he then took up an interest in the microwaves in cosmic radiation which had been discovered by arno allan penzias and robert woodrow wilson in 1964. this work gave new evidence of what the universe is made of. some researchers thought that the universe was rotating, which would mean that temperature of microwaves would seem different when measured from different angles. with the help of alvarez and richard a. muller, professor smoot developed a radiometer to measure the difference in temperature from two angles 60 degrees apart. the radiometer was put on top of a lockheed u-2 plane, but the measurements seemed to show that the universe was not rotating. it did, however, detect another difference in the microwave temperature on one side of the sky. they called this a dipole pattern and a doppler effect of the earth's motion. a doppler effect happens because the sun, and the milky way are moving at nearly 600 km/s. they think this is caused by gravity from the great attractor.