One of the greatest open questions in all of the Universe today is just how abundant intelligent alien life is right at this very moment. We can imagine that extraterrestrial intelligence is common, and that the Milky Way is swarming with civilizations — thousands or even millions of them — just as intellectually advanced or even more technologically advanced than we are. Alternatively, we could be uncommon, where only a scarce few civilizations ever come into existence within the galaxy, and where finding anyone else to communicate with is exceedingly difficult at the moment.
At an even greater extreme, they could be very rare, so rare that perhaps we’re entirely alone in the galaxy, and that we’d have to search at extragalactic distances to find anyone else to communicate with, or perhaps in the most extreme scenario of all, we’re completely unique in all the Universe. Until we find a second example of life of any type somewhere else, we shall remain completely ignorant of what else, or who else, may be out there. But that doesn’t mean we shouldn’t be listening, and on the flip side of that, that we shouldn’t be broadcasting with the intention of being found.
While much effort has been focused on SETI, or the search for extraterrestrial intelligence, we’ve put far fewer resources into METI, or messaging extraterrestrial intelligence. If we got serious about that, what would it look like? That’s what our Patreon supporter Jeff Bonwick wants to know, writing in to ask: “If the governments of the world united and named you Transmitter In Chief, what message and what medium would you choose?
Personally I would choose primes as the message because any civilization that discovers math will discover primes, and there is no natural process that produces them.The medium is less obvious — would you go electromagnetic, gravitational, neutrino, or something else? I would be partial to neutrinos because the Universe is transparent to them regardless of redshift, but then again they’re difficult to receive for the same reason.What would [your] “Hello world” look like?” It’s a great question, and it gives us so much to consider. Here’s what my top priorities would be.
This image of the Very Large Array in the southwestern United States highlights the importance of arrays of radio dishes in measuring many different properties of our Universe, including searching for potential extraterrestrial signals that were created by an intelligent species. Telescope arrays, not just in the radio but in the infrared and optical as well, can achieve superior resolutions to any single-dish effort, but only if the various dishes can be properly synchronized together using VLBI techniques. Let’s start by considering the current limitations of what we could actually detect, since that informs what types of signals we should actually consider sending, noting that all signals can travel no faster than the speed of light in a vacuum.
Electromagnetic signals — all the various forms of light — have a huge benefit to them: they’re easy to detect. Photons are easy to generate, and with large enough, sensitive enough telescopes, they’re easy to detect. In fact, any signal that stands out against the background of cosmic noise in any particular wavelength can be seen.
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