Scientists find a practical test for string theory

Two-minute lectures by Towson University faculty. James Overduin (Department of Physics, Astronomy and Geosciences) explains why a single theory of physics is needed to restore the "house of physics" and enable humans to progress in science and technology.

Scientists at Towson University in Towson, Maryland, have identified a practical, yet overlooked, test of string theory based on the motions of planets, moons and asteroids, reminiscent of Galileo's famed test of gravity by dropping balls from the Tower of Pisa.

String theory is infamous as an eloquent theoretical framework to understand all forces in the universe —- a so-called "theory of everything" —- that can't be tested with current instrumentation because the energy level and size scale to see the effects of string theory are too extreme.

Yet inspired by Galileo Galilei and Isaac Newton, Towson University scientists say that precise measurements of the positions of solar-system bodies could reveal very slight discrepancies in what is predicted by the theory of general relativity and the equivalence principle, or establish new upper limits for measuring the effects of string theory.

The Towson-based team presents its finding today, January 6, 2014, between 10 a.m. and 11:30 a.m., at the 223rd meeting of the American Astronomical Society, in Washington, D.C.

The work also appears in the journal Classical and Quantum Gravity.

This is an image of a two-dimensional hypersurface of the quintic Calabi-Yau three-fold. 

Credit: Jbourjai/Wikipedia.

String theory hopes to provide a bridge between two well-tested yet incompatible theories that describe all known physics: Einstein's general relativity, our reigning theory of gravity; and the standard model of particle physics, or quantum field theory, which explains all the forces other than gravity.

String theory posits that all matter and energy in the universe is composed of one-dimensional strings.

These strings are thought to be a quintillion times smaller than the already infinitesimal hydrogen atom and thus too minute to detect indirectly.

Similarly, finding signs of strings in a particle accelerator would require millions of times more energy than what has been needed to identify the famous Higgs boson.

"Scientists have joked about how string theory is promising...and always will be promising, for the lack of being able to test it," said Dr. James Overduin of the Department of Physics, Astronomy and Geosciences at Towson University, first author on the paper.

"What we have identified is a straightforward method to detect cracks in general relativity that could be explained by string theory, with almost no strings attached."

More information: "Expanded Solar-System Limits on Violations of the Equivalence Principle," m.iopscience.iop.org/0264-9381/31/1/015001