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Power Used by E.T. A modern SETI search using the 300-meter-diameter Arecibo Radio Telescope in Puerto Rico could pick up a 10-million-watt signal from 1000 light-years away (assuming that the broadcasting aliens had a transmitting antenna that was also 300 meters in diameter). Suppose we used Arecibo to search the far side of the Milky Way Galaxy (roughly 80,000 light-years away). Making the same assumptions about our setup and the transmitting antenna, determine how powerful the alien transmitter would have to be for us to detect the signal.
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