Across the Universe | Nature Physics

Access through your institution Buy or subscribe Cosmology has come a long way. The existence of the cosmic microwave background (CMB) was first predicted in 1948 by Ralph Alpher and Robert

Herman, its temperature estimated to be about 5 K. The idea, however, didn't gain much currency among scientists until the early 1960s. Then, in 1964, Arno Penzias and Robert Wilson saw

it — their horn antenna at Bell Telephone Laboratories in New Jersey was blighted by an unexplained excess temperature of about 3 K. This was the echo of the Big Bang — the ripple of

photons released across a universe less than 400,000 years old, as electrons and protons became bound together into hydrogen atoms. The precision of the data from Planck is breath-taking,

and a ringing endorsement of the standard cosmological model. The data also indicate that the Hubble constant is lower than had been thought, and the Universe slightly older; the relative

proportions of matter, dark matter and dark energy have been revised; and there is no evidence of any additional neutrino species beyond the three already known — no sign of a sterile

neutrino. There is more to come: in 2014, the Planck collaboration will release more data, plus its data on the polarization of the CMB, which will be crucial in understanding gravitational

waves and the inflationary history of the Universe. That there was a period of exponential expansion — of single-field, slow-roll inflation — is already strongly signalled. This is a preview

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checkout ADDITIONAL ACCESS OPTIONS: * Log in * Learn about institutional subscriptions * Read our FAQs * Contact customer support Authors * Alison Wright View author publications You can

also search for this author inPubMed Google Scholar RIGHTS AND PERMISSIONS Reprints and permissions ABOUT THIS ARTICLE CITE THIS ARTICLE Wright, A. Across the Universe. _Nature Phys_ 9, 264

(2013). https://doi.org/10.1038/nphys2629 Download citation * Published: 02 May 2013 * Issue Date: May 2013 * DOI: https://doi.org/10.1038/nphys2629 SHARE THIS ARTICLE Anyone you share the

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