= Arno Allan Penzias
{c}
{tag=Physicist}
{wiki}
= Arno Penzias
{c}
{synonym}
= A. A. Penzias
{c}
{synonym}
<Arno Allan Penzias> and <Robert Woodrow Wilson> discovered an unexplained microwave antenna signal at Bell Laboratories. Their measurement compared a horn-reflector antenna with a cooled reference and separately estimated atmospheric emission, instrumental losses and ground pickup.
The remaining excess was approximately isotropic, unpolarized and seasonally stable. Those checks made a purely local instrumental explanation less plausible. Interpreted as <cosmic microwave background>, the signal connected a calibrated radio-noise measurement to the thermal history of the cosmos; the original single-<frequency> result did not yet establish the full <blackbody spectrum>.<A Measurement of Excess Antenna Temperature at 4080 Mc per Second by Arno Allan Penzias and Robert Woodrow Wilson>[pp. 419–421: calibration, noise corrections and residual properties]{ref}
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{title=Portrait of <Arno Allan Penzias>}
{description=Kartik J at English Wikipedia. https://creativecommons.org/licenses/by-sa/2.5/[CC BY-SA 2.5], via Wikimedia Commons.}
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