The Arecibo radio telescope in Puerto Rico can detect a wave with an intensity as low as 1x10-23 W/m2. As a “best-case” scenario for communication with extraterrestrials, consider the following: Assume an advanced civilization located at point A, a distance x away from Earth, is somehow able to harness the entire power output of a Sun-like star, converting that power completely into a radio-wave signal which is transmitted uniformly in all directions from A.
1) In order for Arecibo to detect this radio signal, what is the maximum value for x in light-years?
2) How does this maximum value compare with the 100,000-ly size of our Milky Way galaxy?
The intensity of sunlight at Earth’s orbital distance from the Sun in 1350 W/m2