April 29, 2017 | David F. Coppedge

SETI Belief Doesn’t Need Evidence

Now they’re offering excuses for the silence, saying that it’s exactly what they expect.

“We still haven’t heard from aliens – here’s why we might never.” That’s Leah Crane’s headline on New Scientist.

THE most ambitious search so far for extraterrestrial intelligence has released its first data – and there are no aliens yet. The lack of success could be explained by the result of a new approach to calculating the likelihood of detecting alien signals. This calculation suggests we might never make contact, even if extraterrestrial life is common.

A new effort called Breakthrough Listen, flush with $100 million to spend from a Russian billionaire Yuri Milner, “aims to be the largest, most comprehensive search ever,” she says. It’s hard to see him being happy with his investment with all the new excuses flying around. It’s not just the old needle-in-a-haystack problem everyone in SETI knows about; it’s worse. The probability of finding anything is so low, we may never find anyone out there. This negative assessment comes from Claudio Grimaldi at the Swiss Federal Institute of Technology in Lausanne, Switzerland.

Grimaldi assumed that signals from an extraterrestrial emitter might get weaker or be blocked as they travel, so they would only cover a certain volume of space. It’s relatively simple to calculate the probability that Earth is within that space and so able to detect the signal. “Not all signals can be visible at the same time – only those that intersect with the Earth,” says Grimaldi.

He found that even if half of our galaxy was full of alien noise, the average number of signals that we would be able to detect from Earth is less than one (Scientific Reports, doi.org/b562).

This implies that, even if there are lots of aliens out there, we might never be able to hear from them.

Other SETI enthusiasts take umbrage at Grimaldi’s pessimism. Seth Shostak (SETI Institute) and Avi Loeb (Harvard) question the assumptions he used. Shostak says,

“You have to make some assumptions about what the aliens are doing in all these calculations, unfortunately, and the data set that we have with alien activity is fairly sparse,” says Shostak. Our only example of intelligent life is on Earth, and there’s little reason to expect that ET resembles us.

But if ET doesn’t resemble us in some respect, such as intelligence and the desire and physical ability to communicate with strangers, how do we know they would signal us? That’s why some prefer eavesdropping on their inadvertent leaks. But Douglas Vakoch (SETI Institute) wants two-way communication; that’s why he is a champion of METI (Messaging Extra-Terrestrial Intelligence) and president of the METI International.

He does leave room for a touch of realism. ““In SETI, theory is great, but observation is the gold standard,” Vakoch remarks. Frenetic search activity is not observation. Detection is. So far, detection remains futureware. If something doesn’t turn up in a reasonable time, some joker might say the “S” in SETI means “snipe hunt.”

Update 5/02/17: Phys.org reports on the first results from Breakthrough Listen: no aliens found.

Avi Loeb is a smart and perceptive guy, but he doesn’t seem to catch that SETI is an exercise in intelligent design detection. Here’s what he says in the article: “The question of whether you can detect a signal has nothing to do with whether it’s artificial or natural, and astronomers routinely detect lots of kinds of signals.” By this he implies that SETI is no harder to detect than a natural signal, like the clicks of a pulsar. But the whole rationale of SETI is that unnatural, intentional messages are being sent. Intelligence is a different kind of cause. It doesn’t follow unguided natural processes; it uses laws to encode information (radio signals, laser beacons, spacecraft).

Despite Grimaldi’s calculation that the hope of detection approaches zero, the SETI folk will keep searching. For one, they don’t want to look their giant gift horse in the mouth. For another, it means job security. Finally, it’s a religious quest. It must succeed somewhere down the road, because otherwise those despised creationists will make sport of it.


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