11 April 2005
Alpha Constant May Not Be Constant
by Kate Melville
Dr Michael Murphy of Cambridge University, speaking at the Physics 2005 conference, has suggested that the fine structure constant, one of the cornerstones of physics, might not be constant after all. The fine structure constant, or alpha constant as it is often called, is a critical number which seems to be precisely tuned for life to exist. It governs the electromagnetic force which holds all atoms and molecules together. Scientists have known for many years that if its value was slightly different, life could not exist. Most scientists believe that alpha today is the same as it always has been. But Murphy thinks this sacred number might be changing.
Murphy's theory is based on the knowledge that the constant affects the spectral absorption "fingerprint" of atoms, which can be detected when light shines through gas clouds. Murphy has been using the Keck telescope on Mauna Kea in Hawaii to study light from distant quasars. He has used quasars as distant light sources whose billion-year-old light encounters gas clouds on its way to Earth. The absorption spectra of these distant encounters is recorded and compared to spectra obtained in experiments on Earth. By comparing the gas cloud fingerprints with those obtained on Earth, he concludes that alpha has changed by about one part in two-hundred-thousand during the last 10 billion years.
Other researchers have published results which suggest that alpha does not change but Murphy believes his work is the most detailed survey ever performed. He says that the internal checks in his method, which other research groups did not use, make it the most reliable measurement to date. Murphy is careful not to claim that the case is closed, and he says that nobody can really say that alpha varies until another type of experiment has confirmed it. "We are claiming something extraordinary here," said Murphy, "and the evidence, though strong, is not yet extraordinary enough."