A fundamental constant of the universe may not be so constant after all, according to a new study.
Recent observations of distant galaxies suggest that the strength of the electromagnetic force the so-called fine-structure constant actually varies throughout the universe. In one direction, the constant seemed to grow larger the farther astronomers looked; in another direction the constant took on smaller values with greater distance.
If confirmed, this revelation could reshape physicists' understanding of cosmology from the ground up. It may even help solve a major conundrum: Why are all the constants of nature perfectly tuned for life to exist?
"This is an exciting and potentially important result that challenges astronomers and particle physicists for an explanation," said astrophysicist John Barrow of the University of Cambridge, who was not involved in the new study but has worked with the researchers in the past. "It could be a further hint about new physics."
A changing constant
Astrophysicists have been studying the fine-structure constant known as the alpha constant for years, searching for hints that it might change. Some projects have found evidence that the constant does vary, while other probes confirmed the constant's constancy. [The Greatest Mysteries in Science]
But the evidence supporting the alpha constant's variable nature was ambiguous, because it could also be due to a variation over time, or across different parts of space, researchers said.
The farther out astronomers peer into the universe, the longer it has taken the light they see to reach Earth. Since this light is older, it represents an earlier epoch in the universe's history.
So if scientists measured a change in the fine-structure constant from different observations, it may have been because the constant has different values in different places, or it might have been because it had different values at different times. But determining which case is right has been a challenge.
To settle that question, researchers led by John Webb from the University of New South Wales, Australia, gathered observations from the Keck telescope in Hawaii, and the Very Large Telescope in Chile thereby covering both the northern and southern skies.
"When you look in one direction, you cannot distinguish between variation in space and variation in time," co-researcher Victor Flambaum, also of the University of New South Wales, told SPACE.com. "Now there is nearly complete coverage of the sky. The conclusion is:It's a variation in space, not in time."
To determine how strong the alpha constant was in any given spot, the scientists measured the frequency at which electrons in various atoms would hop from one energy level to the next. This frequency depends on the fine-structure constant.
The researchers found that in the northern sky, the fine-structure constant gets smaller with increasing distance, or as astronomers look farther back in time. In the southern sky, however, the alpha constant value appeared to increase the farther away they looked.
Since those two results would contradict each other if the alpha constant varied with time, the constant must take on different values in different areas of the universe, the researchers concluded.
Why do we exist?
Webb presented the findings last week at the Joint European and National Astronomy Meeting in Lisbon, Portugal. The research has been submitted to the journal Physical Review Letters and is awaiting peer review.
"Now we have an explanation," Flambaum said."If fundamental constants vary in space, we just appear in the area of the universe where constants are good for us."
In other regions of the universe where the constants are different, life may be absent, he said.
Flambaum admitted that such revolutionary results need even more evidence to be believed for sure.
And other experts may take some convincing.
Helge Kragh, a science historian at the University of Aarhus, Denmark, who has written about the history of the fine-structure constant, said it's important to "keep a healthy skepticism" about announcements like these, since past measurements of variation, such as earlier claims that the constant changes over time, have later been disproven.
"If history is a guide — and often it is not — the results of Webb et al. will turn out to be untenable," he said.
Flambaum said the team plans to collect more data from the distant universe, as well as conduct laboratory experiments, to test their results.
"The problem is whether there are systematic biases which the authors have not thought of which can mimic the appearance of varying alpha," Barrow said. "They are a very strong and experienced observational team who have subjected the data to many tests in the search for bias but have failed to find any so far."