≡ Menu

Five Billion Years of Solitude

About a third of the way into his new book Five Billion Years of Solitude: The Search for Life Among the Stars (Current, 2013), Lee Billings describes a time capsule that was sealed in July of 1963 near the Cabrillo Freeway in San Diego, though it has since been moved. Within it was a book that looked a century ahead, with contributions from politicians, astronauts, military figures and others about the world of the future. Copies of the book, titled 2063 A.D. are available, and within them one can find the musings of Nobel-laureate Harold Urey, who worried about our use of energy and noted that largely because of the need for electricity, US fossil fuel consumption had increased eightfold between 1900 and 1955.

Was the trend sustainable over the long haul? Urey doubted it, and he was hardly alone, for the need for energy seems to impose sharp limits on what a society can do. Billings notes the work of Tom Murphy (UC San Diego), who works with a long-term 2.3 percent increase in energy usage per year, yielding a factor-of-ten increase every century. Things happen quickly over time — by 2112 the world is consuming 120 terawatts, a number that rises to 1200 by 2212. Cover every bit of land with photovoltaic solar arrays and assume 20 percent efficiency and you can supply the world of 2287, which will need something on the order of 7,000 terawatts.

Building Toward Kardashev Type III


You can see where this is going, and Billings is expert at connecting the march of numbers with real events and the people who can explain them. First, here is what happens once we’ve got all that land covered with solar-power arrays:

From there, increasing the efficiency of the photovoltaics to a miraculous 100 percent and covering the oceans as well as the continents would allow the 2.3 percent annual growth in energy use to persist for another 125 years, taking our steadily growing civilization into A.D. 2412 before it outpaced the total amount of sunlight falling upon the Earth. Another energy source, nuclear fusion, could potentially sustain an annual 2.3 percent growth rate for some centuries beyond this, at least until the waste heat from the vast amount of power being produced evaporated the oceans and turned Earth’s crust to glowing slag. For a planet-bound civilization, the boiling point of water and the melting points of rock and metal place insurmountable limits upon the expansion of energy use.

A grim prospect, but perhaps an informative one. Talking to planet hunter Gregory Laughlin (UC-Santa Cruz), Billings brings up the search for extraterrestrial intelligence, a bit out of Laughlin’s wheelhouse considering that he spends most of his days teasing out the faint signatures of distant exoplanets, leaving SETI to those who specialize in it. Intriguingly, though, Laughlin tells him that if a SETI detection ever does come, it will likely be extragalactic.That, of course, is a mind-boggling thought, but it follows directly out of the energy constraints above.

After all, Freeman Dyson came up with ‘Dyson spheres’ in their various configurations as a way of solving the energy problem, at least for a time. A Dyson sphere or ‘shell’ operates through a cloud of energy collectors completely surrounding the parent star, perhaps constructed by dismantling entire planets. A galaxy in which Dyson sphere building on a massive scale was occurring would be an interesting one indeed, gradually dimming in the optical while infrared from the enclosing shells became more and more apparent. There have been, in fact, searches made to look for signatures like these, though so far to little effect. James Annis (FermiLab) has studied 137 galaxies looking for candidates for this kind of engineering, and we are on the cusp of further studies looking for what Andrei Kardashev once described as Type III civilizations.

A Dyson sphere, according to Billings, would capture about 400 billion petawatts of power, equalling the Sun’s output, but even here that 2.3 percent growth in energy use catches up with us. A single Dyson sphere can no longer meet its builders’ energy needs after a millennium at this rate, while within about 2500 years, we would be using the energy of an entire galaxy. Billings asks whether the fact that we don’t see stars or galaxies dimming into the infrared may not be telling us something profound about our own expectations of exponential growth. That ever increasing upturn in our charts of the future may, over time, be the result of a temporary historical anomaly.

Science and Character

Although I’ve focused on a specific question out of Five Billion Years of Solitude, it’s a deliberate attempt to get at the jewel-like complexity of the larger work. Open to a page at random and you will find the kind of issues we kick around here on Centauri Dreams under discussion by some of the top minds in the field. Moreover, Billings has a twin purpose. He’s out to illustrate the vistas being opened to us by our exoplanet explorations (and by astrophysics at large) while putting us in touch with many of the remarkable individuals who ply this trade, some of whom may be the first to identify a planet like our own around another star, and perhaps the first to find unmistakable signs of life in its atmosphere.

Thus we meet Frank Drake, whose Project Ozma launched the SETI effort and whose Drake Equation has helped us understand the factors involved in searching for life. Billings’ account of the small SETI conference convened at the Green Bank observatory in West Virginia in 1961 gives us the origins of the equation and its reception among an audience that included such stellar figures as Philip Morrison, Bernard Oliver, John Lilly, a young Carl Sagan and Harold Urey himself, whose Nobel had come from his discovery of deuterium. The Green Bank conference was all about whether SETI made sense, whether there was a serious possibility of detecting signals from an extraterrestrial civilization, and we’ve been parsing the problem ever since.

Billings is expert at finding the telling detail, which in Drake’s case may be his love of orchids (he maintains over 200 hanging in pots and strewn over tables in the greenhouses outside his Santa Cruz home). Even more striking, though, is the stump of a giant redwood that he used to explain growth over time to his children, counting tree rings that extended back 2000 years. What I love about Five Billion Years of Solitude is the way Billings can work with an object like this and its multi-millennial reach while then extracting the larger cosmological message. In the passage that follows, he moves with panache from Earth years to galactic time-frames:

Over the course of the tree’s 2,000-year existence, the Milky Way had fallen nearly five trillion miles closer to its nearest neighboring spiral galaxy, Andromeda, yet the distance between the two galaxies remained so great that a collision would not occur until perhaps 3 billion years in the future. In 2,000 years, the Sun had scarcely budged in its 250-million-year orbit about the galactic center, and, considering its life span of billions of years, hadn’t aged a day. Since their formation 4.6 billion years ago, our Sun and its planets have made perhaps eighteen galactic orbits— our solar system is eighteen “galactic years” old. When it was seventeen, redwood trees did not yet exist on Earth. When it was sixteen, simple organisms were taking their first tentative excursions from the sea to colonize the land. In fact, fossil evidence testified that for about fifteen of its eighteen galactic years, our planet had played host to little more than unicellular microbes and multicellular bacterial colonies, and was utterly devoid of anything so complicated as grass, trees, or animals, let alone beings capable of solving differential equations, building rockets, painting landscapes, writing symphonies, or feeling love.

This is fine stuff, and you will find passages to equal it throughout the book. Along the way, Billings speaks not only to Drake and Gregory Laughlin, but to Geoff Marcy, to Jim Kasting. He talks paleoclimatology with sedimentary geologist Mike Arthur (Pennsylvania State) and ponders space telescope breakthroughs with Matt Mountain, who directs the Space Telescope Science Institute. With Terrestrial Planet Finder in its confusing multiplicity of forms still on ice and starshade proposals for JWST still in the realm of theory rather than practice, Wesley Traub (JPL) explains the maddening frustrations of trying to design cutting-edge equipment. We may not see a true Terrestrial Planet Finder until the 2030s, but that doesn’t mean the effort stops. We still have missions like TESS (Transiting Exoplanet Survey Satellite) in the works.

Working with the Possible

Billings’ conversations with Sara Seager (MIT) offer a wonderful segue from crisis into opportunity. Seager began as a cosmologist but swiftly switched to working on exoplanets with Dimitar Sasselov at Harvard. Moving increasingly toward questions of astrobiology and how to characterize habitable planets, she has been a tireless conference organizer and advocate for exoplanetary studies at a time of budgetary crisis. Her “The Next 40 Years of Exoplanets” conference at MIT’s Media Lab in May of 2011 was in several respects a call to arms, and Billings was there to hear her exhortation: “So I convened all of you here, and that’s why we’re recording this, because we want to make an impact and we want to make that happen. We are on the verge of being those people, not individually but collectively, who will be remembered for starting the entire future of other Earth-like worlds. That’s why we’re here.”

I wasn’t at the MIT conference but did follow most of it via online streaming, and I still recall Geoff Marcy’s anger at the lack of progress that had been exemplified by the failure to follow through with Terrestrial Planet Finder, the interferometric version in particular. It was at this conference that Marcy called for an Alpha Centauri probe “even if it takes a few hundred years or a thousand years to get there.” Such a mission would, he believed, energize and engage young people and jolt a moribund NASA into new life, and it would draw amply on international resources.

But Seager’s announcement that she was going to be devoting a substantial part of her time to the commercial spaceflight industry surprised many in the audience. Seager has a get-the-job-done approach that focuses on solutions no matter how far afield they may take her. As depicted in Billings’ shrewd and graceful prose, she is a complex, driven scholar with a taste for outdoor adventure and a habit of endless invention. If NASA won’t build a TPF, why not build Seager’s ExoplanetSat, on the model of one tiny satellite with telescope and solar panels focusing in on a single star at a time. Fly them in their hundreds on the cheap. Get things done.

You get to know these people through Billings’ words, and he’s adept at capturing their voice for extended quotations, letting them have the lead in describing their own work. In addition to the character portraits that inevitably emerge, the book is studded with the tools and concepts of exoplanetology. It is a poignant and inspiring look at an emerging discipline that mixes the human triumphs and foibles of key scientists (watch them fight over who discovered what) with a scholarly rigor — someone just coming upon the exoplanet field will find everything from planet detection to spectroscopy, habitability, geology and climate laid out with precision. I am hard pressed to think of any book I have read so voraciously, and with such continuing admiration.


Comments on this entry are closed.

  • James D. Stilwell October 8, 2013, 11:08

    Jack Williamson’s 1948 novel, The Humanoids, speculates that biological life will become dated in a few centuries, and the need for endless amounts of energy for humanity will become pointless…static populations of bipedal metal humanoids with neuromorphic brains having IQs of 200 will occasionally take an intelligent human being as a pet…..for interesting conversation during the long hike to Andromeda….JDS

  • Lee Billings October 8, 2013, 11:44


    Thank you so much for this glowing and detailed review! I’m thrilled you liked the book, and I do hope that other Centauri Dreams readers will derive some enjoyment and edification from it, too.

    On a more personal note, I just want to acknowledge that you’ve played a formative role in making this book a reality, by being so generous with your encouragement and support across the years we’ve known each other. Thank you so much. Centauri Dreams, the book and the blog, remains a crucial resource, a nexus for everyone on Earth who dreams of reaching the stars. Any far-future remembrance of those who started “the entire future of other Earth-like worlds” will be incomplete without recognizing you and your important, focused work.

    Ad astra,


  • Paul Gilster October 8, 2013, 12:36

    Very kind of you, Lee. And what a pleasure to see Five Billion Years of Solitude racking up excellent reviews from publications all over. Will be very interested in where your next book heads. By the way, I reminisced a bit with Lou Friedman in Houston about that session we did up in Washington five or six years ago — he was there along with Greg Matloff, Ed Belbruno and Steven Squyres, and as I recall you had set it up through SEED Magazine. Anyway, it occurred to me that that was when our paths first crossed, right? So much has happened on the exoplanet scene since then…

  • Lee Billings October 8, 2013, 13:13

    Yeah, that’s the ticket, we first met at that event. I shake my head thinking about it — Steve Squyres broke the story about the Mars rovers discovering, IIRC, silica related to hot water springs, but for whatever reason further mentions of that finding didn’t seem to escape that small, not-too-crowded conference room. I remember, too, Greg standing up and saying anyone trying to defund and close Arecibo should be brought before the Hague to stand trial, because of the observatory’s vital role in monitoring Earth-threatening asteroids. It was a good time. Hard to believe it’s already more than half a decade in the past.

  • Marshall Eubanks October 8, 2013, 14:16

    What this is telling us is that advanced societies rapidly move out of run-away exponential growth, which is not surprising. One difference between 1960 and 2013 (Dyson’s paper and today) is that population growth in all of the technological societies on Earth has slowed or even stopped in the intervening time, and this has happened without mass starvation and (mostly) without draconian controls. Because of this, while I think space habitats are inevitable, I don’t see us converting the entire Solar System into a Dyson sphere any time soon. If we ever become a Kardashev Type II Civilization, it will be a distributed one.

  • Paul Gilster October 8, 2013, 16:16

    Lee Billings writes:

    I remember, too, Greg standing up and saying anyone trying to defund and close Arecibo should be brought before the Hague to stand trial, because of the observatory’s vital role in monitoring Earth-threatening asteroids.

    I can’t tell you how many times I’ve recycled Greg’s comments on that at various presentations I’ve made!

  • Antonio Tavani October 8, 2013, 17:06

    Il libro segnalato in questo articolo, mi sembra particolarmente interessante, e stimolante.
    L’Autore, sa se verrà pubblicato anche in lingua italiana, prossimamente?

    Un saluto, a voi tutti, da Antonio Tavani

    Via Google Translate:

    The book reported in this article, it seems to me particularly interesting, and challenging. Does the author know whether it will be also published in Italian, in the near future?

    Greetings to all of you, from Antonio Tavani

  • John H October 9, 2013, 7:42

    Downloaded the Kindle edition after reading this, looking forward to reading it.

  • Rev. Richard Prichard October 9, 2013, 15:03

    I’m surprised that there is not a DARPA-sponsored project to enable a Kardashev Type II civilization. When you have all that energy, you should be star-travel enabled.

  • Ken Wisian October 9, 2013, 16:01

    In the search for extra-terrestrial civilizations and in speculation on the future of mankind, there is an almost universal assumption that population (human or otherwise) will inexorably grow. Furthermore this growth, like compound interest gets very large over time, resulting in socio-economic pressure for more living space. Closely coupled with this is the energy needed for a growing civilization, well-expressed by the Kardashev Type I, II and III scale of civilizations. Some SETI strategies look for the signature of these large-scale energy uses. The Fermi paradox is also driven partially by the assumption of expansion (with population pressure driven expansion implicit?). All this inexorable growth line of thinking though rests on a confirmation sample of zero! Our one civilization data set shows strongly that if anything population decline is our future. Decreasing world population could seriously weaken the drive to expand in space. This is not to say that the desire to explore is strongly correlated with population pressure – curiosity appears to be root to human nature (intelligence in general?), but the population driven need to expand is not supported (expanding to avoid planetary or system catastrophe is another matter).

    For humans in our relatively brief existence there is a strong correlation between civilization “advancement” and decline in birth rates to below replacement values. Civilization advancement is a crude term that is used here to capture what used to be called the industrial revolution or westernization, but many countries today are bypassing those stages and entering the modern information age directly – anyone got a good term to use?. The specific causes for the decline in birth rates are not clear, though education and greater independence of women are most often cited. I am not versed in the research enough to go deeper into causes, but the empirical data is clear; that as countries become “advanced”, the birth rate plummets. The crucial question that there is no direct data on is: is this a human phenomenon (or even just a temporary human phenomenon) or is it characteristic of any civilization/intelligence?

    What is the point? In both SETI and in speculating about our own future, the alternative possibility of shrinking population (or at least slowly growing population) must be included. This in turn drives very different motivations and possible paths. Though Life appears to relentlessly push to fill any niche, this is not necessarily the case for intelligence. Is it possible that advanced civilizations simply die off slowly due to lack of reproduction? My guess is that this is not likely, but we should not discount the possibility. However, take away the “pressure” to explore/expand and rates of civilizations spreading through space could be decreased by orders of magnitude. In human history population pressure (e.g. Pacific islanders) or economic incentive (e.g. Columbus and other New World explorers) have been a majority driver of exploration and expansion.

    Slow or no growth does not eliminate the Fermi paradox, but it does alter the problem. In the area of SETI, well, you have to look for what you have the technology to find, but it lessens the impact of a negative result. It is conceivable that as technology improves and if all human population “advances” to the point of population decline, we could actually have less energy use (use per capita increase could offset population decline though). Perhaps the lack of population pressure could increase the relative importance a civilization would attach to robotic exploration – since individual life would presumably be more precious and the economic need for individuals to find additional space would be removed or lessened. Self-replicating robotic explorers could still cover the galaxy in short order, so that even with no population pressure you still end up with a “where are they” problem – none the less, in an area of inquiry such as this, where our data set is exactly one, assumptions must be examined closely.

    Please do not take these comments as implying that I lessen the need for exploration, SETI, or anything along these lines. I am as strident a supporter of pushing SETI and space exploration as anyone and I am looking for a way to more actively contribute, but I have found failure to question assumptions to be too common a flaw in planning.

  • Eniac October 9, 2013, 19:29

    Ken Wisian: Very solid reasoning, there. In my opinion, and as you at least allow for, it is definitely not population pressure that drives expansion. It does not matter if there is overpopulation or not, expansion happens either way. In any case, it would be unrealistic to expect sufficiently large numbers of people to leave the Earth quickly enough to make a dent in population size, even if such dent were desirable.

    In very general terms: whenever there is a boundary between life and no life, life will do all it can to penetrate and thereby shift the boundary. Life itself has done this over the eons, covering the Earth with many waves of more and more advanced forms. We, as intelligent beings, are the latest such wave, covering the Earth on a much shorter timescale than any of the lifeforms before us (bacteria, plants, trees, animals, etc). We now seem to get ready to be the first to penetrate the final boundary: off Earth.

  • Eniac October 9, 2013, 20:05

    About the early part of the original post: The concerns of Murphy and others about steady exponential growth of energy usage are about as profound (and funny) as the concerns expressed in the last century about the exponential increase in traffic was going to clog the streets with horse dung. These “dangerous trends” have a way of becoming irrelevant long before they become a problem.

    The whole Kardashev thing (at least level III) is invalidated once you consider that a coherent civilization on the galactic scale cannot even exist, due to communication delays. You cannot govern, control, fight, or trade over interstellar distances. The largest coherent human society imaginable is restricted to a single star system. Such a civilization does not have more than its own sun to work with, so that is where it has to stop. You could have a galaxy full of such civilizations, of course, but that is not the same thing as one “Kardashev type III civilization”, or is it?

  • Ross Andersen October 9, 2013, 22:47

    “Centauri Dreams, the book and the blog, remains a crucial resource, a nexus for everyone on Earth who dreams of reaching the stars. Any far-future remembrance of those who started ‘the entire future of other Earth-like worlds’ will be incomplete without recognizing you and your important, focused work.”

    Aint that the truth.

    Also, great review, Paul. And *great* book, Lee.

  • Andrew Palfreyman October 10, 2013, 2:32

    I really cannot buy the thesis that we sit around on this beautiful rock piling on the power consumption and cooking ourselves as a result. We will be out and about by then, exploring our system out to the gravitational foci, setting up an interstellar starway, and building space habitats and planet- and moon-side bases.

  • Astronist October 10, 2013, 7:18

    “Billings asks whether the fact that we don’t see stars or galaxies dimming into the infrared may not be telling us something profound about our own expectations of exponential growth.” — Did the fact that early Homo sapiens did not see australopithecene or even saurornithoidean cities covering the globe tell them anything about their own expectations of exponential growth?

    Stephen A.

  • Astronist October 10, 2013, 7:31

    Ken Wisian addresses an important point. But is he correct to claim: “as countries become “advanced”, the birth rate plummets”? In recent history, the period of greatest European progress — the nineteenth century — is correlated with unusually high increase of its population. Now population growth in the most highly developed countries has fallen to replacement level or below, but the rate of technological progress is also faltering, if one considers areas such as harnessing of controlled nuclear fusion or space colonisation.

    Ultimately this becomes, I think, an evolutionary question: species, civilisations and societies with high growth rates inevitably come to predominate over those with low or negative rates. We don’t yet know enough to predict whether humanity will continue to expand as it develops the means for Solar System colonisation, but we can say that species which do expand in space will come to dominate the Galaxy, while those that do not will fade away in a short period of time.

    We therefore need to argue for continued growth of human population, energy consumption and industrial infrastructure, contradicting the point of view of Tom Murphy and those like him who rule out space colonisation.

    Stephen A.

  • Alex Tolley October 10, 2013, 11:11

    @Astronist – species can only increase in numbers until they reach the population carrying capacity. The human species has done that on Earth, give or take some billions. Until the industrial revolution, humans existed in a Malthusian world, and we may well be close to that again.

    Unless some extremely cheap access to space is created, we can be sure that any colonization of the solar system will leave the vast majority of humanity on Earth. Those few that do go off and colonize, their populations can grow as fast as their support systems will allow, but it won’t be due to mass migration from Earth.

    In many respects, I think the O’Neill vision was the correct one, and the most doable approach for a Dyson sphere or swarm.. Build space habitats that can offer a huge expansion of living resources for our species to expand into. In the nearly 40 years since his vision was first published, I would guess that robotic construction will be the means to build the structures, rather than humans. It will also be where we evolve and test our von Neumann replicators to build such structures without getting out of control.

  • Astronist October 11, 2013, 11:43

    Alex Tolley, I agree with you. Obviously, the trick is to ramp down growth on Earth at the same time as ramping it up in space. So while the broad vision is that human numbers, geographical spread and industrial power needs to continue on the up and up for a millennium or more yet, the detail is that almost all of this will be happening off Earth. But those still living on Earth will still benefit by being part of the broader Solar System economy.

    Stephen A.

  • Alex Tolley October 13, 2013, 12:19

    @Astronist – it may be that very scenario – restrictions on reproduction on Earth, while having no restrictions in the colonies – acts as a driver for colony growth, both via emigration and internally. And yes, a growing economy in the solar system should be a rising tide that lifts all boats.

  • Sedjak October 14, 2013, 21:29

    With all this talk of exponential growth, the coming-some-time-in-the-next-century technological Singularity has to be addressed. Depending on how things unfold, we might drive resource usurpation to unforeseen levels perhaps by the automated building of many space elevators, O’Neill ships and off-Earth colonies, etc. Murphy’s 2.3 percent per annum may increase exponentially until war or collapse or our new overlords deem otherwise. There may even be waves where, first, the Earth’s resources are used up, then a long period of reckoning and collapse, and then a new wave gobbling up the rest of the solar system, more implosion, and so on.

    This pattern has happened in Detroit in a way. There was vital development in the core before too much industrialization, then a solid suburban ring developed. Moving forwards we had (have) ensueing decay in the core and later in the suburbs while the exurbs got most of the newest resources. Nowadays, though, there is a slow revitalization of the city core and the exurbs are feeling the pain of high gas prices.

    So after the Earth is wasted in the above model, there is no saying it couldn’t be re-Gaiaed during a reckoning period.

  • Eniac October 14, 2013, 22:46

    The human species has done that on Earth, give or take some billions.

    I don’t know. We have covered the Earth quickly, but we have left a lot of empty space in between our cities. I would not consider it out of the question that those “some billions” could be a trillion. Murphy’s solar energy calculation seems to allow it (at current per-capita energy consumption rates), for all that’s worth.

    Think, for example, about Asimov’s Trantor, or “A Torrent of Faces” by James Blish.

  • Alex Tolley October 15, 2013, 12:50

    I would not consider it out of the question that those “some billions” could be a trillion [people].

    You are talking about 100x the current earth population. Without radical changes in food production methods – factories of some sort – we do not have the land area to feed trillions. Then think about the 100x resource extraction to support the material welfare of that 100 fold larger population. We would probably need either massive substitutions of minerals, and/or well developed extra terrestrial resource extraction. Fresh water would be a critical resource, even if only to support the biomass of the population. The US has relatively low population density compared to Europe, or Japan. I don’t see 100x the density of the EU and JP being possible at all.

    What might such a world look like? Cities would cover the landscape, leaving small pockets of “parks”. The cities would be multi-kilometer high arcologies. Food production would be decoupled from the land, happening in factories/replicators. Energy production might be mostly solar (surface or orbital), with some sort of waste heat removal needed. CO2 outside factories might be very low to minimize the greenhouse effect. Most natural habitats, including the oceans would have disappeared. We might have enclosed habitats in the arcologies to preserve some ecosystems and maybe to experiment with worldship systems.

  • Eniac October 15, 2013, 23:25

    Alex: You make very good points.

    About living space, let’s see: One of the densest cities on Earth today is the borough of Manhattan, with about 27,000 heads per km^2 (it used to be even higher in the early 20th century). At the extreme, as on Asimov’s Trantor, that would allow for 4 trillion people on Earth to live like the inhabitants of Manhattan, most of whom are quite happy with their lot. Isaac Asimov himself was a die-hard Manhattanite who hated to travel anywhere else. If you “only” have 1 trillion, you can leave 75% green space between cities, in addition to one Central Park each. None of this seems a real deal breaker, space-wise, and we have not even touched the oceans.

    As for energy: If I follow the Murphy argument, after 100-fold growth you still only need to cover about 10% of the land area with photovoltaics, so take that from the 75% green space above. I don’t think at this stage there is any question of heat accumulation, that comes in a few orders of magnitude later. Besides, with solar energy that heat is not extra, it would come in from the sun whether we catch it with solar panels or not.

    You have covered food and resources well. We will have to be flexible about what to eat and make our stuff from. Industrial CO2 will not be as much of a problem if we are using solar energy instead of fossil fuels.

    Apparently, a single tree can produce enough oxygen to support 2 humans. Using 50 of the 65% green space for trees, we would need about 8000 trees per km^2, which comes to about 90 m between trees. Those same trees would, of course, also absorb the CO2 that we generate by breathing. They would even produce enough biomass to feed us all, although we should probably consider some other species of plant for this…

    Of course, there are many things left out, and tons of problems to solve. However, the general plausibility is there, I think. Enough to make the assertion that we have just now reached the limit feel shortsighted and small-minded, in the greater scheme of things.

  • Alex Tolley October 16, 2013, 10:17

    The Earth’s surface is not all like temperate, coastal, NE America. Large swathes like the Sahara desert, frozen Antarctica, will not support the “Manhattan” life style. I suppose you could ship in water and dome the areas to try to change that for deserts.

    Solar panels are effectively black, absorbing almost all sunlight. This is not the case for most of the Earth’s surface, so covering much of the Earth in solar panels will reduce the albedo and therefore heat balance. On balance I think we would be better off than burning fossil fuels though.

    I assume that the trees providing biomass would then be factory processed for food? That probably won’t provide enough protein. Better to use algal and fish farms which have much higher productivity and can produce the protein needed. I suspect that phosphorus will be the major constraint in this scenario. It will have to be very carefully recycled, and as we know we cannot do that 100% efficiently.

    However, the current “environmental services” that the Earth provides for free would be more than strained. You are effectively positing worldship population densities and recycling efficiencies.

    …tons of problems to solve…

    Yes indeed. As a California resident, I would prefer not to see my “Solaria” turned into a “Cave of Steel”, thanks.

  • ljk October 16, 2013, 12:08

    Review: Five Billion Years of Solitude

    The last two decades have seen an avalanche of extrasolar planet discoveries, raising hopes that the discovery of a true Earth-like exoplanet is around the corner.

    Jeff Foust reviews a book that offers an eloquent overview of the state of research and the possibility these discoveries will come to a halt just as we’re on the verge of ending our cosmic solitude.

    Monday, October 14, 2013


  • Eniac October 16, 2013, 20:59

    Alex: Of course, you are right that this is not likley a desirable scenario. Nor is it likely to happen, with population growth tapering off as it is. I am just saying, don’t rule it out. What will actually happen will probably seem even less plausible from our stuck-in-the-present point of view.

  • Holger October 17, 2013, 15:02

    Eniac: “I don’t think at this stage there is any question of heat accumulation, that comes in a few orders of magnitude later. ”

    Actually, it does matter at exactly this order of magnitude: Energy flux from waste heat is about 1% of the greenhouse effect due to fossil fuels. So at a 100-fold increase of energy consumption you have climate change as bad as the current one even with zero greenhouse gases! (Assuming nuclear power, or that any solar energy “recycling” effect is offset by the mentioned albedo decrease due to the solar panels. Otherwise it may be somewhat better or worse.)

    Compare Niven’s Puppeteer world of a trillion citizens, with the whole planet being warmed just by their own waste heat.

  • ljk October 17, 2013, 17:27

    Why the odds of spotting E.T. are so slim: It’s the economy

    Alan Boyle, Science Editor NBC News

    20 hours ago

    Hundreds of planets are being found beyond our solar system, including some that just might be habitable. But can we ever confirm signs of alien life beyond our solar system? It’s theoretically possible — but in a new book about exoplanetology, “Five Billion Years of Solitude,” science journalist Lee Billings suggests that the task may be beyond humanity’s financial capabilities.

    The good news is that this is shaping up to be a golden age of astronomy — thanks in part to the Hubble Space Telescope, the data from the Kepler planet-hunting telescope, the yet-to-be-launched James Webb Space Telescope and a host of next-generation ground-based telescopes that will be coming online. The prospects have never been better for finding Earth-size planets in Earth-type orbits around sunlike stars.

    However, it’s not enough to find those alien Earths. Those discoveries just open the way to a bigger question: Does life exist on those distant worlds?

    Full article here:


    To quote:

    “If I could gather the astronomical community in a room, I would implore them to consider the fact that the golden age of astronomy in which we all live has no guarantees of continuing,” Billings said. “It’s not going to be around forever, and it depends on the largesse of taxpayers and the politicians who pull the strings.”

    The way Billings sees it, finding and characterizing other Earths should be at the top of the priority list for space science — and although it’s possible to draw upon the generosity of billionaire philanthropists and crowdsourcing campaigns, it’s impossible to pursue the quest without NASA.

    “If we’re going to be dependent on the largesse of billionaires to answer these scientific questions, these existential questions — you gotta wonder, what the heck is NASA for? Now everyone is trying to find any way but NASA to do it,” Billings said. “We aren’t going to find alien Earths and life beyond the solar system through the fantasies of multibillion-dollar Kickstarter campaigns. That’s a non-starter.”

  • Eniac October 17, 2013, 23:06

    So at a 100-fold increase of energy consumption you have climate change as bad as the current one even with zero greenhouse gases!

    Enough, maybe, to make the arctic areas habitable? :-)

  • Holger October 26, 2013, 13:52

    “Enough, maybe, to make the arctic areas habitable? :-)”

    Possibly, but you might lose more areas due to sea level rise and overheated tropical regions. But I agree that it’s not a showstopper for your “trillion people” scenario; if you can re-engineer half the Earth, you can also cope with some climate change…

  • ljk October 28, 2013, 16:31

    After five billion years of solitude, Earth has become a lot less lonely in the last decade

    Friday, October 11, 2013

    During the last 10 or 15 years astronomers have completely rewritten our understanding of planets around other stars, finding that not only are planets common in our galaxy, but they’re everywhere, and there are lots of Earth-sized planets around. This increases the likelihood of life elsewhere in our universe, and eventually may give humans somewhere meaningful to travel to beyond our solar system.

    This month a new book telling the story of these remarkable discoveries, Five Billion Years of Solitude, was released. I had a chance to interview its author, science writer Lee Billings, about the scientists who made these discoveries.

    The interview, in full:


    To quote:

    So what is their sense of the galaxy, teeming with planets, that they discovered? I know there are many people you interviewed, but was there a common thread?

    Whatever their sense is, it’s bittersweet, and tinged with some sadness. I tried to summarize this in the book’s introduction when I wrote that “time and time again I felt I was witnessing the planet hunters reach for the stars just as the sky began to fall.” There was a common thread of smothered hopes, squandered promise, frozen dreams. Right now we are nearing the confirmation of the 1,000th planet known beyond our solar system. Right now, we already have a handful of exoplanets we can point to that are potentially habitable, potentially somewhat like our own life-bearing world. These are amazing achievements, and they have occurred almost in the blink of an eye in historical terms. And yet I and the researchers I talked to think we will soon come to an impasse where further progress in the search for life beyond the solar system will be slowed. These potentially habitable, potentially inhabited exoplanets are piling up by the dozens. They are barely even newsworthy anymore, because they are pouring out of the sky everywhere we care to look. But right now and for what may be decades to come, we will lack a robust capability to follow-up on these discoveries, to learn whether these promising, tantalizing distant worlds are actually habitable or even inhabited. On the threshold of epoch-making discoveries, the wave of rapid progress seems to have broken, and is now falling back. The major and significant investments in R&D required to deliver the light of other living worlds are presently not being made, and so the dream of finding life beyond the solar system seems to be deferred. That’s a tough thing to deal with when you’ve devoted your life to this search as so many of these researchers have.

    And I think this failure, if it can be called that, is perhaps diagnostic and representative of other great challenges we face as a society and culture in dealing with big problems and bold endeavors. That’s something that deeply informs the book.

    What about reaching out to philanthropy? Certainly we’re seeing that with the Thirty Meter Telescope and Giant Magellan Telescopes.

    Philanthropy can certainly help, but I don’t think it’s a panacea. It seems to me that most billionaires and mega-millionaires make their fortunes by making savvy, careful investments. There is very little capital return on investing in something like a big life-finding space telescope. It would basically be one of the world’s biggest vanity projects, if only the the super-wealthy like Warren Buffett and Bill Gates could be convinced to care. And I do believe that to properly conduct this search, to survey a representative sample of stars, you really do need to take this to space. The ground won’t do. I do hope I’m wrong about that, but I don’t think I am based on all that I’ve heard and learned over the past several years.

    One other thing to consider is that we do have a space agency that, at least on paper, is more than capable of doing this. If we have to just jettison that and rely purely on the beneficence of billionaires, I think you really have to question what the purpose of NASA is and whether or not it’s worth continuing, whether or not it’s really a good investment anymore. One more caveat to that… I truly love NASA. I am a diehard NASA fanboy, and I’m unapologetic about that. But I can still see that something is gravely wrong with NASA right now. People like to bash NASA, but the truth is that NASA is our space agency. It works for us. The fact that NASA is in such a terrible state is, I think, largely due to the American people’s extremely negligent stewardship.

  • ljk February 13, 2014, 11:51

    David Morrison of The SETI Institute has just published a memoir about Carl Sagan. It includes photographs of Sagan I have not seen before.

    The details and the biography may be found here:


    Morrison wrote an earlier biography of Sagan in 2007 that goes into even more detail on the man’s life and work here: