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Alcohol Constrains Physical Constant In The Early Universe

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 PKS1830-211. 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 December 2012.

A fundamental constant such as the proton-to-electron mass ratio cannot be calculated from any currently known theory, it can only be measured. The Earth-bound experiments agree upon its value but the explanation for it is still missing. Therefore, a possibility remains that the proton-to electron mass ratio was different in different places in the universe or at different epochs in cosmic history. The methanol molecule is a very sensitive probe for detecting a drift of the proton-electron mass ratio. Some lines in the microwave spectrum of this molecule would undergo a rather large shift upon a variation of the proton-to-electron mass ratio µ, while other lines are not affected (so-called “anchor lines”). Recently the Amsterdam group found that the hindered internal rotational motion in molecules such as methanol (in fact also a quantum tunneling process) can give rise to very high sensitivity coefficients. The sensitivity of each spectral line can be expressed in a value K, which may be calculated.

Full Story: http://www3.mpifr-bonn.mpg.de/public/pr/pr-methanol-dec2012-en.html

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