A particularly talkative extraterrestrial (El') civilization lives on a planet that orbits a star at a distance of 1.542 x 1014 km from Earth. Imagine they send out a radio signal tuned to a frequency of 1.5 x 108 Hz that is detected at the 305-m Arecibo radio telescope in Puerto Rico (an aerial view is shown below). The signal has a measured flux of 7 x 10-23 watts/m2. Showing all your calculations, have a go at the following action items:
What is the wavelength of ET's signal?
How long did it take the signal to reach the Earth?
How much energy is associated with the EM waves in ET's signal? Hint: think Max Plank and use h = 6.626 x 10-34 JS.
What is the luminosity of ET's signal, and how does it compare with the Sun's luminosity (hint: divide your answer for the luminosity by L? = 3.85 x 1026 Watts)?