Until recently I was unequivocally convinced that aliens would in theory be able to pick up our radio and TV broadcasts and watch them wherever they may reside in the universe. I have been told these signals will propagate through space for all eternity by physics teachers, NASA scientists and many other reliable media sources. Everything changed in an instant when a friend of mine asked me a simple yet insightful question that I had not considered for some reason. “Why don’t the TV and radio signals disperse as they travel farther away from Earth?”. I literally had no answer to this question because when I thought about it, it made complete sense that the signals would get fainter and fainter to the point where they would no longer be recognizable compared to the background static of space.
It turns out that my rather intelligent friend was right on the money. Despite many years of being told that aliens can watch our TV broadcasts, it is very unlikely for this ever to occur. The reason is due to the inverse-square law of propagation that applies to all types of electromagnetic radiation. This law states that signal strength is inversely proportional to the square of the distance from the source (Earth in this case). This means that by the time any signal leave our Solar System, it is already extremely weak and almost unrecognizable without huge radio dishes the size of the Arecibo dish (305 meters in diameter). And considering it only takes ~21.9 hours for any signal from Earth to leave our Solar Systems, that is nowhere near eternity or even long enough to reach the nearest star system.
It has been estimated by researchers that the average TV or radio signal broadcasted from Earth will have faded into the background static of space about halfway before reaching our nearest neighboring star (Alpha Centauri - 4.4 light years away).
So although the thought of aliens watching an episode of Survivor or cheering on their favourite NFL team is rather amusing, it seems as though this old myth is officially dead. And this is probably for the best because it is beleived that the first high-powered television signals that aliens could pick up are Hitler’s broadcasts at the Nuremburg rallies.
