ALMOST as soon as radios were invented, people speculated about using them to listen to—and maybe even talk to—extraterrestrial civilisations. Since the 1960s attempts have been made to do so by sifting through signals from outer space in search of alien chit-chat. More recently, the use of lasers in telecommunications has suggested to some that they might be a better way to communicate across vast distances, so searching for telltale flashes from the sky is now in vogue.
But techniques that work well on Earth are not necessarily ideal for talking across the vast chasms that separate stars. And for several years John Learned of the University of Hawaii and Anthony Zee of the University of California, Santa Barbara, have been promulgating what they believe is a better idea. They suggest that any alien civilisation worth its salt would alight not on the photons of the electromagnetic spectrum—whether optical or radio-frequency—to send messages to other solar systems. Rather, it would focus its attention on a different fundamental particle, one that is rather neglected by human technologists. That particle is the neutrino.
Neutrinos, it must be confessed, are neglected for a reason. Though abundant (the universe probably contains more of them than any other sort of particle except photons), they are fiendishly difficult to detect. That is because they interact only occasionally with other forms of matter. But that is precisely why Dr Learned and Dr Zee like the look of them. Light and radio waves are absorbed and scattered by interstellar gas and dust. Neutrinos would pass straight through such obstacles, and could easily be detected by neutrino telescopes on Earth (which typically consist of giant vats of water or, more recently, huge chunks of Antarctic ice).
The two researchers go further. They argue that powerful beams of neutrinos could be used to turn entire stars into flashing beacons, broadcasting information across the galaxy. Outlandish as this sounds, it is an idea that can easily be checked, for astronomers are already sitting on the data that might contain these extraterrestrial messages. They just need to analyse those data from a new perspective. Dr Learned and Dr Zee are therefore trying to persuade someone who studies the data in question to take their idea seriously and spend a little time having a look.