A spatial variation in the fine structure constant has profound implications for cosmology
Over the years, many physicists have wondered whether the fundamental constants of nature might have been different when the universe was younger. If so, the evidence ought to be out there in the cosmos where we can see distant things exactly as they were in the past.
One thing that ought to be obvious is whether a number known as the fine structure constant was different. The fine structure constant determines how strongly atoms hold onto their electrons and so is an important factor in the frequencies at which atoms absorb light.
If the fine structure were different earlier in the universe, we ought to be able to see the evidence in the way distant gas clouds absorb light on its way here from even more distant objects such as quasars.
As it turns out, exactly this kind of evidence has emerged in the last ten years or so from studies of absorption spectra carried out with the Keck telescope in Hawaii. These indicate that the fine structure constant must have been smaller when the universe was younger. It's fair to say, however, that this evidence is controversial--other studies have not always corroborated the result.
That debate looks set to pale into insignificance compared to new claims being made about the fine structure constant. Today, John Webb at the University of South Wales, one of the leading proponents of the varying constant idea, and a few cobbers 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. That's significant because Keck looks out into the northern hemsiphere, while the VLT looks south
This means that in one direction, the fine structure constant was once smaller and in exactly the opposite direction, it was once bigger. And here we are in the middle, where the constant as it is (about 1/137.03599...)
That's a mind blowing result. One of the biggest conundrums that cosmologists face is explaining why the fundamental constants of nature seem fine tuned for life. If the fine structure constant were very different, stars and atoms wouldn't form and the universe as we know it couldn't exist. No theory explains why it takes the value it does which leaves scientists at a loss.
The implication from Webb and co's data is that the fine structure constant is continuously varying throughout space and is merely fine-tuned for life in this corner of the cosmos: the universe's habitable zone. Elsewhere, presumably well beyond the universe we can see, this constant is entirely different.
That's likely to put the cat among the pigeons. Webb is no stranger to controversy--he has had to fight tooth and nail to have his data and ideas accepted. But this time round, with such a radical new data on the table, the debate is likely to be fiercer still.
So sit back and enjoy the show.
Refs:
arxiv.org/abs/1008.3907: Evidence For Spatial Variation Of The fiFine Structure Constant
arxiv.org/abs/1008.3957: Manifestations Of A Spatial Variation Of Fundamental Constants On Atomic Clocks, Oklo,
Meteorites, And Cosmological Phenomena
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