““Experiments with the COBE (Cosmic Background Explorer) satellite, which was launched in 1989, showed in 1990 with overwhelming precision what was already known from previous experiments-that the cosmic background radiation filling the universe has all the properties of blackbody radiation at absolute temperature 2.735 degrees, save some tiny deviations. It would be very surprising if Earth were at rest with respect to this radiation. The velocity of Earth relative to it was first measured in 1977 from an airplane by investigating the influence of the Doppler effect (fig. 57). The blackbody radiation as received by an observer who moves relative to it displays what is called a "dipolar asymmetry": The radiation coming from the direction in which the observer moves is shifted to higher frequencies, the radiation from the opposite direction to lower frequencies. This shift has the remarkable property that the radiation arriving from any direction has all the properties of a blackbody radiation; only the temperature is shifted-to higher values in front, to lower in the rear. By measuring this temperature difference of about .0035 Celsius, scientists have established that the solar system is moving toward the constellation Leo with a velocity of of approximately 250 miles per second relative to the background radiation. By properly adding velocities, it follows that the Milky Way itself moves at a speed of about 500 miles per second relative to the background radiation.””
