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SETI Is 50 Years Old; No Sign of ET

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  • The problem is time (Score:5, Informative)

    by Todd Knarr (15451) on Sunday March 14, 2010 @08:44PM (#31476460) Homepage

    The problem's basically one of time. Think about this: the first radio transmission on Earth was in 1866. That's 144 years ago. That means that any alien civilization more than 144 light-years away from Earth can't see us in the radio bands. They'd have to be inside the bubble formed by our first radio transmissions to even have a chance of spotting us using the methods SETI does. And that bubble isn't a sphere either, it'll eventually have an inside surface as well as an outer one. We're getting more and more efficient, wasting less and less power beaming radio waves off in all directions. Eventually we'll be broadcasting so little that we won't be detectable at any reasonable distance. Anybody inside that inner surface won't be able to see us either. That'll leave probably a 250-300 light-year thick zone moving steadily outwards that any race looking for us will have to be in to see us by looking for radio transmissions. They won't have to just be looking for us, they'll have to be looking for us during the 3-century period when they're in that zone. Look too early or too late and we're invisible to them.

    And the same applies to us: we can look all we want, but if we're not in the radio-transmission zone for another species they'll be invisible to us.

  • by John Hasler (414242) on Sunday March 14, 2010 @08:53PM (#31476544) Homepage

    > ...the first radio transmission on Earth was in 1866...

    I think you mean 1886 (and that transmission by Hertz was very low power and wideband).

  • by bill_mcgonigle (4333) * on Sunday March 14, 2010 @09:21PM (#31476820) Homepage Journal

    That little blip of 100 years of analog full-blast will not been seen by anyone else either.

    Every time a SETI article comes up somebody posts this problem about detecting radio leakage and then somebody else has to post that SETI isn't looking for accidental leakage - they admit that they're only looking for intentional beacons.

    I guess it's my turn.

  • by Anonymous Coward on Sunday March 14, 2010 @09:33PM (#31476940)

    no that is taking into account slower than light exponential expansion

  • by bill_mcgonigle (4333) * on Sunday March 14, 2010 @09:41PM (#31477006) Homepage Journal

    They'd have to be inside the bubble formed by our first radio transmissions to even have a chance of spotting us using the methods SETI does.

    No, SETI is looking for intentional beacons, not accidental leakage.

    In your terms, our SETI-style space-time bubble is a very very very thin shell from the one (or was it two?) times we actually beamed out a signal. Actually not a shell, because it was directional. Interestingly the small handful of candidate signals fit this pattern.

    Personally, I think until we're unafraid enough to light up a real beacon, any more advanced society won't pay us any attention. We're panicky and prone to irrational behavior, which probably makes us uninteresting peers. It seems none of us will live long enough to see humanity get over itself, though perhaps we can push it a bit in that direction.

  • by Anonymous Coward on Sunday March 14, 2010 @10:13PM (#31477278)

    ...assuming some sort of FTL travel, which is a pretty far-fetched extrapolation.

    A few million years isn't that far-fetched, considering the galaxy is only about 100,000 light years across. You'd have to do your colonization pretty aggressively, but it could certainly be done in a few million years with only fractional c travel.

  • Re:Patience! (Score:5, Informative)

    by quisxt (462797) on Sunday March 14, 2010 @10:52PM (#31477512)
    [citation needed] --cordially, a marine biologist
  • by mrsurb (1484303) on Monday March 15, 2010 @12:09AM (#31478062)
    Indeed, the Vatican has addressed this recently and the Pope's chief astronomer doesn't see a contradiction between the existence of intelligent extra-terrestrials and Catholic belief [abc.net.au]

    Dislaimer: I am not a Roman Catholic but a Reformed Christian. However I broadly agree with this conclusion.

  • by Lloyd_Bryant (73136) on Monday March 15, 2010 @01:01AM (#31478308)

    They're using subspace communications, or ansible, or ultrawave.

    or semaphore...

    Not entirely sure why this was modded "Funny" - it's a very valid point. Just because electromagnetic radiation is the best tool we have for long-range communications does not mean that other, more advanced civilizations aren't using something that we don't even know how to detect (Gravity wave telegraphy? Quantum entanglement semaphores?).

  • Re:Patience! (Score:2, Informative)

    by kd5zex (1030436) on Monday March 15, 2010 @01:44AM (#31478458)

    You are edible as well; my friend....

  • Re:Encryption (Score:3, Informative)

    by digitalchinky (650880) <dtchky@gmail.com> on Monday March 15, 2010 @01:51AM (#31478490)

    I think you have a bit of a misunderstanding about how SETI works. It doesn't matter whether the signal is encrypted or what kind of modulation it might be using - the search itself is simply to detect an energy lobe above the noise floor of the receive equipment. If you're pumping out 40 watts at 300MHz to talk to your buddy on the other side of the city over AM / FM / Whatever, you're going to need the same, or perhaps even a little more power, if you convert your analogue transmission to digital.

    Just detecting a radio signal from deep space would be of tremendous interest all on its own.

    I do wish SETI would give themselves a little more bandwidth to work with though. 1420MHz, the hydrogen line. That's pretty narrow.

    Back when I was military, from time to time on a boring night watch I would occasionally swing the search dish away from the Clark belt and sit glued to the spectrum analyzer. DC to 80 GHz. I never found anything that wasn't "human" though I never really expected to anyway.

    DNA was right, space is big. Even a 30 meter satellite dish pointed at a bird just 36,000 kilometers away, you move that bad boy by so much as a tenth of a degree and your signal goes to crap. A signal 'light years' away, now that's a pretty damn big haystack.

  • Re:Patience! (Score:3, Informative)

    by Schemat1c (464768) on Monday March 15, 2010 @03:46AM (#31478934) Homepage

    But maybe lemmings have invented religion and that's why they kill themselves.

    Snopes [snopes.com] to the rescue!

  • Re:The Atomic beacon (Score:3, Informative)

    by wisebabo (638845) on Monday March 15, 2010 @07:47AM (#31480310) Journal

    I seem to remember (Mr. Google wasn't much help) an Arthur C. Clarke story where a future world government, scarred by a devastating asteroid impact, detonates a very powerful (Gigaton?) nuclear explosive on the other side of earth's orbit (so that the sun blocks it). This is so that an extremely bright "pulse" is created that very briefly illuminates every single object in the Solar System (except the earth) which makes their detection easy by prepared astronomers.

    A few decades later, a signal is detected from aliens. When their position is calculated, it turns out it is precisely twice the distance in light years as the time since the explosion. The implication of course is that the aliens were alerted to our presence from the blast, realized it wasn't natural, and sent a greeting to us. Sorry don't remember what happened in the book after that.

    By the way, you might be interested in my earlier post (just a few posts above; "Look for a short lived temporal phenomenon"). Here, since even atom bombs are pretty weak at interstellar distances, I suggest tagging along rare, super powerful COSMIC events (supernovae in your own galaxy, colliding black holes, etc.). If during or right after the detection of one of these events, you immediately transmit a signal in the opposite direction you will be likely to be "seen" by any astronomers downstream of you (provided you use a part of the spectrum that isn't overwhelmed by the event). Likewise when WE see an event, we should be paying attention not only to the event but the region of the sky immediately adjacent as someone might be trying to tag along with it!

  • by Haxamanish (1564673) on Monday March 15, 2010 @07:54AM (#31480354)

    It seems like there can't have been that many generations of suns before the formation of our planet.

    The sun is a third generation star:

    The sun is a relatively young star, a member of a generation of stars known as Population I stars. An older generation of stars is called Population II. There may have existed an earlier generation, called Population III. However, no members of this generation are known. The remainder of this section refers to three generations of stars.
    The three generations differ in their content of chemical elements heavier than helium. First-generation stars have the lowest percentage of these elements, and second-generation stars have a higher percentage. The sun and other third-generation stars have the highest percentage of elements heavier than helium.
    The percentages differ in this way because first- and second-generation stars that "died" passed along their heavier elements. Many of these stars produced successively heavier elements by means of fusion in and near their cores. The heaviest elements were created when the most massive stars exploded as supernovae. Supernovae enrich the clouds of gas and dust from which other stars form. Other sources of enrichment are planetary nebulae, the cast-off outer layers of less massive stars.

    NASA Sun Worldbook [nasa.gov]

  • Re:The Atomic beacon (Score:3, Informative)

    by John Hasler (414242) on Monday March 15, 2010 @08:41AM (#31480624) Homepage

    > But when you think about it, detonating vast amounts of plutonium releases a
    > tremendous amount of energy all over the EM spectrum. It also gives off a
    > unique signature of the kind that doesn't, or could *never* happen naturally.

    No, not really. The "bomb" is pretty feeble by cosmic standards.

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