08-04-2025
Physicists Think They've Finally Seen Evidence of String Theory
Last month, the Dark Energy Spectroscopic Instrument (DESI) collective reported that dark energy is evolving—specifically weakening—and it could help provide the first observational evidence of string theory.
While a new preprint reports that cosmological models using the string theory framework account for this weakening of dark matter, some physicists aren't convinced that DESI's data alone definitively speaks about the true nature of dark energy.
Luckily, future instruments such as the Nancy Grace Roman Space Telescope and the Vera C. Rubin Observatory will hopefully either confirm these string theory findings or set physicists down a different path toward finding that ever-elusive 'theory of everything.'
The centuries-long Copernican journey of slowly displacing humans from the center of everything has provided our species with an unprecedented understanding of our planet, Solar System, and the known universe. But with every cosmological answer comes an all-you-can-eat buffet of new questions, none of which are quite as enticing as the mystery of dark energy.
Ever since the first observational evidence in 1998, when scientists discerned that the universe's expansion was actually accelerating, dark energy has figured prominently in most leading theories attempting to explain the workings of the universe. String theory—the theoretical roots of which date back to the late 1960s—is one of those explanations, and the framework's fortunes have risen and fallen with the passing decades. Many scientists have declared the theory all but dead (or, at the very least, on life support), but new data from the Dark Energy Spectroscopic Instrument (DESI), which was designed to capture spectroscopic surveys of distant galaxies, has provided some encouraging evidence that string theorists may actually be onto something.
At least, that's the idea behind a new preprint paper, published on the server arXiv. Scientists from Virginia Tech, State University of New York (SUNY) and the University of the Witwatersrand in South Africa argue that the bombshell observations from DESI—primarily, that the dark energy is weakening over time—could provide some of the first direct observational evidence of string theory.
'Given our proposal for the origin of dark energy from the geometry of the dual spacetime, the latest results from DESI might point to a fundamentally new understanding of quantum spacetime in the context of quantum gravity,' the authors wrote in the non-peer-reviewed paper.
Unlike the Standard Model, which considers particles to be point-like, string theory—as its name suggests—conceptualizes these particles as one-dimensional vibrating strings, the vibrations of which dictate the behaviors and qualities of the particles. After the announcement of DESI's discovery last month that the impact of dark energy may be weakening over time, string theorists perked up, as this new piece of data fits well within many existing string theory predictions. Cumrun Vafa, a string theory physicist at Harvard University, told Quanta Magazine last month that 'the theory kind of demands that [dark energy] change.'
According to Live Science, this new study developed a string theory model that yielded a dark energy density that closely mimicked the data found by DESI. They also discerned that dark energy is impacted by two completely different types of lengths: the ultra-small Planck scale and the absolute size of the universe. This connection hints that dark energy is somehow related to the quantum nature of spacetime itself.
'This hints at a deeper connection between quantum gravity and the dynamical properties of nature that had been supposed to be constant,' SUNY's Michael Kavic told Live Science. 'It may turn out that a fundamental misapprehension we carry with us is that the basic defining properties of our universe are static when in fact they are not.'
This doesn't suddenly mean that we've found the ever-elusive 'theory of everything'—a concept that unifies all physics both classical and quantum. For one, independent observations would need to confirm the assertions in this paper (though, the authors believed they've identified ways to possibly accomplish that feat). However, others argue that even the DESI data isn't conclusive on the true nature of dark energy, and that we need superior instruments to really understand what's going on.
Luckily, we're getting just that. NASA is preparing to launch the Nancy Grace Roman space telescope in 2027, and the National Science Foundation is set to achieve 'first light' with the Vera C. Rubin Observatory later this year. DESI's impressive dataset has set physics down a new path of discovery, but these new instruments will hopefully provide long sought-after cosmological answers—and also a few new questions we never even thought to ask.
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