Among the many memorable things Freeman Dyson has said in a lifetime of research, one that stands out for me is relatively recent. “Look for what is detectable, not for what is probable.” This was Dyson speaking at a TED conference in Monterey, CA back in 2003, making the point that the universe continually surprises us, and by making too many assumptions about what we are looking for, we may miss unexpected things that can advance our understanding. Dyson has been thinking about this for a long time considering that it was way back in 1960 that he first suggested looking for the excess infrared radiation that might flag a distant Dyson sphere. I would call this an unorthodox approach to SETI in its day except that when he first came up with it, Dyson didn’t have a SETI effort to consider. It was only in the same year that Cornell’s Frank Drake began SETI observations at Green Bank, and a scant year before that that Philip Morrison and Giuseppe Cocconi published the seminal paper...

One of the first science fiction novels I ever read was The Black Cloud, by astrophysicist Fred Hoyle. I remember that one of my classmates had smuggled it into our grade school and soon we were passing it around covertly instead of reading whatever it was we had been assigned. In Hoyle's novel, scientists discover that the cloud, which approaches the Solar System and decelerates, may be a life-form with which they can communicate. My young self was utterly absorbed by this book and I suspect it will hold up well to re-reading. What brings The Black Cloud to mind is recent work using data from the Green Bank Telescope in West Virginia, where scientists have been studying an enormous gas cloud some 25,000 light years from Earth near the center of the Milky Way in the star forming region Sagittarius B2(N). This cloud is not, of course, behaving as entertainingly as Hoyle's, but it's offering up information about how interstellar molecules that are intermediate steps toward the final...

Are habitable planets the best places to look for life? The question seems odd, because we're assuming life has to have clement conditions to emerge and survive. But step beyond the question of life's formation and the issue can be framed differently. Where beyond its birthplace might life migrate? In SETI terms, where might we look for the signature of a civilization advanced enough to move beyond its home world and expand between the stars? A lot of ideas seem to be converging here. In Huntsville, Ken Roy (whose description at the recent interstellar conference was 'an engineer living and working amidst the relics of the Manhattan Project in Oak Ridge, Tennessee') described potential habitats stretching far out into the Solar System and beyond. Roy has been working for some time with Robert Kennedy and David Fields on colonization scenarios. My own talk covered the kind of places where we might extract resources, ranging from icy dwarfs like Pluto to cometary objects and 'rogue'...

What happens to us if our SETI efforts pay off? Numerous scenarios come to mind, all of them speculative, but the range of responses shown in Carl Sagan's Contact may be something like the real outcome, with people of all descriptions reading into a distant message whatever they want to hear. Robert Lightfoot (South Georgia State College) decided to look at contact scenarios we know something more about, those that actually happened here on Earth. His presentation in Huntsville bore the title "Sorry, We Didn't Mean to Break Your Culture." Known as 'Sam' to his friends, Lightfoot is a big, friendly man with an anthropologist's eye for human nature. His talk made it clear that if we're going to plan for a possible SETI reception, we should look at what happens when widely separated groups come into contact. Cultural diffusion can happen in two ways, the first being prompted by the exchange of material objects. In the SETI case, however, the non-material diffusion of ideas is the most...

In a sobering start to the New Year, at least for partisans of manned missions to deep space, new work out of the University of Rochester indicates that galactic cosmic radiation may accelerate the onset of Alzheimer’s disease. The study, led by the university’s Kerry O’Banion, is hardly the first time that the impact of radiation in space has been studied, with previous work aimed at cancer risks as well as cardiovascular and musculoskeletal issues. But O’Banion’s work points to radiation's effects on biological processes in the brain, reaching striking conclusions: “Galactic cosmic radiation poses a significant threat to future astronauts,” said O’Banion. “The possibility that radiation exposure in space may give rise to health problems such as cancer has long been recognized. However, this study shows for the first time that exposure to radiation levels equivalent to a mission to Mars could produce cognitive problems and speed up changes in the brain that are associated with...

Unexpectedly waking this morning despite Mayan prophecy, I suddenly remembered the storms that had kept me up for an hour during the night. There was little rain, but the winds were gusting and I could hear trees branches slapping against the siding and dogs baying inside nearby houses. When I got up to look out the window, city light under the overcast created a dim bronze aura. You would think it was the end of the world, but this morning I was delighted to see in the paper that a gathering of spiritualists in Mexico says we are not at the end of the world but the beginning of a new one. Up ahead: New powers of telepathy and levitation for us all. I was never into the Mayan thing enough to know whether it involved the end of just our world or the entire cosmos, but I would guess that any extraterrestrial civilizations, if they're out there, have likely had their share of doomsday prophets. And as I await my new powers of levitation (not working yet, but maybe by this afternoon),...

Because I had my eyes dilated yesterday afternoon en route to learning whether I needed new reading glasses (I do), I found myself with blurry vision and, in the absence of the ability to read, plenty of time to think. Yesterday’s post examined a paper by a team led by Jack T. O’Malley-James (University of St Andrews, UK), addressing the question of how our planet will age, and specifically, how life will hang on at the single-cell level into the remote future. It’s interesting stuff because of its implications for what we may find around other stars and I pondered it all evening. Have a look at one of the figures from the O’Malley-James paper, which shows the stages a habitable Earth-like planet (ELP) will pass through as it ages around main sequence stars. I also clip the caption directly from the paper. Image: Time windows for complex and microbial life on Earth analogue planets orbiting Sun-like stars (F(7), G and K(1) stars) during their main sequence lifetimes. Assuming that...

As we begin to identify planets in the habitable zone of their stars, the larger issue becomes what fraction of stars have such planets. This is eta-Earth (?Earth), the percentage of Sun-like stars with Earth-like planets in the habitable zone, a figure we can gradually home in on as statistical surveys like Kepler continue to churn. Right now the estimate depends on whom you talk to, with figures ranging from 1.4-2.7% (Catanzarite & Shao, 2011) to 42% for red dwarf stars (Bonfils et al., 2011). One thing I haven’t seen discussed much is the question of when planets cease being habitable, including what we can call the phases of habitability on a given world. Jack T. O'Malley-James (University of St Andrews, UK) and colleagues have gone to work on the question in a new paper slated for publication in the International Journal of Astrobiology. The researchers note that life emerged on Earth 3.8 billion years ago and perhaps somewhat earlier. The key point is that unicellular organisms...

Astronomy is moving at a clip that sees more data accumulated than can possibly be examined at the time they're collected. We're creating vast storehouses of information that can be approached from various angles of study. Now ponder how we might use these data for purposes beyond what they were collected for. In a new paper submitted to the Astronomical Journal, Ermanno Borra (Université Laval, Québec) looks at how standard astronomical spectra -- including those already taken -- can be used as part of SETI, the Search for Extraterrestrial Intelligence. Here's the idea: Suppose somewhere out there a civilization decides to reveal its existence to the rest of the galaxy. These extraterrestrials reason from their own experience of science that an advanced civilization will study the sky and take spectra of astronomical objects. These spectra become the medium upon which the senders impose their signal. At our end, spectroscopic surveys of vast numbers of stars allow us...

The idea of the multiverse -- an infinite number of universes co-existing with our own -- has a philosophical and mathematical appeal, at least if you're a follower of string theory. Indeed, there are those who would argue there could be as many as 10500 universes, each with its own particular characteristics, most probably inimical to the development of life. But I have to say that I'm far more interested in the universe that is demonstrably here, our own, and thus the news that Geoff Marcy has received a grant to look for Dyson spheres catches my eye more than news of a similar grant to physicist Raphael Bousso to probe multiverse theory. Not that I have anything against Dr. Bousso (UC-Berkeley) and his work, and if he eventually does find a way to make predictions of multiverse theory that can be tested, I'm all for it. But I think the new grants, given to the researchers in a series called New Frontiers in Astronomy & Cosmology International Grants (funded through the UK's...

Back in 2007, science writer Lee Billings put together a panel for Seed Media Group on "The Future of the Vision for Space Exploration." The session took place at the Rayburn House Office Building on Capitol Hill, and I remember flying to Washington with a bad head cold to moderate the event. Miraculously, my cold abated and I enjoyed the company of Louis Friedman (The Planetary Society), Steven Squyres (of Mars rover fame), Edward Belbruno (Princeton University) and interstellar guru Greg Matloff (CUNY). But I particularly remember conversations with Lee. I can't say I was surprised to see him go on to emerge as one of the most gifted science writers now working. Not long afterwards, Lee wrote an essay called The Long Shot for SEED Magazine that took him into the thick of the exoplanet hunt, from which this fine paragraph about the nearest stars and why they have such a hold on us: Alpha Centauri is today what the Moon and Mars were to prior generations—something almost...

I've been fascinated with Edward Belbruno's work on 'chaotic orbits' ever since meeting him at an astrodynamics conference in Princeton some years back. The idea is to develop low-energy routes for spacecraft by analyzing so-called 'weak stability boundaries,' regions where motion is highly sensitive and small changes can create gradual orbital change. A low-energy route was what Belbruno used in 1991 to help the Japanese spacecraft Hiten reach the Moon using almost no fuel, a proof of concept about which the physicist said "It saved the spacecraft, and it saved my career." That comment came from a lecture to the Mathematical Association of America in 2009 that you can listen to here. It's fascinating in its own right, but doubly so since Belbruno is back in the news with new findings on the idea of panspermia, and specifically that version of panspermia called lithopanspermia. In this hypothesis, elemental life forms are distributed between stars in planetary fragments created by...

Several Centauri Dreams readers passed along Seth Shostak's latest article on SETI in IEEE Spectrum, a piece that invokes the 'Wow!' signal at Ohio State and goes on to make the case for continuing the hunt. Shostak thinks both the ongoing search for exoplanets and refinements in our signal detection technology, including optical SETI, should keep us active. "No, we haven't found any signals so far, but there's a growing incentive provided by new findings in astronomy and biology, and the instruments are getting better," he writes. "Thirty-five years from now, we may really find a signal that will make us say 'Wow!'" The IEEE Spectrum piece doesn't break any new ground, but it's another example of the 'Wow!' signal getting broader coverage, and I now find that people routinely bring the Ohio State event up when I talk to audiences about SETI. Meanwhile, let's think about some truly exotic possibilities when it comes to detecting extraterrestrial life. Would it be possible, for...

I'm not surprised that Michael Chorost continues to stimulate and enliven the SETI discussion. In his most recent book World Wide Mind (Free Press, 2011), Michael looked at the coming interface between humans and machines that will take us into an enriched world, one where implants both biological and digital will enhance our experience of ourselves and each other. You'll recall that it was a cochlear implant that restored hearing to this author, and doubtless propelled the thinking that led to this latest book. And it was the issue of hearing and communication that we looked at in an earlier discussion of Chorost's views on SETI. That conversation has continued in Michael's World Wide Mind blog, as he ponders some of the comments his earlier ideas provoked on Centauri Dreams. In particular, how would we ever come to understand an extraterrestrial civilization if it differed fundamentally from us? Chorost thinks the problem is not biological, that no matter how aliens might look, we...

Not all that long ago we assumed habitable planets needed a star like our Sun to thrive, but that view has continued to evolve. M-class red dwarfs may account for as many as 80 percent of the stars in our galaxy, making habitable worlds potentially more numerous around them than anywhere. And let's extend our notion of habitability to what Luca Fossati (The Open University, UK) and colleagues call a Continuous Habitable Zone (CHZ). Now things really get interesting, for a red dwarf evolves slowly, so planets could have a CHZ with surface water for billions of years. But what about white dwarfs? Stellar evolution seems to rule out habitable worlds around them because we normally think of stars entering their red giant phase and destroying their inner planets enroute to becoming a white dwarf. But can a new planetary system emerge from the wreckage? We've already found planets orbiting close to the exposed core of a red giant (KOI 55.01 and KOI 55.02), showing that the end of main...

By Larry Klaes One result of the biennial Astrobiology Science Conference (AbSciCon) held the last week of April in 2010 was to gather SETI specialists from around the world to look at everything from search strategies and signal processing to the best ways of creating an interstellar message. Tau Zero's Larry Klaes has been reading the collected papers from the meeting's SETI sessions, which have inspired him to ponder SETI's place in the scheme of things and how our reaction to the search tells us something about who we are and who we are becoming. Readers with a long memory may recall that the first major conference on interstellar communications, held in Soviet Armenia in 1971, produced a volume of proceedings titled Communication with Extraterrestrial Intelligence, a title editor Douglas Vakoch deliberately echoes in the current work, partly as a nod to the field's past and partly as a measure of how far it has come. I love anthologies. There is nothing like having a collection...

Michael Chorost is a science writer whose research interests grow directly out of his personal experience. You may have already read about his struggle with hearing loss -- a problem he has dealt with since childhood -- in his book Rebuilt: How Becoming Part Computer Made Me More Human (Houghton Mifflin, 2005). It's natural to find Chorost writing often on things like cochlear implants and neurotechnology, but intriguing to find that he is also a SETI advocate, and one who believes his hearing issues have a bearing on a field he has studied passionately all his life. In fact, the book he plans next, which follows on 2011's World Wide Mind (Free Press) will be a SETI title. So what's the connection between deafness and hunting for signs of an extraterrestrial civilization? Chorost sees it as a matter of isolation and communication, as he notes in a recent entry on the Psychology Today site. Is the entire human race subject to deafness? It is in the sense that we have no idea whether...

I haven't even finished the first line of this post and I'm already in a digressive mood. The mental sidetrack comes from yesterday's talk about the Square Kilometer Array, whose primary installations are now to be built in both South Africa and Australia. By observing an object through many instruments simultaneously, astronomers can use the technique called interferometry to combine incoming data and emulate a much larger instrument. The SKA's sensitivity promises to be high enough to allow the detection of possible leakage radiation from another civilization, which prompted me to recall a quote I had buried in my archives: "I know perfectly well that at this moment the whole universe is listening to us -- and that every word we say echoes to the remotest star." The words are those of Jean Giraudoux, a French writer and diplomat whose plays, written between the two world wars, gained him an international audience (Christopher Fry was among the admirers who adapted Giraudoux's work...

We often speak of habitable zones around stars, most commonly referring to the zone in which a planet could retain liquid water on its surface. But the last ten years has also seen the growth of a much broader idea, the galactic habitable zone (GHZ). A new paper by Falguni Suthar and Christopher McKay (NASA Ames) digs into galactic habitable zones as they apply to elliptical galaxies, which are generally made up of older stars and marked by little star formation. Ellipticals have little gas and dust as compared to spirals like the Milky Way and are often found to have a large population of globular clusters. Are they also likely to have abundant planets? The answer is yes, based on the authors’ comparison of metallicity -- in nearby stars and stars with known planets -- to star clusters in two elliptical galaxies. While many factors have been considered that could affect a galactic habitable zone, Suthar and McKay focus tightly on metallicity, with planet formation dependent upon the...

I've been trying to figure out why exomoons -- moons around planets that orbit stars other than our own -- have such a fascination for me. On the purely scientific level, the sheer amazement of discovery probably carries the day, meaning that I grew up in a time long before we had confirmation of any exoplanets, and now we're talking about getting data on their moons. But there's also that sense of the exotic, for we can wonder whether gas giants in the habitable zone, which may be more plentiful than we realize, might have life on their own rocky moons. David Kipping (Harvard-Smithsonian Center for Astrophysics) has been a key player in the exomoon hunt for some time now (search under his name in the archives here and you'll retrieve articles going back for years). David is now working with a 'crowd-funding' source called Petridish.org to fund a new mini-supercomputer that will go to work on the Hunt for Exomoons with Kepler (HEK) project. The idea behind HEK is to use Kepler data...