Big Bang Heard in World of Physics
In 1999, a paper in the prestigious scientific journal Physical Review Letters indicated that one of nature’s fundamental constants--a number that, in effect, reflects how tightly atomic particles stick together--might be different now than it was in the distant past.
In the world of physics, this was a potentially revolutionary result. If the number known as the fine-structure constant--alpha--was, in fact, changing over time, the “standard model” of physics, governing everything from nuclear interactions to the birth, evolution and fate of the universe, needed to be overhauled.
Mario Livio, a leading theorist at the Space Telescope Science Institute in Baltimore, was intrigued by the paper’s conclusions. “I said to myself, ‘Wow, this is really dramatic, if true.’ But it probably is completely crazy.”
To find out, he carried out calculations that extended earlier theoretical work and “more or less convinced myself the explanation for their results must lie elsewhere and not in an actual change in the fine-structure constant.”
“This has by now become a cliche, but extraordinary claims require extraordinary proofs,” he said. “To me, their claim did not quite pass the barrier. . . .”
Since then, an international team led by John Webb, head of astrophysics at the University of New South Wales in Sydney, has collected additional data using one of the world’s most powerful telescopes, the 33-foot Keck 1 reflector in Hawaii. As with their initial study, the researchers focused on light from distant but brilliant celestial objects, called quasars, passing through clouds of gas and dust.
As such background light hits metallic atoms in these clouds, certain wavelengths are absorbed. When the light reaching Earth is examined spectroscopically, dark “absorption lines” are seen in the spectra of the quasars. The spacing of these absorption lines is proportional to the square of the fine-structure constant. By comparing spectra from quasars behind clouds at different distances, and thus different points in the history of the universe, researchers can calculate the value of alpha at different points in time.
In the Aug. 27 issue of Physical Review Letters, Webb’s team published a second paper, this one showing statistical evidence that the fine-structure constant has, in fact, changed by perhaps one part in 100,000 over the past 12 billion years. Not much, perhaps, by everyday standards. But more than enough to send shock waves through the physics community.
“What was true at the beginning is true now,” Livio said. “If confirmed, this is a sensational result. This is really probably one of the major breakthroughs we have seen.”
Although independent confirmation remains down the road, the high quality of the latest data and the use of innovative analytical procedures lend more credence to the team’s conclusions.
“I cannot see anything they are doing wrong,” Livio said. “They have definitely improved on all aspects of their work.”
The fine-structure constant is a pure number; it has no dimensions. It is roughly equal to 1 divided by 137, or more precisely, 0.007297351. That’s what you get when you divide the square of the charge of the electron by the product of the speed of light and Planck’s constant, a fundamental measure of the quantum nature of reality on the atomic scale.
“Anybody who claims that alpha is changing probably thinks in terms of the electron’s charge changing,” Livio said. “What alpha really measures is the strength of the electromagnetic interaction, and the strength of the electromagnetic interaction is the electron charge.”
Christopher Churchill, coauthor of both Physical Review papers and a researcher at Pennsylvania State University, said even tiny changes in the fine structure constant could have measurable effects in the early universe, including the ratio of protons to neutrons.
Of more immediate interest, a changing fine-structure constant would point to fundamental flaws in scientists’ current understanding of the universe and the physical laws governing its behavior.
The standard model of physics unites three of the four basic forces of nature, showing that at sufficiently high temperatures they are manifestations of a single superforce. But physicists have not been able to bring the fourth force--gravity--into this conceptual framework and as a result, Einstein’s relativity theory cannot be reconciled with quantum mechanics.
