Earthlings would have a much easier time detecting alien signals from innumerable light-years away … if we only knew what to look for.
While we’ve endlessly theorized about how intelligent they could be (enough brains to build starships and megastructures?), what they could understand (those recordings still floating around on Voyager 1 and 2?) and how they would try to get through to us (radio transmitters?), it’s all remained in the realm of theory. There has never actually been a confirmed extraterrestrial signal documented by science. SETI has had its share of false alarms and spilled coffee, but the radio signals that seemed to shout “aliens!” were always from some other cosmic source—if you don’t count interfering telescopes right here on our planet.
SETI, the Search for ExtraTerrestrial Intelligence, and METI, or Messaging ExtraTerrestrial Intelligence International, are now wondering whether subatomic particles could be a sign of exotic signals. SETI and METI are essentially alien-seeking mutations of the same DNA. The science SETI employs is meant to search for messages from beyond this world, while METI tries to determine how we could actually succeed at contacting hypothetical aliens. It probably takes more than a text. Assuming aliens have no such things as texting or email, how are E.T.s most likely to phone home—and are we even equipped to receive their messages?
"We are not really sure of how extraterrestrials would communicate with us,” admits space analyst and writer Dr. Morris Jones, a member of the METI advisory council. “Would they use radio waves, lasers or something more exotic? Perhaps the universe is awash in extraterrestrial signals that we cannot even receive. SETI and METI practitioners spend a lot of time wondering how a message would be encoded in terms of language and content. It's also important to consider the medium of transmission."
Radio astronomy fueled past SETI searches because it was the only remotely practical method of detection scientists could use at the time. Optical telescopes and laser signals were later incorporated into its efforts. Fast-radio bursts (FRBs) have looked suspicious for years. Whether their source really is extraterrestrial technology or some bizarre celestial object remains unknown. Looking for artifacts that point to alien megastructures (think Tabby’s Star) hasn’t yielded any evidence yet. Gravitational waves are also potential, but highly unlikely, proof. So are zeta rays. Directed-energy propulsion is now being considered as a search tool, based on the notion that intelligent life from some other planet may be using the same technology to send signals or power their starships.
Enter subatomic particles. Neutrinos, which emerge from the decay of radioactive elements, have weak interactions with solid matter, which they are able to pass through. They could be transmitted through space by aliens, if said aliens have access to a nuclear reactor. Detecting these elusive particles is another matter. It would have to involve expensive subterranean or extremely isolated facilities -- such as Japan’s Super-Kamiokande facility, China’s Daya Bay Reactor Neutrino Experiment, Antarctica’s IceCube Neutrino Observatory and Canada’s Sudbury Neutrino observatory -- that aren’t prone to the same kind of electromagnetic interference that has gotten SETI too excited in the past.
"Is it possible to transmit with something better than we already have?” Jones questioned. Until we know a lot more physics, we just won't know.