…and to Penzias and Wilson for 3 K cosmic background

Arno Penzias and Robert W. Wilson of Bell Laboratories were awarded half the 1978 Nobel prize in physics for their discovery of the cosmic microwave background, which they found accidentally while attempting to measure the intensity of radio waves emitted from the halo of gas surrounding our galaxy. Their 20‐foot antenna had been built in Holmdel for satellite communications with Echo and Telstar. We recently discussed the discovery with Penzias and Wilson, who explained that their antenna was more directionally sensitive than other radio telescopes of the day. The Bell Labs antenna has back lobes more than 30 dB below an isotropic response. Thus, assuming the Earth to be at 300 K, 1/1000th of its radiation intensity (or about 0.3 K) would be received by this antenna from the ground. (Temperature and intensity are linearly related at radio wavelengths.) In an ordinary radio telescope, one might receive 20–30 K from the ground.