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Thursday, April 14, 2005
FROM ALPHA TO WHAT?
Could change be the only constant in the cosmos?
By ROWAN HOOPER
In David Mitchell's compelling novel "Cloud Atlas," two of the characters climb the dormant Mauna Kea volcano in Hawaii, and find giant domes -- observatories -- at the peak of the great mountain. The novel -- published last year -- is comprised of six interweaved strands, starting in the 1800s and moving through time until we reach the characters on Mauna Kea, hundreds of years in the future.
The telescopes are relics of a former age, a lost golden age of science and discovery. That age is now.
Scientists currently working at those observatories -- containing the largest optical telescopes in the world -- are studying light from distant quasars that has been traveling across the universe for billions of years. What they are discovering goes to the core of cosmology and physics, and has consequences for the meaning of life itself.
Because quasars (the word comes from "quasi-stellar radio source") are so bright, we can observe them at huge distances from us: They're the brightest objects in the universe. Their light has been traveling to the Earth for most of the history of the universe, as much as 12 billion years, so by examining that light we can determine what the universe was like when it was young.
And here's where things get strange. Physics is a hard science with hard, immutable facts, such as the constant speed of light and the constant charge on an electron. Another is the "fine structure constant," a fundamental number that governs the electromagnetic force holding all atoms and molecules together.
It is unthinkable to many physicists that these constants could change. Scientists have known for many years that if the value of the fine structure constant, also known as alpha, was slightly different, life could not exist. Only the very tiniest changes over time could be tolerated, and most scientists believe that alpha is the same today as it always has been.
"If alpha were perhaps just 2-3 percent smaller, meaning that electromagnetism was slightly weaker, then water molecules could not exist," said Michael Murphy, a researcher at the Institute of Astronomy at Cambridge University, England. "If alpha were a similar amount stronger then the carbon atom would be unstable. Thus, the consequences for a sudden overnight change in alpha would be catastrophic for life."
But Murphy's work -- the most detailed study of its kind yet performed, involving his analysis of data gathered over 10 years by the Keck telescopes on Mauna Kea -- suggests that alpha has changed.
"On the way to Earth, the light passes through far-off galaxies and the gas in those galaxies imprints very sharp, narrow absorption lines onto the light's spectrum," said Murphy -- who presented the results of his work at Physics 2005, a conference at the University of Warwick in central England this week -- in an e-mail interview. "But what we notice when we look at many different absorption clouds in front of many quasars is that the fingerprints of different atoms are shifted by very small amounts with respect to one another.
"One way, and seemingly the only way, to explain these small shifts is that alpha was somewhat smaller in the absorption clouds -- which we see as they were many billions of years ago -- than on the Earth today."
This does more than put a spanner in the works. If alpha is not constant, then we have a lot to learn about physics. The value of alpha seems finely tuned to allow the existence of life, but is this coincidence, or is there another explanation?
Some commentators explain the match by the anthropic principle. This is the quasi-religious view that the universe must have properties that allow the development of carbon-based life forms. Most cosmologists leave the idea well alone (it is untestable and therefore not scientific), but it has attracted (as flies are drawn to a carcass) proponents of intelligent design.
Another mooted explanation for the fine tuning is the idea that there are many other universes, collectively called the multiverse, and that the physical constants are different in each universe making up the multiverse.
The Astronomer Royal, Martin Rees (he is also a cosmologist at Cambridge) favors this view. It is speculative, to say the least, because there's currently no direct way to observe the multiverse.
"One good way around the philosophical difficulties of the anthropic principle," said Murphy, "is exactly what Martin Rees thinks: That we live in a multiverse and the values of the constants might be very different in different parts of it, and at different times."
Physicists long for a "theory of everything," one that unifies the fundamental interactions of nature. Observing a change in alpha could be an important step toward this, and a deeper understanding of physics.
For example, said Murphy, "If there really do exist many more dimensions of space, albeit too small for us to observe normally, a varying alpha might be a window into extra dimensions. By looking for varying constants, it may very well turn out that we're looking for the shadows of those other universes."
The giant telescopes on Mauna Kea will indeed be remembered for hundreds of years if that is what they help us see.
A book of Natural Selections columns translated into Japanese, "Nou to sekkusu no seibutsugaku (Evolution, Sex and the Brain)," is published by Shinchosha. Rowan Hooper is a biologist at Trinity College, Dublin. He welcomes readers' comments at firstname.lastname@example.org