shake nature's constants

The basic constants of nature aren't called constants for nothing. Physics is supposed to work the same way across the universe and over all of time. Now measurements of the radio spectra of a distant gas cloud hint that some fundamental quantities might not be fixed after all, raising the possibility that a radical rethink of the standard model of particle physics may one day be needed.

The evidence comes from observations of a dense gas cloud some 2.9 billion light years away which has a radio source, the active supermassive black hole PKS 1413+135, right behind it. Hydroxyl radicals in the gas cloud absorb the galaxy's radio energy at certain wavelengths and emit it again at different wavelengths. This results in so-called "conjugate" features in the radio spectrum of the gas, with a dip in intensity corresponding to absorption and an accompanying spike corresponding to emission.

The dip and spike have the same shape, which shows that they arise from the same gas. But Nissim Kanekar of the National Centre for Radio Astrophysics in Pune, India, and colleagues found that the gap in frequency between the two was smaller than the properties of hydroxyl radicals would lead us to expect.

The gap depends on three fundamental constants: the ratio of the mass of the proton to the mass of the electron, the ratio that measures a proton's response to a magnetic field, and the fine-structure constant, alpha, which governs the strength of the electromagnetic force. The discrepancy in the size of the gap thus amounts to "tentative evidence" that one or more of these constants may once have been different in this region of space, Kanekar says.


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