String theory is perhaps the greatest tragedy of modern science. Mathematically elegant and celebrated savior of divided physics, it is nonetheless crippled by one simple fact – it is utterly untestable.
Nonetheless, it may still be an inevitable truth, according to a small team of physicists from the California Institute of Technology, New York University, and the Autonomous University of Barcelona, whose recently published study goes back to basics in search of clues on string theory’s uniqueness.
By starting with the fewest assumptions possible, the team formed a “bootstrap” rationale suggesting that the properties of a grand theory of everything are likely to look suspiciously string-like.
While it’s far from the kind of proof needed to claim string theory is true, the findings do make it a touch harder to dump the theory in the scrap bucket of science and set it on fire.
For the uninitiated, 20th-century physics was blessed and cursed with two of the best ideas ever concocted.
One, known as the general theory of relativity, provides a mathematical framework for describing how the stage upon which the Universe stands bends and warps beneath its feet.
The other, called quantum mechanics, directs the Universe’s actors based on the mathematics of probability, once used exclusively to predict outcomes in matters of gambling.
General relativity is perfect for predicting the motion of planets and galaxies under gravity’s dictation. Quantum mechanics is incredibly precise when you want to predict the behavior of subatomic particles, especially when it comes to electromagnetism and atomic forces.
Where the two meet, there is no agreement, leaving physicists to search for a single theory with the predictive power of each that might explain tiny colossal things like the core of a black hole or the earliest moments of the Big Bang.
String theory – or, more appropriately, string theories – is a category of frameworks that replace point-like particles with one-dimensional loops that vibrate in multiple dimensions. Waves along the string give matter its fundamental properties, such as mass or charge, sidestepping critical limitations in general relativity and quantum mechanics.
This isn’t to say matter consists of itty-bitty buzzing circles. It is to say that the mathematics we use to describe the hum of a plucked rubber band may also be useful in reconciling the warring factions of physics.
One major problem with all of these theories is that none describe the Universe we live in. Or, to be more precise, they all describe countless possible Universes with equal conviction.
Knowing how to tweak any one theory so it uniquely describes the Universe we live in demands a successful prediction, such as a particular excitation under specific conditions at or below a scale we simply have no known way to check experimentally.
Which is a problem.
While we wait for somebody to come up with a better idea, our bold team of theoretical physicists pared back the complexities of nature in search of unique consequences of a handful of broadly accepted assumptions.
Several of those assumptions involved particle collisions, scattering, and conservation in Quantum Field Theory. Another was a basic principle about the consistency of laws. None of these are controvertible in any way.
Building a model based on these assumptions from the ground up, the team landed on a set of figures that naturally deliver the scattering formula that famously gave rise to string theory in the first place, back in the 1960s.
In some ways, this might not be all that surprising. Something in string theory has held our attention for the better part of half a century, after all.
Yet such bootstrapping approaches may show us which strings to pull and which to keep, and just maybe reveal a way to finally probe the chasm between the two mighty continents of modern physics.
This research was published in Physical Review Letters.
Source: Science
Fact-checked by Bronwyn Thompson
