January 9, 2013
Controversial Theory Could Provide First Test Of Quantum Gravity
John P. Millis, Ph.D. for redOrbit.com — Your Universe Online
Two of the greatest scientific achievements of the last century were the establishment of the theories of Quantum Mechanics and General Relativity, both of which have withstood continual experimental scrutiny. However, a problem remains. The two theories seem to be at odds with each other.
Researchers, for decades, have sought a theory that would combine the two realms — the large-scale gravity fields, and the tiny quantum scales — while Einstein himself spent the latter part of his life searching for just such a theory.
While a definitive solution remains elusive, there are several viable theories, each falling within two general categories: String Theory (to include M-theories) and Quantum Gravity. One of the greatest challenges with developing such theories is creating an experiment that could test them.
But a controversial take on quantum gravity may hold the key. University of Arizona physics professor Andrei Lebed has suggested that one of the fundamental tenants of Einstein´s theories could be wrong.
General relativity is predicated on the notion that a gravitational field is indistinguishable from an accelerating reference frame. In other words, a spaceship accelerating at 9.8 meters per square second would feel exactly the same as falling near the surface of the Earth.
But Lebed argues that there is a difference, because a gravitational field manifests itself as a curvature in space-time. And it is this curvature that would affect motion on a quantum level.
If correct, this would mean that atoms would behave slightly different depending if they were in a gravitational field (curved space-time) or absent any such fields (flat space-time).
In a gravitational field, Lebed contends, the energy from the field can cause an electron in an atom to become excited and briefly enter an excited energy state. When the electron relaxes back to its ground state a photon is emitted. If true, then such excitations would not be expected absent gravitational fields.
Therefore Lebed proposes that sending a probe filled with hydrogen gas out into our solar system, far from significant gravitational energy, would allow for a test of this theory. If no excitations are measured, it would indicate that gravitational fields are responsible for the excitations, and that his theory on quantum gravity is on the correct path.
However, many researchers are not convinced. While the cause of electron energy fluctuation is still a mystery, scientists believe that there could be a cause other than gravity fields. But this only makes an experiment like the one proposed by Lebed, all the more exciting. If ever launched, it could be an important step toward a unified theory of quantum gravity.