Frank D. Drake, an investigator in the SETI (Search for Extra-Terrestrial Intelligence) program, once said that the large radio telescope in Arecibo, Puerto Rico, can detect a signal which lays down only a picowatt of power over entire surface of the Earth. What is the power received by the radio telescope if the diameter of the antenna is 300 m? What would be the power of the source at the center of our galaxy which could provide such a signal? The center of galaxy is 22000 light years away. Assume that source is radiating uniformly in all directions and that the Earth is a disk with the radius of 6378 km.