How much electromagnetic transmission noise does Earth have to emit to be noticeable?

From time to time I'll see things talking about how thanks to all of our radio communications, we're effectively broadcasting our existence to the entire universe. However, when I did some back-of-the-envelope calculations a while ago I found something interesting - by the time a radio station's broadcast reaches Alpha Centauri (the solar system closest to ours), ignoring any effects of our atmosphere, a 1 m^2 receiver would, on average, receive a single photon every seven hours. Of course that is only a single radio station, but throwing more radio stations into the mix would just make the signal less coherent and indistinguishable from random noise. When you consider the sun as well, it seems like all of the Earth's radio signals would be a drop in the bucket.

How much noise would the Earth have to broadcast in order to change that? For this question, the goal is for the noise broadcast from Earth to still be noticeable by the time it reaches a distance of 500 light years (that only covers about 0.01% of the galaxy). You can assume that alien civilizations are looking for signals of intelligent life, but not that they are focused on our solar system.

posted about 6 years ago

Rob Watts‭

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