Suppose for a moment that life really is rare in the universe. That when we are able to investigate the nearby stars in detail, we not only discover no civilizations but few living things of any kind. If all the elements for producing life are there, is there some kind of filter that prevents it from proceeding into advanced and intelligent stages that use artifacts, write poetry and build von Neumann probes to explore the stars? Nick Bostrom discusses the question in an article in Technology Review, with implications for our understanding of the past and future of civilization. Choke Points in the Past Maybe intelligent beings bring about their own downfall, a premise that takes in more than the collapse of a single society. Alaric's Goths took Rome in 410, hastening the decline of a once great empire, but the devastated period that followed saw Europe gradually re-build into the Renaissance. And as Bostrom notes, while a thousand years may seem like a long time to an individual,...

Alexander Zaitsev's latest contribution to the debate over sending messages to the stars is a short paper that looks at how visible our planet might be thanks to transmissions from planetary radars like Arecibo, Goldstone or the Evpatoria site from which directed transmissions have already been sent. METI (Messaging to Extra-Terrestrial Intelligence) is broadly dedicated to transmitting messages to stars likely to have habitable planets, but so far the number of transmissions is relatively sparse. The debate over METI discusses the wisdom of continuing them without broader discussion. But tucked within that debate is the specific question of our civilization's visibility. For in addition to the messages that have already been sent, beginning with the Arecibo message in 1974 and continuing in the far more targeted transmissions from Evpatoria between 1999 and 2003, we are using our planetary radars to perform crucial astronomical studies. The work these dishes do in refining our...

Larry Klaes tackles the METI question -- do we intentionally broadcast to the stars? -- in Athena Andreadis' Astrogator's Logs today, looking at the pros and cons of an issue that continues to bedevil the scientific community. Of METI advocate Alexander Zaitsev (Russian Academy of Science), for example, Klaes writes this: In a paper Zaitsev published in 2006, the scientist notes that "SETI is meaningless if no one feels the need to transmit." Zaitsev also feels that if there are advanced cultures bent on harming humanity, they will find us eventually, so it is in our best interests to seek them out first. Zaitsev sees the great distances between stars and the physical limits imposed by attempting to attain light speed serve as a natural protective barrier for our species and any other potentially vulnerable beings in the galaxy. David Brin among others takes the other side of the debate in an article tuned for newcomers to these issues. And that's an important audience. Most...

Although I suspect that intelligent life is rare in the cosmos, I'm playing little more than a hunch. So it's interesting to see that Andrew Watson (University of East Anglia) has analyzed the chances for intelligence elsewhere in the universe by looking at the challenges life faced as it evolved. Watson believes that it took specific major steps for an intelligent civilization to develop on Earth, one of which, interestingly enough, is language. Identifying which steps are critical is tricky, but in the aggregate they reduce the chance of intelligence elsewhere. A linguist at heart, I wasn't surprised with the notion that the introduction of language marks a crucial transition as intelligence develops. But what are the other steps, and how do they feed into the possibility of life elsewhere? These interesting questions relate to how long the biosphere will be tenable for life as we know it. If, as was thought until relatively recently, Earth might support life for another five...

"Were the chemicals here on Earth at the time when life began unique to us? We used to think so. But the most recent evidence is different. Within the last few years there have been found in the interstellar spaces the spectral traces of molecules which we never thought could be formed out in those frigid regions: hydrogen cyanide, cyano acetylene, formaldehyde. These are molecules which we had not supposed to exist elsewhere than on Earth. It may turn out that life had more varied beginnings and has more varied forms. And it does not at all follow that the evolutionary path which life (if we discover it) took elsewhere must resemble ours. It does not even follow that we shall recognise it as life -- or that it will recognise us." -- Jacob Bronowski, from The Ascent of Man How accurate do you think we are in projecting what extraterrestrial civilizations might do? The question is prompted by recent speculation on Dyson spheres and the supposition that advanced cultures will...

Was the early Earth seeded with amino acids from deep space? The variety of molecules found between the stars makes the supposition provocative, but finding interstellar amino acids has been a challenge. Various amino acids have indeed been found in meteorites, but it has been argued that these could have been produced right here in the Solar System within asteroids. Yet laboratory experiments have shown that amino acids can form among the molecules found in interstellar clouds, including such important ones as glycine, alanine and serine. What's next is to identify amino acids in the interstellar medium, and we're coming close. Ponder this: Since 1965, more than 140 molecules have been identified in space, both in interstellar clouds and circumstellar disks, many of them organic or carbon-based. Now researchers from the Max Planck Institute for Radio Astronomy in Bonn have detected amino acetonitrile (NH2CH2CN), a potential precursor of the simplest amino acid, glycine. The odds are...

The line in the title above is from a Jimmy Buffett song. A friend who knows all Buffett songs line by line uses it on his answering machine, invariably provoking a chuckle when I ponder the implications. If the phone doesn't ring, just what kind of message is being sent? Or is any message being sent at all? Thus does the singer capture the bewildered funk of romantic attachments, which can make hash out of all our logic. Like the dog that doesn't bark (think Sherlock Holmes), the phone that doesn't ring carries its own meaning, one we must now try to parse. For the SETI phone isn't ringing. If extraterrestrial civilizations are out there, is their silence a way of sending us a message? Alan Tough created a Web site with the express purpose of offering a communications venue to any nearby alien probes, spacecraft designed to study us and report home. The Invitation to ETI contains a number of essays explaining the project and more or less asking for participation by ET (Paul Davies'...

I've always found the idea of panspermia oddly comforting. Growing out of the work of Swedish chemist and Nobel Prize winner Svante Arrhenius, panspermia assumes that life can move between worlds by natural means, and implies that planets with the right conditions will wind up with living things on them. That idea of all but universal life, and the weird notion that we might all be in some way 'related,' was exhilarating to thinkers like Fred Hoyle and Chandra Wickramasinghe, who went on to suggest that the influx of life from space triggers continuing changes on Earth today, which might involve epidemics and new diseases. Now comes a variant called lithopanspermia, which questions whether rocks blasted off a planetary surface by impacts might not be the transfer vehicles for microorganisms that travel between planets and perhaps further. After all, we have found Martian meteorites in Antarctica, forty or so to date, so the real question becomes the survival possibilities. Can a...

Even the most adamant enthusiasts for METI -- Messaging to Extraterrestrial Civilizations -- haven't come up with anything as audacious as what virtual reality guru Jaron Lanier is now talking about. Writing for Discover Magazine, Lanier has the notion of rearranging basic material objects to make them not just noticeable by aliens but blindingly obvious. Nothing new there, as the concept of such messaging goes back to the 19th Century. Mathematician Karl Gauss considered geometric plantings of trees and wheat to create shapes that might be visible from space, while Joseph von Littrow (perhaps basing the idea on Gauss' work) talked about digging huge ditches and setting kerosene within them on fire at night, for the edification of beings on other worlds. But Lanier isn't talking about anything quite so mundane. This is a guy who thinks big -- he wants to arrange stars. If you can find a way to create stable patterns of stars that are obviously artificial, then you have a celestial...

So far we know of only one place in the cosmos that has life, our own Earth. That makes the study of interesting organisms, and in particular the so-called 'extremophiles' that stretch our understanding of livable habitats, a key part of astrobiology. Finding an organism living around a deep-water vent on the ocean floor doesn't prove life exists in such environments on other worlds, but by understanding the limits of the possible, we're learning more about where and how to look. And sometimes we find unusual life forms in seemingly benign places like Australia's Great Barrier Reef, which brings us to Acaryochloris marina. That tongue twister identifies a bacterium that is unusual because it uses a rare type of chlorophyll -- chlorophyll d -- to take advantage of near infrared long wavelength light. Acaryochloris marina is actually a cyanobacterium, meaning a bacterium that use photosynthesis to derive its energy. Its huge genome (8.3 million base pairs) has now been sequenced for...

Thoughts on Enceladus as a home to life have kept astrobiological debate lively, an unexpected but welcome development from the Cassini mission. The interest is understandable: Cassini has shown us plumes that seem to be the result of some kind of geothermal venting, with liquid water and geothermal energy sources all possible drivers for the formation of life. We don't exactly know what's going on here, but the possibility of a hydrological cycle -- liquid, solid, gas -- has kept theorists active, as witness a research note by Christopher Parkinson (Caltech) and team. The early Earth serves as a possible model for life elsewhere. With photosynthesis not available, life would depend on abiotic sources of chemical energy. It's believed this would have come in the form of oxidation-reduction processes driven by factors like hydrothermal activity, impacts, electrical discharges, or solar ultraviolet radiation. Organics may have been synthesized from inorganic molecules near submarine...

Just off the phone with Seth Shostak, I can report that the KTVU story discussed below about a possible SETI reception is bogus. Apparently the reporter involved misinterpreted the conversation, as we had surmised. We may get a successful reception of an extraterrestrial civilization's signal one of these days, but this wasn't it.

This looks like a case of extremely poor science reporting, but because I've already received e-mail about it, I will point you to a report from KTVU, a San Francisco television station, claiming that a mystery signal has been received at Arecibo, with obvious SETI implications. Cosmic Variance has also picked up on this and seems as skeptical as I am. A quick call to the SETI Institute revealed there is absolutely no buzz about any sort of successful reception making the rounds there. I have a voicemail in to Seth Shostak in hopes of a comment.

Our recent discussions of active SETI, otherwise known as METI (Messaging to Extraterrestrial Intelligence), highlighted many of the key issues involved while demonstrating just how controversial the topic has become. But is there a way to look at METI experiments more objectively? The San Marino Scale has been widely suggested as a method for assessing the risks we incur with deliberate transmissions from the Earth to other stars. Introduced by Iván Almár in 2005, the Scale is a work in progress that draws on the model of the Richter Scale, which quantifies the severity of earthquakes. The IAA SETI Permanent Study Group continues to work on it, hoping to measure "...the potential exposure of employing electromagnetic communications technology to announce Earth's presence to our cosmic companions, or replying to a successful SETI detection." More on the background of the Scale here. Hungarian theorist Tibor Pacher has been calling my attention to the San Marino Scale for some time,...

When it comes to understanding possible extraterrestrial civilizations, I'm with Freeman Dyson, who had this to say: "Our business as scientists is to search the universe and find out what is there. What is there may conform to our moral sense or it may not...It is just as unscientific to impute to remote intelligences wisdom and serenity as it is to impute to them irrational and murderous impulses. We must be prepared for either possibility and conduct our searches accordingly." As quoted in a 2005 essay by Michael Michaud, Dyson saw two alternatives: Intelligent races may rule their domains with benign intelligence, occasionally passing along the knowledge they have accumulated to a universe eager to listen. Or intelligence may be purely exploitative, consuming what it encounters. We don't know which of these alternatives prevails, if either, and that's one reason that Michaud, a former diplomat who became deputy assistant secretary of state for science and technology, resigned...

Lately I've been thinking about cosmic killers, the kind of extinction events that could destroy an entire ecosphere and any civilization living within it. It's a natural enough thought given our speculations about life elsewhere in the universe. Just how hostile a place is the Milky Way? We're beginning to learn that planets are abundant around stars in our region of the disk, with the encouraging expectation that habitats for evolving lifeforms must be widespread. But maybe there are natural caps other than technological suicide that could end a civilization's dreams. You can't help pondering this when you run into the recent news about a long duration gamma-ray burst (GRB) that took astronomers by surprise. GRBs are normally thought to flag the death of a massive star, but in this case the burst seems to come out of nowhere. What caused the event in a region of space where the nearest galaxy is 88,000 light years away? And no question about GRB 070125's credentials. It was...

One thing I'm always asked when I talk about interstellar topics is how long it would take a spacecraft like Voyager to get to the nearest star. After explaining how far away Proxima Centauri and the slightly farther Centauri A and B really are, I tell the audience that Voyager, if headed in that direction, would be facing a travel time of over 70,000 years. That usually shifts the conversation considerably, because many people assume that if we can get to the outer planets, the nearest stars can't be that far behind. If only it were so. The Centauri stars are, of course, only the closest known (and who knows, perhaps there's a brown dwarf a bit closer). Assume a space technology able to travel at close to the speed of light and you're still dealing with travel times that amount to years, although time for the crew would be shorted according to those interesting Einsteinian effects that cause the crew of a vehicle traveling at 86 percent of lightspeed to experience half the elapsed...

By Larry Klaes Larry Klaes' look at the Allen Telescope Array reminds us of the power of philanthropy at getting serious projects funded. It's a topic we'll be re-visiting as the Tau Zero Foundation comes online early in the coming year. I'm reminded also of the One Laptop Per Child project, which is seeing private donations for these educational tools supplanting government shortfalls in some developing countries. Properly targeted, the philanthropic dollar is a powerful thing, and think of the results if the ATA finds a genuine signal! Cornell astronomer and science popularizer Carl Sagan left quite a legacy in a number of science fields, including and especially those which were considered to be somewhat fringe at one time. One prime example of his support of a science field that was not universally accepted in earlier eras was SETI, the Search for Extraterrestrial Intelligence. At a time when many astronomers did not seriously consider the possibility of other beings existing...

As a coda to our recent SETI discussion, two newspaper stories on the subject ran over the weekend. I follow how the media handle this subject because public interest in SETI seems to remain high, and the cultural expectations that show forth in these articles may give us a glimpse of what would happen in the event of an actual detection. Moreover, the Allen Telescope Array has re-focused attention on this quixotic endeavor. Sometimes it seems that we humans give ourselves too much importance in the cosmic scheme of things. After all, what would our little planet have to offer in a galaxy that, as The Age (Melbourne) notes, is made up of 100 billion stars (and there's that number again, 100 billion, which reminds me that estimates of our Galaxy's stellar population range from this low-ball figure all the way up to Timothy Ferris' whopping one trillion). Aren't humans, we ask, just one more backward species trying to evolve? Maybe, but the problem is that we have no way of knowing the...

When Alexander Zaitsev presented his recent paper at the International Astronautical Congress in Hyderabad (India) recently, he spoke from the center of a widening controversy. The question is straightforward: Should we broadcast messages intentionally designed to be received by extraterrestrial civilizations, thereby notifying them of our existence? Zaitzev, chief scientist at the Russian Academy of Science's Institute of Radio Engineering and Electronics, addressed the question by seeing a necessary relationship between SETI (the search for ETI) and METI (messaging to other civilizations). Indeed, the Russian scientist, working at the Evpatoria Deep Space Center in the Ukraine, has the experience to discuss METI from a practical standpoint. Evpatoria has already transmitted a number of messages, the so-called 'Cosmic Call' signal (1999) being made up of various audio, video, image and data files submitted by people around the world. The later 'Teen-Age Message,' aimed at six...