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posted by martyb on Thursday October 11 2018, @12:30AM   Printer-friendly
from the CAN-YOU-HEAR-ME-NOW? dept.

Smart aliens might live within 33,000 light-years of Earth. A new study explains why we haven't found them yet.

[An] upcoming study in The Astronomical Journal, which we learned about from MIT Technology Review, suggests humanity has barely sampled the skies, and thus has no grounds to be cynical. According to the paper, all searches for extraterrestrial intelligence, or SETI, have examined barely a swimming pool's worth of water from a figurative ocean of signal space. "We haven't really looked much," Shubham Kanodia, a graduate student in astronomy who co-wrote the study, said during a NASA "technosignatures" workshop in Houston, Texas on September 26.

[...] In their study, Kanodia and his colleagues built a mathematical model of what they consider a reasonably sized cosmic haystack.
Their haystack is a sphere of space nearly 33,000 light-years in diameter, centered around Earth. This region captures the Milky Way's bustling core, as well as many giant globular clusters of stars above and below our home galaxy.

They also picked eight dimensions of a search for aliens — factors like signal transmission frequency, bandwidth, power, location, repetition, polarization, and modulation (i.e. complexity) — and defined reasonable limits for each one. "This leads to a total 8D haystack volume of 6.4 × 10116m5Hz2s/W," the authors wrote. That is 6.4 followed by 115 zeros — as MIT Technology review described it, "a space of truly gargantuan proportions."

Kanodia and his colleagues then examined the past 60 years' worth of SETI projects and reconciled them against their haystack. The researchers determined that humanity's collective search for extraterrestrials adds up to about 0.00000000000000058% of the haystack's volume. "This is about a bathtub of water in all of Earth's oceans," Kanodia said. "Or about a five-centimeter-by-five-centimeter patch of land on all of Earth's surface area."

Those numbers make humanity's search efforts seem feeble. But Kanodia views it as an opportunity — especially because modern telescopes are getting better at scanning more objects with greater sensitivity and speed. For example, he said, a 150-minute search this year by the Murchison Widefield Array covered a larger percentage of the haystack than any other SETI project in history.

Related: Stephen Hawking and Yuri Milner Announce $100 Million "Breakthrough Listen" SETI Project
Narrow SETI Targets by Looking at Places Where Earth Transits can be Seen
Either Stars Are Strange, or There Are 234 Aliens Trying to Contact Us
New Theory Suggests Radio Bursts Beyond Our Galaxy Are Powering Alien Starships
A New Theory on Why We Haven't Found Aliens Yet
Russian Physicist Proposes New Solution to the Fermi Paradox
Are We Alone? The Question is Worthy of Serious Scientific Study


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  • (Score: 2, Informative) by Anonymous Coward on Thursday October 11 2018, @01:02AM

    by Anonymous Coward on Thursday October 11 2018, @01:02AM (#747227)

    Our SETI technology is not actually all that sensitive. Sure, we could detect a powerful beacon sent at us from some highly advanced civilization that really wanted to make contact. But if there was an identical copy of our planet and civilization at Alpha Centauri, we'd barely be able to hear it. Anything much farther than that and we wouldn't have a chance. We're not sending out those beacons - at least not very often - so why do we think they are?

    And as technology gets more advanced, we are actually getting quieter. Lower power transmissions let us pack more signals into our space, and faster data transmissions look increasingly like noise to an outside observer that doesn't know the protocol (or the compression and encryption). We're getting harder to hear. Technologically advanced aliens would naturally follow the same progression, so there's a relatively short period of time in which a civilization could be detected if they aren't actively trying to establish contact.

    We probably have a better shot of seeing evidence of alien biology in their planet's atmosphere with advanced telescopes. Of course, that's also only possible with planets that are relatively close by, and positioned the right way.

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