(Phys.org)—Radio-astronomical observations of a distant galaxy
indicate that the ratio of the proton's mass to that of the
electron has hardly changed over cosmic history. This
fundamental constant of nature has changed by 10-7 or less,
equivalent to a maximum of one hundred thousandth of a percent,
in the past 7 billion years. Scientists from VU University
Amsterdam and the Max-Planck-Institut für Radioastronomie
(MPIfR) used the Effelsberg 100-m radio telescope to obtain
accurate measurements of methanol absorption at several
characteristic frequencies. Methanol, the simplest form of the
family of alcohol molecules, was observed in a distant galaxy at
redshift z = 0.89 toward the quasar system PKS 1830-211. The
resulting stringent limit on the proton-to-electron mass ratio
shows that molecules and molecular matter are, with high
accuracy, the same now as 7 billion years ago. The work is
published online in Science Express on 13 Dec. 2012. A
fundamental constant such as the proton-to-electron mass ratio
cann