Fundamental Constant May Depend on Where in the Universe You Are

A fundamental physical constant akin to the charge of the electron or the speed of light may depend on where in the universe you are, a team of astronomers reports. If true, that observation would overturn scientists' basic assumption that the laws of physics are the same everywhere in the universe. Other researchers are skeptical, however.

The constant in question is the so-called fine-structure constant. A number with a value of about 1/137, the constant dictates the strength of the electromagnetic force and, hence, determines the exact wavelengths of light an atom will absorb. The idea that the constant may have changed over the age of the universe isn't new. Astrophysicist John Webb of the University of New South Wales in Sydney, Australia, and his colleagues first rang that bell in 1998, using data from the 10-meter telescope at the W. M. Keck Observatory on Mauna Kea, Hawaii, which peers into the Northern Hemisphere.

Back then, the team looked at the brightly shining centers of ancient galaxies known as quasars. Light from the quasars must pass through clouds of gas on its several-billion-year journey to Earth, and the atoms in the gas absorb light of specific wavelengths. So the spectrum of the light reaching Earth is missing these wavelengths and looks a bit like a bar code. The overall shift of the lines tells researchers how far away a gas cloud is and, hence, how long ago the light passed through it. The relative spacing of the lines lets them estimate the fine-structure constant at that time. Analyzing such data, Webb and colleagues argued that the fine-structure constant was about 1 part in 100,000 smaller 12 billion years ago than it is today. That was a radical proposition, as the laws of physics are supposed to be the same no matter where you are in the universe.

The result was not universally accepted, however. In 2004, Patrick Petitjean, an astronomer at the Institute for Astrophysics in Paris, and colleagues used observations of 23 clouds from the Very Large Telescope (VLT) on Cerro Paranal in Chile, which peers into the southern sky, and found no discernible variation in the fine-structure constant.

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