Detection of Anisotropy in the Cosmic Blackbody Radiation

We have detected anisotropy in the cosmic blackbody radiation with a 33-GHz (0.9 cm) twin-antenna Dicke radiometer flown to an altitude of 20 km aboard a U-2 aircraft. In data distributed over two-thirds of the northern hemisphere, we observe an anisotropy which is well fitted by a first-order spherical harmonic with an amplitude of (3.5 ±{} 0.6) ×{} 10^-3 ^∘{}K, and direction [11.0 ±{} 0.6 h right ascension (R.A.) and 6^∘{} ±{} 10^∘{} declination (dec)]. This observation is readily interpreted as due to motion of the earth relative to the radiation with a velocity of 390 ±{} 60 km/sec.