with the picture of reality emerging from other approaches to quantum gravity, like string theory.

Konrad Gös for Quanta Magazine

Another is that this is a very conservative approach to quantum gravity. You take quantum field theory, which has never failed in the lab, and you ask: What do you need to do to make it predictive for all scales? And as far as we know, adding scale symmetry is the only thing we can do.

How can you test this idea?

First we need to check whether quantum fields can actually fluctuate in such a way that they achieve a special balance between them that makes all scales look the same. We work with a procedure that is sort of the mathematical version of a microscope: We set up a mathematical representation of the fields and their interactions, and we calculate how the interactions between the ripples in the fields change as we zoom in. Then we look for a place where that change stops, a place we call a fixed point.

Have you found any?

We have tons of simplified examples of idealized theories with fixed points. The community at large has worked a lot on empty space-time, just pure gravity. Actually, most of us work in an even more simplified setting where there are only quantum fluctuations of space, rather than fluctuations of both space and time. But nevertheless, people have tested this in literally hundreds of papers and found very robustly that this fixed point where things stop changing exists.

And then the next question to ask is: What happens when I throw in matter fields? This is one of my earliest papers that I wrote as a postdoc in 2013. My collaborators and I included all the known matter and force fields and found that the fixed point was still there, albeit in this funny space-only setting. We gave the paper this catchy title, “Matter Matters,” and it became a bit of a slogan for me.

Last summer we tied things up by showing that there is likely a fixed point even when we include all of the ways that the known fields can interact with each other — something we left out of the 2013 paper. We have now looked at the complete picture for the first time.

Eichhorn and her collaborators make predictions by assuming scale symmetry and asking what kind of a world they will see when they zoom back out to our level.

Konrad Gös for Quanta Magazine

So far, this sounds like mainly a math question. Where does the physics come in? How can you test whether our universe really works this way?

To test it, we turn the logic around. Instead of zooming in and looking for mathematical evidence of a fixed point in our models, we assume that a fixed point exists and zoom out, asking: What physical implications would a fractal-like realm have for our macroscopic world?

And what implications would it have?

We have good indications that it would force the macroscopic world to look a lot like the world we see. In 2009, Mikhail Shaposhnikov and Christof Wetterich showed that zooming out from a fixed point forces the mass of the Higgs boson, the particle that accounts for mass, to be almost exactly the value we measure.

It’s a natural assumption to say that at the fundamental level, maybe there are no special scales.

And in 2018, my Ph.D. student Aaron Held and I had a memorable moment. The previous year, we had already found that a fixed point would force the top quark to have close to the measured mass. And we were investigating whether it could also account for the mass of the top quark’s sibling, the bottom quark. They’re supposed to be identical twins in the eyes of gravity, because their distinctive quantum properties are not things that gravity is sensitive to, but experiments have found that they have different masses.

I remember this afternoon distinctly. Aaron and I sat together in my office in front of my laptop, and we were looking at plots of our results in the software Mathematica. We saw that indeed there is this point where the predictions match up to within 10%.

In a world with no fixed point, the masses could be anything. But if there is a fixed point, a very particular conversation starts up between gravity and the electroweak force, and a result of that conversation is that these quarks basically have to have the two different masses that they do.

To this day we call it the OMG plot. It was just so mind-blowing to us that this idea really works out in a quantitative way.

If the world is fundamentally “scale symmetric,” Eichhorn says, then the textbook quantum theory may perfectly capture the behavior of gravity and the structure of space-time.

Konrad Gös for Quanta Magazine

Can you predict all particle properties from the existence of a fixed point?

We’ve made more progress since 2017. We were able to connect the fixed point with a few neutrino properties, including their weirdly light mass, which we found simultaneously with another group.

But we also know that asymptotic safety is quite far from explaining everything. The real proton mass is consistent with a fixed point, for instance, but it could also be 10 or 100 times as heavy.

As far as we can tell, though, there are no particle properties that are incompatible with asymptotic safety. If there were, we could rule the theory out. But for now, everything works, and it looks like we might explain a little bit more about the properties of particles and their interactions than we could before. That might be progress. That makes me happy.

If someone had done this work in the 1980s, before anyone had measured the mass of the top quark, what do you think the quantum gravity landscape would look like today?

We’ve made these “retrodictions,” and that’s nice. But sometimes I think, “Man, we were too late!” If someone had made these as actual predictions back then, maybe asymptotic safety would be the largely established view of quantum gravity.

Eichhorn suspects that if you zoom in far enough, the laws of physics may stop changing.

Konrad Gös for Quanta Magazine

Or maybe they would have advanced beyond where we are now and found a point where asymptotic safety doesn’t work out. Then they might have abandoned it for strings and other exotic theories with a complete confidence that such a drastic move is necessary.

Well, are there any bona fide predictions you can make about unknown particles?

We’ve looked at various proposals for dark matter, and I can tell you a number of things that probably don’t work in asymptotic safety.

Like what?

Several of the popular dark matter models, actually. The simplest versions of weakly interacting massive particles, for instance; the simplest type of axionlike particles most people look for; and the kind of ultralight dark matter that could influence upcoming nuclear clocks all don’t seem to be compatible with the fractal world, although we cannot exclude them with absolute certainty.

So do you think hunters looking for WIMPs, axions, and ultralight dark matter are all wasting their time?

Definitely not! Experimentalists are bravely going forward and testing as much as they can. And those tests can be seen as tests of asymptotic safety. If an axion experiment finds dark matter tomorrow, that would actually put our theory under pressure. So these hunts are indirectly informing us about the quantum structure of space-time, and I find that a rather cool by-product of these experiments.

Related:

1. Why an Old Theory of Everything Is Gaining New Life

2. Old ‘Ghost’ Theory of Quantum Gravity Makes a Comeback

3. How Mathematical ‘Hocus-Pocus’ Saved Particle Physics

If you could predict a specific dark matter candidate someday and then someone found it, what would that mean for the other theories of quantum gravity?

You might think it would rule them out, but this is not necessarily the case. Asymptotic safety could be compatible with these other approaches. Perhaps at the fundamental scale there are strings or loops or something, but then as you zoom out you hit a realm where things change so slowly for a while that it looks as if you’re at a fixed point. That’s possible, and it means that distinct quantum gravity approaches may actually not be competitors, but rather different perspectives on the same physics.

It sounds like one should be humble about any picture of space-time.

In quantum gravity research, it’s always a good idea to be humble.

2026 Mar 9

- Disorder Drives One of Nature’s Most Complex Machines

MOLECULAR BIOLOGY | VIEW ON WEBSITE

Disorder Drives One of Nature’s Most Complex Machines

By Yasemin Saplakoglu

March 9, 2026

Every second, hundreds to thousands of molecules move through thousands of nuclear pores in each of your cells. A new high-definition view reveals the machine in action.

The inner channel of the nuclear pore complex in all its messy glory. Far from a simple pore, the complex is filled with dynamic proteins that move molecules into and out of the nucleus. In this computer model, green strands represent disordered nucleoporin proteins and blue knots are karyopherin transport proteins.

Nat Commun 16, 11497 (2025)

Introduction

At the dawn of complex life, evolution created a container for DNA, its most treasured item. A few billion years later, 20th-century microscopists looked at this container — the nucleus — up close and saw that it was covered in tiny openings. At the time, they didn’t know what to make of these structures, but as microscopy improved, something grand came into focus: what we now call “nuclear pore complexes,” some of the largest and most marvelous molecular machines ever formed.

Every nuclear pore complex is constructed from hundreds of proteins, of around 30 different types. From the front, it looks like an eight-petaled flower; from the side, like a flying saucer. Its center opening spills over with spaghetti-like proteins tethered to the inner walls of the complex.

“It’s a thing of enormous beauty,” said Brian Chait, a chemical biologist at Rockefeller University. “It’s marvelous. It’s a wonder. … It’s phenomenal.”

This machine has a vital job: directing molecular traffic into and out of the nucleus. More than an open door, the protein complex recognizes different molecules as they approach — and lets only some through. “The nuclear pore complex is ultimately the gatekeeper for the nucleus,” said Roderick Lim, a biophysicist at the University of Basel in Switzerland. “Everything that has to get in and out of the nucleus has to go through these pores.”

Nearly every eukaryotic cell has a nucleus punctured with nuclear pore complexes, and the main components of the complex are incredibly conserved across species, from single-celled yeasts to multicellular humans. Evolution “came up with that thing one time and got stuck with it,” said André Hoelz, a structural cell biologist at the California Institute of Technology.

A single mammalian nucleus can contain thousands of them. Every second, each nuclear pore lets hundreds to thousands of molecules of all shapes and sizes pass through so that they can travel to their destinations to make proteins, regulate genes, and generally help the cell function. Some large molecules are carried through the channel by proteins, while small ones diffuse across on their own. And while some effortlessly glide through, to others it is an impenetrable barrier.

How this gate works with such selectivity is a mystery. Over decades, biologists have worked out what most of the static parts of the machine look like. But its center is restless, endlessly moving and morphing, which makes it difficult for even the best methods to visualize.

That’s gradually changing. In a study published in Nature Cell Biology at the end of 2025, high-resolution microscopy showed the central barrier in motion at millisecond resolution, revealing a flexible structure that constantly rearranges itself. The experimental imaging, backed by computational modeling, suggests that the function of the nuclear pore complex is guided by flexibility and movement.

A nuclear pore complex’s outer ring, which fits into the membrane of a cell’s nucleus, is built from hundreds of proteins of around 30 different types. But most of the action flows through its center channel, which allows molecules to enter and exit the nucleus.

S J Kim

This is more than an intellectual curiosity. A surge of recent research has linked neurodevelopmental disorders, viral disease, and cancers to problems with the complex. If biologists can discern how its cellular trafficking system works, they could develop methods to stop unwanted pathogens from getting through — and also try to guide therapeutic molecules into the cell nucleus, where the genome itself awaits.

“We are starting to approach a near-atomic picture of nuclear pores from various organisms,” said Mike Rout, a cell biologist at Rockefeller University who led the new work that offers insight into a molecular machine at the heart of eukaryotic life.

A Thing of Beauty

For many scientists who study the nuclear pore, it was an instant fascination: They were awed that this (relatively) massive biological machine could allow so many kinds of molecules, and so many of them, to move in and out of the nucleus efficiently, with little room for error.

“It is beautiful,” Hoelz said. “How do you generate an aircraft hangar that has a door where a 747 can go through,” but a small marble can’t fly out?

Somehow the gate itself must play bouncer for life’s important molecules. RNA molecules must get out of the nucleus to the cytoplasm to make proteins. Ribosomes, the structures that do the protein-making, are themselves made of molecules assembled in the nucleus and moved out through the pores. Meanwhile, molecules involved in regulating the genome must be ushered into the nucleus preferentially. As these processes unfold, the nuclear pore is also blocking things that don’t belong, such as harmful enzymes or misfolded RNAs.

The cell biologist Mike Rout has spent decades studying the nuclear pore complex. This vital structure, built from hundreds of individual proteins, is the gatekeeper and traffic controller of a cell’s nucleus.

Lori Chertoff/Rockefeller University

In the decades since the discovery of the nuclear pore complex, biologists have slowly gained a greater understanding of its structure using electron microscopy, tools of physics, and computer modeling. With the advent of cryo-electron microscopy, a powerful technique that images cells after flash-freezing them, they have been able to assess the static parts of the machine. These efforts have generated a near-atomic view of each individual protein that builds the eight petal-like radial units. But the technique hasn’t worked for the very center, called the transport channel, where most of the pore’s action happens.

“Whenever anyone uses some of these microscopes to peer inside nuclear pores, they just see this amorphous cloud inside,” Lim said. “It’s like a haze.”

The reason, which became apparent in the 1990s, is that the center of this giant machine is filled with proteins that have no obvious or specific structure. These proteins, called FG-nucleoporins, have tails that wiggle around like seaweed and that can’t be captured in static images. These tails are “the dark matter of the nuclear pore complex,” Hoelz said.

It’s not order that generates this function. It’s disorder.

Patrick Onck, University of Groningen

Most proteins fold into specific structures or shapes essential to the functions they perform in a cell. But intrinsically disordered proteins, a category that includes these nucleoporins, don’t have a single structure. They flail about, changing shape and binding to different molecules.

This means that in the center of the nuclear pore complex, “everything is mediated by disorder,” said Patrick Onck, a computational physicist at the University of Groningen in the Netherlands. “It’s not order that generates this function. It’s disorder.”

In the early 2000s, the field was awash with bickering about the organization and behavior of FG-nucleoporins in the transport channel and how they might traffic molecules into and out of the nucleus. Researchers agreed that most macromolecules can’t get through the channel without the help of cargo-carrying proteins called transport factors. Transport factors, which mingle with the nucleoporins in the channel, bind only to those molecules that include a specific short stretch of amino acids — a molecular tag that “says, in effect, ‘send me into the nucleus,’” Rout said. But researchers differed on how the channel itself might be organized, which would impact how molecules move through it. Some argued that nucleoporins snap onto one another, forming a gel-like mesh network. Others argued that the disordered proteins don’t interact with each other much, but rather constantly undulate like bristles on a brush.

The debate became contentious. “It used to be very hostile,” Hoelz recalled. “People are very passionate about what they’re doing. It’s not a personal animosity.”

“For a very long time, it was like, ‘Are you a gel person, or are you a brush person?’ You’re one or the other,” said Siegfried Musser, a cell biologist at Texas A&M University.

The biophysicist Roderick Lim and his team used high-speed atomic force microscopy to image the inner workings of the nuclear pore complex.

Biozentrum, University of Basel

In recent years, new collaborations and discussions, including at an annual conference where the principals gather to chat, have quieted the conflict. But the truth about the structure and functioning of the transport channel hadn’t been resolved. The researchers would need to get more creative to understand how the complex functions in its native environment.

“We wanted to simply go back to the nuclear pore complex and really ask the nuclear pore to tell us what it’s doing,” Rout said, “not for us to impose on it what it’s doing.”

Fast Tapper

How do you interrogate a molecular complex? Rout and Lim, who have both advocated for a more dynamic model of the nuclear pore, started with a simple idea: Poke it.

Rout has spent decades characterizing yeast pore complexes. Lim is an expert on high-speed atomic force microscopy, a technique that runs a very sharp probe over a surface, lightly and rapidly tapping it, to get a sense of how it moves.

A few years ago, in a dark basement laboratory, Lim’s graduate student Toshiya Kozai began unpacking plastic vials containing millions of yeast nuclear pore complexes. He toiled for days in the “dungeon of our department,” Lim recalled, working nonstop to get the samples into the high-speed atomic force microscope while they were fresh. “It’s a real labor of love.”

His efforts enabled the team to watch the transport channel change, millisecond by millisecond. “We could see very clear, super rapid motion,” Rout recalled. The resulting videos may look blurry to us macroscopic creatures, but they are some of the highest-definition looks at the behavior of the nanoscopic transport channel.

Lim used high-speed atomic force microscopy, which taps a probe over a molecule’s surface, to create this real-time video of the transport channel of a yeast nuclear pore complex. The pink arrow points to the central plug — an elusive structure in the pore that, until now, hadn’t been confirmed.

Nature Cell Biology 27, 2089-2101 (2025)

At the edges of the channel, near the walls, Rout and Lim’s team saw rapid fluctuations of molecules — those were the wiggly nucleoporins. At the center they saw a fuzzy blob, known as the central plug, that continuously moved around and repositioned itself within the transport channel. For a long time, biologists had suspected that a central plug might exist, but in previous microscopy images it wasn’t always visible.

“Seeing is believing,” said Hoelz, who was not involved in the study. To be able to show this “is a beautiful thing.”

Led by Chait and using mass spectrometry, the team discovered that the plug was made of transport proteins called karyopherins, or “kaps” for short, plus their molecular cargo. As kaps move through the nuclear pore, they latch onto the nucleoporins, tugging them toward the channel’s center. This creates a temporary, dynamic obstacle that slows other molecules or stops them from moving through. In that way, kaps not only help carry molecules across, but also push away anything that’s not supposed to be there, Rout said. When they added in more transport factors, they saw the plug grow bigger.

The heart of the nuclear pore complex is being constantly rearranged by kaps, creating an ever-changing environment. The results suggest that the pore’s organization and behavior are much more dynamic than a gel network, Rout said, and much closer to a brushlike environment. The findings support a model he previously proposed called the “virtual gate” in which the dynamics of the environment is critical for directing proteins away or through. He likened it to a crowded dance floor.

The inner channel of the nuclear pore complex is organized by disordered nucleoporin proteins (green), which lack a stable structure. Cargo-carrying transport proteins (pink) interact with the dynamic nucleoporins to shuffle molecular cargo (not pictured) through the pore to go into and out of the nucleus.

Animation by Enrique Sahagun, Scixel

“If you know how to dance, you can simply enter the dance and swing from partner to partner, holding hands, just quickly exchanging going across,” he said. “If you don’t know how to dance, all you see is this turbulent melee, and you try to get in. No one’s taking hold of you to help you enter the dance, so you just get pushed away.”

To further test their observations, Rout and Lim created synthetic pores the same size as natural nuclear pore complexes. When they tethered nucleoporins inside and added transport factors, the synthetic pores behaved like the wild yeast nuclear pore complexes. They saw the central plug appear.

“What I find actually very striking is that they reproduce the result with a very simple model,” Musser said. “It’s a pretty stunning result.”

Door Not Closed

Hoelz is not totally convinced that this is a nail in the coffin for the gel model. The “answer is [probably] somewhere in the middle, which is very often the case in science,” he said. Researchers likely catch the central channel in different configurations because it’s changing all the time, he suggested, or perhaps the inner channels of some nuclear pores are more like a gel and others are more like a brush.

One recent modeling study led by Onck and published in Nature Communications suggested that the central transport channel could have some parts that are brushlike and others that are similar to condensates — membraneless, liquidlike compartments that have characteristics of gels and brushes. It could even be the case that the channel’s denser center has qualities more like a gel or condensate, Musser said, while the periphery is more brush-like.

Hoelz said that only new technologies that can fully see inside the pore will resolve the debate — and they could come any day now.

“People are constantly trying to develop new tools or new strategies to try to figure out what’s going on,” Musser agreed. In 2025, he and his team published results in Nature that used a powerful 3D imaging tool called Minflux to trace molecules in high resolution as they move through nuclear pore complexes in intact nuclei of human cells. Learning of this method was “a complete game changer for me,” said Hoelz, who was not involved.

Related:

1. How AI Revolutionized Protein Science, but Didn’t End It

2. Did Viruses Create the Nucleus? The Answer May Be Near.

3. How Colorful Ribbon Diagrams Became the Face of Proteins

4. The Shape-Shifting Army Inside Your Cells

Musser’s team observed molecules moving only near the edge of the transport channel. This also complements Rout and Lim’s study, given that the central plug might be blocking the center. “But it doesn’t make sense for the middle not to be used,” Musser said. “I think we just haven’t found the right substrate or developed the right tools to see stuff go through the middle.”

No matter what the inside looks like, it’s clear that the nuclear pore complex is incredibly malleable and robust — which also makes it the cell’s “Achilles’ heel,” Rout said. It is critical to a cell’s health, and central to its most important processes: protein production and gene regulation. But because it is resilient and can endure damage, it can be altered by disease without shutting down.

Some proteins that make up the nuclear pore “show up again and again and again as weak spots for disease,” Rout said, including neurodevelopmental disorders, viral diseases, and cancers. Both cancer cells and viruses likely interfere with proteins in the complex to swing the protein-making machinery in their favor or shut down an immune response.

In that sense, the nuclear pore complex is far more than a molecular gate. “It’s a nexus for integration of information,” Rout said. “And I think if the cell had thoughts, that would be how it thinks of its nuclear pores.”

2026 Mar 6

- New Strides Made on Deceptively Simple ‘Lonely Runner’ Problem

NUMBER THEORY | VIEW ON WEBSITE

New Strides Made on Deceptively Simple ‘Lonely Runner’ Problem

By Paulina Rowińska

March 6, 2026

A straightforward conjecture about runners moving around a track turns out to be equivalent to many complex mathematical questions. Three new proofs mark the first significant progress on the problem in decades.

Is every runner sometimes far from all the others? For a few runners, the answer is yes. Adding more runners makes the problem exponentially harder.

Mark Belan/Quanta Magazine

Introduction

Picture a bizarre training exercise: A group of runners starts jogging around a circular track, with each runner maintaining a unique, constant pace. Will every runner end up “lonely,” or relatively far from everyone else, at least once, no matter their speeds?

Mathematicians conjecture that the answer is yes.

The “lonely runner” problem might seem simple and inconsequential, but it crops up in many guises throughout math. It’s equivalent to questions in number theory, geometry, graph theory, and more — about when it’s possible to get a clear line of sight in a field of obstacles, or where billiard balls might move on a table, or how to organize a network. “It has so many facets. It touches so many different mathematical fields,” said Matthias Beck of San Francisco State University.

For just two or three runners, the conjecture’s proof is elementary. Mathematicians proved it for four runners in the 1970s, and by 2007, they’d gotten as far as seven. But for the past two decades, no one has been able to advance any further.

Then last year, Matthieu Rosenfeld, a mathematician at the Laboratory of Computer Science, Robotics, and Microelectronics of Montpellier, settled the conjecture for eight runners. And within a few weeks, a second-year undergraduate at the University of Oxford named Tanupat (Paul) Trakulthongchai built on Rosenfeld’s ideas to prove it for nine and 10 runners.

The sudden progress has renewed interest in the problem. “It’s really a quantum leap,” said Beck, who was not involved in the work. Adding just one runner makes the task of proving the conjecture “exponentially harder,” he said. “Going from seven runners to now 10 runners is amazing.”

The Starting Dash

At first, the lonely runner problem had nothing to do with running.

Instead, mathematicians were interested in a seemingly unrelated problem: how to use fractions to approximate irrational numbers such as pi, a task that has a vast number of applications. In the 1960s, a graduate student named Jörg M. Wills conjectured that a century-old method for doing so is optimal — that there’s no way to improve it.

In 1998, a group of mathematicians rewrote that conjecture in the language of running. Say N runners start from the same spot on a circular track that’s 1 unit in length, and each runs at a different constant speed. Wills’ conjecture is equivalent to saying that each runner will always end up lonely at some point, no matter what the other runners’ speeds are. More precisely, each runner will at some point find themselves at a distance of at least 1/N from any other runner.

Mark Belan/Quanta Magazine

When Wills saw the lonely runner paper, he emailed one of the authors, Luis Goddyn of Simon Fraser University, to congratulate him on “this wonderful and poetic name.” (Goddyn’s reply: “Oh, you are still alive.”)

Mathematicians also showed that the lonely runner problem is equivalent to yet another question. Imagine an infinite sheet of graph paper. In the center of every grid, place a small square. Then start at one of the grid corners and draw a straight line. (The line can point in any direction other than perfectly vertical or horizontal.) How big can the smaller squares get before the line must hit one?

Jörg Wills made a conjecture in number theory that, decades later, would come to be known as the lonely runner problem.

Courtesy of Jörg Wills

As versions of the lonely runner problem proliferated throughout mathematics, interest in the question grew. Mathematicians proved different cases of the conjecture using completely different techniques. Sometimes they relied on tools from number theory; at other times they turned to geometry or graph theory.

But this meant that they didn’t have a general strategy for how to tackle the problem. Rather, they had a bunch of clever but ad hoc techniques that might work for four runners, say, but not five. With each additional runner, they had to go back to the starting line.

By the mid-2000s, mathematicians had proved that when there are seven or fewer runners sprinting around a track, each of them will eventually get lonely. They’d also found ways to simplify the problem. For instance, they realized that they didn’t need to prove the conjecture for all (infinitely many) combinations of speeds. Instead, if they could show that it was true for any combination of whole-number speeds, it would have to be true more generally; they could ignore fractions and irrationals.

This was a much easier task, but it still involved dealing with infinitely many possible speeds. Something more was needed.

Speed Limits

In 2015, Terence Tao of the University of California, Los Angeles planted the first seed. He showed that if the lonely runner conjecture held for relatively low speeds, it would also hold for high speeds. For any given number of runners, mathematicians would only have to consider whole-number speeds up to a particular threshold.

This reduced the problem to a finite number of calculations — at least in theory. In practice, even when you’re dealing with only a few runners, the number of combinations of speeds you have to check is still “astronomical and completely impractical,” said Noah Kravitz of the University of Oxford.

Tao’s advance would eventually catch the eye of Rosenfeld, who was interested in proofs that use a computer to check many examples.

He reframed the problem by considering possible counterexamples to the conjecture: What features would the runners’ speeds have to have so that at least one runner would never end up alone?

Matthieu Rosenfeld was drawn to the lonely runner problem because it gave him the opportunity to explore his interest in computer-assisted proofs.

Virginie Fèche

It turned out that their speeds would need to be highly constrained. Rosenfeld used a computer program, along with ideas from number theory, to show that if he multiplied all the speeds together, their product would have to be divisible by certain prime numbers. Now all he needed to do was prove that no combination of speeds could satisfy this condition.

To do so, he returned to a modified version of Tao’s threshold. He then rewrote it in terms of the product of speeds: If the lonely runner conjecture was true for products up to a given size, it had to be true in general. This implied that if the conjecture was false, it would be possible to find a counterexample with a product below the threshold.

But Rosenfeld had already shown that in any counterexample, the product would have to be divisible by all those primes. Such a product would have to be massive. So massive, in fact, that it would far exceed the threshold.

In other words, a counterexample to the lonely runner conjecture couldn’t exist — at least, not for eight runners. The conjecture was true.

Off Track

Rosenfeld started thinking about how to extend his proof to nine runners. In the meantime, Kravitz saw Rosenfeld’s paper and showed it to a promising undergraduate he’d been mentoring at Oxford, Paul Trakulthongchai. He advised Trakulthongchai to work on the conjecture for nine runners.

Trakulthongchai used Rosenfeld’s overall approach, but he developed a more efficient computational technique for pinpointing the prime divisors that a counterexample would have to have. This allowed him to more quickly rule out all counterexamples for both nine and 10 runners: The conjecture was true in both cases. (Rosenfeld independently proved the conjecture for nine runners as well, just a few days after Trakulthongchai did. He was happy to see the other mathematician’s burst of progress. But “at the same time, I was a bit bummed out,” he said with a laugh.)

Tanupat (Paul) Trakulthongchai solved two new cases of the lonely runner problem as an undergraduate.

Evan Nedyalkov

Both Rosenfeld’s and Trakulthongchai’s methods are too computationally expensive to work for more runners, leaving them stuck on the problem’s next case. “In order to achieve 11, I think you need an entirely new sort of way of looking at things,” Trakulthongchai said.

But mathematicians are excited by these recent advances — and by the fact that a single approach solved three cases at once, when previously each new case had required an entirely new proof. “I really see a new way of getting a hold on the whole conjecture by this new idea,” said Matthias Schymura of the University of Rostock in Germany.

Related:

1. Smaller Is Better: Why Finite Number Systems Pack More Punch

2. A Master of Numbers and Shapes Who Is Rewriting Arithmetic

3. The Core of Fermat’s Last Theorem Just Got Superpowered

Although a proof of the whole conjecture still feels far off — and mathematicians don’t yet agree on whether it will hold true for any N runners — “things are starting to move after not moving for a while,” Kravitz said.

Inspired by the new results, Schymura and others are organizing a workshop on the lonely runner conjecture, to be held in Rostock this October. It will bring together researchers from the different fields in which the conjecture appears. The hope is that they’ll approach the problem from various angles and “communicate and bridge the different areas,” Schymura said, to find a potential proof or counterexample.

“I’m convinced the problem will be solved,” Wills said. “But it might be some 20, 30 more years.”

2026 Mar 4

- Can the Most Abstract Math Make the World a Better Place?

QUALIA | VIEW ON WEBSITE

Can the Most Abstract Math Make the World a Better Place?

By Natalie Wolchover

March 4, 2026

Columnist Natalie Wolchover explores whether applied category theory can be “green” math.

Celsius Pictor for Quanta Magazine

Introduction

“I’ve spent a long time exploring the crystalline beauty of traditional mathematics, but now I’m feeling an urge to study something slightly more earthy,” John Baez wrote on his blog in 2011. An influential mathematical physicist who splits his time between the University of California, Riverside and the University of Edinburgh, Baez had grown increasingly concerned about the state of the planet, and he thought mathematicians could do something about it.

Baez called for the development of new mathematics — he called it “green” math — to better capture the workings of Earth’s biosphere and climate. For his part, he sought to apply category theory, a highly abstract branch of math in which he is an expert, to modeling the natural world.

It sounds like a pipe dream. Math works well at describing simple, isolated systems, but as we go from atoms to organisms to ecosystems, concise mathematical models typically become less effective. The systems are just too complex.

In philosophy, “qualia” refers to the subjective qualities of our experience: what it’s like for Alice to see blue or for Bob to feel delighted. Qualia are “the ways things seem to us,” as the late philosopher Daniel Dennett put it. In these essays, our columnists follow their curiosity, and explore important but not necessarily answerable scientific questions.

But in the years since Baez’s post, more than 100 mathematicians have joined him as “applied category theorists” attempting to model a variety of real-world systems in a new way. Applied category theory now has an annual conference, an academic journal, and an institute, as well as a research program funded by the U.K. government.

Skepticism abounds, however. “When I say we’re underdogs and nobody likes us, it’s not completely true, but it’s a bit true,” one applied category theorist, Matteo Capucci, told me.

I set out to learn what this burgeoning research area is about. How could one of the seemingly most rarefied realms of pure math help demystify a system as complex as the biosphere? Is it a significant improvement on other approaches to modeling? Can mathematics really be green? It didn’t seem promising.

To my surprise, I’ve learned that applied category theory has had some wins lately. The applications are not yet as green as Baez had hoped, but the approach is showing potential in important areas, including epidemiology and artificial intelligence safety. It seems plausible that the most abstract idealizations can help make greater sense of the messiest realities.

Category theory originated in 1945 as an effort to formalize relationships between mathematical objects, and it soon grew into a powerful and productive branch of math.

What do we mean by mathematical objects? Numbers, functions, and sets are examples. To a category theorist, what defines an object is its relationships to others. What is a black king in chess? “You can say it’s a bit of wood carved into a certain shape and painted black, but that’s not important; it could be a saltshaker,” said Tom Leinster, a mathematician at the University of Edinburgh. Rather, the black king is defined by how it moves on a chessboard and how it can capture opposing pieces or be checked by them.

Jeremy Howard via flickr, modified by Quanta

A category is a collection of objects and these relationships, or morphisms. Let’s consider that chess set as a category. To do so, you might depict it as a diagram featuring little boxes for each object — legal chess positions — and then connect the boxes with arrows to represent the morphisms, or possible moves. Category theorists study how to map, overlap, or connect various categories.

We’re all intuitively aware of categories. We know, for example, that 5 feet and $5 are not the same mathematically. You can multiply 5 feet by 3 feet to get 15 square feet. But you can’t multiply $5 and $3 — there’s no such thing as square dollars. You can add $5 and $3, or you can multiply $5 by 3 (the number, not dollars). But $5 times $3 is meaningless.

To a category theorist, dollar values are elements of a one-dimensional vector space.  Picture the number line; a dollar amount is like an arrow (or “vector”) anchored at zero that reaches some distance along the line. You can add two vectors by placing them tip to tail, but multiplying vectors isn’t something you can do in the category of one-dimensional vector spaces.

Despite knowing nothing of vector spaces or morphisms, we somehow manage to avoid making embarrassing category errors at the checkout counter. But when concepts are more varied and complex than distances and dollars, we run into problems.

“It shows up all the time in modeling, for example epidemiological modeling,” Baez told me. “If you’re writing a model in conventional software and you type ‘35’ into your program, that doesn’t tell you whether it’s 35 dollars or 35 people or 35 doses of a drug. And so you’re conflating those all as just numbers, and that makes it easier to make mistakes.”

Applied category theory provides a framework for modeling real-world systems in terms of objects and morphisms. “Categories are ways of organizing logical structures,” said Brendan Fong, the co-founder and CEO of the Topos Institute in Berkeley, which is devoted to applications of category theory.

The physicist Bob Coecke applied it to quantum mechanics in the 2000s, which has since been extended to reasoning about quantum computation. A few years later, Baez started mulling over the categorization of the biosphere, while the mathematician David Spivak, who co-founded the Topos Institute, independently pioneered applied category theory by thinking about databases. “David has a real imperative to formalize and make legible the world,” Fong said. “The thing he hates most in the world is miscommunication.”

Xenja Santarelli, modified by Quanta

In a 2022 lecture I watched online, Spivak envisioned how applied category theory might work in practice. An accountant tells an applied category theorist about the objects in their database, such as employees and dollar amounts. The category theorist then develops a formal model of the system — a category with a rigorous logical structure — which can then be connected to other categories, corresponding to other databases and spreadsheets, to model the whole company. In this way, applied category theory is a lingua franca for talking about the heterogeneous parts of some giant system.

Climate modeling — one of Baez’s initial candidates for green mathematics — attempts to simulate the archetypal giant system: Earth itself. Experts in different parts of the Earth system must assemble their knowledge and streams of data in a logical way to understand the whole. But Baez and others told me that applied category theorists don’t have any purchase in climate science, partly because climate models are already sophisticated enough to function, despite a lack of mathematical rigor in how they’re patched together. That rigor could make models stronger, more flexible, and better able to integrate new information, the mathematicians argue, but starting over takes both convincing and effort.

“It’s one of the challenges we always face in applied category theory,” said Amar Hadzihasanovic of Tallinn University of Technology in Estonia. “We can go to people and tell them, ‘Your model would be better if you would assemble it according to these first principles.’ And they tell you, ‘OK, well, how long is it going to take?’ It’s a big investment before you can reap the benefits.”

There’s little math can do to address the inadequate political response to the climate crisis, but applied category theory is further along in other areas of public concern.

For example, Baez has been collaborating with Topos and a Canadian computer scientist, Nate Osgood, who specializes in epidemiological modeling of disease outbreaks. While working on Canada’s pandemic response at the University of Saskatchewan, Osgood was frustrated that existing modeling software didn’t allow experts to combine knowledge from different fields.

Robert Koorenny, modified by Quanta

To predict how an outbreak will progress, epidemiologists often use stock-and-flow diagrams: illustrations featuring stocks of people (susceptible, infected, recovered, dead) and arrows showing flows between them based on factors such as exposure or virulence. Stocks and flows are just objects and morphisms of a category. The arrangement of boxes and arrows in the diagrams translates into equations describing the system’s evolution.

Over the last few years, Osgood, Baez, and their team have developed a software package called StockFlow that formalizes this kind of modeling. Specialists can model different aspects of an outbreak, such as how health disparities affect the infection rates of susceptible people, and these categories can be composed into larger ones. “Category theory is able to handle those fancier forms of composition,” Baez said.

StockFlow has yet to spread among epidemiologists, but Osgood teaches it to his students in hopes of inoculating the next generation of modelers. “This is genuinely something that could be used,” said Leinster. “It’s serious stuff.”

Meanwhile, Hadzihasanovic and Capucci are both part of Safeguarded AI, a project funded by ARIA, a U.K. government–funded advanced research agency, that’s applying category theory to the problem of AI safety. How, the program asks, can unpredictable and error-prone AI systems be trusted to operate essential real-world systems, such as nuclear plants or power grids?

I can see the need here, and the team’s answer is clever: Build formal models of complex systems for the AI to practice on. These models must have the same logical structure as the real system, correctly representing the morphisms between many different types of objects.

“Category theory gives you a modular and compositional way of doing this,” Capucci said. “We are developing fundamental technology that we can deploy in so many situations.”

There’s a sense among applied category theorists that their approach will pay off in the long run, as systems grow ever more complex and interconnected, and as AI gets more involved. Winging it won’t cut it. “This is going to be, eventually, very important work,” Hadzihasanovic said.

Many practitioners got into the field because they share Baez’s environmental ethos and hope to take on greener problems in time. Baez still has high hopes. A cousin of Joan Baez, the folk singer and activist, he was heavily influenced by his uncle (her father), a physicist who was also a socially active Quaker. It’s “infused in me,” he said, to help the world and “not just enjoy myself.”

I asked what it is about the biosphere that he thinks category theory can help us understand.

In his view, we improperly categorize biological systems. We mistake them for machines, objects that perform specific tasks by taking in matter and energy and producing desired outputs and waste. “We focus on the part we care about and ignore the waste and where is the energy coming from,” Baez said. “Our whole technology and indeed our whole mathematics is based on that attitude.”

Living systems are a different category, though. They’re not built to perform tasks. Evolution has made life “incredibly subtle and complicated in ways we can’t fully fathom,” he said. Genes aren’t discrete parts of a machine with their own purposes, for instance; they all have numerous roles and impacts. In an ecosystem, there’s no waste; one creature’s poop is another’s feast.

Related:

1. Where Does Meaning Live in a Sentence? Math Might Tell Us.

2. Conducting the Mathematical Orchestra From the Middle

3. With Category Theory, Mathematics Escapes From Equality

4. How Climate Scientists Saw the Future Before It Arrived

5. Climate Physicists Face the Ghosts in Their Machines: Clouds

“I don’t think we have the math to understand such systems yet,” said Baez, who thinks modeling these systems will involve new categories with previously unstudied logical structures. “That’s the kind of mathematics I would like to develop, because I have this hope that it will help us be kinder to the world if we understand the world a bit better and not think of the natural world as raw materials for our machines to take advantage of to do what we want to do. That attitude that we have right now is running into a wall. That attitude winds up destroying the whole planet.”

Indeed, we might value nonhumans, ecosystems, and the climate more by conceiving of them and ourselves as objects in a shared category.

Like these mathematicians, I yearn to make the world a better place while doing what I love. (Don’t we all?) Philosophically, I see the promise in applied category theory. Time will tell whether the approach will genuinely help humanity or the planet. But for those who feel called to do good and to do math, it’s worth a try.

Correction: March 9, 2026

An earlier version of the text described a one-dimensional vector space as a “category.” Rather, they are considered objects in a category in which the morphisms are linear maps.

2026 Mar 2

- What Crystals Older Than the Sun Reveal About the Start of the Solar System

ASTRONOMY | VIEW ON WEBSITE

What Crystals Older Than the Sun Reveal About the Start of the Solar System

By James Dinneen

March 2, 2026

Microscopic crystals extracted from meteorites could help settle a debate about the birth of our patch of the Milky Way.

Presolar grains, found in meteorites, are smaller than a bacterial cell.

Photos courtesy of Nan Liu

Introduction

The standard story of the origin of our solar system has gone like this: 4.6 billion years ago, a giant cloud of dust hung frozen in space. Then the explosion of a nearby star caused part of that dust cloud to collapse. Pulled by gravity toward a central point, the dust coalesced into a radiating ball of hydrogen and helium about 1.4 million kilometers in diameter — what would become our sun. The remainder, which fell into orbit, collected into our solar system’s planets, along with a mess of asteroids and other cosmic leftovers.

To test the validity of this story, researchers need to peer back in time to the solar system’s first moments and beyond. And the cosmochemist Nan Liu has a way to do that: Locked in a safe on her desk at Boston University’s Institute for Astrophysical Research is a shard of meteorite flecked with material older than the sun.

“It’s the most pristine [type of] meteorite, not altered by water or heat,” Liu said as she took out and held up the specimen — a shiny, dark stone about the size and shape of an arrowhead.

Meteorites like this one formed around the time of the dust cloud collapse. The collapse of the cloud and the ignition of the sun melted away much of the chemical information contained in the meteorite, but within it some microscopic crystals — smaller than a single bacterial cell — survived intact. These crystals, called presolar grains, are far and away the oldest material accessible to us on Earth.

Nan Liu, a cosmochemist at Boston University’s Institute for Astrophysical Research, holds up a piece of meteorite that contains grains of material older than the sun.

James Dinneen for Quanta Magazine

Over the past decade or so, scientists have used meteorites like Liu’s to challenge the story of how the solar system formed. Instead of a supernova, the solar system and everything in it might owe its existence to a more placid-sounding cosmic scenario: Maybe our solar system cobbled itself together from the winds blown off of a gargantuan star. New studies of presolar grains could offer a way to determine whether this new story is correct.

Starts With a Bang

Scientists got their first clue about what could have triggered the formation of the solar system when a fireball appeared over Mexico in 1969. The now-famous Allende meteorite spread its debris over more than 500 square kilometers.

In 1976, researchers reported that samples from Allende contained a surprise: an unexpectedly large amount of a stable isotope called magnesium-26. They proposed that the meteorite formed with an abundance of aluminum-26, which is radioactive and leaves behind magnesium-26 when it decays.

Yet aluminum-26 was not known to be a normal component of the interstellar medium — the dusty space between stars that would have provided the materials for Allende. Ordinary stars don’t make that particular isotope. “Most of these isotopes as we observe them in the early solar system, they were just the natural product of galactic chemical evolution,” said Maria Lugaro, an astrophysicist at the Konkoly Thege Miklós Astronomical Institute in Hungary. “The most important exception is aluminum-26.”

Pieces of the Allende meteorite landed across the Mexican state of Chihuahua.

Matteo Chinellato

So where’d it come from? In 1977, two eminent astrophysicists proposed that the anomalous aluminum likely came from a nearby supernova explosion. Other phenomena can produce aluminum-26, but the supernova shock wave could also have caused the collapse of the cloud. With a single event, astronomers could explain how two rare occurrences — the injection of aluminum-26 and the formation of a new solar system — happened at virtually the same moment. “Everybody felt that we needed something to trigger the collapse,” said Vikram Dwarkadas, an astronomer at the University of Chicago.

The supernova trigger remained the favored scenario for decades, supported by detailed astrophysical models, as well as further measurements of enriched magnesium-26 in pristine meteorites. But over the past decade or so, that view has run up against other measurements that don’t seem to match. The problem: The solar system has an iron deficiency.

Not So Ironclad

Supernovas don’t just make aluminum. Any nearby supernova would likely also have injected lots of the radioactive isotope iron-60. Therefore, if a supernova launched the formation of the solar system, “we should see quite high initial [iron-60] abundances in the early-formed objects,” wrote Linru Fang, a cosmochemist at the University of Copenhagen, in an email.

Some studies have reported finding enough iron-60 in meteorite samples to support the supernova story. But not all scientists agree with those findings; several researchers told Quanta that most cosmochemists now think that, while there was an abundance of aluminum-26 at the start of the solar system, there wasn’t much iron-60 after all.

Early last year — in a study described by its authors as the most precise measure of iron-60 in the early solar system to date — Fang and her colleagues reported low levels of iron-60 (measured via its stable decay product nickel-60) in a planetesimal formed just after the collapse of the cloud. The result is inconsistent with a supernova scenario, she said.

The Vela Supernova Remnant formed after the explosion of a star in a supernova.

Alan Dyer/Stocktrek Images/Science Source

Researchers have come up with explanations for the missing iron. “Meteoricists are famously argumentative folks,” wrote Alan Boss, an astronomer at Carnegie Science in Washington, D.C., in an email. “There always seems to be a counterexample to anything someone claims to be the case.”

For instance, the aluminum could have exploded out of the supernova, while the iron — coming from deeper in the star’s core — could have fallen back into the dead star. Or the explosion could have come from a quirky supernova that didn’t generate iron-60 at all. It could also be that iron-60 wasn’t distributed evenly in the cloud, which could mean measurements from individual meteorites aren’t giving us the full picture.

Dwarkadas dismisses these explanations as “hand-waving” attempts to fine-tune the models to match the data rather than finding a more general solution. “Many people seem to accept the idea that it’s not a supernova,” he said.

But if the solar system didn’t start with a supernova, where did it get all that aluminum?

Born in a Bubble

A possibility many researchers now favor is that the aluminum-26 was delivered on the winds of a Wolf-Rayet star.

Compared to our sun, a Wolf-Rayet star is much shorter-lived, dozens of times larger, and thousands of times as luminous. A star becomes a Wolf-Rayet star when its outer hydrogen shell is stripped away, either by the gravitational attraction of another star or by the strength of its own solar winds.

A Wolf-Rayet star’s exposed core can send out solar winds at speeds of up to 3,000 kilometers a second. “It basically sweeps up the surrounding material like a snowplow,” Dwarkadas said. That swept-up material forms a shell around the star that can be 100 light-years across. The shell, which creates a bubble around the Wolf-Rayet star, is tens of thousands of times denser than the surrounding interstellar medium.

The Dolphin Head Nebula is a Wolf-Rayet star surrounded by a bubble an estimated 60 light-years across.

Image processed by Sauro Gaudenzi, original data from Telescope Live.

The shell contains enough material to build a solar system. It should contain a lot of aluminum-26, and — crucially — it should contain very little iron-60. “I’m looking for a star that produces only aluminum-26,” Lugaro said. “The place where we can make only aluminum-26 is in the winds of these very massive stars.”

Astronomers have observed suns forming within the shells of Wolf-Rayet stars, Dwarkadas said. By his estimate, as much as 16% of all sun-size stars in our galaxy could have formed this way. “If it’s true, there’s no reason it should be true only for our solar system,” he said. “Ours will not be unique.”

Dwarkadas and his colleagues have laid out perhaps the most complete model for how the solar winds of a Wolf-Rayet star could have blasted aluminum-26 into our solar system as it formed. Afterward, the Wolf-Rayet star, with a lifetime of only a few million years, would most likely have collapsed into a black hole, although evidence for this would be long gone, Dwarkadas said.

There are problems with the Wolf-Rayet idea, Lugaro said. For instance, a Wolf-Rayet star creates such an energetic environment that it should have torn our newly formed solar system apart.

Boss still favors the theory that our cloud of dust was ignited by a supernova. Lugaro does not. “At the moment, from the nuclear-physics point of view,” she said, “I favor the winds of the Wolf-Rayet stars.” However, she said, new information could change her mind next week. “This is a problem that needs to be looked at from different angles. We are still fighting a bit about this.”

Gone Fishing

In Boston, Liu put the meteorite back in its safe. On her computer, she opened a live view through the microscope of a nanoprobe that can measure the chemical composition of tiny pieces of material. She and other researchers are using the device to study bits of meteorite dissolved in acid, on the hunt for grains with the right chemical composition to have come from a Wolf-Rayet star.

Related:

1. In a Grain, a Glimpse of the Cosmos

2. New Proof Finds the ‘Ultimate Instability’ in a Solar System Model

3. Astronomers Reimagine the Making of the Planets

Liu operated the nanoprobe remotely (it was in Washington, D.C.), slowly scrutinizing the meteorite bits scattered across a field of gold foil. “This is like a fishing expedition,” Liu said. Her next step, assuming she can find a good number of grains with the right chemical composition to have come from a Wolf-Rayet star, would be to measure whether they show signs of having been enriched in aluminum-26. This chemical information could then be used to constrain astrophysical models of the Wolf-Rayet scenario for the start of the solar system.

Liu acknowledged that the presence of such grains wouldn’t be a slam dunk for the Wolf-Rayet star theory; for instance, aluminum-enriched dust could have been produced by much older stars long before our solar system formed. But the absence of such grains would suggest that the Wolf-Rayet idea is off.

She watched the nanoprobe at work, delving billions of years into the past. Studying these grains, Liu said, gives her a new sense of the unique circumstances that led to the existence of our planet. “If you think about these radioactive isotopes — these rock-forming elements and life-forming elements,” she said, “when you know how they are produced in stars, you realize it is not so easy to get the right amount. You have to form at the right time and place.”

Table of Contents

Quanta Magazine: 2026 Mar 11

2026 Mar 11

Where Some See Strings, She Sees a Space-Time Made of Fractals

2026 Mar 9

Disorder Drives One of Nature’s Most Complex Machines

2026 Mar 6

New Strides Made on Deceptively Simple ‘Lonely Runner’ Problem

2026 Mar 4

Can the Most Abstract Math Make the World a Better Place?

2026 Mar 2

What Crystals Older Than the Sun Reveal About the Start of the Solar System