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The Echo of the Big Bang: How Two Astronomers Heard the Birth of the Universe

Two radio astronomers thought an annoying persistent microwave hiss in their antenna was caused by pigeon droppings; Arno Penzias and Robert Wilson were actually listening to the dying thermal echo of the Big Bang. Awarded the 1978 Nobel Prize in Physics, this discovery of the Cosmic Microwave Background proved that our universe was born in a fiery cosmic explosion fourteen billion years ago.

Author
A. A. Penzias et al.
Published
1965
Journal
The Astrophysical Journal
Last updated
September 2026
The Echo of the Big Bang: How Two Astronomers Heard the Birth of the Universe

In the 1960s, astronomy was deadlocked in a fierce cosmological war between two theories: the "Steady State" model (which said the universe was eternal and changeless) and the "Big Bang" model (which said the cosmos erupted from a single hot explosion). Science lacked physical proof to decide between them.

Bell Labs radio astronomers Arno Penzias and Robert Wilson pointed a giant 20-foot horn antenna at the sky. No matter where they aimed, they heard a steady, uniform microwave hiss at 3.5 Kelvin—a background noise so uniform they scrubbed the antenna clean of pigeon nests, only to realize the noise was the 13.8-billion-year-old afterglow of the Big Bang itself.

Their discovery definitively settled the origin of the cosmos. By proving the Big Bang theory, by providing the cosmic microwave background map that reveals the seeds of all galaxies, and by founding modern precision cosmology, this radio hiss changed human history.

Reference

Penzias, A. A., & Wilson, R. W. (1965). A Measurement of Excess Antenna Temperature at 4080 Mc/s. The Astrophysical Journal, 142, 419.

Title

A Measurement of Excess Antenna Temperature at 4080 Mc/s.

Abstract

Measurements of the effective zenith noise temperature of the 20-foot horn-reflector antenna (Crawford, Hogg, and Hunt 1961) at the Crawford Hill Laboratory, Holmdel, New Jersey, at 4080 Mc/s have yielded a value of about 3.5 K higher than expected. This excess temperature is, within the limits of our observations, isotropic, unpolarized, and free from seasonal variations (July, 1964 - April, 1965). A possible explanation for the observed excess noise temperature is the one given by Dicke, Peebles, Roll, and Wilkinson (1965) in a companion letter in this issue.

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