Finding single reasons for major events is curiously satisfying. Thus the notion that an asteroid strike did away with the dinosaurs -- pinning their mysterious demise on one hammerblow from outer space makes sense out of what had seemed inexplicable. But a new theory challenges the single-cause notion of mass extinctions, and questions whether sudden catastrophes in combination aren't needed to deliver the punch. The work, to be presented today at the annual meeting of the Geological Society of America in Philadelphia, divides the last 488 million years of geologic history into distinct groups and characterizes each. So-called Pulses are times of sudden, catastrophic events like asteroid impacts, whereas Presses are periods of multigenerational stress on ecosystems, such as massive volcanic eruptions. Nan Crystal Arens and Ian West (Hobart & William Smith Colleges) chart the history of marine organisms and extinctions through the fossil record to conclude that extinctions in times...

When is a space mission too expensive to fly? It's a question much in the mind of proponents of robotic exploration, who can point to lower cost as one excellent reason to leave human crews out of our deep space missions. But robotic missions can suffer the same fate as human ones, with technology advances like miniaturization exploited not to pack more instruments on board but to reduce costs. Faster, cheaper, better, but bureaucratic inefficiencies can trump the savings. Giancarlo Genta (Politecnico di Torino) offers up an interesting perspective on the cost question. In a keynote he delivered last year at the Fourth IAA Symposium on Realistic Near-Term Advanced Scientific Space Missions in Aosta, Italy, Genta compared the cost of space missions to other public enterprises like the construction of motorways or infrastructure projects like Alpine tunnels. In that light, the notion that space missions are unbearably costly is simply false. And he goes on to say this: The same if we...

by Marc Millis Apropos of our recent discussion of species differentiation and what may happen when humans spread into the Solar System and beyond, Marc Millis forwarded a whimsical piece he wrote for Aerospace Frontiers, the internal news publication of NASA Glenn Research Center. The item ran in August of 2000 and makes for an enjoyable weekend diversion. From the Author: The visions presented here do not necessarily reflect the opinions of NASA Glenn, "Aerospace Frontiers," or even the author himself. What this story does represent, however, is a light-hearted glimpse of an unintended turn of events. History itself is a collection of unplanned twists and turns, so our visions of the future should prepare us for more of the same. Prepare yourself. ------- It finally happened. Access to space became cheap enough so that the average "Joe" and "Joanne" could venture beyond the bounds of Earth, and long-duration space habitats became robust enough to provide reliable places to live...

Freeman Dyson among others has speculated about the physical changes that could occur as the human species spreads into the cosmos. How will evolution deal with a colony world in a distant star system, and how long will it take before serious differentiation begins to occur? For that matter, what about the crew aboard a multi-generational starship -- will humans have adapted so thoroughly to a space-borne environment when they arrive that some opt to make their planetary excursion no more than a brief research stop before pushing on to yet other solar systems? Or will they one day adapt to the vacuum itself? Such questions are called to mind by recent work from Virginie Millien (McGill University), whose new paper in the open source journal PLoS Biology examines islands as test beds for evolution on Earth. It has long been assumed that isolation would create selective pressures unique to an island environment. A so-called 'island rule' has small animals evolving into outsized...

The idea of interstellar flight forces long-term speculation. Barring unexpected breakthroughs, we are looking at mission times that, at best, are counted in the decades if not centuries. One of the purposes of Centauri Dreams is to encourage the kind of long-term thinking that plans and executes such missions. That such thinking -- focused well beyond individual human lifetimes -- is a worthy goal in and of itself should also be obvious, and it is actively championed in projects like the 10,000 year clock of the Long Now Foundation. A partial spinoff from the Long Now called the Long Bets Foundation is increasingly active in providing a competitive arena for predictions about the future. It's a fascinating concept, both a forum for discussion about long-range issues and a tool for philanthropic giving. People make predictions which, if challenged, become bets. Each prediction requires a $50 fee to the foundation, while a minimum of $200 is required to challenge a prediction. After a...

A recent acquisition has me looking backward rather than forward to begin the week. It's the January 1940 issue of Astounding Science Fiction, a magazine then in its glory years under the editorship of John Campbell. Some of the authors here ring few bells: Sam Weston, for example, weighs in with "In the Day of the Cold," as does D.L. James with "Moon of Delirium." But this is also the issue of Robert Heinlein's "Requiem," and it contains good work by Lester del Rey and Edward E. Smith as well. Astounding's science articles mixed with its ever reliable stories gave it a special place in the history of the pulp magazines, and many a scientist has told me that it was through Astounding or its later incarnation as Analog Science Fiction & Fact that a career path in physics or astronomy emerged. Which brought to mind science fiction writer Frederick Pohl, a distinguished editor in his own right. Pohl's 1978 memoir The Way the Future Was catches the magazine's exciting heyday. He evokes...

Centauri Dreams continues to admire the clarity of the draft IAU resolution on the definition of a planet. Although the criteria are easily understood, they also present teaching opportunities (imagine all those schoolchildren learning what a barycenter is, and why Pluto/Charon make a double planet thanks to the location of their center of gravity!). This sound definition also grows from the properties of the planets themselves and is based on the best current information on planetary formation. Galileo Galilei had some thoughts on naming things that seem apropos, and what better source to consider when defining a planet? The Tuscan astronomer/mathematician (1564-1642) could have been speaking of the current controversy when he said, "Names and attributes must be accomodated to the essence of things, and not the essence to the names, for things come first and names afterward." I submit that the draft resolution does a fine job accomodating the named thing to its essence -- that...

It was Tennyson whose narrator, recalling youthful wanderings and celestial vistas in the poem 'Locksley Hall,' wrote about 'the fairy tales of science, and the long result of Time.' That long result is something we seldom look at in our feverish and accelerated world, but in these closing paragraphs from a book written with Chesley Bonestell in 1972, Arthur C. Clarke thinks about the Pioneer spacecraft, the distant future and the things that may survive man. For the Pioneers will keep going. "As our space-faring powers develop, we may overtake them with the vehicles of a later age and bring them back to our museums, as relics of the early days before men ventured beyond Mars. And if we do not find them, others may. "We should therefore build them well, for one day they may be the only evidence that the human race ever existed. All the works of man on his own world are ephemeral, seen from the viewpoint of geological time. The winds and rains which have destroyed mountains will make...

One summer night last year I found myself at a dinner party that had stretched late into the evening. Enjoying a good Côtes du Rhône and watching distant lightning flickering through the trees outside, I hadn't been saying much until the subject came around to space. Suddenly I was challenged to justify the notion of exploring not just distant stellar systems but even the nearby planets. And before long I was talking about the need to develop technologies that could help us deflect a potential life-threatening asteroid. At which point one of the guests stopped me cold by saying, "Why should we deflect it? The human race has done little enough. What does it matter if we're all destroyed?" Try to talk someone out of that. It's early 21st Century weltschmzerz in its purest form, writing off all future generations because of a perceived sense of human failure. Not even half a bottle of Côtes du Rhône could take the edge off it. Reading a recent essay in Acta Astronautica by Giancarlo...

Centauri Dreams' fascination with the history of science occasionally yields to forgetfulness. Which is why this piece on German mathematician and astronomer Friedrich Wilhelm Bessel, runs two days after his birthday rather than on the occasion itself. Bessel (July 22, 1784 - March 17, 1846) would go on to perform remarkable work in the study of stellar distances that in many respects anticipated the work of today's exoplanet hunters. He became, in fact, the first person to predict the existence of an unseen companion around another star. That was quite an accomplishment in 1844, when Bessel announced the find around Sirius, based on minute deviations in the motion of the star. The discovery would be verified by Alvan Graham Clark in 1862 with the first observations of Sirius B. We now know that Sirius B orbits the primary at a distance of roughly 20 AU, not so far off the 23.7 AU mean separation between Centauri A and B, although there the resemblance stops -- Sirius B is a white...

"The urge to explore, the quest of the part for the whole, has been the primary force in evolution since the first water creatures began to reconnoiter the land. We humans see this impulse as the drive to self-transcendence, the unfolding of self-awareness. The need to see the larger reality -- from the mountaintop, the moon, or the Archimedean points of science -- is the basic imperative of consciousness, the specialty of our species. If we insist that the human quest await the healing of every sore on the body politic, we condemn ourselves to stagnation. Living systems cannot remain static; they evolve or decline. They explore or expire. The inner experience of this imperative is curiosity and awe. The sense of wonder -- the need to find our place in the whole -- is not only the genesis of personal growth but the very mechanism of evolution, driving us to become more than we are. Exploration, evolution, and self-transcendence are but different perspectives on the same process." Wyn...

Stewart Brand is a leading proponent of long-term thinking, the sort of thing that builds cathedrals and, perhaps one day, starships. In this excerpt from his book The Clock of the Long Now (New York: Basic Books, 1999), Brand discusses science fiction and the various forms of futurism. According to Kevin Kelly, 'Isaac Asimov once said that science fiction was born when it became evident that our world was changing within our lifetimes, and therefore thinking abut the future became a matter of individual survival.' The nanotechnology futurist Eric Drexler concurs: 'I have found over the years that people familiar with the science fiction classics find it much easier to think about the future, coming technologies, political effects of those technologies, and so on.' At Global Business Network (GBN), the scenario-planning business that employs me, we frequently send out science fiction books to the Network membership, and when we can get writers such as William Gibson, Bruce Sterling,...

Centauri Dreams returns to its normal schedule on Monday, following a week devoted to the emergence of the Tau Zero Foundation. Next week will be a busy one, with a new and significant study of Proxima Centauri, a more detailed than ever look at the complicated happenings around Beta Pictoris, and a paper presenting a fast, beamed propulsion mission to Alpha Centauri serving as the highlights. Thanks to all who wrote asking for further information about the Tau Zero Foundation and its plans to support research practitioners in work that may one day lead to interstellar flight. I'll continue to follow Foundation news here as the group works towards the launch of its own Web site. It's heartening to see the spirit of exploration embraced by readers and advocated on the Net, as noted, for example, in this post on Brian Wang's Advanced Nanotechnology site. A snippet: If we had the will we would mount a D-Day scale invasion of space. The current space effort, as noble as it has been, was...

Going to the stars is a matter of hard science, but it's also a question of inspiration. I know scientists who found their calling by reading Poul Anderson's novel Tau Zero, and others whose love of the early Star Trek forever changed their career path. But for some of us, growing up in the 1950s, it was Tom Corbett, Space Cadet that did the trick, and for me, it was a book by Carey Rockwell called Danger in Deep Space (New York: Grosset & Dunlap, 1953). The second in the Tom Corbett series, the book exposed this space-crazy kid to a planet orbiting one of the Alpha Centauri stars, and before long the thought of habitable worlds around stars other than our own became an obsession. Which brings us to Frankie Thomas, who died recently of respiratory failure at the age of 85. A workmanlike actor who appeared in a number of pre-WWII films and Broadway plays, Thomas took up radio and television work after leaving military service and was cast as Tom Corbett in 1950 (beating out a young...

Centauri Dreams often uses planetary peril as one good reason for expansion into the universe. As the human species spreads out onto multiple worlds, the chances of survival continue to increase even if our planet meets catastrophe in the form of a rogue asteroid or comet. But another good reason is the need for exploration that seems to be hard-wired into our nature, in which case interstellar expansion becomes more or less inevitable if we can solve the technological riddles it involves. Do humans really have an innate drive for exploration, and if so, how does it operate? References for the notion are numerous, but a new study out of University College London gives a highly analytical look at what may be going on. Nathaniel Daw and John O'Doherty argue that pushing into the unknown involves a different part of the brain than staying on familiar territory. By analyzing how the brain works while people gamble, they show that what exploration demands is an overriding of the desire...