Centauri Dreams
Imagining and Planning Interstellar Exploration
Exomoons: A New Technique for Detection
A friend asked me the other day whether my interest in exomoons — moons around exoplanets — wasn’t just a fascination with the technology of planet hunting. After all, we’ve finally gotten to the point where we can detect and confirm planets around other stars. An exomoon represents the next step at pushing our methods, and a detection would be an affirmation of just how far new technology and ingenious analysis can take us. So was there really any scientific value in finding exomoons, or was the hunt little more than an exercise in refining our tools?
I’ve written about technology for a long time, but the case for exomoons goes well beyond what my friend describes. We’ve found not just gas giants but ‘super-Earths’ in the habitable zones of other stars, and it’s a natural suggestion that around one or both classes of planet, an exomoon might he habitable even if the parent world were not. It’s a natural assumption that moons exist around other planets elsewhere as readily as they do around the planets of our own Solar System, and given the sheer number of planets out there, the prospect of adding potential sites for life — perhaps more common sites than habitable planets themselves — is irresistible.
Then in catching up with work after my recent trip, I noticed René Heller’s work on the exomoon question, as reported in Astrobiology Magazine. Heller (McMaster University, Ontario) is proposing a new method of detection that involves the particular eclipsing effect of moons during the kind of transit studies that Kepler has provided so much data on. What is striking here is that if Heller is right, we may be able to detect not just moons several times larger than Ganymede — this is where the current state of the art seems to be — but moons much smaller still, on the scale of the moons we find in our own Solar System.
Heller’s paper, recently published in The Astrophysical Journal, picks up on further scientific advantages in studying exomoons. Such objects can offer us insights into how exoplanets formed. Consider this (internal references omitted for brevity):
The satellite systems around Jupiter and Saturn, for example, show different architectures with Jupiter hosting four massive moons and Saturn hosting only one. Intriguingly, the total mass of these major satellites is about 10-4 times their planet’s mass, which can be explained by their common formation in the circumplanetary gas and debris disk…, and by Jupiter opening up a gap in the heliocentric disk during its own formation… The formation of Earth is inextricably linked with the formation of the Moon…, and Uranus’ natural satellites indicate a successive ‘collisional tilting scenario’, thereby explaining the planet’s unusual spin-orbit misalignment.
And so on. Between astrobiology and planet formation, I’d say there is plenty of reason to be interested in exomoons, though my friend is right that I still get jazzed by the ability of skilled researchers to develop the strategies we need for their detection. We’ve followed the fortunes of the Hunt for Exomoons with Kepler (HEK) for some time in these pages, and it’s fascinating to me that what Heller is proposing would also make use of the abundant Kepler data. But while HEK works through the study of variations in transit timings and durations, Heller’s method, which he calls the ‘Orbital Sampling Effect,’ relies on a different kind of analysis.
Addendum: My mistake. A note from exomoon hunter David Kipping, who heads up the Hunt for Exomoons with Kepler, sets this straight. Let me quote it:
“This is not true, actually HEK uses dynamics and photometric effects in combination. We model both the moon transit effects (which Heller is talking about) plus the dynamical perturbations, such as transit timing and duration variations, simultaneously. The difference is that Heller stacks all of the transit data on top of itself and we do not. An important point to bear in mind is that this stacking process does not give you any more signal-to-noise than using the entire time series and fitting it globally, as HEK does. Since one does not actually gain any greater sensitivity by using the OSE method, one cannot finds moons smaller than the sensitivity limits we’ve achieved thus far in HEK and I can tell you that Galilean satellites are only detectable in very exceptional cases- generally Earth-like radius sensitivity is the norm.
“Let me say though, the OSE method is fast and computationally cheap but lacks the dynamics of our models, which ultimately allow for an exomoon confirmation. So I think this method could be useful tool for quickly scanning the Kepler data to identify interesting anomalies worthy of further analysis.”
And back to the original post:
What more can we tease out of an exoplanetary transit? Observation of a moon orbiting an exoplanet around its equatorial midline and passing in front of the planet, then behind it, should — over the course of time and numerous observations — build up a series of dots representing its position at any given moment in its orbit. With enough observations, the effect is of two ‘wings’ coming out of the sides of the planet, an effect that will appear lighter at the inner edges and darker at the outer edges. Astrobiology Magazine explains:
That’s because when the moon reaches the extent of its orbit and then starts circling back around the planet, its positions overlap more in a tighter space. As such, the “wingtips” look darker; that is, there is increased eclipsing of background starlight at the moon’s farthest apparent positions from the planet.
And of course to spot this effect requires constant observation of the star over a long period of time, allowing the moon to complete a large number of orbits “in order for its light-blocking effect to preferentially stack up at the wingtips.” And voila, what we have with the Kepler spacecraft is an observatory that gave us precisely this, observations of about 150,000 stars through its long stare of data gathering, some four years before equipment failure laid it low. Heller’s point is that we need wait for no future technology to hunt today for moons like those in our Solar System.
Image: This figure from Heller’s paper depicts the effects of a transiting exoplanet with exomoon averaged over time. We would expect a drop in starlight as the exoplanet moves in front of the host star, but Heller’s method focuses on the change to the lightcurve caused by the exomoon before and after it crosses the stellar disk, an effect which repeats on the other side. Credit: René Heller.
The ‘stacking up’ effect of these transit observations over time as the moon and planet transit the star in different configurations allows the detection. Because we need plentiful statistical data to make all this work, red dwarf stars are ideal candidates because habitable zone planets there have extremely short years and thus make many transits. According to Heller, moons down to Ganymede size should be detectable around M-dwarfs, while around warmer orange dwarf stars, exomoons about ten times Ganymede’s mass would be within range. G-class stars like the Sun are not represented well enough in the Kepler data because they lack sufficient transits.
The minute effects discernible in an exoplanet’s regular transit are what make the exomoon detection possible. Heller notes that the Orbital Sampling Effect (OSE) yields data indicative of the moons’ radii and planetary distances, while study of the planet’s transit timing variations (TTV) and transit duration variations (TDV), in conjunction with Orbital Sampling Effect, allow measurements of the moon’s mass. More complex transit signatures could, using this method, even allow the detection of multiple exomoon candidates.
The paper is Heller, “Detecting extrasolar moons akin to solar system satellites with an orbital sampling effect,” The Astrophysical Journal, Vol. 787, No. 1 (2014), abstract and preprint available. Thanks to Dave Moore for the pointer to this work.
A New Marker for Planet Formation
Given how many planet-hosting stars we’re finding, any markers that can tell us which are most likely to have terrestrial worlds would be welcome. New work out of Vanderbilt University is now providing us with an interesting possibility. Working with the university’s Keivan Stassun, graduate student Trey Mack has developed a model that studies the chemical composition of a given star and relates it to the amount of rocky material it has ingested during the course of its lifetime. Stars with a high amount of such material may be places where small, terrestrial worlds are rare.
What Mack has done is to look at the relative abundance of fifteen specific elements. According to this Vanderbilt news release, he was most interested in elements with high condensation temperatures like aluminum, silicon, calcium and iron, the kind of materials that become building blocks for planets like the Earth. In this context, it’s important to remember that stars are 98 percent hydrogen and helium, with all elements heavier than these being referred to as ‘metals.’
Bear in mind how stellar metallicity may be affected during planet formation, as discussed in the paper:
There are at least two planet formation processes that may alter stellar surface abundances: (1) the accretion of hydrogen-depleted rocky material (Gonzalez, 1997), which would result in the enrichment of the stellar atmosphere, and (2) H-depleted rocky material in terrestrial planets may be withheld from the star during their formation, which would result in the depletion of heavy elements relative to H in the stellar atmosphere (Melendez et al. 2009).
All of this can lead to scenarios involving planetary migration:
For the enrichment scenario, Schuler et al. (2011a) suggest that stars with close-in giant planets (?0.05 AU) may be more enriched with elements of high condensation temperature (TC). This is thought to be a result of giant planets which form in the outer planetary system migrating inward to their present close-in positions. As they migrate, they can push rocky material into the host star (e.g., Ida & Lin 2008; Raymond et al. 2011). For the depletion scenario, Melendez et al. (2009) and Ram?rez et al. (2009) propose that the depletion of refractory elements in Sun-like stars may correlate with the presence of terrestrial planets.
For the Vanderbilt work, the wide binary pair HD 20782/81 proved a useful study, chosen by Mack because both stars have planets and both evidently condensed out of the same cloud of dust and gas, thereby beginning their lives with the same chemical compositions. To my knowledge, this is the only known wide binary in which both stars host detected planets. The two stars are G-class dwarfs like the Sun, one being orbited by two Neptune-class planets, the other by a single Jupiter-size world in a highly eccentric orbit. The spectra of the stars indicates that both show an abundance of refractory materials significantly higher than the Sun.
The abundances of these metals is high enough, in fact, to indicate that each of the two stars would have had to consume an amount of rocky material equal to 10-20 Earth masses to produce the observed spectra. On that score it is significant that both stars host giant planets on eccentric orbits closing as tightly as 0.2 AU. Mack summarizes the finding:
“Imagine that the star originally formed rocky planets like Earth. Further, imagine that it also formed gas giant planets like Jupiter. The rocky planets form in the region close to the star where it is hot and the gas giants form in the outer part of the planetary system where it is cold. However, once the gas giants are fully formed, they begin to migrate inward and, as they do, their gravity begins to pull and tug on the inner rocky planets. With the right amount of pulling and tugging, a gas giant can easily force a rocky planet to plunge into the star. If enough rocky planets fall into the star, they will stamp it with a particular chemical signature that we can detect.”
Image: What if we could determine if a given star is likely to host a planetary system like our own by breaking down its light into a single high-resolution spectrum and analyzing it? A spectrum taken of the Sun is shown above. The dark bands result from specific chemical elements in the star’s outer layer, like hydrogen or iron, absorbing specific frequencies of light. By carefully measuring the width of each dark band, astronomers can determine just how much hydrogen, iron, calcium and other elements are present in a distant star. The new model suggests that a G-class star with levels of refractory elements like aluminum, silicon and iron significantly higher than those in the Sun may not have any Earth-like planets because it has swallowed them. Credit: N.A.Sharp, NOAO/NSO/Kitt Peak FTS/AURA/NSF.
With this in mind, the possibility that either of the binary twins hosts terrestrial planets is sharply reduced. The star orbited by two Neptune-class planets seems to have ingested more rocky material than its twin, with Mack and Stassun speculating that the two planets proved to be more efficient orbital disruptors for any terrestrial worlds that may have once been there. Even so, the other star, orbited by a Jupiter-class world, evidently pushed a large amount of rocky material into its star as well. The chemical composition is telling us that G-class stars with such high metallicities probably lack the kind of inner rocky planets many astronomers are searching for.
If these signatures are born out by subsequent study, we may have found a way to quickly determine whether a given G-class star is likely to have terrestrial planets, simply by analyzing its chemical composition. Several previous studies have linked star metallicity with planet formation, with one concluding that gas giants are found around high-metallicity stars, while terrestrial planets can be found around stars with a wide range of metal content. This work extends the use of metals as a marker in interesting new directions, playing off the link between a G-class star’s chemical composition and the kind of solar system it is likely to produce.
The paper is Mack et al., “Detailed Abundances of Planet-Hosting Wide Binaries. I. Did Planet Formation Imprint Chemical Signatures in the Atmospheres of HD 20782/81?” The Astrophysical Journal Vol. 787, No. 2 (2014), p. 98 (abstract / preprint).
GU Piscium b: Tuning Up our Imaging
How do you go about characterizing a directly imaged planet around another star? In the absence of a transit, one way is to apply theoretical models of planetary formation and evolution to the light spectrum you’re working with. When a team of researchers led by Marie-Ève Naud (a graduate student at the Université de Montréal) used these methods on direct imaging data from four different observatories to characterize a planet 155 light years from the Earth, they arrived at a temperature of some 800 degrees Celsius. The work drew inferences based upon the location of the newly detected world. For the planet, GU Piscium b, orbits a star that is a member of the AB Doradus moving group, some 30 stars that move together with the star AB Doradus.
The AB Doradus association is helpful because a moving group is made up of stars of roughly the same age and metallicity, a sign they probably formed in the same location. The fact that these are young stars, perhaps 100 million years old, also helped the team pull together an estimate of the planet’s mass, some 9 to 13 times that of Jupiter. The striking thing about GU Piscium b is that it orbits at about 2000 AU, the farthest exoplanet from its host that I am aware of. A single trip around its star would take GU Piscium b some 80,000 years. That distance makes infrared detection possible, particularly since young planets like this are still cooling and are therefore brighter.
Image: The planet GU Piscium b and its star GU Piscium. This image is composed of visible and infrared images from the Gemini South telescope and an infrared image from the CFHT. Because infrared light is invisible to the naked eye, astronomers use a color code in which infrared light is represented by the color red. GU Piscium b is brighter in infrared than in other filters, which is why it appears red in this image. Credit: Gemini Observatory/OMM/CFHT/W.M. Keck Observatory.
René Doyon, director of the Observatoire Mont-Mégantic (OMM) some 200 kilometers east of Montreal, calls GU Piscium b “a true gift of nature,” noting that its large distance from the star means a number of instruments can study it in depth, including smaller telescopes like the one at OMM. In this case, the work also involved the Gemini Observatory, the Canada-France-Hawaii Telescope (CFHT) and the W.M. Keck Observatory, whose combined resources produced images at a variety of wavelengths. Having such a clearly defined object for direct imaging studies should be helpful as we work on imaging planets closer to their stars.
On that score, a nod to the debut of the Gemini Planet Imager (GPI), whose first image produced the high-quality result shown below. This is Beta Pictoris b, some 63 light years from Earth, seen through a single 60-second exposure. The GPI’s advanced optics can detect planets down to Jupiter mass orbiting stars similar to the Sun, whereas the previous generation of adaptive optics could image planets no smaller than three times Jupiter’s mass, and only planets as far from their star as Saturn or Neptune is from the Sun.
Image: The bright white dot is the planet Beta Pictoris b, glowing in the infrared light from the heat released when it was formed 10 million years ago. The bright star Beta Pictoris is hidden behind a mask at the center of the image. (Image processing by Christian Marois, NRC Canada).
So we’ve had only a few planets directly imaged, but we’re making progress. Enough so that Bruce Macintosh, principal investigator on the GPI project, predicts in the team’s paper on this work that the planet may transit the host star in 2017, based on information gleaned from the GPI dataset, which yielded clues to the planet’s orbit. A transit of a directly imaged planet would open up in-depth investigation of the planet’s characteristics — remember that Kepler, although it has found thousands of transiting worlds, cannot produce direct imagery of any of them.
And no, not even the Gemini Planet Imager, in operation since November at its site in Chile, will let us see planets as small as the Earth. But Macintosh sees a continued and positive evolution in our capabilities. “…[I]t’s a step on the road,” he added. “Some day a future space telescope will use the same technology, and be able to see an Earth around one of these nearby stars.”
The Beta Pictoris b paper is Macintosh et al., “First light of the Gemini Planet Imager,” published online by Proceedings of the National Academy of Sciences (abstract). The GU Piscium b paper is Naud et al., “Discovery of a Wide Planetary-Mass Companion to the Young M3 Star GU Psc,” The Astrophysical Journal Vol. 787, No. 1 (2014). Abstract and preprint available.
Time Out
Over the past months, enough projects have piled up in need of attention that I finally have to decide to get serious about them. That means a short break here. No Centauri Dreams posts this week, therefore, with publication resuming next week on Monday or Tuesday. While I’m putting various things — some space-related, some not — in order, I’ll try to keep up with comment moderation, though it may get sporadic for a time. Meanwhile, do keep plugging into Heath Rezabek’s book survey as we try to isolate not only what books from my shortlist are the most useful, but also search for books you think should be on the list. Please add any titles you think worthwhile in the space provided on the survey form. I look forward to watching this survey grow, and to Heath’s reflections on it once it has grown to sufficient size. See you in a week.
An Emerging Interstellar Bibliography
Today begins Heath Rezabek’s survey as we look at the curation of a booklist on interstellar flight, using as basis a list of books I’ve gradually accumulated over the years. Before Heath introduces the survey, a few words about my methods: Many of the books listed below are ones that I used in preparing my 2005 book Centauri Dreams: Imagining and Planning Interstellar Exploration. But in the time since, I’ve added a number of more recent titles. I’m hoping this curation project will reveal other books that may be useful as we flesh out the list. Please glance over the entire list and be thinking of additional possibilities as you engage with Heath’s survey.
As to the choices made, these are non-fiction science books, although several recent titles contain a mix of non-fiction and science fiction stories. Feel free to suggest SF titles that specifically broaden our thinking about interstellar flight — we can either integrate them into the main list or develop a second list focused on fiction. The latter may be more practicable. Also, books on SETI and exoplanetology are under-represented in favor of books on spaceflight and propulsion. Given how often we discuss these matters on Centauri Dreams. I’d like to see recommendations for more titles in both these areas.
I also restricted the selection to books that have been through serious peer review from the publisher itself or qualified people chosen by its editors. Books that largely compile previously published papers that have been through rigorous peer review also make the list. While self-publishing is a growing phenomenon, if no peer review is evident, I cannot add such titles to the short list. With that in mind, let’s see what happens as Heath’s work develops.
by Heath Rezabek
In yesterday’s entry, I summarize my work to this point as an Intern with the Long Now Foundation, assisting and advising on the community curation of the Manual for Civilization collection.
In today’s entry, we’ll undertake our own experiment in community curation, by asking the readers of Centauri Dreams to compare the books in Paul Gilster’s Centauri Dreams shortlist, and most importantly, to recommend titles which you don’t see represented but which you feel are integral to the themes explored here over time. We’ll end up with two resources which Paul can use in the future: The list itself, and the relative rankings based on community comparison of titles’ relative importance to a core Centauri Dreams community collection.
In the Centauri Dreams Vessel Survey (link immediately below), participants are encouraged to add as many titles as they wish — particularly newer or older titles not yet reflected — and sort between titles as often as they like. Over time, we’ll end up with our own wish list for a core collection reflecting the Centauri Dreams readership community.
This survey tool works a bit differently from other surveys you might have taken, but may be familiar if you’ve run across our use of it here before. At the link below, your task to complete as many times as you wish to weigh in is simply to pick between two titles from the list in any given round.
Once you’ve picked one as more integral than the other, another pairing will come up. You are encouraged to sort between titles as many times as you can, as the more data such a survey has, the more useful its results. You may stop when you’re weary, and return later if you wish.
You are also greatly encouraged to add related titles, items which have informed your thinking on these themes as a member of the Centauri Dreams community of readers. Duplicates are not much of a problem, as they cluster over time and we can deactivate them once they do. Again, the more data, the better the results. Click on the image or the link below it to participate in the survey.
Centauri Dreams Vessel Survey: Community Curation
We will revisit this survey as time passes, as votes accrue, and as titles are added.
Thank you, Paul, for giving the nod to try community curation on Centauri Dreams; thank you, readers of Centauri Dreams, for lending your voice as community members.
Paul’s original list is below, though because of character limits in the surveys, annotations and publisher details are not always included in the survey version.
[PG note: The breakdown of my list into General Audience, College, Graduate and Professional was an attempt at sorting that I’ve grown uncomfortable with — many of these titles could go in more than one such category. So don’t let the categories concern you at this point].
General Audience
Adler, Charles (2014) Wizards, Aliens and Starships. Princeton, NJ: Princeton University Press.
Caleb Scharf calls this “…a delightful, funny, and immensely interesting romp through science and fiction,” which precisely nails the spirit of the book. Adler looks at the wonders of science fiction from alien civilizations to teleportation and warp drive, framing the discussion against judiciously explained physics. It’s hugely entertaining and scientifically sound.
Berry, Adrian (2000) The Giant Leap: Mankind Heads for the Stars. New Yorks: Tor Books.
A look at the technologies that might one day lead to the nearest stars and beyond. Discusses the options for making such journeys, along with the political and philosophical imperatives that might drive such a mission. Interesting chapters on interstellar navigation and suspended animation.
Boyce, Christopher (1979) Extraterrestrial Encounter: A Personal Perspective. Secaucus, NJ: Chartwell Books.
Speculations on the nature of alien intelligence and the possibilities for understanding and communicating with it. The odds on SETI and the possible use of Bracewell or von Neumann robotic probes for studying other planets play a role in this lively discussion.
Burrows, William E. Exploring Space: Voyages in the Solar System and Beyond. New York: Random House, 1990.
One of the best histories of the space program ever written, this book gives full weight to automated probes rather than manned flight, and speculates on the technologies that will take us outside the Solar System. Burrows’ look at the politics behind programs like the Space Shuttle resonates today.
Calder, Nigel (1978) Spaceships of the Mind. New York: Viking Press.
Speculations on space technologies including many interstellar concepts. Numerous useful though dated illustrations. The driving factors pushing space colonization are carefully examined.
Forward, Robert L (1995) Indistinguishable from Magic. New York: Baen Books.
Perhaps the greatest interstellar theorist of them all, Robert Forward offered mission concepts galore in the course of his career, many of them entertainingly discussed in this collection of essays. The author’s wry humor often shows through in discussions that range from wormholes to antimatter engines.
Friedman, Louis (1988) Starsailing: Solar Sails and Interstellar Travel. New York: John Wiley & Sons.
Friedman’s background working at the Jet Propulsion Laboratory on a once-considered solar sail mission to Halley’s Comet allows him to tap deep resources in explaining how solar sails will one day open up the Solar System, with potential for interstellar flight via particle or laser beam.
Kaku, Michio (2008) Physics of the Impossible: A Scientific Exploration into the World of Phasers, Force Fields, Teleportation, and Time Travel. New York: Doubleday.
Kaku discusses three levels of ‘impossibility,’ ranging from things we may one day puzzle out to technologies that would strike us as indistinguishable from magic, to use Arthur Clarke’s fine phrase. This wide-ranging study includes a look at interstellar technologies now under active study.
Krauss, Lawrence (1995) The Physics of Star Trek. New York: Basic Books.
A theoretical physicist offers thoughts on the scientific wonders of the popular TV series, discussing such issues as teleportation, time travel, warp drive and black holes. Excellent at untangling the futuristic but possible from the hugely improbable, based on known physics.
Macvey, John W. (1977, 1991) Interstellar Travel: Past, Present and Future. New York: Stein and Day.
Revised in 1991, this book examines interstellar travel technologies ranging from space arks to wormholes, with a long discussion of the nature of extraterrestrial life and how it might communicate with humans. Wide-ranging and easy to read, this is a good choice for young readers.
Myrabo, Leik and Dean Ing (1985) The Future of Flight. New York: Baen Books.
Starship drives are only one of the topics covered by this survey of future flight technologies, but the interstellar chapter is strong, surveying concepts from the Bussard ramjet to the laser-driven lightsail and antimatter engines. A good though now backgrounder for those wanting a quick survey of these ideas.
Nicholson, Iain (1978) The Road to the Stars. New York: William Morrow & Co.
A well-illustrated and lively survey of future space technologies, with a useful discussion of SETI and the possibilities of communicating with extraterrestrial intelligence. The major ideas for upgrading today’s engines are presented, beginning with ion drives and carrying forward to the Bussard ramjet.
Sagan, Carl (1980) Cosmos. New York: Random House.
Carl Sagan’s classic offers some of the most captivating illustrations ever made available in a space book. While the book, like the TV series it parallels, offers perspective on the entire human experience of the heavens, it places the possibilities of interstellar flight in a readable, powerful context.
Wright, Jerome L. (1992) Space Sailing. New York: Taylor & Francis.
A history of the solar sail concept, one that uses momentum from the Sun’s own light to drive a space vehicle, without the need to carry heavy fuel. Well illustrated, this book examines all the ways solar sails may change our future in space, both in the near term and the far.
College Level
Adelman, Saul J. and Benjamin Adelman (1981). Bound for the Stars: Space Travel in our Solar System and Beyond. Inglewood Cliffs, NJ: Prentice-Hall.
The exploration of space from travel in the nearby Solar System to interstellar missions. The latter chapters discuss interstellar propulsion, navigation, the search for extrasolar planets and the first starship. Useful discussions as well about a plausible program for long-term interstellar planning.
Andreadis, Athena (1999) To Seek Out New Life: The Biology of Star Trek. New York: Three Rivers Press. A professional biologist goes to work on life sciences as depicted in Star Trek, with thoughts on everything from telepathy and the genetic code to the cultural sameness of the societies the Enterprise’s crew encounters. Entertaining and instructive.
Benford, Gregory and James (2013) Starship Century. Lucky Bat Books.
Starship Century is an anthology by authors from both science and fiction writing backgrounds, illustrating some of the tech and ideology behind the illustrious goal of traveling to another star within the next century. Edited by Gregory Benford, New York Times bestselling science fiction author, and James Benford, leading expert on space propulsion, Starship Century includes science fiction by Neal Stephenson, David Brin, Joe Haldeman, Nancy Kress, Stephen Baxter, Gregory Benford, John Cramer, Richard A. Lovett, and Allen Steele, as well as scientific articles by Stephen Hawking, Freeman Dyson, Robert Zubrin, Peter Schwartz, Martin Rees, Ian Crawford, James Benford, Geoffrey Landis, Paul Davies and Adam Crowl.
Billings, Lee (2013) Five Billion Years of Solitude. New York: Current.
The exoplanet hunt as seen through Lee Billings’ eyes as he interviews the major players in the field, from Frank Drake to Jim Kasting, Sara Seager, Greg Laughlin, Geoff Marcy and more. Within their individual stories Billings weaves in the technological and science breakthroughs that have made current work possible, and points eloquently toward the next stages in the journey as we look for a genuine Earth. 2.0. There is no better examination of the basic techniques and issues surrounding exoplanet detection and the human impact of this work.
Clarke, Arthur C. and David Brin, ed. (1990) Project Solar Sail. New York: Roc.
Useful essays from leading theorists examine the role of solar sails in future space missions, with attention to missions in the Solar System and beyond. The essays are interleaved with short fiction and even poetry that explores plausible scenarios for putting sails to work.
Dole, Stephen H. and Isaac Asimov (1964) Planets for Man. New York: Random House.
This is the popular version of a RAND Corporation study originally performed by Dole. The later version includes the thoughts of Isaac Asimov, and examines the factors necessary for planets to be habitable for humans, and our chances of finding them. Although dated, this book still offers useful information about the concept of a habitable zone and the factors that will one day make particular planets useful destinations for our probes.
Dyson, George (2002) Project Orion: The True Story of the Atomic Spaceship. New York: Henry Holt and Co.
Freeman Dyson’s son tackles the great attempt to wed nuclear technology to deep space missions, Project Orion. Told with flair and access not only to key documents but the recollections of the major players, this history shows how one team of experts viewed journeys to the outer Solar System and beyond before the realities of the Test Ban Treaty put the concept beyond reach.
Forward, Robert L. and Joel Davis (1988) Mirror Matter: Pioneering Antimatter Physics. New York: John Wiley & Sons.
Interstellar theorist Robert Forward offers a thorough background to the history of antimatter research. Propulsion concepts that could drive our first starships are examined, while the methods for creating and storing antimatter and using it here on Earth receive solid scrutiny. The chapter on antimatter in science fiction is particularly energetic.
Genta, Giancarlo (2007) Lonely Minds in the Universe. Berlin: Springer.
A valuable study of astrobiology and the search for extraterrestrial intelligence, unique in the extent to which it explores the philosophical and religious background of humanity’s awakening interest in the cosmos. The discussion of biology both on Earth and elsewhere offers insights into the possibilities of living organisms around other stars, while the author’s speculations about consciousness and intelligence remind us just how unique each alien ecosystem and its inhabitants may be. How we may interact with any intelligence we discover forms an insightful part of the narrative.
Gilster, Paul (2004) Centauri Dreams: Imagining and Planning Interstellar Exploration. New York: Copernicus Books.
Surveys methods for moving an interstellar probe to speeds that could reach nearby stars in a single human lifetime. These range from fusion to antimatter, beamed lightsails, magnetic sails, Bussard ramjets and other concepts. Also covers interstellar navigation and exoplanet detection.
Grinspoon, David (2003) Lonely Planets. New York: Ecco.
I found this a useful and deeply entertaining overview of current and historical thinking on extraterrestrial life, with interesting arguments against the hypothesis that the Earth is in any way unique when it comes to the ability to produce living organisms. What intelligent life might become both on Earth and elsewhere is considered with a leavening of personal anecdotes and humor, and a plea that we move beyond definitions of life too firmly attached to our own planet.
Impey, Chris and Holly Henry (2014) Dreams of Other Worlds. Princeton, NJ: Princeton University Press.
Read Impey and Henry for an overview of where we’re coming from in unmanned space exploration and robotics. The book lays out our explorations from Viking on Mars to Cassini, WMAP and Spitzer, chronicling the interplay of new technologies and emerging science. Manned missions invariably get more buzz, but until we ramp up our methods, the outer system belongs to increasingly sophisticated machines. This is where they come from.
Johnson, Les and Jack McDevitt, eds. (2012) Going Interstellar. New York: Baen.
A collection of tales by an all-star assortment of award winning authors including Ben Bova, Mike Resnick, Jack McDevitt, Michael Bishop, Sarah Hoyt and more together with essays on high technology by space scientists and engineers – all taking on new methods of star travel. The essays include reports on propulsion technologies including antimatter, solar sails and fusion. The science fiction speculations tackle the human consequences of travel to another star and how our descendants will master issues from species survival to alien contact.
Kaku, Michio (1995) Hyperspace: A Scientific Odyssey Through Parallel Universes, Time Warps and the Tenth Dimension. Oxford University Press.
Understanding the possibilities of interstellar flight demands a look at the things that may warp space and time, including wormholes that could offer fast transit without exceeding the speed of light. Michio Kaku explains the options with a minimum of jargon and clear, readable prose.
Mallove, Eugene F., and Gregory L. Matloff (1989) The Starflight Handbook: A Pioneer’s Guide to Interstellar Travel. New York: John Wiley.& Sons.
A classic of interstellar studies, Matloff and Mallove’s book provides the necessary theory to understand the various propulsion methods proposed to reach the stars. All major concepts are considered by two authors who have been involved in interstellar concepts for decades.
Matloff, Gregory, Les Johnson and C. Bangs (2007) Living Off the Land in Space: Green Roads to the Cosmos. New York: John Wiley & Sons.
Space travel as we do it today requires large amounts of fuel that take up a major part of the rockets we launch. How we can learn to use resources in space itself may determine how soon we push into the outer Solar System and beyond. The science behind space tethers, solar sails and other techniques for in-System voyaging are here explored, along with speculations about even more audacious concepts that could take us to the stars.
Matloff, Gregory, Les Johnson and Giovanni Vulpetti (2010) Solar Sails: A Novel Approach to Interplanetary Travel. Berlin: Springer. A comprehensive survey of solar sail concepts ranging from near-term designs like the Solar Polar Imager to interstellar possibilities enabled by laser-driven lightsails, this book summarizes our sail knowledge at the beginning of the solar sail era, with numerous thoughts on sail design, construction, deployment and trajectories.
Michaud, Michael (2006) Contact with Alien Civilizations: Our Hopes and Fears about Encountering Extraterrestrials. New York: Copernicus.
A thorough discussion of the consequences of our encounters with extraterrestrial civilizations, with background studies of the history of human speculation about extraterrestrial intelligence, our searches for life and for the signals of other cultures, and the various ways contact might play out. In an era when some are trying to extend the SETI (listening) paradigm to METI (broadcasting), this book offers sober analysis of how humanity should weigh these options, and opts for multidisciplinary negotiation and consensus before acting in ways that could impact the entire species.
Savage, Marshall T. (1994) The Millennial Project: Colonizing the Galaxy in Eight Easy Steps. New York: Little, Brown & Co.
An optimistic look at how mankind can spread into the cosmos, offering a program to transfer a large proportion of the world’s population into venues off-planet. Step by step improvements lead to terraforming Mars, using the resources of the outer system, and moving to the nearby stars.
Strong, James (1965) Flight to the Stars. New York: Hart Publishing Company.
An early classic of interstellar studies, Strong’s book offers a rationale for the human expansion to the stars, while considering a variety of propulsion concepts to get the job done. While dated in specifics, the scenarios considered here paint possible futures for a star-faring race with vigor and enthusiasm.
Thorne, Kip S. (1994) Black Holes and Time Warps: Einstein’s Outrageous Legacy. New York: W.W. Norton & Co.
Thorne is a major player in the theory of wormholes, and thus the kind of distortions of spacetime that may one day make it possible to travel vast distances quickly without ever exceeding the speed of light. This book places his theories into the Einsteinian context in readable if challenging fashion.
Zubrin, Robert (1999) Entering Space: Creating a Spacefaring Civilization. New York: Tarcher/Putnam, 1999.
The case for becoming a spacefaring civilization is made with enthusiasm and panache. The action ranges from terraforming nearby Mars to exploiting the resources of the outer planets, with solid chapters on interstellar propulsion and contact with extraterrestrial civilizations.
Graduate/Professional Level
Carroll, Michael (2011) Drifting on Alien Winds: Exploring the Skies and Weather of Other Worlds. New York: Springer.
From the Soviet Venus balloons to the advanced studies of blimps and airplanes for the atmospheres of Mars and Titan, Drifting on Alien Winds surveys the many creative and often wacky ideas for exploring alien skies. Through historical photographs and stunning original paintings by the author, readers also explore the weather on planets and moons, from the simmering acid-laden winds of Venus to liquid methane-soaked skies of Titan.
Czysz, Paul and Claudio Bruno (2009) Future Spacecraft Propulsion Systems: Enabling Technologies for Space Exploration. Berlin: Springer.
Space propulsion systems from near-Earth to the outer Solar System and beyond. Focus on applied engineering working within the known principles of physics, with emphasis on fusion rocket designs and the extension of today’s technologies to missions into deep space.
Doody, Dave (2009) Deep Space Craft: An Overview of Interplanetary Flight. Berlin: Springer.
Descriptions of interplanetary spacecraft with detailed looks at their instrumentation and the Earth-based operations needed to acquire and process their incoming data. Flight operations and the interactions between a mission’s science team and the light team are examined, with detailed appendices on the range of instruments that have so far flown, and those likely to be aboard spacecraft in the future.
Finney, Ben R. and Eric M. Jones (1985) Interstellar Migration and the Human Experience. Berkeley: University of California Press.
This is a compilation of papers from the Conference on Interstellar Migration held at Los Alamos in May of 1983, which examined not only the scientific possibilities, but also the social, ethical and even legal ramifications of our move into the cosmos. Its look at how humanity has coped with past challenges, such as the settlement of the Pacific islands, places interstellar migration in context.
Kondo,Yoji, ed. (2003) Interstellar Travel and Multi-Generational Space Ships. Apogee Books Space Series 34. Collector’s Guide Publishing Inc (June 1, 2003).
Papers from a symposium of the American Association for the Advancement of Science in 2002, exploring propulsion concepts and the solutions needed for flight to the stars. The book also addresses the cultural and psychological issues related to long-term voyaging and ponders ‘generation ships,’ in which crew members spend their entire lives on voyages several centuries in duration.
Long, Kelvin (2011) Deep Space Propulsion. New York: Springer.
The technology of the next few decades could possibly allow us to explore with robotic probes the closest stars outside our Solar System, and maybe even observe some of the recently discovered planets circling these stars. This book looks at the reasons for exploring our stellar neighbors and at the technologies we are developing to build space probes that can traverse the enormous distances between the stars. All the propulsion concepts seriously considered for interstellar flight are examined here.
Maccone, Claudio (2009) Deep Space Flight and Communications: Exploiting the Sun as a Gravitational Lens. Berlin: Springer.
Maccone has long been the champion of a mission to the Sun’s gravitational lens at 550 AU and beyond. Here he lays out the results of his two decades of study of the concept, discussing possible probe designs, the best targets for investigation, and the underlying principles of lensing. Section 2 examines the challenge of communicating between an interstellar spacecraft and the Earth, focusing on the opportunities found in the Karhunen-Loève Transform (KLT) for optimal telecommunications.
Matloff, Gregory L. (2005) Deep Space Probes: To the Outer Solar System and Beyond. Berlin: Springer/Praxis Books.
Recently revised, Matloff’s look at deep space technologies offers abundant references in its examination of current theories of interstellar propulsion, including nanotechnology and ramscoops that draw their fuel from hydrogen between the stars. Also included are speculations on astrobiology and the development of self-reproducing von Neumann probes that could saturate the galaxy.
Mauldin, John H. (1992) Prospects for Interstellar Travel. American Astronautical Society Science and Technology Series, Vol. 80. San Diego, CA: Univelt.
A thorough study of interstellar flight possibilities that covers, in addition to the relevant propulsion concepts, every aspect of starship design, including the navigation problem and the difficulties posed by lengthy voyages with human crews. The overall engineering of space probes designed for such missions is discussed at length, with abundant references for follow-up reading.
McInnes, Colin R. (1999) Solar Sailing: Technology, Dynamics and Mission Applications. Chichester, UK: Praxis Publishing.
The most exhaustive study of solar sail technology available, offering a rich list of references for specialists. Applications for near-term missions are considered in detail, with the relevant equations for understanding the forces at work. A thorough examination of sail materials and design explains where we are now and how solar sails may change the economics of propulsion. Beamed lightsails for interstellar missions.
Millis, Marc and Eric Davis, eds. (2009). Frontiers of Propulsion Science. Reston, VA: AIAA.
A compilation of essays from specialists about the prospects for breakthroughs that could revolutionize spaceflight and enable interstellar flight. Five major sections are included in the book: Understanding the Problem lays the groundwork for the technical details to follow; Propulsion Without Rockets discusses space drives and gravity control, both in general terms and with specific examples; Faster-Than-Light Travel starts with a review of the known relativistic limits, followed by the faster-than-light implications from both general relativity and quantum physics; Energy Considerations deals with spacecraft power systems and summarizes the limits of technology based on accrued science; and, From This Point Forward offers suggestions for how to manage and conduct research on such visionary topics.
Seedhouse, Erik (2012) Interplanetary Outpost: The Human and Technological Challenges of Exploring the Outer Planets. New York: Springer/Praxis.
Interplanetary Outpost follows the mission architecture template of NASA’s plan for Human Outer Planet Exploration (HOPE), which envisions sending a crew to the moon Callisto to conduct exploration and sample return activities. To realize such a mission, the spacecraft will be the most complex interplanetary vehicle ever built, representing the best technical efforts of several nations. A wealth of new technologies will need to be developed, including new propulsion systems, hibernation strategies, and revolutionary radiation shielding materials. Step by step, the book will describe how the mission architecture will evolve, how crews will be selected and trained, and what the mission will entail from launch to landing.
Smith, Cameron (2012) Emigrating Beyond Earth: Human Adaptation and Space Colonization. New York: Springer.
Based on the most current understanding of our universe, human adaptation and evolution, the authors explain why space colonization must be planned as an adaptation to, rather than the conquest of, space. Emigrating Beyond Earth argues that space colonization is an insurance policy for our species, and that it isn’t about rockets and robots, it’s about humans doing what we’ve been doing for four million years: finding new places and new ways to live. Applying a unique anthropological approach, the authors outline a framework for continued human space exploration and offer a glimpse of a possible human future involving interstellar travel and settlement of worlds beyond our own.
Vakoch, Douglas and Albert Harrison, eds. (2013) Civilizations Beyond Earth: Extraterrestrial Life and Society. Berghahn Books.
This collection of essays takes in the search for extraterrestrial intelligence and offers a sociological and philosophical entry into a field that is often dominated by the hard sciences. Vakoch, a sociologist, brings a useful new dimension to the question of how humanity would react to extraterrestrial contact, and the essays chosen for this volume form a discussion that meshes well with Michael Michaud’s work in Contact with Alien Civilizations. Harrison, a psychologist from the University of California, helps to ensure that SETI analysis will continue to deepen its multidisciplinary links as the field evolves.
Woodward, James (2012) Making Starships and Stargates: The Science of Interstellar Transport and Absurdly Benign Wormholes. New York: Springer/Praxis.
A study in three parts: The first deals with information about the theories of relativity needed to understand the predictions of the effects that make possible the “propulsion” techniques, and an explanation of those techniques. The second deals with experimental investigations into the feasibility of the predicted effects; that is, do the effects exist and can they be applied to propulsion? The third part of the book – the most speculative – examine the questions: what physics is needed if we are to make wormholes and warp drives? Is such physics plausible?
Curation of an Interstellar Booklist
As a librarian with a futuristic bent, Heath Rezabek has developed the Vessel Project as a way of studying how we can preserve our knowledge and culture against future risk. That work — and Heath’s ongoing engagement with the Long Now Foundation — asks what we might put into a long-term archive housing the essence of our community. Finding the answers involves ‘community curation,’ asking varying interest groups to develop and discuss their choices. We’re going to run such a survey with the Centauri Dreams readership, helping to firm up a shortlist of books on interstellar topics that I’ve been wanting to return to for some time. That list will appear tomorrow, but today Heath explains strategies for building archives to represent communities like the one that clusters here around interstellar flight.
by Heath Rezabek
In my first Centauri Dreams installment, I noted that I had recently begun an Internship with the Long Now foundation, assisting and advising in their initial community curation of a 3,500 volume collection called the Manual for Civilization. At that time, I promised updates on the project as it progressed, since it bears such a kinship to themes and objectives reflected in the Vessel Project. I have not yet done an update.
Image: The Interval: Long Now Foundation, San Francisco, CA.
With the site of the collection soon to open — the name of their headquarters space being The Interval — and with myself about to make a trip out to San Francisco for part of those opening activities at the end of May, now seemed like a good time to reflect upon my experience as an Intern on the Manual for Civilization. The Internship draws to a close, and I look towards the future, by considering the importance of community curation at all levels and in all kinds of communities. I will also tie these thoughts back to current and prior work on the Vessel proposal, and launch an effort towards community curation of a core reading list for Centauri Dreams readers based on Paul Gilster’s existing shortlist on interstellar research.
As a brief summary, the Long Now Foundation is a nonprofit organization whose purpose is to foster long term thinking through concrete projects which catalyze public debate and discussion about the very long term, while at the same time striving for substantial real-world goals. Its cornerstone project is the construction of a 10,000 Year Clock, “designed to run for ten millennia with minimal maintenance and interruption. The Clock is powered by mechanical energy harvested from sunlight as well as the people that visit it. The primary materials used in the Clock are marine grade 316 stainless steel, titanium and dry running ceramic ball bearings.” No completion date is set, but construction work at the first site in west Texas is in preparation.
Image: The Rosetta Disk.
Another project with concrete utility as a key for decoding 1,500 human languages is the Rosetta Disk. At the ESA’s invitation, an early copy of this disk is on the Rosetta probe.
Image: The Rosetta Probe (ESA).
Over time, Long Now has undertaken numerous other concrete efforts, and the Manual for Civilization is one. This collection is to be a 3,500 volume book collection and library, housed at its new headquarters in San Francisco, The Interval. At time of launch, their plan is to have 1,000 of those volumes on the shelf, and to build the rest of the collection over time through various community-driven means. These include annual vetting of the existing collection and the chance to debate the addition or removal of items in what is proposed to be a fixed number of items.
The overarching question used to drive curation is “What books would you most want to help rebuild civilization?” To ask this question of a small subset of individuals is, obviously, to push them to think well beyond their means (much as is true of asking designers and engineers today to plan towards building an eventual interstellar starship). Yet this is a community dedicated specifically to long-term thinking, and to fostering that activity through its efforts.
Image: The 10,000 Year Clock Prototype (Power and Winder test).
One of the earliest critiques and responses to the Vessel proposal on Centauri Dreams was from a reader who could not see the point of attempting comprehensive archival of cultural content in the first place (much less other material, such as endangered biomass or scientific knowledge). The reader suggested that individuals and communities would always be undertaking archival tasks and the passing-down of their own heritage, making any kind of concerted effort unnecessary.
As a librarian, I continue to disagree; yet working on the Manual for Civilization project has reminded me that there is a spectrum of appropriate response to the need for remembrance as a mitigation of permanent stagnation or flawed realization. While the first draft of the Manual for Civilization does strive to be comprehensive, there is also significant room for interpretation and opinion in its scope. Its primary categories, at this stage, are a blend of comprehensive and community-focused topics: Cultural Canon and Mechanics of Civilization are both categories which point at widespread and general utility (once fleshed out by the addition of unfamiliar or more broadly global materials). The two other initial categories, Rigorous Science-Fiction and Long Term Thinking/Futurism, are there in part because of their direct interest to the specific community doing the curation — in this case, the Long Now Foundation.
Image: Categories in the Manual for Civilization (as of January 2014)]
With the facility and its opening events now in sight, Long Now has been bringing together existing physical copies of many works on the shortlist, as well as seeking out donor copies to fill out the collection. I myself have committed several to those shelves, including two signed editions. I have been impressed by the positive response seen both in the public, as well as in myself, to the prospect of helping to build a physical reference collection meant to endure over time.
It has also convinced me that similar processes could be carried out for other communities of interest, and perhaps with different types of materials. Empowering a community to build what amounts to an extended wishlist for that collection becomes the first step in establishing and stewarding its cohesion over the long term.
One of my own contributions to the process was the proposal that we create a customized build of the allourideas.org A/B sorting platform, (which I find useful for a great many things). This was done, allowing the project to pull ISBNs and other metadata into the survey from a custom metadata entry system. The community was invited to propose titles, and begin the process of sorting the ones already in the list.
Additionally, and appropriately, the core collection was seeded with the personal shortlists of Long Now’s founding members and some community exemplars (as I call them). (See Brian Eno; Neal Stephenson; Stewart Brand; Kevin Kelly. A blending of the lists — the community curated A/B lists and the shortlists of community exemplars — was undertaken by Long Now leadership, and thus the first curation list was born.
Image: Neal Stephenson selects titles for his shortlist, as a community exemplar.
During this process, we encountered a few questions regarding the diversity of the collection and its sources. The most public and illuminating of these questions came from Maria Popova, who runs an outstanding literary blog called Brainpickings. Her list and discussion was illuminating in itself, but it also helped me over a mental hurdle in understanding the purpose and point of such a process, and this has enriched my own conception of the larger long term goals of the Vessel Project.
As I wrote in my comments-response to a similar inquiry on the Long Now blog,
“I do think it’s important to remember that this particular collection is meant, initially, to serve as a core collection reflective of its hosting organization, housed at their headquarters site. While the question of what would most help rebuild or preserve a cultural core is a crucial one to ask, there might also be as many answers as there are communities of interest willing to ask it. I think that’s a good thing, actually: it reminds us that no such collection could ever be absolutely authoritative unless it were nearly exhaustive, but at its best might strive to be a reflection of its constituents’ ideals and aspirations. The wider that circle, the more comprehensive the collection — but universal representation right from the start would be nearly impossible.
The core lists being submitted by founders and community [exemplars] is only one current going in to the process. […] Every such collection is bound to differ in its details, and in those differences lie a strength. Who’s to say which resources will confer the greatest resilience or remembrance for a given community, other than that dynamic community itself? We can aspire, but more importantly, I think, is that the question “What do we feel is most worth passing on over the long term?” be asked, by as many unique communities as can.”
In articulating this, I had arrived unexpectedly at a middle-ground between the original ideal of Vessel — the seeding of numerous institution-level comprehensive collections, secured against unforeseen catastrophes in a range of ways — and the default remembrance strategy of throwing seeds to the wind, come-what-may, suggested by the critique that everyone will already save whatever matters for themselves.
The community of interest is the place where those two strategies meet.
Image: Interior visualization of The Interval.
This middle ground suggests a larger role for what I call community curation and community collections. Community may be very broadly defined, to include everything from a small family to a whole nation or colony. It seems useful to consider the possibility that larger collections might be built up of smaller collections: if each item and set of items bequeathed to a community collection is vetted for its long-term importance (however one wishes to define that), then as a whole the collection will reflect this objective even if the sets within it differ significantly.
The key element is to ensure the asking of the question. It can be phrased in different ways, complete with the differences those many ways suggest. “What would you place in a vessel containing the essence of your community?” “What is important enough to you to pass on beyond your own time?” “What best reflects the essence of your community’s knowledge and influences?” “What is most worth saving?” “What is at most risk of being lost?” And so on.
There will always be space and a place for those who answer this question simply with their lives, by saving what they value in their own collections and passing it on when they themselves pass on. However, given the complex challenges which face future generations (wherever they may make their homes), the asking of these questions and the community curation of collections which result may serve as crucial guidance in the short and medium term. Perhaps surprisingly, and perhaps controversially, we can propose that the greater the number of these communities and diversity of their resulting collections, the greater these collections’ value to communities in the future.
In other words, the idiosyncrasies seen in the Long Now Foundation’s collections, far from being a weakness, are a source of hybrid vigor and a carrier wave for the priorities this particular community will have as it evolves. A community has asked a particular question, and preserved its own unique approach to adapting as it moves into the future.
Image: Manual for Civilization (Logo).
At the end of May, I will travel to San Francisco to celebrate this Internship and to see the collection in its seedling stage. I will return with a renewed sense of direction and purpose for the Vessel Project, clear to me already in outline. Future efforts will continue to ask the question of curation to, hopefully, a range of communities. Each will answer somewhat differently, and in these differences will lie those communities’ particular traditions.
The results of these Vessel Surveys will be made openly available whenever possible; books are perhaps an increasingly controversial medium to use as a baseline, but they are also surprisingly resilient as media, and in the short term are good markers for particular ideas, priorities, and influences. Vessel Surveys which embrace other media are possible as well.
Not all will focus immediately on core materials for rebuilding civilization, but might initially focus simply on the themes and ideas integral to that community. Such would be the case with a thematic community like Centauri Dreams.
In this spirit, and with Paul’s blessing, I would like to facilitate a community curation of the Centauri Dreams readership. Initially, we will start with books; but if comments suggest that ideas or some other carrier for influence is preferable, we can launch a survey for that type. This is an experiment and a gift, from one member of the Centauri Dreams to all others, and from all of us to all who come.
Image: Centauri Dreams: Community Curation Vessel Survey (Live tomorrow).
In the fullness of time, who knows who might find these influences pivotal to their own exploration?
Tomorrow, we’ll present Paul’s initial shortlist of key books as influences, and then we will open up a Vessel Survey for suggestions of others from the community.
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