14 Jan 2012

Sci Fi Geek Fact Check

All Posts 24 Comments

Bryan Caplan desperately wants there to be more to life than arguing with Robin Hanson over population growth, so he believes in the existence of aliens (Martian, not Hispanic) despite serious evidence against it. Part of Bryan’s case was this claim:

Our powers of detection are bad enough to overlook hundreds of billions of planets. Detecting intelligent life will be vastly harder than detecting planets – maybe prohibitively harder.

That sounded like a bogus claim to me, so in the comments I asked if anyone could justify it. One guy said:

Non-directional electromagnetic communications (radio, TV, etc) follows an inverse cube law (I think, though it might be inverse square) meaning we can’t detect anything at what we would consider realistic power levels from more than a light year or so away. So, in order for us to detect intelligent life, they would either have to come here or send a coherent beam communication directly at us, one of 100 billion stars in the galaxy. Furthermore, it’s entirely possible that their communication isn’t even something we would recognize as a signal, like a stream of neutrinos using muon neutrinos as 0 and tau neutrinos as 1 the way we use high/low current for digital communications today. Not to mention that they might not be as outgoing as we are.

So detecting extrasolar life is hard because a.) they have to be intentionally trying to talk to us (among the 100 billion other possible stars) and b.) we would have to recognize that they are trying to do so.

We wouldn’t be able to detect ourselves from any of the planets we’ve found so far.

Does that sound right to people? Haven’t we been deliberately sending out probes and broadcasting messages for decades, with the express purpose of demonstrating our intelligence in things that would (we hope) be universally recognizable? Did all of the scientists working on those projects fail to consider that a guy could blow up their efforts in 5 seconds in an EconLog comment?

24 Responses to “Sci Fi Geek Fact Check”

  1. Ivan Ivanov says:

    I don’t think anyone sent probes with the express purpose of showing ourselves to anyone.
    The voyager probes have just barely left the solar system, so it will take them quite a while to get to anywhere where someone might find them.
    Yeah they put some hopefully universally recognizable messages in them, but I think it’s just a cute little trick they decided to do. Their real mission was to study the far reaches of our solar system.

    I don’t know anything about broadcasting messages, so someone else will have to explain that, tough again I don’t think anyone had any huge expectations of them being detected, and it was more of “meh, you never know” thing.

  2. Joseph Fetz says:

    In my opinion, human knowledge is a balance between ignorance and certainty in a way that only humans can understand (relate to). However, we are always and forever a curious bunch.

  3. Martin says:

    That it is extremely difficult does not make it impossible and thus the efforts of said scientists futile. Besides how much could it possibly cost to send out those signals for decades? What alternatives would be better served by those expenses, given the end that ultimately we do want to contact E.T.’s? It therefore does not even seem clear to me that it is inefficient.

    • Martin says:

      it is obviously should include it was.

    • konst says:

      It’s actually not that difficult to build a telescope (radio or light) that will detect features of intelligent life on other planets. It just takes a significant amount of resources.

  4. Greg Diderich says:

    That is basically correct. We use parabolic dishes to send the energy directionally, but the signal still expands and loses energy. We can barely still communicate with Voyager with a 230 foot diameter dish.

    Even then, the signal is traveling at the speed of light, so the message we receive is thousands or millions of years old.

    So why would an alien race be sending a message to someone a million years in the future to a planet that a million years ago had electromagnetic radio producing civilization, with a transmitter that would have to be powered by the stars themselves?

    It seems to me that any communication between advanced races would have to be faster than light. So I rather doubt we’d see any messages from any relevant beings using media that is limited to the speed of light.

    • Greg Diderich says:

      oops, i didn’t account for some types of narrow beam radar, and I overestimated the distance to the nearest extrasolar planets…

  5. DT says:

    So the whole SETI program was a complete waste of time?

    • Greg Diderich says:

      I’ll keep looking into it because the SETI guys are zeroed in on microwave radiation as something special, but I don’t see how it would be at detectable levels by the time it got here…

      • Tel says:

        Here’s a link about the “water hole” between the natural radiation of Hydrogen and Hydroxyl.


        Unfortunately most of SETI has been searching right near the Hydrogen side and they are looking for some sort of pattern. I must say that if I wanted to be seen I certainly would not radiate right next to a strong natural radiation source where the receiver would be in some doubt as to what they were looking at.

        I would radiate at some deliberately artificial magic ratio between Hydrogen and Hydroxyl and make it look as unnatural as possible (e.g. PI or something). Also, only a very pure narrow band carrier will be the only thing that has a chance of being detectable at ultra-low signal levels (the narrower the band, the better the signal-to-noise characteristics), so I’d be sending a very narrow band, not a coded message.

        What other message can you say other than, “Hello I’m here?”

    • MamMoTh says:

      At worst it would be a waste of energy, not time.

  6. Rob says:

    Statistically speaking there is almost certainly a planet out there somewhere where the government once borrowed some money that did not lead to a future generation having lower utility.

  7. Daniel Kuehn says:

    “Serious evidence against it”?

    I’m shocked you could say that sort of thing. What evidence are you thinking of? This will be news to a lot of people, Bob.

    I’m also amazed that you can doubt that life exists outside of Earth but you are so confident in the existence of God. Perhaps you could dedicate Sunday’s post to why you are willing to commit your life to a very specific story about a very specific deity that is relatively low on evidence, but you’re willing to so quickly dismiss the prospect of alien life – a prospect that most scientists take quite seriously.

    • Robert Fellner says:

      I agree with Daniel. Which is so gross for me. Going to take a long walk by a lake and reflect on things now…

  8. Tel says:

    It’s kind of difficult to have strong evidence for the absence of a thing, especially when you don’t have a clear definition of what that thing really is. Atheists have been trying for years to say, “OK, here is an empty room, show me where God is in this room, or show me a soul.” You could postulate that God does not exist because we can’t build a God detector, but you could equally postulate that we just don’t know enough about what we are doing.

    Here’s a real measurement for you. The Hubble Ultra-Deep Field registered celestial object UDF 423 which is estimated at 10 billion light years away. To put this in context, if every dollar in the US National Public Debt (today) was equivalent to 40 billion miles, then that’s about the distance from here to UDF 423, and that’s not actually the edge of the universe, only the edge of what we can see right now. We are talking about a big place.

    Very hard to believe that Earth is unique within that much space, especially if you believe that evolution on Earth started out with some freak event, triggering a chain of ever more complex life forms. However, it’s not hard to believe that evolution is slow, and also interstellar travel is slow (unless we postulate that faster-than-light drive might exist). Let’s suppose we set off right now to get to UDF 423 and we had a spaceship that could travel at the speed of light… that’s another 10 billion years to get there plus a bit extra because the universe is expanding, but the universe itself is (probably) only 14 billion years old, so one can presume that evolution on UDF 423 has gone about the same speed as evolution on Earth and we certainly would get to that party rather late. It’s probably not worth making the effort to go there, especially when the fastest thing we have is nowhere near the speed of light.

    The other problem of course is that even if you do believe that evolution is a perfectly logical statistical process, we only have very limited ability to measure the early years in that process (we have plenty of examples of selective breeding in recent years). No one has managed to duplicate the early origin of life so one has to presume it’s a rare event, but taking a guess about how rare is pure speculation. You can’t do statistics with a sample size of 1.

  9. John Dougan says:

    > Did all of the scientists working on those projects fail to consider that a guy could blow up their efforts in 5 seconds in an EconLog comment?

    Short answer: No. It doesn’t blow up anything.

    Longer answer:
    The Search for ExtraTerrestrial Intelligence (SETI : http://en.wikipedia.org/wiki/SETI ) efforts divide into 2 areas: sending and receiving.

    For sending (Active SETI) there have been only a handful of formal attempts, the radio transmissions and the incidental stuff on the probes. The sending attempts using the Arecibo radio telescope and the moderately well known image they tried to send are probably the best known. ( http://en.wikipedia.org/wiki/List_of_interstellar_radio_messages ). These are mostly symbolic, just as time capsules are.

    Informally we have been radiating in all directions for 100 years. There are some transmitters, such as the over–the-horizion ICBM early attack warning radars, that would be detectable over quite a range. Those are very high power, semi directional, and have a signature that doesn’t really resemble anything natural so it should be straightforward for anyone listening to detect them over the background chaff and solar noise, assuming they care to try. We may not want them to do this, depending on their intentions.

    The stuff on the Voyager and Pioneer probes (recordings, plaques) was more of a long shot cry into the void during the Cold War. If nothing else survived WW3, those would.

    There is lots of arguing on various points, but in general it seems that that if a civilization gets older and more powerful it will use a lot more energy and the effects of large scale energy use should be visible, either by signs of waste release or signs of heavy drain on the energy sources (Dyson sphere). And of course they may have their own equivalent to the powerful radars we are radiating with or have done other obvious-from-a-distance things like re-arranging their local planetary system. A lot of the existing search protocols are tuned for these assumptions, such as SETI@Home (http://setiathome.berkeley.edu/ ).

    So what we have done a lot of is scanning the sky and listening carefully (Passive SETI). This is usually done of a shoestring budget. Often they get the telescope time in gaps in others usage. Lots of volunteer effort as well.

    If you aren’t listening, you aren’t going to hear anything, so tossing a small budget at it is considered reasonable considering the impact should they actually find someone either close by enough for a slow conversation or just the traces of a long extinct civilization. Possibly we can find out the answer to the Fermi Paradox ( http://en.wikipedia.org/wiki/Fermi_paradox ) before it gets us.

    (BTW, the signal drop off is is indeed inverse-square.)

  10. Greg Diderich says:

    ok, well, learn something new everyday. There are certain powerful narrow beam radars and such that are detectable out to ~1000 light years. With detectable planets as close as 10 light years, there is a chance. Unfortunately, something like TV or radio would be completely impossible to detect, so I’m afraid karaoke youtubes are confined to this solar system.


  11. Cody S says:

    Bob, are you really assuming that scientists who get a grant or found a government initiative are working on relevant issues rather than collecting a paycheck?

    The signals we have sent increase our chances of being detected by aliens immensely, which is to say from zero to something which is not zero. It’s comparable to the difference between buying a lottery ticket and not buying a lottery ticket: your chances of winning increase almost infinitely, even if it’s still only a 1:200,000,000 shot.

    Think of the difficulty of being found on a tiny treeless island in the pacific, if the searchers had no idea where in the Pacific you were, and you had nothing but a mirror to signal with. Also consider that space consists in an infinite number of planes, where the Pacific is just one (approximately).

    The dirty secret of being discovered by aliens is that their initiative in exploration far outweighs anything we humans can do to make finding us easier.

    The long and short of it is, the guy doing the “blowing up” is pretty much correct. But the honest SETI-type researchers have always basically posed such programs as buying a chance at winning the galactic lottery.

  12. Adam H says:

    Cody that sounds correct. To put it this way, say there is a civilization 2,000 light years away who detects our planet has oxygen and is a good candidate for life (we could do this with today’s technology). They would have to be willing to send a concentrated signal directly at our planet with the expectation of not hearing back for at least 4,000 years, if at all. And there might be 100,000 such planets in our solar system, so which planet would they choose? From the alien’s perspective it seems like a big waste of energy. So it’s not surprising we have not yet seen anything. The SETI guys know this, but why not give it a shot? The benefit is so great it is worth the effort.

    I think the biggest bottleneck to the search is computing power, and I remember hearing an interview from someone at SETI who said with advances in computing power, they should be able to greatly speed their search. His guess was they should know conclusively either way by around 2030 or so.

  13. Greg Diderich says:

    I’ll add that most of SETI is volunteer and private money. The government got out in the 80s.

  14. Tom says:

    Bob, have you ever read about the martian rock’s found with what looks like fossilized bacteria? In the late 90’s, I went to a science exhibit in San Jose, CA where they showed pictures of “known” earth bacterial fossils and the fossils on a martian rock. Many mainstream scientists thought they were evidence of aliens….not that it proves anything one way or the other.

    But I also find it strange that you believe in Jesus, but not aliens. I love you, Bob, but do you really think we’re that special? You need to read some Stephen Hawking books or something because its nearly impossible to wrap ones head around the amount of planets in the universe and the distance between them. Its like going to a beach and counting the grains of sand.

    I’m willing to wager that out of the thousands and thousands and thousands and thousands of planets out there, more than one harbors life. But hey, maybe you’re right and humans really are the pinnacle of intelligence. (Yeah, right)

    • Tom says:

      Please ignore my spelling an punctuation errors. I’m super stupid.

  15. konst says:

    If there were aliens (from our point of view) on those planets we have detected and they were advanced enough (our level or slightly more advanced) they can certainly detect our EM signals if they chose to create a radio telescope with those capabilities (mainly large enough collecting power).

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