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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) by deimtee on Thursday October 11 2018, @11:33AM (5 children)

    by deimtee (3272) on Thursday October 11 2018, @11:33AM (#747385) Journal

    Doesn't matter. Any species which sends colonists to other stars at even 0.01 C will colonise the whole galaxy remarkably quickly.
    It's a bit like evolution, there's a selection effect.
    Some won't get there. Doesn't matter. Others will.
    Some that get there won't send any further colonies. Doesn't matter, they become irrelevant.
    The societies that send colonists that send further colonies will quickly fill the galaxy. The GP's million years is probably about right.

    The problem of 'where are they?' is known as the Fermi paradox.

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  • (Score: 2, Informative) by khallow on Thursday October 11 2018, @11:49AM (4 children)

    by khallow (3766) Subscriber Badge on Thursday October 11 2018, @11:49AM (#747391) Journal

    The GP's million years is probably about right.

    At 0.01 C it would take 10 million years to reach the other side of the galaxy, give or take. No way it would take a million years without some really fast spacecraft in use.

    • (Score: 2) by takyon on Thursday October 11 2018, @01:25PM (2 children)

      by takyon (881) <reversethis-{gro ... s} {ta} {noykat}> on Thursday October 11 2018, @01:25PM (#747413) Journal

      Bump it down to 0.001c. If an intelligent civilization formed billions of years ago, such as on an older planet than Earth, then it would have the time to spread. The mystery remains.

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      • (Score: 1) by shrewdsheep on Thursday October 11 2018, @02:21PM

        by shrewdsheep (5215) on Thursday October 11 2018, @02:21PM (#747431)

        Oh, these orders of magnitudes! The universe is ~12 Bio yrs old. Life needs 2nd generation stars (heavy elements or metals how the astronomers say; ~ 2 bio yrs) + planet formation (1 bio yrs) + evolution of life to intelligence (~4 bio yrs). If you toss in a 3rd generation (more heavy elements) you are about where we are now. So it does matter whether it's 1 billion yrs or 1 million yrs. I would see 1 mio yrs as totally unrealistic. 1 billion yrs might mean, they are not yet here but will arrive some time soon.
        We discussed that at length before, there are other solutions to the Fermi paradox: aliens would be undetectable (you need to be small to travel efficiently, no sci-fi starships would be involved). Also, it does not make sense for biological life to travel in space (why?, that's left as an exercise to the reader).

      • (Score: 1) by khallow on Thursday October 11 2018, @03:39PM

        by khallow (3766) Subscriber Badge on Thursday October 11 2018, @03:39PM (#747465) Journal

        Bump it down to 0.001c. If an intelligent civilization formed billions of years ago, such as on an older planet than Earth, then it would have the time to spread.

        Actually at that point, they could still be spreading and just haven't arrived yet.

    • (Score: 2) by deimtee on Saturday October 13 2018, @01:41AM

      by deimtee (3272) on Saturday October 13 2018, @01:41AM (#748136) Journal

      True, and it also doesn't account for the time to build the infrastructure at each new system. But (big but) that selection effect will also apply to speed. There are enough stars in the milky way to apply evolution at the colony level.
      Given an expanding species, the slightly faster descendants will colonise more systems. Eventually a wave of settlement will be marching across the galactic disk, at the optimum speed for [surviving the journey | building new ships | building more ships | building faster ships].

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