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String theory suddenly emerged from simple physics rules

Physicists may have found that the universe secretly “wants” string theory to exist.

Date:

May 19, 2026

Source:

Caltech

Summary:

Physicists may have uncovered a surprising new clue that string theory—the idea that the universe is built from unimaginably tiny vibrating strings—could be more than just a mathematical fantasy. Instead of assuming strings existed from the start, researchers began with a few simple rules about how particles behave at extreme energies and discovered that the equations naturally produced the telltale fingerprints of string theory all on their own.

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FULL STORY

Artwork illustrating how string theory emerges from a few simple mathematical assumptions about particle collisions. Credit: AI-generated art by Clifford Cheung

If you kept dividing an apple into smaller and smaller pieces, you would eventually reach molecules, then atoms, and later the tiny particles inside atoms such as protons, quarks, and gluons. But according to string theory, the journey does not stop there. At scales roughly a billion billion times smaller than a proton, physicists propose that everything may be made of incredibly tiny vibrating strings.

String theory first emerged in the 1960s as a possible way to solve one of physics' biggest problems: combining quantum mechanics, which governs the smallest particles, with general relativity, Einstein's theory describing gravity and the large-scale structure of the universe. Scientists have long struggled to unite the two because the equations often spiral into mathematical infinities when gravity is included at quantum scales.

String theory offers a potential way around that problem. In the theory, every particle, including the hypothetical graviton that would carry the force of gravity, comes from different vibrations of tiny strings. The mathematics also requires the strings to exist in at least 10 dimensions rather than the four dimensions humans experience.

One major obstacle remains. Testing string theory directly would require energies so extreme that researchers would need a particle collider as large as a galaxy.

Bootstrap Physics and String Theory

Since direct experiments are impossible with current technology, physicists are exploring other methods. One promising strategy is known as the "bootstrap" approach. Instead of assuming a detailed theory from the start, scientists begin with a few broad principles they believe nature must obey and then determine what laws naturally emerge.

In a new study titled "Strings from Almost Nothing," accepted for publication in Physical Review Letters, researchers from Caltech, New York University, and Institut de Fisica d'Altes Energies in Barcelona used this strategy to investigate particle behavior at extremely high energies. Starting from just a couple of assumptions about how particles scatter during collisions, they unexpectedly arrived at the core features of string theory.

"The strings just fell out," says Clifford Cheung, professor of theoretical physics and director of the Leinweber Forum for Theoretical Physics at Caltech. "We didn't start with any assumptions about strings at all, but then the solution contained the cornerstone signatures of strings."

Although the findings do not prove string theory experimentally, Cheung says the results are striking because many different mathematical outcomes could have been possible. Instead, the calculations pointed toward only one solution.

The Infinite Tower of Particles

One of the most important features to emerge from the calculations is known as the string spectrum. In the late 1960s, Italian theoretical physicist Gabriele Veneziano at CERN developed a mathematical function describing a mysterious "tower" of particles seen in collider experiments. The particles appeared in a sequence where mass and spin increased in orderly steps.

"At Veneziano's time, particle colliders were seeing this spray of junk come out of the collisions, particles of different masses. It was fascinating and nobody had any idea what was going on. Veneziano wrote down a function to describe all the masses, revealing an infinite tower of particles," Cheung says.

Researchers later realized this pattern resembles the harmonics of a vibrating string. When a violin string is plucked, it produces a main tone along with a series of overtones. String theory proposes that particles arise from similar vibrational patterns.

In 1974, Caltech physicist John Schwarz and French physicist Joël Scherk recognized that string theory could also include gravity. That discovery created one of the first meaningful links between string theory and general relativity.

"Like all particle physicists in that era, we had no prior interest in gravity. String theories are well-behaved at very high energies, unlike Einstein's general theory of relat