by Paul Gilster | Dec 20, 2006 | Culture and Society |
When I think about Carl Sagan, the tenth anniversary of whose death we remember today, the first thing that comes to mind is a quote about the wonders of relativistic interstellar flight. It’s worth quoting at length:
If for some reason we were to desire a two-way communication with the inhabitants of some nearby galaxy, we might try the transmission of electromagnetic signals, or perhaps even the launching of an automatic probe vehicle. With either method, the elapsed transit time to the galaxy would be several millions of years at least. By that time in our future, there may be no civilization left on Earth to continue the dialogue. But if relativistic interstellar spaceflight were used for such a mission, the crew would arrive at the galaxy in question after about 30 years in transit, able not only to sing the songs of distant Earth, but to provide an opportunity for cosmic discourse with inhabitants of a certainly unique and possibly vanished civilization. Despite the dangers of the passage and the length of the voyage, I have no doubt that qualified crew for such missions could be mustered. Shorter, round-trip journeys to destinations within our Galaxy might prove even more attractive. Not only would the crews voyage to a distant world, but they would return in the distant future of their own world, an adventure and a challenge certainly difficult to duplicate.
That’s from Intelligent Life in the Universe, which Sagan and Iosef Shklovskii published in 1966 (Holden-Day, pp. 443-444). It’s actually a translation and extended revision of Shklovskii’s older Universe, Life Mind, and the quote draws on a 1963 Sagan paper called “Direct Contact Among Galactic Civilizations by Relativistic Interstellar Flight” (Planetary and Space Science 11, pp. 485-98). Sagan had sent Shklovskii the paper even before the latter’s book appeared. The result in English became a collaborative effort that drew on the wisdom of two outstanding minds.
I don’t know how many space scientists were fired by this vision of human voyaging not just to another star but another galaxy, but I suspect this book still sits on the shelf of many a researcher. It awoke in me the sense of awe that Poul Anderson would go on to tap in Tau Zero, his fine novel about a runaway starship that makes Sagan’s 30-year voyages to Andromeda seem tame by comparison. But that’s what Sagan did. He could render hard science into celestial mental voyaging.
Good scientists do that in their own minds. Sagan’s genius was the ability to convey it to a broad audience, using prose that was supple and keen as a knife-edge. The great mystery writer Ross Macdonald once said of Raymond Chandler that he wrote ‘like a slumming angel.’ It’s the perfect phrase for Sagan as well, whose voice was distinctive and marked by a preternatural clarity. When Cosmos widened his reach to television, he was able to bring the discoveries of our telescopes and spacecraft into the home and (with a kind of poetry) show us where we stood in the universe.
Pale Blue Dot (1994) was Sagan at his best as he ranged through the Solar System and looked back on a distant Earth. Here’s the memorable conclusion:
The Cosmos extends, for all practical purposes, forever. After a brief sedentary hiatus, we are resuming our ancient nomadic way of life. Our remote descendants, safely arrayed on many worlds through the Solar System and beyond, will be unified by their common heritage, by their regard for their home planet, and by the knowledge that, whatever other life may be, the only humans in all the Universe come from Earth.
They will gaze up and strain to find the pale blue dot in their skies. They will love it no less for its obscurity and fragility. They will marvel at how vulnerable the repository of all our potential once was, how perilous our infancy, how humble our beginnings, how many rivers we had to cross before we found our way.
A slumming angel indeed. Thank you, sir.
Note: As Larry Klaes just pointed out in a comment to this post, Joel Schlosberg is conducting an ongoing Sagan tribute centered on this day, and Larry also notes the Celebrating Sagan weblog in his honor. Larry’s own tribute to Sagan in the Ithaca Times is here. Music of the Spheres has a fine recollection as well. Be sure to read Airminded’s homage, and finally, check Ann Druyan’s thoughts about her late husband.
by Paul Gilster | Dec 19, 2006 | Deep Sky Astronomy & Telescopes |
What were the first objects in the universe? They may have been enormous stars a thousand times more massive than the Sun. If so, new observations suggest the apparent clusters found by the Spitzer Space Telescope could be the first galaxies, tiny by Milky Way standards and containing the mass of less than a million Suns. By contrast, the Milky Way today seems to house at least a 100 billion stars, and may be the result of the merging of far smaller galaxies like these.
This is remarkable stuff. Spitzer is looking at patchy infrared light found across the entire sky, light that comes from vast objects more than 13 billion years away. That number catches the eye, of course, because the universe is now thought to be some 13.7 billion years old. The light, which is either from stars or violent black hole activity, was once ultraviolet or optical, but the expansion of spacetime has stretched it into the infrared.
Image: The right panel is an image from NASA’s Spitzer Space Telescope of stars and galaxies in the Ursa Major constellation. This infrared image covers a region of space so large that light would take up to 100 million years to travel across it. The left panel is the same image after stars, galaxies and other sources were masked out. The remaining background light is from a period of time when the universe was less than one billion years old, and most likely originated from the universe’s very first groups of objects — either huge stars or voracious black holes. Darker shades in the image on the left correspond to dimmer parts of the background glow, while yellow and white show the brightest light. Credit: NASA/JPL-Caltech/GSFC.
Ancient light. Its fluctuations, visible when the light from foreground stars and galaxies is removed, reveal the clustering. Says Alexander Kashlinsky (NASA GSFC), “We are pushing our telescopes to the limit and are tantalizingly close to getting a clear picture of the very first collections of objects. Whatever these objects are, they are intrinsically incredibly bright and very different from anything in existence today.”
Kashlinsky is co-author on two reports slated to appear in the Astrophysical Journal Letters. A preprint of “New measurements of cosmic infrared background fluctuations from early epochs” is available here, and “On the nature of the sources of the cosmic infrared background” is also online at the arXiv site. Once again, Spitzer does yeoman work, but it may take the James Webb Space Telescope to definitively nail the identity of these clusters down.
by Paul Gilster | Dec 18, 2006 | Culture and Society |
Now here’s a grand idea for a book: describe propulsion systems that can propel spacecraft with little or no fuel onboard. That’s just what Greg Matloff and NASA’s Les Johnson are doing with their new title Living Off the Land in Space (Copernicus & Praxis), which should be available come January. Matloff (New York City College of Technology) is well known in these pages as the co-author of The Starflight Handbook: A Pioneer’s Guide to Interstellar Travel (Wiley, 1989). It’s the seminal text, the one interstellar buffs return to again and again for the broad view of the kinds of technologies that might eventually get us to the stars.
Matloff produced The Starflight Handbook with the late Eugene Mallove and went on to write Deep Space Probes (Springer/Praxis 2000), now in its second edition. His new book with Johnson grows out of their work together in Huntsville at NASA’s In-Space Propulsion Technology Program, where mission concepts include everything from solar sails to solar electric, nuclear electric and other propulsion options. Can we one day make sails big enough to carry generation ships to other stars? Perhaps, but for now space trials of sail designs are what we shoot for, and even those are at least a decade off. That doesn’t stop the work from continuing.
If you’ve read The Starflight Handbook, you’ve seen the fine illustrations created by Greg’s wife C Bangs. Her work is exhibited on four continents as well as online, and she has appeared in numerous publications as well as doing work for a variety of NASA reports and workshop proceedings. I remember a wonderful dinner in Princeton with Greg and C where the discussion ranged from solar sails to the fascinating work going on at Princeton’s Engineering Anomalies Research program, where C had spent the afternoon.
For this is an artist whose fascination with the physics of consciousness propels her work. Her collaboration with the late Evan Harris Walker on quantum consciousness led her to incorporate his equations into many of her paintings, blending mythology with technology in absorbing ways. But this artist looks outwards as well as in. Her technology demonstrator of a rainbow hologram message plaque is a case in point. It could one day fly on an interstellar solar sail (think of the plaque on Pioneer), using images of the human form, a diagram of the Solar System and various equations describing the sail’s mission. That one grew out of a 2004 NASA grant.
Bangs’s “Dying/Evolved Star” paintings were recently exhibited in Brooklyn. And if you make the trip to Huntsville, you can view her holographic designs on display at Marshall Space Flight Center, where Les Johnson has the pleasure of seeing them every day. I like what Matloff says about his relationship with Bangs: “We sometimes edit each other’s writing, and that can add sparks — but in this case they’re good ones. We’re generally working from different hemispheres: C is very much tapped into the left and I, the right.”
That seems like a solid combination to me. You should hear these two in conversation — the ideas are electric.
As to Matloff’s current work, he’s active with both NASA and the Italian space program and continues research on solar sail technologies. And talk about living ‘off the land’ — Matloff and Johnson have kicked around concepts for using large solar sails embedded with electrodynamic tethers to propel spacecraft deep into the Solar System, drawing on the magnetic fields around the destination planets to capture them into orbit. That’s living with little fuel indeed, and less is more when it comes to deep space, where minimizing your fuel consumption pays off in bigger and better payloads.
Image credit: Michele Forsten for NYC College of Technology.
by Paul Gilster | Dec 16, 2006 | Missions |
Centauri Dreams defers to no one in admiration of Project Daedalus, the 1970s-era starship design that emerged from the British Interplanetary Society. It’s a pleasure to see continuing interest in the craft, as witness Alan Bellows’ backgrounder about it on the Damn Interesting site. Daedalus was the first serious and thorough design for a starship, a robotic interstellar probe that would reach Barnard’s Star in about fifty years, moving at twelve percent of the speed of light.
Be sure to check the Bellows story for the overview. But let me fill in a little more background: The British Interplanetary Society, founded in 1933, used to meet regularly at London’s Mason’s Arms pub on Maddox Street, a setting that Arthur C. Clarke readers may recognize from his later collection Tales from the White Hart. Daedalus was designed by about a dozen scientists and engineers, many of its sessions occurring in pubs and similar venues. When I talked to Geoffrey Landis about Daedalus some years back, he was as bemused about this as I was, saying “Imagine designing a starship while you’re sitting around in a bar. I mean, that’s just an incredibly ballsy thing to do!”
So I always think about Clarke’s book and wonderful evenings in similar pubs in London when I hear about Daedalus. Those long bar sessions in the 70’s produced extraordinary work, including a propulsion system that would provide thrust for a staggering four continuous years using fifty billion pellets of deuterium and helium-3, burning 250 of them every second in its combustion chambers. Daedalus was gigantic in every dimension, including the demands it placed upon the society that built it. The project, said the BIS final report, “… fits naturally into the context of a solar system-wide society making intelligent use of its resources, rather than a heroic effort on the part of a planet-bound civilization.”
Which is why industrializing the Solar System itself seems a prerequisite. When we do fly our first interstellar probes, they’ll doubtless be of different design that Daedalus, but they’ll still take advantage of the good work that went into its concept. Project Daedalus: The Final Report on the BIS Starship Study, edited by Anthony Martin, was published in the Journal of the British Interplanetary Society in 1978 and is thus hard to come by. My own dog-eared copy is the result of a marathon copying session at a nearby engineering library, carefully spreading the oversized JBIS pages to get a good image while not hurting the tight binding of the old volumes.
Interesting stuff? You bet. I’m always referring to this 1 1/2-inch stack of printouts. The introductory page quotes Immanuel Kant: “On the basis of a slight assumption I have undertaken a dangerous journey, and I already see the promontories of new lands. Those people who have the resolution to set forth on this undertaking will enter these lands and have the pleasure of designating them with their very own names” (from Kant’s Universal Natural History and Theory of Heaven, 1755). Those ‘new lands’ include designing a shield for interstellar dust, evaluating nearby stars for planetary systems, creating robotic systems for onboard maintenance and a communications capability to bring the data home.
I count twenty-one papers in all, most of them highly technical yet utterly absorbing even today. As to Barnard’s Star, here’s a link to a story in these pages that covers Peter Van de Kamp’s apparent detection of planets around it, which led to the BIS’ interest in the star as a destination for Daedalus. Turns out the data were flawed, but we still can’t rule out planets below current detection limits. And it’s intriguing that red dwarfs like this one have climbed well up the scale of interest when it comes to possible rocky worlds in habitable zones.
I hope someone will publish a new edition of the Final Report because my photocopies are getting pretty ragged, not to mention well marked up with notes. It would be a nice testament to a dramatic and visionary idea carried out by people who wanted to produce realistic designs using near-term technology. Talk about stretching the limits of the possible. And as Geoffrey Landis notes, they did it in a pub!
Addendum: Tibor Pacher reports that the British Interplanetary Society makes the Daedalus Final Report available on CD. This is good news indeed. Thanks, Tibor!
by Paul Gilster | Dec 15, 2006 | Outer Solar System |
It would be easy to keep this site filled with outer Solar System news, so various and captivating are the images that stream in from our spacecraft. Exoplanet studies keep us focused primarily on nearby stars, but I do want to keep up with Cassini, and decided some time back that Centauri Dreams would leave inner system coverage to others and pick up the pace as we moved to Saturn and beyond. And what a story keeps unfolding there.
For Cassini remains healthy and the news from Enceladus intriguing. We’ve known since last year about the plume erupting on the satellite, leading to speculation of liquid water beneath the ice of its surface. The south polar region of the tiny moon is geologically active in ways that challenge the imagination. After all, isn’t the rest of Enceladus as cratered and ancient-looking as the surface of our own Moon?
The ‘Cold Faithful’ model, which patterned the Enceladus geyser on Yellowstone’s Old Faithful, has apparently run into problems. Susan Kieffer (University of Illinois at Urbana-Champaign) is lead author of a paper in Science that points to the issue at hand: 10 percent of the plume is made up of carbon dioxide, methane and nitrogen. Says Kieffer: “You might get a carbon dioxide-driven liquid geyser there, but you can’t put this much nitrogen and methane into liquid water at the low pressures found inside Enceladus.”
Image: Plumes of icy material extend above the southern polar region of Saturn’s moon Enceladus as imaged by the Cassini spacecraft in February 2005. Credit: NASA/JPL/Space Science Institute.
No liquid water beneath the ice? Kieffer’s alternative depends on clathrate — an ice phase of nitrogen and methane in frozen water. Put those plume gases in a reservoir of clathrate in Enceladus’ southern polar region and the environment could be up to 100 degrees Celsius colder than liquid water, with the plume bursting directly from the clathrates. Fractures at the pole would cause the clathrates to decompose violently. “Some ice particles and ice coatings,” adds Kieffer, “evaporate to produce the water vapor observed with the other gases.”
Did I say geologically active? According to this theory, Enceladus’ ice cap could be opening and closing continuously. And stepping back from Enceladus, consider that our exploratory spacecraft uncover the unexpected at almost every destination. Who knows what New Horizons will find at Pluto/Charon? We can assume that, just as Cassini has done at Enceladus, and Voyager when it found Triton’s strange, geyser-like eruptions, New Horizons will uncover something that will force a re-thinking of the physical processes at work in the outer Solar System.
The Enceladus paper is Kieffer et al., “A Clathrate Reservoir Hypothesis for Enceladus’ South Polar Plume,” Science Vol. 314. No. 5806 (15 December 2006), pp. 1764-1766, with abstract here.
