When you're looking for signs of extraterrestrial intelligence, it helps to know what you're looking for and to go about it in the most efficient way. But work so far has generally not done so, writes Benjamin Zuckerman, an astrophysicist and emeritus professor in the Department of Physics & Astronomy at the University of California at Los Angeles (UCLA).
Zuckerman suggests our searches via the electromagnetic spectrum should be redesigned, making use of astronomical surveys done independently of the search for extraterrestrial intelligence (SETI), and he offers an improved search technique suggested by his research.
Because there are apparently no alien probes in our solar system, his methodology allows the conclusion that "no alien civilization has passed within 100 lt-yr [light-years] of Earth during the past few billion years." His work has been published in The Astrophysical Journal.
Most published work (by humans at least) has assumed that the alien extraterrestrial intelligence (ET) will be power-limited—the electrical power available to aliens will be increasingly difficult to generate and is ultimately capped. To optimize the signal-to-noise ratio at the receiving end, it's been thought the ETs will employ very narrow transmission and reception bandwidths.
And so, human searches of received radio transmissions use algorithms that look at very small frequency bands of only a few Hertz. Even using sophisticated hardware and software, the total bandwidth covered so far is only a "modest percentage of the full radio/microwave window," writes Zuckerman.
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