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Quasar Study Suggests a Physics Constant Isn’t so Constant

By Joseph Calamia
Sep 11, 2010 2:08 AMNov 20, 2019 12:57 AM


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After analyzing light coming from distant quasars, some researchers have asked a physical constant a blunt question: Are you really constant at all? And since the "fine structure constant" that they're interrogating is important for how physicists understand things like electrons' behavior in atoms and fusion in stars, other physicists are asking their own question: Are your measurements correct? The paper, which appeared last month in arXiv, argues that the constant might vary depending on location. This controversial claim is a new twist on a previous controversial claim--made over the past decade by some of the same physicists--which said that the constant varied with time.

Craig Hogan of the University of Chicago and the Fermi National Accelerator Laboratory in Batavia, Ill., acknowledges that “it’s a competent team and a thorough analysis.” But because the work has such profound implications for physics and requires such a high level of precision measurements, “it needs more proof before we’ll believe it.” [Science News]

Because the constant determines how atoms absorb light, researchers looked at how distant gas clouds in space appeared to absorb the quasars' light. The light they get from these far away clouds has traveled for billions of years to reach them and therefore is a means to look into the universe's past. Some of the same researchers previously argued, using observations from the Keck telescope in Hawaii, that the constant was smaller when the universe was younger. Now, measurements from a different telescope seem to say it was larger in the past.

Today, John Webb at the University of South Wales, one of the leading proponents of the varying constant idea, and a few [colleagues] say they have new evidence from the Very Large Telescope in Chile that the fine structure constant was different when the universe was younger. But get this. While data from the Keck telescope indicate the fine structure constant was once smaller, the data from the Very Large Telescope indicates the opposite, that the fine structure constant was once larger. [Technology Review]

Now for the twist. Since the Keck observations measured light in the Northern Hemisphere while the Very Large Telescope measures light from the Southern, the two results together suggest that the constant varies with location. The difference is small, the researchers note, and apparently only varied during the first several billion years of the universe's life. Still, Paul Davies of Arizona State University says that if correct the find could mean questions for other fundamentals.

If the fine-structure constant really does vary in both space and time, says Davies, it’s an obvious extension that other presumed constants of nature--such as the gravitational constant that determines the strength of the gravitational force--might vary in a similar lopsided manner. “If we can accept a varying fine-structure constant, then all bets are off.” [Science News]

Despite the constant's importance and the fact that changing the rules of physics would be a mite confusing for everybody, coauthor Michael Murphy of Swinburne University in Australia declares that it's his job to test assumptions:

[Murphy] understands the caution. But he says the evidence for changing constants is piling up. "We just report what we find, and no one has been able to explain away these results in a decade of trying," Murphy told New Scientist. "The fundamental constants being constant is an assumption. We're here to test physics, not to assume it." [New Scientist]

Related content: 80beats: Far-Off Quasar Could Be the Spark That Ignites a Galaxy 80beats: Researchers Spot an Ancient Starburst from the Universe’s Dark Ages 80beats: How to Create a Black Hole on a Lab Bench 80beats: We Knew That Black Holes Were Massive. Now Double That. DISCOVER: Quasars Say Earth is 1/2 a Pinkie Smaller

Image credit: NASA/ESA/ESO/Wolfram Freudling et al. (STECF)

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