The constant also affects the absorption fingerprint of atoms, which can be detected when light shines through gas clouds. Murphy has used quasars as incredibly distant light sources, whose light encounters gas clouds on its way to Earth. The light takes time to reach Earth, so he sees the fingerprints as they were billions of years ago. By comparing these fingerprints with those obtained in experiments 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. However Dr Murphy’s 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 this the most reliable measurement to date.

Dr Michael Murphy is a Research Associate at the Institute of Astronomy in the University of Cambridge, and a Research Fellow of Darwin College, Cambridge.

From an IoP press release.