A Dyson Sphere makes an extraordinary setting for science fiction. In fact, my first knowledge of the concept came from reading Larry Niven's 1970 novel Ringworld, a book that left such an impression that I still recall reading half of it at a sitting in the drafty little parlor of a house I was renting in Grinnell, Iowa. Ringworld had just come out as a Ballantine paperback with the lovely cover you see below. I was hooked after about three pages and read deep into a night filled with wind and snow. It could be argued, of course, that a ring made out of planetary material, a habitat so vast that it completely encircles its star, is actually one of the smaller Dyson concepts. It was in 1960 that Freeman Dyson suggested how a civilization advanced to the point of such astro-engineering might use everything it found in its solar system to create a cloud of objects, a swarm that would make the most efficient use of its primary's light. And as you keep adding objects, you point to the...

Now here's a comprehensive task for you. Take about a dozen primordial minerals found in interstellar dust grains and figure out what processes -- physical, chemical, biological -- led to the appearance of the thousands of minerals we find on our planet today. The job was undertaken by Robert Hazen and Dominic Papineau (Carnegie Institution Geophysical Laboratory) and colleagues, and it produced startling results: Of the roughly 4300 known types of minerals on Earth (fifty new types identified each year), up to two-thirds can be linked to biological activity. Mineral evolution? In a sense, although Hazen is quick to qualify the statement: "It's a different way of looking at minerals from more traditional approaches. Mineral evolution is obviously different from Darwinian evolution — minerals don't mutate, reproduce or compete like living organisms. But we found both the variety and relative abundances of minerals have changed dramatically over more than 4.5 billion years of...

Using eleven of the Allen Telescope Array's 6.1-meter dishes, the SETI Institute and the Radio Astronomy Laboratory at the University of California (Berkeley) have detected the New Horizons spacecraft on its way to Pluto/Charon. New Horizons transmits an 8.4 GHz carrier signal that showed up readily on the SETI Prelude detection system. What I hadn't realized was that snagging distant spacecraft transmitters is a standard part of SETI operations, as Jill Tarter notes in this brief article on the event posted at the New Horizons site: "We look forward to checking in with New Horizons as a routine, end-to-end test of our system health. As this spacecraft travels farther, and its signals grow weaker, we will be building out the Allen Telescope Array from 42 to 350 antennas, and thus can look forward to a long-term relationship." Image: New Horizons as tracked by the Allen Telescope Array. This plot shows 678 hertz (Hz) of spectrum collected over 98 seconds. The New Horizons signal can...

The Moon is, for obvious reasons, rarely considered an interesting venue for astrobiology. But I've been looking through Joop Houtkooper's presentation at the European Planetary Science Congress, noting his contention that some lunar craters might hold samples of life from the early Earth, and perhaps even from Mars. If the name Houtkooper rings a bell, it may stem from the splash he made last year by suggesting that the Viking probes to Mars may have discovered Martian microbes consisting of fifty percent water and fifty percent hydrogen peroxide. Although some extremophiles here on Earth put hydrogen peroxide to use, the theory is quite a long shot. But then, Houtkooper (University of Giessen, Germany) seems to thrive on remote possibilities. His lunar theory works like this: Certain craters on the Moon are effectively shielded from sunlight, at least deep within their recesses. Shackleton crater at the south pole is a case in point, a place that may contain sub-craters free of...

I've spent so much recent time on two SETI/METI papers by James, Gregory and Dominic Benford because they contain powerful arguments for re-thinking our current SETI strategy. By analyzing how we might construct cost-optimized interstellar beacons, the authors ask what those beacons might look like if other civilizations were turning them toward us. The results are striking: A distant beacon operating for maximum effect consistent with rational expense would offer up a pulsed signal that will be short and intermittent, recurring over periods of a month or year. It will, in other words, be unlike the kind of persistent signal that conventional SETI is optimized to search for. Searches designed to sweep past stars quickly, hoping to find long-lasting beacons whose signature would be apparent, would rarely notice oddball signals that seem to come out of nowhere and then vanish. Tracking such signals, looking for signs of regularity and repetition, calls for a different strategy. Image:...

If we want to consider how to pick up transmissions from a distant civilization, it pays to consider the most effective strategies for building interstellar beacons here on Earth. This is the method James, Gregory and Dominic Benford have used in twin papers on SETI/METI issues, papers that should be read in conjunction since the METI questions play directly into our SETI reception strategies. It pays to have a microwave specialist like James Benford on the case. Our METI transmissions to date have used radio telescopes and microwaves to send messages to nearby stars. Longer distances will cost more and take much more power. How much would a true interstellar beacon cost, one not limited to the relatively short ranges of recent METI transmissions? Count on something on the order of $10 billion. As to power, Jim is able to quantify the amount. To reach beyond roughly a thousand light years with a microwave beacon, an Effective Isotropic Radiated Power (EIRP) greater than 1017 W must...

Several interesting papers on SETI have appeared in recent days, among them Gregory, James and Dominic Benford's attempt to place SETI in the context of economics. Equally useful is Duncan Forgan's new look at the Drake Equation, presenting a way to estimate the distribution of the crucial parameters. I'll bypass the Forgan paper temporarily because I've asked Marc Millis to tackle it as soon as he gets back from the Jet Propulsion Laboratory, where he's gone to attend a workshop. Forgan's study has direct bearing on a Tau Zero initiative we hope to have in place by the end of the year and thus is a natural for Marc to write up. But back to the Benfords, who have offered up twin papers (as seems reasonable for the brothers), one on SETI (with Gregory as principal author) and the other on its METI offshoot (transmitting messages rather than listening for them). James Benford is lead author on the latter. This work is so rich that I won't try to encapsulate it in a single post, but...