For more than six decades, a small group of scientists (including me), has been trying to pick up radio transmissions from other planetary systems, motivated by the fact that doing so would demonstrate that someone intelligent is out there. This effort, known as SETI (the Search for ExtraTerrestrial Intelligence), is straightforward and technically fairly simple, as it doesn’t require interstellar travel for either the aliens or the earthlings. It’s a strictly passive endeavor that uses big antennas with highly sensitive receivers to sniff out signals over a broad range of the radio dial. Case in point: Reports this week say Chinese researchers may have picked up signs of alien civilizations (or maybe it was just radio interference.)
In any case, some researchers believe we should be taking a more active role in probing nearby space. They argue we should prod the aliens with signals of our own, inviting them to respond; an idea known as “active SETI.” Rather than hope that the extraterrestrials have launched signals our way, maybe we could knock on their door and get their attention.
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