Studying how light was absorbed by metallic atoms in gas clouds some 12 billion light-years away, researchers found that the fine structure constant, as it is called, may be changing subtly as the universe grows older. The universe is thought to be roughly 13 billion years old, so the light observed in the new study was emitted when the universe was roughly a billion years old.
The research was met with caution by many scientists, who also said that if it is accurate, then the adjustment to theories would be significant and far-reaching.
A paper on the study, led by John K. Webb of the University of New South Wales in Sydney, Australia, will be published in the Aug. 27 issue of the journal Physical Review Letters. Webb and his colleagues reported similar but inconclusive evidence in 1999.
The apparent change in the fine structure constant, also called alpha, was very small, amounting to 1 part in 100,000. And the researchers calculated that there is a 1-in-10,000 chance that the result is a statistical fluke.
Alpha and the standard model
The fine structure constant explains how electromagnetic forces hold atoms together.
"This constant governs the structure of atoms, and it governs how light interacts with atoms," said Christopher Churchill, a member of the research team from Pennsylvania State University.
In a telephone interview, Churchill explained the physics of the finding. Imagine an atom as looking something like the solar system, he said, with the planets representing electrons orbiting around the nucleus. As light passes through an atom, certain wavelengths alter the positions of the electrons.
"It's like taking Earth's orbit and changing it to Mars' orbit," he said. The fine structure constant dictates that these interactions are precise. Certain wavelengths of light have predictable effects on each type of atom.
But when Churchill and his colleagues looked back in time at light passing through atoms in the young universe, they saw something else.
"What we've seen is that the structure of these atoms must be very slightly different, just so slightly, that the frequency of light that's involved in bumping the electrons from one orbit to the next is just a little bit different."
This implies that something in the early universe behaved differently. Because the speed of light is one factor in the fine structure constant equation, it might be it that has changed over time, Churchill said. Or it could be that unknown properties of the early universe forced atoms and electrons to behave in ways researchers don't understand. |
