Centauri Dreams takes an optimistic view of the human future, one in which interstellar flight becomes a reality at some point in this millennium. My impression is that we'd all better be optimists. Think about the Drake Equation. Perhaps its most significant variable is the lifetime of a technological civilization, a figure that has implications for any creatures who have developed the tools to go into space. If the lifetime of such a civilization averages a million years, then the 'where are they' question Fermi asked becomes more charged. Shouldn't we be detecting them? But if the average lifetime of a technological culture is, say, five hundred years, then we may be confronted with a galaxy filled with wreckage, planets where life persists in evolving and forming intelligent beings who bring about their own destruction. Like I say, I'd rather be an optimist, but none of us knows the real answer. I note that Jan Zalasiewicz (University of Leicester) has offered up a new book that...

The latest Carnival of Space is stuffed with good things, among them Dave Mosher's manipulations of an asteroid impact calculator run by Cardiff University's Ed Gomez. Dave works through a worst-case scenario -- a 1300-foot wide asteroid striking the East River, turning most of New York City into a crater. Fascinatingly, the impact calculator lets users adjust the parameters on such strikes, so that turning the impactor into a 400-meter piece of ice produces a crater 3.5 miles wide, two miles less than the first scenario. The calculator looks to be a great educational tool. NextBigFuture continues to study the electric sail concept, developed at the Finnish Meteorological Institute and under active examination. Electric sails ride the solar wind, but unlike magsails, they use a mesh of tethers kept at high positive voltage, held in place by centrifugal acceleration from the spinning spacecraft. Solar wind protons, repelled by the positive voltage of the mesh, create the needed...

The staggering difficulty posed by interstellar flight pushes us to imagine alternatives to today's technologies. Using conventional rocketry we're forced to amass so much propellant that the craft we want to send seem impossible to build, even if we could afford the vast fuel bill. A jacked up rocket engine is, of course, nothing but an old technology pushed to its extreme imaginative limits. And you could sense the constraints in that vision at the recent Joint Propulsion Conference in Hartford (CT), discussed not only in these pages but also here by Ray Villard. I mention Villard's comments because while I focused on Robert Frisbee's antimatter rocket concepts in my Centauri Dreams post, Ray tackles the much broader question of how we place technologies within the context of scientific progress. The news director for the Hubble Space Telescope, Villard is well versed in the rewards and challenges of spaceflight, but he's nonplussed with some of the reaction to the Hartford...

Hugh Everett's 'many worlds' interpretation of quantum mechanics spawned not just the idea of a multiverse, but apparently quite a few interpretations on what a multiverse implies. If you're intrigued by the notion that our cosmos is one of what may be an infinite number of universes, you'll want to read Dan Falk's report in Sky & Telescope on the recent multiverse conference held at the Perimeter Institute for Theoretical Physics (Waterloo, ONT). Particularly interesting is the growth of multiverse thinking as string theory has come to the fore, with all the controversy that implies. And then there's the notion of 'eternal inflation,' which conceives of endless big bangs, each creating a separate cosmos. Laura Mersini-Houghton (University of North Carolina) is concerned about how multiverses spawned by quantum theory, string theory and inflation can be reconciled, as Falk notes: ...it's not at all clear how these different kinds of multiverses - grounded in quite different physical...

What should be the goals of the next generation of X Prizes? Peter Diamandis is just the man to ask the question. It was Diamandis' foundation that led to the launch of a private manned spacecraft in 2004, and since then his team has gone on to sponsor an automotive X Prize offering $10 million to anyone who can produce a marketable car that can get 100 miles per gallon. Sixty teams are at work on that one, and prizes focusing on renewable energy are also in the works. The big fish in the pond is the Google Lunar X Prize, which offers $30 million for the first privately funded robotic mission to the Moon. Nor is Diamandis alone. In fact, the landscape is awash in prizes. The Virgin Earth Challenge, brainchild of British aviation mogul Richard Branson, offers $25 million to anyone who designs a viable way to remove greenhouse gases from the Earth's atmosphere. For that matter, what about the Saltire Prize, for which Scotland has found £10 million for renewable energy breakthroughs?...