Molecular clocks may provide deeper insights than atomic clocks

New Scientist : Stephan Schiller of the University of Düsseldorf in Germany and his colleagues believe a molecular hydrogen clock might be better than an atomic clock for measuring the mass ratio of protons and electrons. They calculated that the two atoms of H₂ would provide a combination of frequencies whose average would allow for greater measurement precision. That increased precision could reveal whether hydrogen’s proton–electron mass ratio changes as the universe expands. If so, that would challenge the long-held belief that the value is a fundamental constant. However, there are still significant difficulties in creating a molecular hydrogen clock that must be dealt with before such measurements can be made. Schiller’s proposal appears in Physical Review Letters .