Second, the big error in that mentality is that radio signals don’t go on forever. A lot of people had just assumed that with each passing year, the “radio bubble” in a sphere around Earth expands precisely one light year per year, and therefore more and more star systems would be able to hear Earth broadcasts. What they all forgot was the law of inverse squares for electromagnetic transmission and reception. If you move twice your current distance from the light bulb, the light from it will be one-fourth as strong, three times from it, one-ninth as strong, and so on and so forth. And it also applies to radio, which is just another form of electromagnetic TX/RX — SETI has figured that even the strongest regular Earth-bound transmissions will fade and and become indistinguishable from the background radio noise our galaxy makes at those frequencies from anywhere between one and two light years from Earth, which means “Wheel in the Sky” won’t even make it to Alpha Centauri in late August 2018.
Incidentally, that’s going to be a problem for when we have the ability to do interstellar unmanned probes. Sure, we may eventually develop the ability to send a big toilet bowl to Alpha Centauri, but how is it going to be able to phone home?
Upon reaching Alpha Centauri, there will be no possibility of slowing down. The nanocraft will have a few hours to take pictures and collect other measurements. Getting the data back to Earth over such vast distances will be another major challenge. You might think that a signal sent from Alpha Centauri would be hopelessly buried in the background noise of interstellar space, but it turns out that lasers can once again provide a solution. Thanks to much lower diffraction than radio waves, optical systems have much higher gain than radio systems of similar size. In fact, NASA recently performed a record-breaking laser communications demonstration at lunar distances as part of the LADEE mission. If the square-kilometer laser launch system can be made to double as a phased-array receiver, data rates of several kilobits per second could be achieved from Alpha Centauri with a 1-W laser transmitter on the spacecraft. It should even be possible to receive data at lower bit rates with the next generation of large optical telescopes set to come online in the 2020s.
I was getting worried there for a moment. Worried that we would launch an interstellar probe before thinking of the phone home problem.