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SETI: Project Argus and the Long Stare

I think you’ll find Jon Lomberg’s new essay in Slate as interesting as I do. We Need a World Cup for SETI uses a familiar figure at many sports events — the guy in the stands holding up a Biblical reference on a poster — to dig into a far more interesting issue. How does one go about maximizing visibility? The guy with the sign knows how to do it and if we think about his methods, we can better understand SETI.

For as we think about radio and optical SETI, we’re usually looking for signals that have been intentionally sent. Here we run into the particularly tricky business of trying to understand the thinking of an alien being, but there are certain principles that may apply to any civilization trying to send out a beacon-like message. The message needs to be short, cheap, easy to find, and in a place where it’s likely to be seen. So what kind of beacon is this going to be?

We’ve discussed ‘Benford beacons’ in these pages before (see, among others in the archive, Detecting a ‘Funeral Pyre’ Beacon). A beacon announcing little more than ‘We Are Here’ could be used to attract the attention of any receiving culture, after which we (the receivers) would apply our resources to looking harder at the source. But from the standpoint of efficiency and economy, a brief, bright beacon is best. James and Gregory Benford have addressed the matter in two key papers cited at the end of this essay. Let me quote a brief bit of one:

No technology available in the near-term will allow us to deliver powerful signals every minute of the day over a span of multiple epochs… But we might be able to make a beacon that works more efficiently, by targeting only those star systems where life seems most likely, and then pinging them each in turn, repeating the cycle every few months or so. Presumably, if a curious civilization caught one transmission, it would train its telescopes on that exact spot until the next part of the beacon’s message arrived. This more sensible approach—a sort of Energy Star specification for SETI—would save enough power to keep the beacon running for millions of years.

The Benfords bring useful synergies to bear on the matter. Jim is a plasma physicist — he knows all about beaming — while Greg is both physicist and science fiction author, a man who has speculated for decades on the workings of extraterrestrial civilizations. Jim’s son Dominic, also active in the beacon work, is a physicist at NASA GSFC. Beacons like the Benfords are suggesting are different from the kind of directed beacon SETI has long looked for, one that demands intense focus on stars in the hopes of finding continually broadcasting signals. A Benford beacon puts out a signal we would perceive as intermittent, a brief pulse.

milky-way

Image: What kind of signal to look for amidst 200 billion stars? Credit: Center for Planetary Science.

The Long Stare

You can see that this puts the premium on what SETI people call ‘dwell times,’ i.e., the time we look at a particular target. In his Slate essay, Lomberg points out that there is a major timing issue here. Just how long would a beacon like this take before it repeated?

If you ever detect a possible beacon, you have to remain on target long enough for it to repeat—and who knows how long you have to wait? For an ancient and long-lived society, with perspectives far longer than our 10,000-year civilization, that might be a long time. Their notion of patience might be very different from ours. They’re aliens, after all. Of one thing I am sure: Any brief, potentially artificial signal should be closely watched for a repeat. A new approach to SETI could involve unbroken observation of some of the special directions on the sky.

Given that open question, we still need to maximize the possibilities, and I think Lomberg is right in emphasizing a strategy of constant listening. How to do this? Paul Shuch, the canny and deeply dedicated executive director of the SETI League, has long advocated getting away from what he calls ‘soda straw’ SETI, in which we perform a deep study of a target for only a short period of time before moving on. Instead, Shuch backs attempts like Project Argus, the SETI League’s microwave SETI effort aimed at providing continuous, full-sky coverage.

The notion here is to deploy and coordinate about 5000 small radio telescopes around the world, an attempt to provide continuous monitoring of the sky in real time. A station for Project Argus is not a huge dish but an amateur installation fully capable of detecting a Benford beacon’s transient signal if it should occur. In terms of cost, such a site has more in common with amateur radio than with Arecibo-style astronomy. It could be built for no more than a few thousand dollars and, depending on the builder, perhaps for less.

horn0302

Image: H. Paul Shuch, N6TX, uses the SETI Horn of Plenty antenna for portable operations when away from his Project Argus station FN11lh. The horn, which fits in the back of a minivan, is ideal for classroom demonstrations, exhibiting +20 dBi of gain at 1.4 GHz. Credit: SETI League.

And yes, the famous “Wow Signal,” a one-off detection via Ohio State’s Big Ear radio telescope in 1977, does seem to fit the model of a Benford beacon, in being powerful, brief, and never seen again. How should we look for the next “Wow Signal”? Science fiction author David Brin backs the Project Argus idea in The Search for Extraterrestrial Intelligence (SETI) and Whether to Send “Messages” (METI):

Clearly SETI would benefit from a supplementary system that covers the Earth, searching continuously and broadly for pings that are sent by ETCs narrowly. That system would be ready to detect and pounce upon any new Wow Signals and automatically net-notify larger telescopes to zoom quickly on the source. Not a competitor with classic SETI, this second layer could serve as an ideal alert-generating system, filling a glaring deficit in the current approach.

An Expanded Project Argus

In Greek mythology, Argus was a giant whose epithet “all seeing” (panoptes) spawned depictions of him with multiple eyes. Argus always had a few eyes open, thus becoming the perfect watchman. Can we find a way to maximize the potential of Project Argus?

For while the endeavor is loaded with promise and benefits from the skills and energies of people like Shuch, it has been unable to reach anything like the needed 5000 stations for continuous coverage. This is why a comment by the above-quoted David Brin on a SETI-oriented mailing list recently caught my eye. Brin notes that even as ‘soda straw’ SETI continues, we have the option of energizing the Project Argus idea. We already see wealthy people like Paul Allen and Yuri Milner becoming deeply involved in SETI. What if we could find a similar figure to create a Project Argus kit?

The idea here would be to take the building of a home receiving station for SETI out of the realm of sophisticated electronic technology and into into a turn-key kit that could be purchased for several hundred dollars and simply attached to a basic backyard dish. Like SETI@Home, a Web-based collection system could be used to track the ongoing datastream. A global system for transient detections like this is the kind of network that could find a Benford beacon.

gingell

Image: My friend Mike Gingell, KN4BS, shows off his two dishes, 12 and 10 feet in diameter, used for radio astronomy, satellite TV, and of course SETI. I’m sorry to say that Mike passed away last year, but he remained fascinated by SETI prospects until the end. Credit: Mike Gingell / SETI League.

We need to keep an eye on the possibilities that can emerge from private funding and the work of skilled amateur radio astronomers. But we also need to grow the numbers of those who have the means to participate. An updated version of Project Argus could supplement and extend the original, taking what began as a superb idea for engineers working with home equipment into the realm of everyday users with a yen to use digital tools to explore SETI’s possibilities. Make the kit cheap enough and straightforward to operate and the transient detection system we need emerges, an approach to SETI that widens our capabilities even as traditional SETI continues.

The papers are Benford, “Messaging with Cost Optimized Interstellar Beacons,” Astrobiology Vol. 10(5) (June, 2010), pp. 475-490 (preprint) and “Searching for Cost Optimized Interstellar Beacons,” Astrobiology Vol. 10(5) (June, 2010), pp. 491-498 (preprint). Paul Shuch’s Searching for Extraterrestrial Intelligence: SETI Past, Present, and Future (Springer, 2011) is an essential resource on SETI issues.

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Comments on this entry are closed.

  • DCM December 14, 2015, 12:44

    Listening is one thing, but getting their attention is dangerous. Listening is also cheaper.

    There’s another odd assumption at work in much of the speculation here, which is that technological development follows the same trajectory as ours.
    I remember, for example, reading an article that mentioned all the ingredients to invent photography existed before the American revolution but successful, repeated, carefully documented experiments weren’t done till the 1820s.
    Photography and the telegraph were used in the US civil war, along with various precursors of machine guns and aerial surveillance but armies still charged and fought on horseback using swords when they couldn’t reload their single shot small arms.
    People are so amazed by wet cell batteries from the 800s AD that they easily believe aliens brought them rather than that people discovered them just was they were later rediscovered after being lost because they were guild trade secrets.
    We could receive faint radio signals from somebody whose technology otherwise resembles Julius Caesar’s….

  • NS December 14, 2015, 12:47

    Another “Argus”, this one at Ohio State University:

    http://ohioargus.org/

    Unfortunately, the scientists involved have moved on and the project appears to have been on hold for several years now.

  • Tom Mazanec December 14, 2015, 13:27

    As well as “WOW!” were the signals mentioned in Sagan’s “Pale Blue Dot” and TYC 1220-91-1.

  • Larry Kennedy December 14, 2015, 14:13

    Sounds like one of the best thought out ideas for SETI in a while.

  • Charlie December 14, 2015, 14:16

    “People are so amazed by wet cell batteries from the 800s AD that they easily believe aliens brought them rather than that people discovered them just was they were later rediscovered after being lost because they were guild trade secrets.”
    WHAT ?! Wet cell batteries were around in the 800 A.D. ? Where did you get that piece of information, I’d be very interested

  • Joy December 14, 2015, 14:37

    For a dark vision on why METI is a really bad idea – check out “The Three-Body Problem” by Cixin Liu. Both that extraordinary book and the sequel, “The Dark Forest” are now available in paperback English translations. (I imagine the final act of the trilogy wil be published shortly.) Like all SF, it contains rubbish science. But the storytelling is first rate. My highest recommendation!

    PS: On a time scale of millions of years, our nearest neighbour star system likely is chaotic. Proxima is probably near the apastron of a very long period cometary orbit and may very well come screaming through the centre of the A-B binary every million years or so. However, as mass Proxima <<A or B, the central stars are probably only slightly perturbed by each encounter.

  • Alex Tolley December 14, 2015, 14:38

    It seems to me that if you want to attract attention, you would be better off transmitting at wavelengths that do not require special equipment, i.e. optically. Then you have 7 billion potential receivers and a the possibility of receiving the signal regardless of technological development. Imagine if a star brightened every century or so from antiquity. That would signal modern astronomers to start observing that star as soon as their equipment was suitable.

    BTW, that doesn’t stop you from transmitting at other wavelengths too, but the “beacon” to attract attention should be easily observable by simple eyes.

  • Tom Baty December 14, 2015, 14:49

    @ Charlie….There are several articles on the “Baghdad battery” on the internet. Here is one of them.You can Google the others if you want more info.

    http://www.ancient-code.com/the-baghdad-battery/

  • Kappy December 14, 2015, 14:56

    @Alex Tolley: That makes the assumption that an intelligent species will have eyes that detect the same wavelengths as we do. I would think the evolution of eyes would be dependent on the atmosphere and their star’s output. Isn’t it possible that some ETI has eyes that see in other frequencies than we do?

  • Tom Baty December 14, 2015, 14:56

    Incidentally I am not a believer in ancient astronauts…… So I think the Baghdad battery was developed by some clever people from long ago. Interesting!!

  • lepton December 14, 2015, 16:16

    If we really want to get attention (not a good idea IMHO), we can build big SPSes. Not only they give us energy, defend planet from rongue astroids, launch sail probes, but also act as billboard to announce our presence.

  • Alex Tolley December 14, 2015, 17:31

    @kappy. Terrestrial life can see from UV to IR, although we mammals are more limited. Where light is absent, animals revert to using pressure waves, detected by ears or other body sensors.

    We can rule out long wavelengths of EM radiation as the size of the organ increases to unmanageable limits (think radar dishes). So unless teh life is like those huge Jupiter floaters in Clarke’s fiction, radio wave sight won’t work. In teh other dirrection, it is very hard to focus X-rays or gamma rays, which are also so energetic that they destroy organic matter. They also won’t penetrate an atmosphere. So they cannot be used. So practically, the UV to IR range is required to be used to evolve practical sight organs which must focus the rays for good vision. Obviously pressure waves cannot be transmitted directly through vacuum, so they make no sense. I hope this isn’t too much like a “just so” story.

    Therefore visible light makes most sense when signaling to other intelligent, planetary bound life forms.

  • Andrew Palfreyman December 14, 2015, 18:24

    Orbiting an optical mask around the sun in various planes is a step towards omnidirectionality. The general idea is to use a mask big enough to provide a recognisably intelligent pattern of holes and a good enough signal to noise ratio. It’s completely passive of course, and requires no station keeping maintenance.

  • V. L. Teofilo December 14, 2015, 18:38

    Deja Vu all over again. This has been discussed before on Centauri. Again the probability of Com with another ETI at the same level of technology is quite small . see http://arxiv.org/abs/0707.0011

  • Daniel Suggs December 14, 2015, 22:02

    @Alex Tolley Perhaps, instead of visible, or radio waves, might they use some sort of energy vortex to form patterns in fields? Maybe we need to be looking at crop circles seriously?

  • Joe G December 15, 2015, 0:04

    Can anyone recommend a receiver design that uses readily available components? Im thinking something relatively easy to fabricate that could feed a signal into a pc for processing and filtering.
    Not to date myself, but, I have a couple of ancient radio astronomy books that feature schematics that use vacuum tubes… Not that antique radios wouldn’t be interesting to build, but there has to be cheaper, better way to listen for alien Top 40 radio…

  • DCM December 15, 2015, 5:36

    ‘Charlie December 14, 2015 at 14:16

    “People are so amazed by wet cell batteries from the 800s AD that they easily believe aliens brought them rather than that people discovered them just was they were later rediscovered after being lost because they were guild trade secrets.”
    WHAT ?! Wet cell batteries were around in the 800 A.D. ? Where did you get that piece of information, I’d be very interested’

    I don’t remember when they were discovered but it was fairly recent. They are from Iraq and were used for electroplating. I can confidently say that aliens didn’t bring the technology, which is relatively simple and needn’t be understood in terms of modern theory to work any more than paint requires modern chemical knowledge to work.
    Probably assembling the apparatus was a trade secret of some guild, discovered by observation, and lost when members died as a result of some invasion like the Mongol massacre of Baghdad in the 1200s.

  • Mike Fidler December 15, 2015, 6:00

    One idea that has not been discussed that may make a big difference is that we may be trying to communicate with long lived beings. We are on the verge of understanding the process of ageing and the ability to create parts of the body from your own stem cells, so living possibly hundreds or maybe thousands of years? How would that change our view on intersteller travel and communicating with other civilizations if we could become immortal? Where would all these beings be, without consuming the whole universe. The huge number of red dwarfs with their erratic flares would fit the bill, trillion year lifetime, signaling via something like
    Andrew Palfreyman concept but via a natural flare mecanism, created by the immortals in that system! Sounds like it would make a great SciFi too!

  • ljk December 15, 2015, 10:12

    And speaking of inoperative Ohio SETI projects, the Big Ear radio telescope – the one which detected the (in)famous Wow! Signal of 1977 – was torn down in 1997 by Ohio State University to make way for condos and a golf course.

    http://www.w1ghz.org/bigear/bigear.html

    http://www.setileague.org/photos/bigear00.htm

  • Frank Smith December 15, 2015, 10:54

    @ Joe G

    Rather than build-it-yourself, I’d recommend a software designed radio like the new SDRPlay. SDRPlay software designed receiver. It receives to 2 GHz.

    Apache Labs amateur radio transceivers offer a radio astronomy option, but you’d need a transverter to get to UHF. <a href=" https://apache-labs.com/cart.php&quot;

    Frank Smith, WS1MH

  • Ron S December 15, 2015, 11:03

    Joe: “Can anyone recommend a receiver design that uses readily available components? Im thinking something relatively easy to fabricate that could feed a signal into a pc for processing and filtering.”

    Start here, especially the second half of the article:
    https://en.wikipedia.org/wiki/Software-defined_radio

    I’m not directly involved with SDR technology though I use it every day. It’s pretty straight-forward with off the shelf hardware and open source software. But, as they say, some assembly required. It’s not for the faint of heart.

    You may be better off waiting for the SETI League to come up with their turn key kit. There is a lot involved if the receiving system is going to actually be useful. The trickiest part is the DSP (demodulating, searching, etc.) that uses the received data. After all, no one really knows what we’re looking for. It’s difficult enough even if you do know.

  • Dani Eder December 15, 2015, 14:10

    One possibility is we are looking *from* the wrong place: Earth. Most of you are familiar with gravitational lensing. Stars like the Sun focus incoming photons at 500-1000 AU radius. If you place a transmitter at Alpha Centauri, in the position aimed at our Sun, the beam is made parallel by that star’s gravity. In turn our Sun would refocus the parallel beam to a point. You can get a usable signal with immensely less power than an omnidirectional transmitter, or even a large dish. Besides the power savings, the aliens would know anyone in a position to detect the signal has reached some level of space travel.

    Of course, we are not yet in such a position. Our farthest probe is ~130 AU, which isn’t far enough, and it is not directed at the focus from any particular star. In order to test this idea, we would need to send probes to the various foci of nearby stars (or one probe that can maneuver a lot), with wideband receivers, because we have no idea what frequency the transmitter might use.

    For all we know there is an interstellar Internet chattering away across the Galaxy, using stars as amplifiers and repeaters. Even using a star to focus a beam, it would not be perfectly parallel. So every so often you want pick up the signal, amplify it, and send it on to the next star.

  • ljk December 15, 2015, 14:30

    The most important question about SETI / METI is to ask WHY someone would want to transmit into the galaxy? There are reasons, as I listed in my article I link to next, but even an advanced species who does not need to worry about resources and money still needs a reason.

    https://www.centauri-dreams.org/?p=9489

    And perhaps it is because I am a member of a species that rarely seems to do anything for anyone out of purely altruistic reasons, I have a lot of trouble with the idea Carl Sagan often espoused that ETI would beam the equivalent of the Encyclopedia Galactica across the stars merely to uplift other species so we could all be one big happy family. Rich and powerful humans residing on Earth seldom share their power and wealth, not without ensuring they get a lot back in return. They also don’t like to make themselves vulnerable in the same way that states with nuclear weapons don’t just share that knowledge with just anyone.

    You might reply that the idea listed in the article is just about a beacon designed by scientists who are naturally curious to see who else resides in the Milky Way. Perhaps. However note that on this world many people object to METI out of fear of attracting malevolent species and many science projects in general are designed to make a profit and thus only get their financial support first and foremost for those reasons. Or there is a political motive such as with Project Apollo: If it were not for the Cold War, it is more than likely we would still be wondering when someone would one day see a human being walk on the Moon.

  • ljk December 15, 2015, 14:38

    ETI might use supernovae as galactic attention getters. Perhaps those who monitor for SN (along with every other kind of astronomer) might also want to do a little SETI in the process.

    http://www.iar.unlp.edu.ar/SETI/seti-boston.pdf

  • ljk December 15, 2015, 14:47

    And how deeply are we really thinking about the whole SETI enterprise anyway? It still remains dominated by the radio realm going back to 1959 and even earlier if you count the 1924 radio searches for Martians.

    Scientists still tend to think the ones who might conduct METI will be fellow scientists. Maybe, if they have more clout that human society often gives.

    See here:

    https://www.centauri-dreams.org/?p=27889

    And there are alien beacons in our galaxy sending pings, really keep in mind that they are either very naive and trusting of others, or they have very little to worry about shouting into the forest.

    Some more food for thought:

    http://www.projectrho.com/public_html/rocket/aliens.php#id–Alien_Contact–The_Fermi_Paradox–The_Killing_Star

  • Coacervate December 15, 2015, 16:51

    Am I missing something? This is probably a negative on my part that I do not intend…but whenever I look for scholarly data on SETI results over the purported “50 years of SETI”, what I find are the miniscule OZMA, Phoenix and “WoW” signal. The list is a bit longer but where are the data from the long-running programs. Shouldn’t there be more analysis on those millions of hits from the Arecibo data? What about Hat Creek, Argus …how long have these projects been running?

    It would be just as important to the science to publish the results of listening programs. These may not have the journalistic appeal of a WoW signal, they will however serve as the basis of another window on space.

  • ljk December 15, 2015, 18:57

    Just because many humans are afraid of the unknown, or think we are not advanced enough, or cannot look or think past their immediate surroundings, does not mean that the rest of the Universe isn’t going to come calling some day.

    We need to be ready and aware as possible for a variety of scenarios, because hiding is not much of an option for a species with over seven billion members and rising and a slowly but surely expanding technological footprint.

    http://www.huffingtonpost.com/john-w-traphagan/active-seti-and-the-peril_b_8805904.html

  • Larry Kennedy December 15, 2015, 19:47

    @ ljk
    I still hold that we have a very large argument against predators roaming the galaxy. If they are doing so, then why aren’t they here?

  • DCM December 15, 2015, 21:20

    “Tom Baty December 14, 2015 at 14:56

    Incidentally I am not a believer in ancient astronauts…… So I think the Baghdad battery was developed by some clever people from long ago. Interesting!!”

    And you are right.

    Note that when Western and Chinese people contacted less technologically advanced groups that while it’s true they gave them trinkets and gadgets to amuse them they also took note of politics. Thus they may have armed and trained some groups to carry out long standing feuds to weaken all of them militarily and economically for easier conquest.
    They may have imparted what they considered superior religious beliefs, but these too were to make them weaker and to gain allies.

    We can’t really imagine what they’d be like. Consider the original “Day The Earth Stood Still”. No superior wisdom was imparted, though that’s supposed to be the message. The aliens demonstrated greater military power to an Earth caught up in the Cold War and said they’d kill everybody if we didn’t do what they said.

    Would aliens actually try to impart superior wisdom, assuming they even had such a concept? Not hardly. They’d have their own motives humans might never grasp except through objective study.

    Listen to the stars, send no messages, and develop Mars and artificial biospheres in space.

  • ljk December 16, 2015, 10:01

    Larry Kennedy said on December 15, 2015 at 19:47:

    “I still hold that we have a very large argument against predators roaming the galaxy. If they are doing so, then why aren’t they here?”

    There are about 400 billion star systems in the Milky Way galaxy. It has been determined that most if not all of them have planets, which in turn means belts of comets and planetoids as well. It is probably safe to assume that many of them are unoccupied by at least complex life.

    If you were a starfaring ETI, would you not prefer to mine resources from systems where there are no intelligent natives, even primitive ones, if for no other reason that you don’t want the hassle? Even then, if such an ETI wanted to start mining our comet and planetoid belts, what could humanity do at present to stop them even if we did notice, other than to stand their with our mouths open first then panic in general.

  • Steven White December 19, 2015, 16:22

    “The message needs to be short, cheap, easy to find, and in a place where it’s likely to be seen. ”

    Flawed assumptions and human bias abound here in this statement. Short? Why not very long? A better chance of catching someone listening who is NOT afraid to answer back in time. Cheap? The most egregious assumption of all. That of assuming to have ANY idea of what kind of economic system ANY alien species might have, if it even has a system we would see as “Economic.” And that could even involve political, philosophical even religious factors we would have still LESS of a clue about.

    Easy to find and in a place likely to be seen? Not at all. Hard as heck to find and well hidden, since this would help to determine how advanced an alien contacting civilization might be, if advanced enough AND clever enough to even know where to look. That way, they could weed out populations where, say, about a quarter of the public still thinks their sun orbits their planet and the whole universe was made in a few days for their benefit.

    In short we don’t know where and how to look and listen, bogged down by our own human conceptions.

  • Alex Tolley December 19, 2015, 18:00

    It would make no rational sense to have an expensive (i.e. high resource use) system that was devilishly hard to find. Cheap and hard, yes. Expensive and easy, yes.

    While it is easy to say that aliens might think very differently from us, resulting in very different social organizations, we can say that unless they have an organized social system they won’t be very advanced, and part of that advanced state will tend to use optimizing solutions that include cost optimization.

    If you want to talk to non-technological squid, that is a different matter.

  • Eniac December 20, 2015, 13:56

    Wikipedia has (among other things) this to say about the Baghdad Battery: “This interpretation is generally rejected today.” and “… does not know a single archaeologist who believed that these were batteries.”

    Please let us not use this forum to try and fan the flames of hyperspeculative UFO myths like this one.

  • Eniac December 20, 2015, 14:03

    LJK:

    If you were a starfaring ETI, would you not prefer to mine resources from systems where there are no intelligent natives, even primitive ones, if for no other reason that you don’t want the hassle?

    It makes no sense to mine resources at a system if you are not going to live there. And almost all of the time in the last 4 billion years, there would have been no intelligent natives on Earth, so no hassle.

    Even then, if such an ETI wanted to start mining our comet and planetoid belts, what could humanity do at present to stop them even if we did notice, other than to stand their with our mouths open first then panic in general.

    Right. But more likely this would have happened a billion years in our past, before we were here, and the ETI would still be living here. We would be them.

  • Dana Andrews December 20, 2015, 14:42

    I’m afraid there is so many transmitters in orbit around earth, that false signals will happen every few minutes. Maybe a dedicated listening post at the Earth-Sun L2 point would be better served.

  • Eniac December 21, 2015, 0:55

    Dana Andrews: On the other hand, when you have a lot of receivers working together, it becomes possible to distinguish very well between local and remote origin of a signal, as long as it is picked up by more than one receiver.

    An object in Earth orbit, for example, would only be picked up by receivers close to its current orbital position, and from a large variety of directions. A galactic signal, on the other hand, could be picked up by all receivers on the signal-facing hemisphere, and come from the exact same direction, everywhere.

  • Alexey Borisenko January 9, 2016, 13:13

    Why not using H-alpha ultra-narrowband signalling? It will be much cheaper for transmissions over interstellar distances.
    Transmitter power requirement proportional to fourth power of L/D (L/D= wavelength/diameter, which is also angular resolution)
    Compare currently state-of-the-art L/D values:
    Radiotelescope: L/D about 1e-3
    Optical telescope: L/D about 1e-7
    Total power effect: 1e+16!!!
    Yes, there are many other factors, but it is very unlikely that anything other can overcome this 16-order difference.
    Why exactly H-alpha wavelength? It is obviously, well recognizible by any civilization in the universe as most prominent spectral hole of typical star, which is very convenient for interstellar communications.

  • ljk January 11, 2016, 12:52

    Was the famous Wow! Signal caused by comets from this Sol system:

    https://www.newscientist.com/article/dn28747-famous-wow-signal-might-have-been-from-comets-not-aliens/

  • ljk January 20, 2016, 18:46

    When you send a METI and you don’t know the recipient’s native tongue (or even if they have tongues or use them for communication), always start with science, particularly in picture format:

    http://www.planetary.org/blogs/guest-blogs/2016/0120-the-pioneer-plaque-science-as-a-universal-language.html

  • ljk February 5, 2016, 14:10

    From exile to eminence: How the alien hunters conquered astronomy
    Jill Tarter tells Ars how technology and discovery have primed the search for life.

    by Eric Berger – Feb 5, 2016 at 10:34 am EST

    When Jill Tarter first began to look for aliens, she drew looks askance from her friends and colleagues. The perception was “What’s a nice girl like you doing in a subject like this?” she recalled in an interview with Ars. Tarter, now 72, would go on to rise above that perception, becoming a leading figure at the SETI Institute. And the astronomer played by Jodie Foster in the movie Contact, which was largely based on Tarter, would further bolster her reputation.

    She and her fellow searchers haven’t found E.T. yet, but they have become respected members of the scientific community. These days, when NASA plots future explorations of Mars or ice-covered moons in the outer solar system, they’re driven by the search for microbial life. And with the discovery of billions of planets in the Milky Way, no one snickers any more at the idea of sniffing atmospheres around other worlds for biosignatures.

    The search for aliens has become respectable because it no longer is a philosophical or religious matter to ask if we are alone. During Tarter’s lifetime, scientists and engineers have developed the tools and technology to finally probe this question in a meaningful way.

    “When I first started in this field, we were coming off the bad science done by Percival Lowell and Martian canals,” Tarter said. “It made the field odoriferous.” [Yeah, it was all Lowell’s fault.]

    Lowell, an American businessman and astronomer, popularized the idea that the long, somewhat linear features seen on Mars were canals. This influence pervaded the public mind through the middle of the 20th century and featured in science fiction works by both Robert Heinlein and Ray Bradbury. But then NASA probes to Mars, beginning in 1964 with Mariner 4, found a cold, barren, and likely dead world. Many scientists began to dismiss the notion of aliens.

    Full article here:

    http://arstechnica.com/science/2016/02/from-exile-to-eminence-how-the-alien-hunters-conquered-astronomy/

  • ljk February 17, 2016, 12:17

    Just like in The Hitch-Hiker’s Guide to the Galaxy, it’s asking the right question that counts:

    http://www.slate.com/articles/technology/future_tense/2016/02/asking_whether_extraterrestrial_life_exists_is_the_wrong_question.html