Current state of mp/me = μ measurements versus cosmic time

Research output: Chapter in Book/Report/Conference proceedingConference contribution


This article reviews the current state of measurement of μ = M P=Me the ratio of the proton to electron mass in the early universe. Unlike the contribution in this volume by Webb et al. on the value of the fine structure constant α there is no current evidence for a different value of μ in the early universe at the one part in 105 level Astronomical observations provide a determination of this ratio in the early universe through observations of molecular absorption and emission lines in distant objects. Observations of molecular hydrogen in distant damped Lyman Alpha clouds provide a measurement of μ at a time when the universe was only 20% of its present age. The limit of Δ μ/ μ≤10-5 produces a significant observational constraint on quintessence theories for the evolution of the universe and Super Symmetric theories of elementary particles. It is expected that future work will improve this limit even further. It would be very difficult to reconcile a constant value of with a varying value of α

Original languageEnglish (US)
Title of host publicationFrom Varying Couplings to Fundamental Physics - Proceedings of Symposium 1 of JENAM 2010
PublisherKluwer Academic Publishers
Number of pages11
ISBN (Print)9783642193965
StatePublished - 2011
Event1st JENAM Symposium: From Varying Couplings to Fundamental Physics, JENAM 2010 - Lisbon, Portugal
Duration: Sep 6 2010Sep 7 2010

Publication series

NameAstrophysics and Space Science Proceedings
ISSN (Print)1570-6591
ISSN (Electronic)1570-6605


Other1st JENAM Symposium: From Varying Couplings to Fundamental Physics, JENAM 2010

ASJC Scopus subject areas

  • Astronomy and Astrophysics


Dive into the research topics of 'Current state of mp/me = μ measurements versus cosmic time'. Together they form a unique fingerprint.

Cite this