How string theory lost its strings

String theory was once hailed as the “theory of everything” — a unified model of nature built on tiny vibrating strings. But after decades of expansion, the field has evolved beyond its namesake, embracing branes, dualities, and abstract geometry. Some physicists now wonder: is it time to rename the theory entirely?

In June of 2014, string theorists from around the world convened at Princeton University for the annual Strings Conference to discuss the latest discoveries and puzzles of their field. 

Juan Maldacena, one of the most influential figures in theoretical physics, posed a very meta question: is “string theory” even the right name for their field? 

Juan Maldecena, theoretical physicist, Harvard (Credit: Lumidek via Wikimedia Commons)

After all, strings–infinitesimally small threads of vibrating spacetime for which the theory is named–weren’t really the stars of the show anymore. The theory had outgrown its own name. 

Was it time, Maldecana asked his peers, for string theory to get a rebrand? A panel of leading figures engaged in a spirited session called “What is String Theory?”

Maldecena, half-jokingly, suggested an acronym that would preserve the spirit of the original name while embracing the field’s expanded purview: S.T.R.I.N.G.S. (Solid Theoretical Research Into Natural Geometric Structures). 

“Solid" reflects the mathematical consistency guiding the field. “Theoretical," Maldacena clarified, acknowledges its lack of experimental confirmation. And “Natural Geometric Structures" refers to the broad framework of general relativity, quantum field theory, gauge theories, supersymmetry, and their generalizations through string theory.

“They are mathematical structures which are natural in the sense that either we already use them to describe nature," he said, “or they are ‘natural' in the sense of simple or straightforward generalizations of structures that appear in nature."

The proposed acronym drew some chuckles at the conference, but it also underlined something real: the field called “string theory" has quietly evolved into something far more expansive–and far less reliant on tiny strings vibrating in 10 dimensions.

String theory: The legacy name

“It's really not about strings anymore," says astrophysicist Janna Levin, who doesn’t describe herself as a string theorist but has long followed the field's arc. 

Janna Levin, astrophysicist (Credit: Columbia University)

“It’s a legacy name. String theory's early ambition was to find the single theory, but instead of delivering one unifying model, it gave us a potentially infinite number of possible theories." 

In the early 1980s, string theory tantalized physicists because it promised something unprecedented: a “theory of everything." Instead of point particles, it proposed that the universe's fundamental ingredients were tiny, vibrating strings—an idea that could unify quantum mechanics and general relativity (a holy grail of modern science).  

Early breakthroughs helped fuel that hope. The theory naturally included the graviton—the hypothetical quantum particle of gravity—suggesting it could bridge the deep divide between bedrock theories. 

By the mid-’80s, the “First Superstring Revolution" was underway, with work by Michael Green and John Schwarz showing that string theory could be made mathematically consistent in 10 dimensions, solving problems that had stymied other approaches. String theory quickly rose to prominence, drawing in researchers from across physics and reshaping the direction of theoretical physics.

In those early years the dominant vision was excitingly tidy: all particles and forces—electrons, quarks, gravity—would emerge from tiny, vibrating loops of string. But that vision grew increasingly knotty. Instead of one tidy model, physicists discovered five distinct string theories, all mathematically consistent. Then came the realization that these were all different limits of a deeper theory.

Enter M-theory: A framework beyond strings 

That deeper theory emerged during a 1995 conference at the University of Southern California, when Edward Witten—arguably the world’s leading string theorist—proposed what became known as M-theory. 

Illustration of the relationship between M-theory, superstring theories, and eleven-dimensional supergravity. (Credit: Derivative work: Alex Dunkel via Wikimedia Commons)

This new theory unifies the five string theories, introducing higher-dimensional objects called branes (short for membranes) and expanding the framework into 11 dimensions.

What does the “M" stand for? Magic? Matter? Mystery? Membrane? Witten has never given a definitive answer, and string theorists seem happy to leave it ambiguous.

Sylvester James Gates Jr., a pioneer of string theory and supersymmetry, has watched string theory's transformation up close—and helped shape it. The M of M-Theory, in his interpretation stands, for “meta.” Gates has long advocated for viewing modern “string theory" as part of a broader intellectual movement–a meta-theory about theories. 

Sylvester James Gates Jr., theoretical physicist (Credit: energy.gov via Wikimedia Commons)

“Generally for those of us who work on ‘post-string theory,' we call it M-theory," he told FirstPrinciples. “And in my mind, M equals meta."

Gates traces string theory's broadening focus to the realization that one-dimensional strings were only part of a richer mathematical landscape. By the late 1990s it had become clear to him that branes, dualities, and higher-dimensional structures were just as fundamental as strings.

In 2020, he and his PhD students at Brown University helped solve a 40-year-old mathematical problem in M-theory. The breakthrough relied on a new mathematical tool he calls adynkras  (a hybrid of African Adinkra symbols and Dynkin diagrams, used to map out the complex relationships in supersymmetric systems).

Adinkra deconstructed into two smaller adinkras (Credit: On Being)

These visual tools allowed Gates and his team to analyze vast numbers of functions that had previously defied classification.

Adynkras, essentially graphical representations of supersymmetric relationships, show just how far the field has moved from the idea of tiny loops vibrating in 10 dimensions. 

Notably, this string theory breakthrough hinges on no actual strings. 

“The reason we could do this when no one else could is because we used the 2.0 version of the tools,” he told FirstPrinciples. “If we had stayed focused purely on literal strings, we would have missed an entire vista of structures governing how the universe might actually work." 

In other words, string theory’s evolution has been driven less by strings themselves and more by the deep mathematical structures they helped uncover.

Gates acknowledges that “string theory” is no longer an ideal name for his field, but he’s also unconcerned about semantics.  

“Mathematics is my first language,” he says, “and English is my second.” 

Demoted to second-string

Shiraz Minwalla, a leading string theorist based at Tata Institute in India, has watched this shift unfold firsthand.

Shiraz Minwalla, theoretical physicist and string theorist (Credit: IAS)

“It's not like these little strings are not part of it," Minwalla told FirstPrinciples. “You know, in the 1980s, when people were developing string theory, it looked very promising that the electron would be a little vibrating string and the quarks would be some other little vibrating string—and that might still be the case. But we now realize strings are only one corner of this thing.” 

In many current models of string theory, he said, “the electron would not be naturally described as a vibrating string but as something else, like a D-brane or something more complicated."

The Physics Tommyknockers?

Not all observers are convinced the field’s evolution represents meaningful progress. Sabine Hossenfelder, a theoretical physicist and author known for her YouTube critiques of foundational physics, sees the transformation of string theory as part of a wider issue. 

Sabine Hossenfelder, theoretical physicist. (Credit: YouTube @SabineHossenfelder)

“My big problem with string theory has always been that the amount of people, time and effort that went into it isn’t justifiable,” she told FirstPrinciples in an interview. “It’s just become this huge bubble of research.”

Hossenfelder is skeptical of the field’s sprawling offshots. “For a long time they had this idea—there’d be a unique theory of everything—that didn’t pan out,” she said. Instead, she sees a pattern: whenever string theory ran into trouble, “they fixed the problem” by adding supersymmetry, then R-parity, then extra dimensions. 

She likens string theorists to a character in Stephen King’s The Tommyknockers, who stumbles upon a mysterious metal object and begins digging obsessively to uncover it, but it only becomes more mysterious and otherworldly the deeper she digs.  

“Fifty years later they’re still digging, and they’re not sure what they have there,” says Hossenfelder. 

Over the past few decades string theory has been something like a string of theories: a framework for exploring quantum gravity and the landscape of possible universes.

And that’s part of the problem. One reason strings faded from center stage was the so-called ‘landscape problem’—the realization that string theory doesn’t predict one unique universe, but rather an almost unfathomable number of consistent solutions. 

These solutions—known as vacua—are often estimated at around 10^500. That’s a number so enormous it’s nearly impossible to conceptualize.

As a result, the field shifted. Rather than fixating on reproducing the Standard Model, many string theorists now study more abstract features of symmetry, duality, and the structure of spacetime itself.

S.T.R.I.N.G.S. revisited: A new name for an evolving field?

There is merit to Maldacena’s proposal to rename the field as “Solid Theoretical Research Into Natural Geometric Structures.” It’s a decent description, not as limiting as “strings,” though it doesn’t roll off the tongue as nicely.  

Thankfully, Maldecena’s other contributions to the field have had much greater impact. 

His 1997 discovery of the AdS/CFT correspondence was a turning point. Maldecena and others developed the concept of holography, pushing string theory beyond particle descriptions and into the study of quantum spacetime itself. 

The holographic principle has reshaped everything from black hole thermodynamics to condensed matter theory. It’s one of the most widely cited theoretical breakthroughs of the past 30 years—and it emerged not from studying strings per se, but from examining the symmetries and dualities that string theory helped illuminate.

As Shiraz Minwalla puts it, “The insights we've gained into the structure and workings of quantum gravity... would have been unimaginable without early days of string theory.”

Whether it remains string theory or naturally evolves into M-Theory is an open question. One thing is clear: the theory that started with vibrating strings has transformed into something far more expansive.

And Maldacena’s playful S.T.R.I.N.G.S. acronym—will it ever catch on?

“I don’t think so,” he replies.  

Colin Hunter is a science communicator, filmmaker, and contributor to FirstPrinciples. He previously led the communications teams at the Perimeter Institute for Theoretical Physics and the Institute for Quantum Computing (IQC) at the University of Waterloo.