The times, they are a-changin', and so are the fundamental constants of physics, according to an international group of physicists. After analyzing light from distant quasars, the team reports that the so-called fine-structure constant--whose value, like that of the speed of light, was thought immutable--has shifted over billions of years. But the claim is bound to be extremely controversial.
The fine-structure constant is an amalgamation of the speed of light, the charge of the electron, and the quantum-mechanical number known as Planck's constant; combined, they provide a measure of the inherent strength of electromagnetic interactions, such as those that bind an electron to an atom. The constant's value is approximately 1/137, and scientists believe it's been that way since the dawn of time.
In the 27 August edition of Physical Review Letters, however, a team of astronomers and physicists present evidence to the contrary. "The physics is pretty straightforward," says team member Jason Prochaska, an astronomer at the Observatories of the Carnegie Institute of Washington in Pasadena. When light passes through a cloud containing, magnesium, iron, nickel, and other atoms, the atoms absorb certain wavelengths of light, leaving dark lines in the spectrum. The fine-structure constant determines the relative position of those bars, as the absorption of light by an atom is governed by the electron-atom interaction. The spacing of absorption lines from 72 distant quasars seems to indicate that the fine structure constant was 0.001% smaller billions of years ago--a conclusion that would dash fundamental assumptions in physics.
Lennox Cowie, of the University of Hawaii's Institute for Astronomy in Manoa, is skeptical. He believes that the absorbing clouds vary in composition, which could cause a similar change in spacing. But the team believes it has accounted for that effect, and Prochaska says that the case is strengthened further by more recently analyzed data. Yet, to convince the skeptics, another team needs to repeat the observation with a different telescope and instrument, he admits. "That would be the proof of the pudding."