The mass of a proton is 1836.152672 times as big as the mass of an electron. That ratio, and with it the structure of all molecular material, has remained precisely the same for 7.5 billion years – at least within a margin of 100,000th of a percent. Ubachs and his colleagues concluded that when they observed methanol molecules outside the Milky Way last year, using the Effelsberg radio telescope.
Methanol (CH3OH, the simplest form of alcohol) is sensitive to changes in the proton-electron mass ratio. A small deviation would affect the structure of the molecule and the associated absorption spectrum. An absorption spectrum reveals precisely which radiation frequencies are absorbed by a particle. Each molecule has its own characteristic spectrum. The spectrum of methanol was found to be ideally suited for analysing the natural constant: if the proton-electron mass ratio changes, some lines in the methanol spectrum will strongly shift while others will remain the same (the so-called anchor lines).
Read more at: Phys.org