≡ Menu

Will Humans Ever Walk on Exoplanets?

Searching for biosignatures in exoplanet atmospheres is something we can look forward to in as little as a decade, judging from the progress now being made in planning future ground- and space-based telescopes. A key challenge is to catalog habitable zone planets upon which to practice our methods, and our tools for doing this are steadily evolving. Take ESPRESSO (Echelle Spectrograph for Rocky OxoPlanet and Stable Spectroscopic Observations), which can reduce a star’s movement to or away from us down to a minute 10 centimeters per second.

You can imagine what this means for radial velocity studies, which now routinely parse the to-and-fro of stellar motions as a way of detecting exoplanets. The smaller the gravitational effect we can detect, the sharper our observations, bringing much smaller planets in range. We move from hot Jupiters and Neptunes into the realm of Earth-mass worlds around stars like the Sun. Commissioned in 2017, ESPRESSO is installed at the European Southern Observatory’s Very Large Telescope in Chile, and exoplanet hunter Nuno Santos intends to put it to good use.

Image: The Echelle SPectrograph for Rocky Exoplanet and Stable Spectroscopic Observations (ESPRESSO) successfully made its first observations in November 2017. Installed on ESO’s Very Large Telescope (VLT) in Chile, ESPRESSO will search for exoplanets with unprecedented precision by looking at the minuscule changes in the properties of light coming from their host stars. This view shows the inside of one of the ESPRESSO front-ends where all the active components of the spectrograph are located. Credit: Giorgio Calderone, INAF Trieste.

I’m looking at a recent Bruce Dorminey article about Santos in Forbes, but before going deeper into ESPRESSO, I want to note the headline of the article: “‘Nonsense’ To Think Humans Will Ever Move to Nearby ExoEarth, Says Leading Planet Hunter.” This is what Santos (University of Porto, Portugal) believes, and it’s a sentiment that’s getting a fair bit of play around the Net. My first impulse was to agree with Santos, but then I realized how much is packed into that verb ‘move.’

If the idea is that we will never move humanity en masse to another star system (presumably because of some catastrophe on Earth), then I think Santos is exactly right. Try to imagine gigantic fleets of generation ships setting out to escape a dying Earth and the whole picture starts to pixelate. This reminds me a bit of a J.T. McIntosh novel called One in Three Hundred, which grew out of three novellas published in Fantasy and Science Fiction in 1953 and 1954. Their titles: “One in 300” (February 1953), “One in a Thousand” (January 1954), and “One Too Many” (September 54). You get the idea.

But I’d hate to think that an uncritical reading of Santos’ comment might fix in the public imagination the idea that research into interstellar travel is pointless. After all, when people from Europe began to explore the other side of the planet and settle in places like Australia and New Zealand, only a small percentage of the European population ever made the daunting journey. A few pioneers risk everything, then commerce gradually emerges amidst scientific follow-ups, and over time a new population, born and raised in the new territories appears. If we somehow solved the problem of getting humans to other stars, that pattern could conceivably reappear.

There are no guarantees that human interstellar travel will happen in the first place, but if it does, it will be because robotic probes have led the way — our AI Captain Cooks, if you will — while early attempts to colonize, if we were actually able to find a place where these could occur, would doubtless be the work of small groups with a variety of agendas. If the Earth they leave behind really did succumb to disaster, most of its population would die with it, another reason to keep this world healthy, study its systems and try to undo self-inflicted damage.

Recommended reading on this latter point is David Grinspoon’s Earth in Human Hands (Grand Central Publishing, 2016), which accepts a human future in space within the context of a healthy Earth and the moral choices that accompany action in the Anthropocene era, as Grinspoon would have it. But assuming human survival on a healthy Earth, my guess is that we’re going to find sending robotic probes with a reasonable travel time much harder than we’ve imagined. I do think that sometime within the next 100 years or so, we’ll accomplish it. Whether we get to humans aboard interstellar craft is dependent on so many contingencies that I can’t assign a probability to it. I hope we figure it out.

But back to ESPRESSO. Santos is a former grad student who worked under Michel Mayor (not bad to come up under the tutelage of a Nobel Prize winner!) He sees us building a catalog of potentially habitable planets from which we can choose the best candidates for biosignature analysis, presumably through space-based instruments and the coming generation of extremely large telescopes (ELTs). ESPRESSO, which can combine the light of all four of the VLT’s telescopes to achieve the light-collecting power of a 16-meter telescope, is a game-changer.

Low mass planets require stable instruments, but even the famed HARPS spectrograph (High Accuracy Radial velocity Planet Searcher) at the ESO La Silla 3.6m telescope can only get us down to a bit lower than 1 meter per second. ESPRESSO’s 10 centimeters per second takes us into the realm of detecting a habitable zone planet that allows radial velocity methods to keep contributing, along with transits and gravitational microlensing, to the biosignature target list.

Will humans someday walk on such worlds? The first goal will be to survive all the traps our increasingly complex technologies set for us. This is the L term in Frank Drake’s famous equation, measuring how long a technological society lasts. If we manage to get through this filter, robotic probes will take our sensors increasingly far from Earth. It will only be through the lessons learned from such craft, and the decisions we make about the value of human vs. artificial presence on worlds like these, that we will learn how to answer this question.


Comments on this entry are closed.

  • Antonio December 18, 2019, 10:40

    Why do you assume that the first interstellar travellers will leave Earth? I think it much more probable that they will be inhabitants of the outer Solar System.

    That, too, makes the current obsession with “habitable” (in the stupidly geocentric mainstream definition) worlds quite pointless.

    As for survival, I think the danger of extinction for humanity now is lower than ever.

    • JH December 18, 2019, 12:34

      Yes the danger of extinction for humanity is very low. However the probability civilizational decline or a Malthusian population loss is desturbing high in the next 100 years or so.

      • Antonio December 18, 2019, 15:01

        Nope, it’s disturbing low. Indeed, we have just the opposite problem. For a long time now, we are facing an underpopulation problem. And, since it’s tied to human progress (industrialization, advances in medicine, access of women to jobs and education, universal education, etc.) it will stay with us.


        • alexandertolley@gmail.com December 18, 2019, 18:06

          You and JH are talking at cross purposes. We have had many civilizational declines but no extinctions. I doubt humans can go extinct, but we could very easily lose our technological civilization permanently, forcing a much smaller global population to live in cinditions that persistem for most of history prior to teh industrial revolution.

          Technology is increasing so fast and declining in cots so that individuals have teh power to do immense damage. That increases teh odds of a major collapse.

          We do not have an underpopulation problem. Fertility has little to do with this for the next few generations. Even if it became a “Children of Men” scenario with zero births, the population would remain relatively high for the rest of the century. The impact of trying to raise standards of living to western standards for the global population would mean vastly more food and consumer goods production than we have today.
          As we cannot go anywhere else, the strains on this planet continue to grow. Just look out your window and have a look.

          • allan levine December 20, 2019, 15:37

            we have had a ‘nearly extinct’, situation on Easter Island. Interesting scenario on many different levels.

        • Enzo December 18, 2019, 19:40

          I wonder what happens when the population grows faster than pro-capita wealth that is supposed to stabilize it. Like in Africa:

          Only a few years ago it was thought that world population would stabilize at 9B, now it looks like 11+ B.
          Is this a problem for global human extinction? Possibly not. Does it mean lower quality of life, personal freedom restrictions and a lot of misery in multiple places ? Absolutely.
          Not to mention flora and fauna if you care for those sort of things.

          • Charley December 19, 2019, 20:17

            Absolutely no surprise there; does anyone actually really believe that the human population is going to stabilize at 11 B ? With increasing consumption and the ability to prevent death at birth, I think were going to go pretty far north of just eleven billion.

        • Gary Wilson December 20, 2019, 16:38

          With all due respect to think we are not approaching a massive population die back requires ignoring a massive amount of accumulated data about: climate change caused by humans which in turn leads to global warming, reduced arable land due to desertification, acidification of the oceans leading to crashes in fish populations, loss of vital coastal areas with huge human populations, increasing numbers of refugee crises, and on and on. This information has been provided by tens of thousands of scientists over several decades. It will be ignored at our own peril. We have very little time left to change direction. Unfortunately many people have been raised with massive amounts of propaganda in many countries. They are not aware of the facts. Some wish to both deny them and put out false narratives. Look at the evidence objectively, without reference to nationality or political beliefs. It’s absolutely essential. Everyone should inform themselves as thoroughly as possible.

          • Antonio December 21, 2019, 11:45

            With all due respect, it’s you who ignores even the most basic data.

            • Gary Wilson December 21, 2019, 16:07

              Can you help me understand what you are saying Antonio? What data am I ignoring? You would need to point out specific papers in peer reviewed journals such as Science, Nature, PNAS, etc. I can help you with many summary articles of our current understanding of climate change and its causes if you are truly interested in learning the facts. I am very interested in learning what you are talking about so please send me some reference material to read. Best wishes.

            • Chris January 6, 2020, 19:06

              Link? You seem to have an argument that you’re basing these statements on, but without a little more than bold proclamations, I’m not convinced. Don’t be coy. Show us what you’re talking about.

        • Andrei January 2, 2020, 18:48

          Underpopulation? No that’s certainly not the case – unless you live in ‘alt reality’.
          Though most of the population growth currently happen in Asia, China and India are pushing hard to avoid society collapse – even a basic commodity like drinking water in short supply
          Some advocate the idea the western world is stagnant – that is false. Some good charts on this page:
          Despite the claim that the western world is in decline we can see that USA have a growing population and only Belgium and Sweden show a sensible population growth in another table.
          Else and IMO I’d say that JH probably is correct, we face serious problems but Homo sapiens as a species is unlikely to be at risk, our current society and civilisation is in dire straits.

    • Norm Davison December 18, 2019, 16:37

      I think the usual optimism re extinction is misplaced. Species often go extinct when they are hyperspecialized, and then conditions change. We are extremely dependent on our technology. Seriously perturb that and we are in real trouble, perhas not complete extinction, but quite possibly collapse of our current civilization. And there is no coming back if we fail just once because all the readily available high density energy sources are gone. We really need to look after this planet, and we’re not doing it. It is actually quite easy to identify perturbations that could take down our civilization.

      • Antonio December 18, 2019, 17:27

        Being dependent on technology is not the same as being specialized.

        It’s quite the opposite. We can live now in more diverse environments than ever before.

        “Seriously perturb that and we are in real trouble”

        On the contrary, a more industrialized society, with more advanced technology, is more difficult to perturb, and it’s technology/industrial/agricultural network is more difficult to perturb than a more primitive one.

        “readily available high density energy sources are gone”

        That’s simply plain false.

        “It is actually quite easy to identify perturbations that could take down our civilization.”

        For example? For any existential treat I can imagine, we are much better off now than ever. Asteroid impact? We know more NEOs than ever. A crop plague? People only 20 years ago would be amazed by our biotechnology. Wars? We never had so less war deaths than now, porcentually. Loss of knowledge? Even in the poorest country in the world, you can find a university were you can read the Theory of General Relativity, Aristotle complete works, a medicine book, a manual of electronic design, a political science collection or a modern engineering treatise:


    • Al Jackson December 19, 2019, 7:52

      I too think the solar system will have to colonized before humankind leaves it. This is a theme that ran throughout modern prose science fiction, especially as it matured under John Campbell in Astounding in the 1940s. The most prominent proponent of this, or at least the best known, is Robert Heinlein, his Future History is structured this way. My sense of things it is going to take longer than the standard 200 years, which has been a benchmark in prose SF for a long time.

      The recent Expanse novels by James S. A. Corey have been exploring this in detail in recent times. I have only skimmed over a few of these books … they are the synthesis of a vast number of ideas about colonization of the Solar System in prose SF , lord the number of authors is almost too many to mention… I mean Heinlein, Asimov and Clarke explored this back in the 1940s and 1950s.

      The TV show made from The Expanse novels is just down right jaw dropping. I mean this is the ‘future history’ of the solar system we SF readers know so well. The great domesticated space suit story is in it, with its verisimilitude. The show even pays attention to the factual universe! Zero g is a character on the show! I have never seen this dirt-under-the-finger-nails space opera ever done before on TV.
      There is a stepping off point into interstellar travel by season 4… tho it comes about by way of a Clarke-style-Big-Thinks XT civilization., almost Kardashev III.
      The essence of this show will be very familiar to the SF readers.

      Did anyone see this? Yesterday in the NY Times?


      Nobel Laureate Paul Krugman is a long time science fiction reader.

      • Antonio December 19, 2019, 16:09

        Heh, interesting article. I haven’t seen season 4 yet, tough.

        The series has some errors (Mars is not so water poor that it needs to import water from the belt, so one of the conflicts in the plot is highly improbable) but it’s a great series nevertheless and I love it.

        • Rick Collins December 25, 2019, 2:11

          Great series, superb storyline, and outstanding characters! Of course, technology from a long-dead (massacred) civilization “solves” the intractable problem of viable (if unrealistic solution) human interstellar space travel .

    • ict December 19, 2019, 15:38

      I believe that’s a reasonable perspective, but at the same time, I also see Earth as a hotbed of activity and growth for centuries to come even if we build a thriving interplanetary civilization. There’s just no other place like home to offer the impetus for us to uproot ourselves and leave everything behind in such ambitious and risky ways.

  • Robert December 18, 2019, 14:00

    Maybe if will discover that Pluto originated as an exoplanet.

    • Antonio December 18, 2019, 15:04

      Dwarf exoplanet ;)

      BTW, exoplanet hunter CHEOPS was launched today.

  • ljk December 18, 2019, 14:03

    Their proxies will.

  • Alex Tolley December 18, 2019, 14:51

    Really good essay. However, the idea that humans 1.0 will ever really colonize an exoplanet as English people colonized Australia is unlikely IMO. This is not because of the difficulties of interstellar travel, but rather the problem of biology.

    Exoplanets in teh HZ will either be sterile or already living. If sterile, the atmosphere will be unbreathable and the planet will need to be terraformed. This is a non-trivial task. Robotic seed ships can start the process, and industrial level machines can aid this, but to build up terrestrial ecosystems in biomes to manufacture a biosphere that is at least Earthlike is not something that can be done quickly with transplantation. It is the work of many, many generations of humans, living in “domes” to slowly build such a world. This is a huge task even if we had vast interstellar ships that could travel at FTL velocities. If you can build domes, then why not stick to O’Neills instead and leave the planet sterile, or start terraforming knowing that even a near-perfect planet will take thousands of years at a minimum to terraform?

    OTOH, suppose the planet is a classic, lush, fertile world. While the Botany Bay penal colony relied on food shipped from England, they could eventually start to eat the local fauna and farm. That may not be possible in such a world. If the amino acids are an overlapping set with ours or have the opposite chirality, the colonists would starve to death trying to live off the land. They could try farming with Earth crops, but those crops might only survive by being planted on freshly sterilized soil or isolated in their own environments. To colonize the whole planet might require a slow process of terraforming. Then we are back to a preference for space colonies instead, but with the moral dilemma of destroying a living world first.

    One way out of the second scenario is for the colonists to engineer their offspring to have a biology to match the local biosphere. In that sense, humans 1.0 will never colonize an exoplanet, but humans 1.x may.

    When one considers the difficulties of biology, the obvious solution is for non-biological colonizers. Robots, with or without human minds are the likely way forward. Think of Robert Sawyers “Mindscan” where the final solution was for the artificial embodied human minds to live on Mars. IMO, the more likely model is the artificial boy David, in “A. I. Artificial Intelligence”. He has the human qualities of a real human, yet is artificial and can live on either a sterile or living world. All he needs is a power source. An industrial base will need to be built to construct his ilk as well as repair them. The reproduction rate could be extremely fast and conceivably each individual could start with a developed mind to build upon. Unlike humans, such artificial beings can take as long as they need to cross between the stars, using whatever propulsion technology is available and optimized for conditions. No need to try to create a starship technology for human biology.

    Colonization may well avoid planets altogether. For artificial humans, space colonies can be huge, open structures with no artificial g except where needed locally for some processes. Far easier to build than human space colonies. They can slow boat their way to the stars too, going dormant like Rama between the stars. This solves the energy and recycling issue of biological world ships.

    Unless we hit a technological roadblock, it seems to me this is the more likely scenario for “humans” to colonize the galaxy.

    • Paul Gilster December 18, 2019, 15:26

      Alex, re your statement:

      “…the idea that humans 1.0 will ever really colonize an exoplanet as English people colonized Australia is unlikely IMO. This is not because of the difficulties of interstellar travel, but rather the problem of biology.”

      Yes, I’m in complete agreement with this. Another layer of complication onto getting humans colonizing an exoplanet beyond the sheer magnitude of getting them there in the first place!

    • Antonio December 18, 2019, 16:22

      Humans don’t need a complete terrestrial ecosystem (let alone a completely terraformed planet) to survive. See for example any current Mars colonization plan. You only need some fertile soil, some water, CO2 to make plastics for greenhouses and voila. Terraformation can come later. If we, 21st century humans, can do it, certainly it will be a piece of cake for a colony that has travelled light years to another star system.

      Why not stick to O’Neill colonies? Because their population can’t be expanded without the resources of celestial bodies, be it planets or other minor bodies. And, if you plan to use the resources of a planet anyway, it’s usually much easier to build your habitat on it than to build it from scratch in the middle of empty space and live there, with no resources at all.

      And it’s totally non-sense to compare domes with O’Neill colonies. They play in totally different leagues. It’s like comparing to build a city in the coast and to build it as a ship for living in the open sea, without supplies from coast cities.

      • Alex Tolley December 18, 2019, 17:55

        Humans don’t need a complete terrestrial ecosystem (let alone a completely terraformed planet) to survive.

        We don’t know that. No human has been kept alive much beyond 1 year isolated from Earth. No new generations have been born off Earth. All plans for Mars colonies assume that the inhabitants can survive in a simplified ecosystem, like those shrimp and algae glass globe baubles. Maybe we can, maybe we cannot. But even if we can, we still need to terraform the planet unless you want those enclosed environments to expand across the planet.

        Why not stick to O’Neill colonies?
        It has been shown that in our solar system, just using asteroidal material we can construct orders of more surface to live on than Earth has available. Make them big enough and they offer a vast variety of environments and polities. Planets would always remain a lesser space to live. Furthermore, O’Neills offer the same physical conditions as earth – gravity, air mixture, radiation, etc, etc. Most planets in teh HZ will not offer that. In our solar system, only Venus is close for gravity, and no planet satisfies all conditions without a huge amount of engineering modifications.

        And it’s totally non-sense to compare domes with O’Neill colonies.

        Let’s just leave it that both “domes” and O’Neills have largely enclosed environmental systems. A “dome” conceptually is just an O’Neill on a planetary surface.

      • Robert December 19, 2019, 13:21

        The relevant distance from an O’Neill colony is not physical separation but energy. The energy cost to get material from the Moon or asteroid belt is low. Space colonies allow independent control of variables such as gravity which living on other planets of smaller bodies do not.

    • Ronald December 19, 2019, 9:53

      “This is not because of the difficulties of interstellar travel, but rather the problem of biology.”
      Agreed entirely, but for a different reason than you elaborate upon (the exoplanet itself): I think the greatest challenge *by far* for human exoplanet colonization would not be in the target planet, but in the journey. Reasonably assuming subluminal speed (say 10% of c), reaching an exoplanet 10 – 30 ly away would take something like 1 – 3 centuries. Keeping humans in a state of suspended animation and healthy for this period would be an enormous challenge and risk.

      “When one considers the difficulties of biology, the obvious solution is for non-biological colonizers”.
      Obviously, but not necessarily: another way I can envisage human exoplanet colonization is by using the most compact possible version of human beings: egg cells and sperm cells (or zygotes, fertilized egg cells). Everything human and potentially human is in there in its most reduced form. Ok, some extreme futurists might argue to use even pure genetic codes, however, I think that is too reductionist: ultimately you will need to assemble that code into a complete package, and the egg cell *is* the most complete, well-proven, and ready-to-use miniature-factory for the production of a human being, or almost any (higher) being for that matter. So, why not use that.

      Advantages of sending egg/sperm cells are, beside of course the enormously reduced space requirements: relative ease of preservation and suspended animation (even freezing), selection of best individuals on arrival, control of the (timing of) incubation/release of organisms (i.e. after the planet has been assessed and/or made suitable), and even the possibility of genetic adaptation where needed.

      So, I think that colonization and ‘terra-seeding’ (my term!), possibly after terra-forming, would likely take place using egg and sperm cells, or zygotes.

      I think, the challenge of incubating and raising the various species’ embryo’s after arrival on the planet would be a small one compared with sending mature individuals.

      No coincidence that even the international Doomsday Vault in Norway (https://en.wikipedia.org/wiki/Svalbard_Global_Seed_Vault) is a seed vault, not a zoo or a botanical garden.

  • Robin Datta December 18, 2019, 16:02

    Substantially subluminal velocities, such as around 0.20c will make for interstellar travel times approaching or exceeding a human lifetime. Even with the nearest star the round trip time would be around forty years. A biologic solution to the aging phenomenon, or effective techniques for suspended animation may span those stretches of time.

    Otherwise, if humans walk on extrasolar planets, they may report it back to Earth over communications channels. But with the exception of the very nearest extrasolar planets, it would have to be their descendants (born elsewhere) that carry the narrative back to Earth.

    Resource depletion is considered by some to be a valid concern. So is environmental degradation, pollution and depredation.

  • Paul Oechsli December 18, 2019, 17:30

    If humans are successful in navigating the impact of climate change, mega species extinction event that will adversely impact the ecosystem and global food chains, it will require a tremendous “investment” and reallocation of finite Earthly resources towards sustainability. Economic and consumption sacrifices will have to be made in a SIGNIFICANT way. This may likely crowd out/eliminate the “investment” necessary to develop interstellar travel. Solving the clear and present problem of converting the world to something much closer to a “sustainment economy” will be difficult but in my view a prerequisite in investing in multi-generational technology that will take centuries to start to possibly see a “payback”.

    • JH December 18, 2019, 20:55

      While many people point out the need for a “sustainment economy” that doesn’t depend on constant growth, I’ve never seen any realistic ideas on how to achieve this. Population control would be mandatory to make such an economy work. But even with the power of a communist dictatorship, the Chinese one child policy is considered by most to be a failure. Robert Heinlein once pointed out that homo sapiens is a very cantankerous species. Rebellion against authority (and central planning) has been going on since the dawn of history. Although wars and violence have generally declined in the last few centuries, we are still far from where we need to be to face the growing problems we face.

      • Alex Tolley December 18, 2019, 22:11

        And yet without coercion, some countries in Europe, and Japan have below-replacement birth rates. For most of history, there have been long periods of “sustainable” economies, with populations held in check by Malthusian mechanisms, disease, and war. The problem we have now is that global inequality means that we might suppress economic growth in poor countries. I consider that immoral.

        No amount of solar system colonization is going to alleviate this condition. Even if a Heinleinian “Tunnel in the Sky” teleport device was available, the vast majority of people on Earth would not move. Britons didn’t depopulate the UK when the free passage to Australia was available, despite the opportunities, and the poor living conditions of many at home.

        The way we are headed, dystopia seems likely. Maybe Malthus will have the last laugh before we can create a livable and sustainable world not just for humans, but all its inhabitants.

        • Antonio December 19, 2019, 16:15

          If it only were a problem of “some countries in Europe and Japan”… It’s a global phenomenom. For example, Iran, China and Thailand are well below replacement rate. They have 1.69, 1.62 and 1.50 children per woman, respectively.

          • Alex Tolley December 19, 2019, 17:54


            Global population is still increasing. Therefore, almost by definition the fertility rate must be higher than replacement. Obviously increased mortality rate can offset this. Global heating causing crop failures, starvation, and violence will offset some of the growth.

            Global population growth

            Fertility rates by country. Global fertility rates are still above replacement rates. China had a high fertility rate, but the one-child policy resulted in a huge sex imbalance, resulting in a [temporary?] steep decline in fertility rate.
            Iran, of course, is under global sanctions, which is impoverishing its citizens. Is anyone surprised that this impacts having children?

            List of sovereign states and dependencies by total fertility rate

            Earth is not underpopulated, nor is it currently facing a population decline at the moment. A rising mortality rate might start reducing absolute population, although we should be horrified if that becomes the means to stabilize or reduce the global population. Educating women is the by far the best policy to reduce the birth rate, as it is non-coercive and improves lives.

            • Antonio December 20, 2019, 2:56

              “Therefore, almost by definition the fertility rate must be higher than replacement.”

              Replacement rate in 2015 was 2.3. Total fertility rate was 2.49, and it has been decreasing every single year since 1964 (from 5.04).

              “Global heating causing crop failures, starvation, and violence will offset some of the growth.”

              Global heating favours crops: it extends the growing season (it has been doing so for quite some years now). And 75% of people in the world die from aging. In the developed countries, it’s more than 90%, and the rest of the world is catching very fast. Starvation and violence deaths are very very low.

              “China had a high fertility rate, but the one-child policy resulted in a huge sex imbalance, resulting in a [temporary?] steep decline in fertility rate.”

              WRONG. China passed from 6 children per woman to 3 children per woman in only 11 years (1967-1978) BEFORE the one-child policy (that was implemented from 1978 to 1980).

              “Iran, of course, is under global sanctions, which is impoverishing its citizens.. Is anyone surprised that this impacts having children?”

              WRONG. The descent in fertility rates is much older. For example, it passed from 6 children per woman to 3 children per woman from 1986 to 1996 (faster than China, BTW).

              “Earth is not underpopulated, nor is it currently facing a population decline at the moment.”

              We probably are at replacement rate just now, according to the trends, but we will not know for sure until 2020 or 2021, since global statistics are usually published every 5 years.

              Please educate yourself before talking about a topic you don’t know.

              • Alex Tolley December 21, 2019, 11:57

                Without CO2 fertilization, effective adaptation, and genetic improvement, each degree-Celsius increase in global mean temperature would, on average, reduce global yields of wheat by 6.0%, rice by 3.2%, maize by 7.4%, and soybean by 3.1%.

                Source: Temperature increase reduces global yields of major crops in four independent estimates

              • Gary Wilson December 21, 2019, 16:16

                Again with respect you need to provide peer reviewed articles from established journals to support your position Antonio. I think your point of view would be greatly strengthened with respect to our fellow readers if you do this. Unsupported opinions don’t really count for much in the scientific world. Have you had a paper reviewed for publication in a journal? I and many others on here have. If so you would know what it takes to produce accurate information supported by the scientific literature. This is a crucial point when trying to make arguments about whether or not human caused climate change exists and is threatening our survival as a civilization.

        • JH December 20, 2019, 21:26

          Well I should have clarified that I have yet to hear of any practical ideas for a no growth, sustainable economy EXCEPT for primitive tribes where life tends to be nasty, brutal, and short.

  • Geoffrey Hillend December 18, 2019, 18:15

    One does not have to colonize a planet to land on it. I think we will eventually land on an exoplanet, but I am biased against world ships since I don’t think anyone will want to sacrifice their whole life to be on one. We have not even learned to take care of this world and we will have to because we can’t leave it anytime soon. Surviving anywhere else in our solar system including interstellar space is a lot harder than living on Earth.

    If we invent FTL propulsion technology, landing on an exoplanet will be a piece of cake, but so will making robot shuttle craft or probes to do the remote sensing which could use cameras, specrometers, laser spectrometers, high definition radar, infra red night vision, etc. Man would never have to land. These probes could collect samples etc. They could have many fail safes like complete automation, manual control, and radar map topography and emergency back up circuits. They could examine hostile environments.

    Remote sensing probes might be necessary because we would not want to contaminate another world with life with our bacteria, viruses, etc because a world early in it’s evolution could be endangered by a virus which was much more advanced and evolved. Consequently, a high energy ultra violet sterilization cargo bay for the probes and it’s robot arms would be necessary. I don’t think we would have to worry that much about being contaminated from ET bacteria since by then we would have a knowledge of microbiology and DNA built up over half a million years, but sterilization procedures would still be used. A man with a sterilized space suit might not contaminate an exoplanet and it could be used for human’s to walk on the surface of an exoplanet, but we would not have to land people on an exoplanet with remote sensing probes. I predict this is a potential once we have FTL.

    • Alex Tolley December 18, 2019, 21:32

      I’m not clear what your position is here. It seems as if you are saying that robots can do everything without people even going to these worlds, let alone settling them.

      If so, then I think tourism is possible assuming very easy travel to such worlds and world ships unpleasant. But if it needs slow travel to reach such worlds and if that travel is expensive and habitats unacceptable then I would imagine people would try to colonize.

      As we saw with the recent loss of life on White Island, tourists will set foot in dangerous places. However, when travel is hard, as it was throughout human history, then travelers will colonize even what looks like inhospitable territory.

      I don’t think we can assume either FTL travel or FTL communication. I think robots will be vaster cheaper than humans, just as they are when exploring the solar system. This suggests to me that robots will be the explorers, assuming we can afford such explorers on an interstellar scale.

  • P December 18, 2019, 19:32

    I find it indicative that the good readers and responders to this site – some of the sanest and most civil Ive come across in a cyberspace that increasingly resembles a cesspit – cant agree on some prima facie ideas.

    Are humans irreversibly harming the planet? Is human technological civilisation – a necessity for space travel – sustainable? Will humans really live, work, breed and die in space? Will they ever leave the solar system? How are these connected?

    I note that Kim Stanley Robinson, one of my favourite authors, has been RIDICULOUSLY villified by some in the ‘hard’ SF community for daring to suggest that humans will probably never leave the solar system and that perhaps our efforts might be better spent fixing our home planet first. He’s been called all sorts of very silly things for suggesting that a future solar system as amazing as the one depicted in ‘2312’ and especially for the doomed interstellar flight in ‘Aurora’, is at best ‘defeatist’, or silliest of all, ‘communist’! Peoples fantasies are one thing, but fantasies have a habit of leaping over the everyday – thats fine until in your reverie you forget to notice youre about to get hit by a bus.

    Fires are burning in my country as I type this. Temperature records are not being broken, they are being smashed. Old growth forests are being destroyed on an epic scale. People are choking in capital cities. My dreams of space float away like ashes. Heres to a sane and safe 2020.


    • Antonio December 19, 2019, 2:29

      We can’t agree on basic ideas because some people refuse to accept basic facts, like demographic data. They prefer the Malthusian hysteria promoted by the media and some organizations.

      Same for the ecohysteria. Yes, climate change is a fact and we are causing it, but we aren’t facing the climate apocalipsys the politicians and the media scream about. We have better food supply than ever, we live longer than ever, we don’t have specially extreme wheather, etc. This is clearly shown by the statistical data to anybody that wants to read them.

      • Alex Tolley December 19, 2019, 11:15

        “If you can keep a calm head while everyone else is running around like headless chickens then …… you don’t understand the problem”
        – well known joke in management.

      • Gary Wilson December 26, 2019, 16:00

        There is no ecohysteria at all Antonio. Again, read the scientific literature to get a clear idea of what is going on. That means peer reviewed journals. We are in a climate crisis. Thousands of accredited climate scientists say so. With respect, many in the U.S. live in a sort of bubble of misinformation provided by the current administration, social media, and so-called news outlets such as Fox news. They perpetuate lies and myths. Accurate information is absolutely essential in understanding what is actually happening. Good luck in learning this. Take some courses at an accredited college or university in science and you will be far better informed. We here in Canada have a similar and growing problem of misinformation thanks to social media and “leakage” of misinformation from the US. We are in an information crisis as well as a climate crisis and certain leaders are taking advantage of this thanks to there own ignorance and delusional thinking.

    • Gary Wilson December 26, 2019, 16:39

      I totally agree with you about the work of Kim Stanley Robinson P. He is an absolutely brilliant visionary. His novels are, I believe, very prescient and timely. His In The Capital trilogy is particularly powerful for me as it describes the near climate future so well. The details are fiction of course, but the general trends have been repeatedly predicted by experts. I also believe humans are unlikely to successfully inhabit worlds in different star systems. Robotic exploration is the obvious route that will be taken for hundreds of years to come if we can successfully prevent climate catastrophe. And thanks to Paul we have a site where we can discuss many issues in a frank but respectful manner.
      It will be absolutely essential that informed electorates show their power and elect responsible, educated and law-abiding leaders who can organize our response to climate change. My own country has a man who clearly is in the thrall of the petroleum industry, despite his claims to the contrary. Reading Rachel Maddow’s new book Blowout: Corrupted Democracy, Rogue State Russia, and the Richest, Most Destructive Industry on Earth will help people understand what we are up against.

  • Michael C Fidler December 19, 2019, 0:13

    I was born in Santa Anna California and grew up for my first 5 years visiting Disneyland and seeing tommorow land. A disabled veteran had one the first color TV’s and the tube was round, this was in 1959. Man has a strong curiosity and when he wants to accomplish something he can. We are talking about a future that is still being looked at in it’s infancy. How many countries are now going into space? Back in 1959 the US and the USSR were it and the whole idea was about beating each other in technology. We have faced many challenges in the last 300,000 years and have been on the edge of extinction for most of it. The moon and Mars will be colonized in the next 50 years and even if Earth has a major ecological collapse humans will survive. I just think of the astronomer that said humans can not reach the moon and that it was physicly inpossiable in the early part of the 1900’s.

    • Alex Tolley December 19, 2019, 11:33

      The moon and Mars will be colonized in the next 50 years and even if Earth has a major ecological collapse humans will survive.

      Lunar and Martian colonists will not be able to survive if an ecological collapse reduces the Earth’s population such that is no longer can or will resupply those colonies with essential manufactures. This isn’t like American colonists joining the indigenous population, or a similar result by the remaining Vikings in Greenland. These colonists have nowhere to go. Colonists in the industrial era – e.g. the Americas, Australia, relied on manufactures from Europe. It took a long time just to be able to manufacture industrial goods locally. Lunar and Martian colonists are going to need imported hi-tech manufactures just to stay alive in their cities. An exercise is to consider the minimum population size to maintain a certain level of technological civilization. Probably many millions.

      Ecological collapse on Earth is going to make the mass starvations we experienced in the 20th century look like gentle warmup episodes.

      • Michael C Fidler December 19, 2019, 19:07

        Alex you have to be kidding, man has survived on this planet for hundred of thousands of years with no modern technology. A three D printer can be used to manufacture anything they need on any planet. Mars and the moon have enough iron nickel lying around on the surface to make spacecraft parts. You can grow crops via hydroponics and magenta grow lights with very lttle energy. Even producing water and oxygen on the moon from dirt and a solar furnace is feasible. Man’s ingenuity to survive is much greater then you think or are you still sitting around the campfire in your cozy cave.

        • Michael C Fidler December 20, 2019, 4:54

          Case in point!

          Solving the Challenges of Long Duration Space Flight with 3D Printing.


          • Robin Datta December 20, 2019, 22:06

            The proof of the pudding will be in the eating.

          • Michael C Fidler December 22, 2019, 19:37

            New technique increases 3-D printing speed by 1,000 to 10,000 times.

            “Ultraprecise 3-D printing technology is a key enabler for manufacturing precision biomedical and photonic devices. However, the existing printing technology is limited by its low efficiency and high cost. Professor Shih-Chi Chen and his team from the Department of Mechanical and Automation Engineering, The Chinese University of Hong Kong (CUHK), collaborated with the Lawrence Livermore National Laboratory to develop the Femtosecond Projection Two-photon Lithography (FP-TPL) printing technology.

            By controlling the laser spectrum via temporal focusing, the laser 3-D printing process is performed in a parallel layer-by-layer fashion instead of point-by-point writing. This new technique substantially increases the printing speed by 1,000—10,000 times, and reduces the cost by 98 percent. The achievement has recently been published in Science, affirming its technological breakthrough that leads nanoscale 3-D printing into a new era.”

            • Alex Tolley December 23, 2019, 1:33

              On its face, this looks very impressive. The Science paper seems to suggest to me that this technique requires the print material to be uniform for each layer, which might make it unsuitable for objects that need to be made of different materials. The authors do suggest a number of applications where their technique could drastically reduce print times and reduce costs.

              Now can it be successfully commercialized?

        • Alex Tolley December 20, 2019, 12:10

          I consider this “Star Wars” thinking. Star Wars has all this hi-technology (to us) and immense planet busting capabilities, yet nowhere is there a manufacturing site to be seen, even on Coruscant.

          In our world today, technology requires a very large network of suppliers and coordination to work. We are almost wholly dependent on computers to do anything. The largest chipmaker is Taiwan Semiconductor, almost entirely based across the Pacific. Just suppose China captures Taiwan and restricts semiconductor exports? Food is paramount, yet US grocery stores have just 3 days of inventory (I believe it was more than 7 days when I was young). IOW, if systems and supply chains start to break down for any reason due to the global heating, the effects will ripple out. If you are older then you are dependent of Rx drugs. If that supply is disrupted, you die.

          When I was young, technology was far less important than today, food supplies more local (and seasonal), and technology could be mostly repaired. That is no longer true.

          SciFi author Charlie Stross once had a blog post considering what level of technology was achievable and still repairable should we have a setback. IIRC, the 1950s was about as hi-tech that was still repairable and possible to remanufacture. Anything later, and that includes all microprocessor controlled tools and artifacts would not be possible.

          Consider farming. For all the innovations we have had, especially hield yield crops, farming is highly weather dependent, and that is not under our control. Whether drought conditions or excess rainfall, farms are dependent on the right conditions to produce crops. And that is before we consider diseases to crops that have so far proven untreatable.

          With close to half the global population now living in cities, any major disruption of food production and distribution could result in social breakdown very quickly. Look what happened in Buenos Aires when the water supply was extremely restricted. Technology does no solve short term life threatening situations.

          Humans will not go extinct, there are too many of us, living in myriad different ways. But I would bet that those that best survive will be populations living in less technological dependence than those that do. For similar reasons, if you want to populate an exoplanet, it may be best to start with a population that can live as hunter-gatherers and simple farmers, rather than try to install a hi-tech civilization.

          The bottom line is that technology creates co-dependency. If technology is disrupted due to its fragile nature, then co-dependent humanity will suffer. We accept that choice, but it has risks. It may even be the “great filter” ahead of us.

          • Michael C Fidler December 20, 2019, 19:16

            I would think that any major breakdown would take us back to pre industrial revolution before the 1850’s, a farming society that was not so interdependent. In this day and age especially in the cities we have many utilities supplied from outside the home -water, electricity, gas, gasoline, garbage disposal, telephone and appliances, etc. Here in the Philippines when I moved to Bohol Island 15 years ago most of the people lived in a pre industrial state. Now in just those many years they have become dependent on outside sources to a much larger degree. So yes, we will have to learn to live in a much less dependent society as global warming takes over for the politicians and most of the high society will live in their glass houses. Sorry, but it is too late for suburbia.

          • Robin Datta December 20, 2019, 22:52

            Increasing complexity in nature is associated with increasingly robust mechanisms for resilience (=resistance to collapse). These mechanisms include redundancy (inventories/stocks), networking (robust: with multiple species of pollinators, earthworms, trees, etc.) and flexibility (alternate foods, habitats, etc.) They evolve in response to stressors that threaten to cause collapse.

            Each of these reduces profitability in industrial civilization, and are assiduously pruned away. As a result, industrial civilization has multiple points of potential failure. Just one of them.

            • Alex Tolley December 21, 2019, 12:16

              We managed without trucks until the 20th century. I still recall horsedrawn carts for vegetable and beer deliveries (admittedly a bit of an anomaly in London, even then). We have definitely painted ourselves into a corner requiring trucks to deliver almost everything. However, I see no particular problem if trucks become powered with electric engines juiced with non-fossil fuel power. One counterpoint is that traffic speeds in London are now slower with the ubiquity of parcel delivery by truck. On the plus side, a self-driving truck just made a journey across the USA with a very fast time.

              Just as controling everything with microprocessors is an example of a potential single point failure, so might be converting our whole energy infrastructure to electricity. Do we have a good means to prevent a Carrington Event disaster?

            • Antonio December 21, 2019, 17:14

              Technology makes us more resilient, not less. See Figure 2 here:


              • Alex Tolley December 22, 2019, 16:17

                Good to see you following Gary’s suggestion and offering journal sources to support your claims.  The paper contains an analysis of the deaths and death rates from extreme weather events from 1900 to 2008.    The death rate declines over this period.  So far so good.  
                The author claims that this decline in the death rate due to extreme weather events is due to increasing wealth and improved technology.  That may be so.  Just being able to evacuate people from predicted weather events (satellite data and weather forecasting) is likely a factor.

                As economists say, “a trend will continue..until it doesn’t”.  In this case, the rapidly rising extreme weather events figure 1 if continuing to increase with global heating may well change that trend.  But perhaps more importantly, this study only looks at deaths directly attributable to these weather shocks.  It says nothing about climatic change effects on starvation as crops fail, water availability and the relation to (violence in the Mideast), the deaths due to migration, and unregistered shortened lives due to disruption.  

                Famines by world region since 1860 show that Europe no longer has the famines of the early 20th century, the huge Asian famines, particularly the caused by the Chinese “Great Leap Forward” in the 1960s are over, but those in Africa are rising again.  The US has been protected by unsustainable water extraction which will eventually drain the aquifers.  We saw the effects of drought in Texas and California farming is reducing its acreage as water supplies become scarcer and less reliable.  I don’t see much sign that technology will come to the rescue.  Farming practices are very conservative and remain dependent on weather and climate conditions.  Where I live, we seem to be losing the freeze days needed for some fruit trees to produce.  That must push these crops further north over time.  Canadian wheat will not grow on thawing tundra soils, so moving north has limits.

                It has been a long fight to get people to accept that the changing weather conditions and rising sea levels are due to global heating.  But as the heating continues, the increasing weather extremes and coastal flooding with become impossible to ignore.  Crop failures and water wars will likely become more common, as well as the problems associated with climate migrants.
                If I am too pessimistic, please show me where technology and social policy are mitigating these problems.    

              • Project Studio December 22, 2019, 23:50

                It is worth considering that Dr. Goklany’s report tallies the the increasing causes of death listed below as if they unrelated and independent of climate change. Many of these causes are likely to be increased in both frequency and severity as a side effect of climate change.
                • Infectious and parasitic diseases
                • Tuberculosis
                • STIs excluding HIV
                • HIV/AIDS2
                • Diarrheal diseases1
                • Childhood diseases1
                • Meningitis
                • Hepatitis B and Malaria C
                • Other infectious & parasiticdiseases
                • Respiratory infections
                • Maternal conditions
                • Perinatal conditions
                • Hunger and malnutrition
                • Malignant neoplasms
                • Cardiovascular diseases
                • Respiratory diseases
                • Digestive diseases
                • Other non-communicable conditions
                • Injuries
                • Road traffic accidents
                • Fires
                • Drowning
                • Other unintentional injuries
                • Self-inflicted
                • Violence
                • War

                In addition, the types of events characterised as ‘extreme weather events’ indicate that this statistical study is one of short term weather impact, rather than that of long term climate change:
                • Excess cold
                • Excess heat
                • Floods
                • Lightning
                • Hurricanes
                • Tornados

                Any inference that these statistics disprove the increasing human impact of climate change is specious. A scientific study, based on facts, must explore the interrelationship between climate change and such factors as disease, hunger, fires, drowning, and warfare; not to mention the human toll caused by forced migration as regions become arid or otherwise uninhabitable. As Gretta said, people are dying.

                • Michael Fidler February 9, 2020, 6:43

                  Two points that make this happen, overpopulation and history repeating itself. The overpopulation is self explanatory but history is repeating in the form of scientific ostracization from the powers that be. The church in the 1600 now the industry and politicians from carbon production.

  • Laura December 19, 2019, 2:12

    Re: “‘Nonsense’ To Think Humans Will Ever Move to Nearby ExoEarth, Says Leading Planet Hunter.”

    Never says never.

  • ole burde December 19, 2019, 4:05

    Much of what I would like to say here has been said by Antonio, so I will only add two things :
    First the real hard problem will be if no life is found in a relevant distance , causing terraforming to start from a very hostile beginning , probably demanding a very long terraforming process , which can only be sped up by periodic interferrence from humans.
    Second , if an exoplanet has a non-edible but carbon-based ecosystem , humans could very quickly convert earthbacteria into digesting the local stuff and so convert it in to edible biomass for eart-buggs , earthworms and other cool stuff !

    • Alex Tolley December 19, 2019, 11:46

      if an exoplanet has a non-edible but carbon-based ecosystem , humans could very quickly convert earthbacteria into digesting the local stuff

      If the local biology used right-handed amino acids, it would be indigestible by any Earth organisms. We have no idea today how to make organisms use a different biology, and even if we did, why would we expect it to outcompete the evolved organisms on this distant world? While it may be possible to do this in the future, I find the idea that we would convert a living world to human requirements morally repellant. This is the same moral issue in ST: The Wrath of Khan with the Genesis Device. It was also the [unfounded] fear of nanotechnology turning Earth’s life to “gray goo”. It is so horrifying that no-one has yet, AFAIK, filmed an alien invasion movie where that is their approach to taking over the Earth, although Peter Watts introduces a similar scenario in his “Rifters” series of novels.

      • ljk December 19, 2019, 16:34

        Extraterrestrial ethics. Now there is a slippery slope for which we can only guess at. Is it survival of the species everywhere? Are all the cultures that make it to an interstellar level altruistic to those less advanced? Will we be considered the invaders one day?

      • ole burde December 22, 2019, 7:13

        ´´If the local biology used right-handed amino acids, it would be indigestible by any Earth organisms´´ ? …..NOTHING containing chemical energy is indigestible by the combined powers of a variated microbial comunity , given a bit of time…..and thats even without counting on genetic engineering….or perhabs you , Alex, have just invented the perfekt solution to the problem of earth-bacteria learning much-too-fast how to digest ANY new kind of antibiotict that we throw at them ?

        • Alex Tolley December 22, 2019, 15:23

          Fair point I was being far too extremist with my comment.  Plants and animals do synthesize amino acids, although animals and many bacteria cannot synthesize all the amino acids.  Humans need to acquire essential amino acids from proteins in the diet.  The wrong chirality of these essential amino acids will not create the proteins with the correct functions.  We saw a similar effect when the indigestible oil, “Olestra” was introduced, that just passed through our digestive systems.    This would mean that human colonists on a world with d-amino acid proteins would need to grow their own food with terrestrial plants.  Living off the land eating the local fauna and flora would not be possible.

          Chemistry ensures that almost all compounds can be broken down.  E.g. our stomach acids are responsible for breaking peptide bonds in proteins.  Chemistry also provides synthesis possibilities, so a “replicator” or industrial process could use local life as feedstock to synthesize all the food needed by the colonists.  [It was claimed that the Greenland Vikings would not eat the abundant fish around them as the increasing cold diminished their domesticated food animals, and therefore either starved or joined the local natives to survive.  In such a colony world, if the terrestrial plants failed, or the food synthesizers stopped working, there would be no fallback and the colony would fail.]  

          I am not sure that bacteria can evolve to digest everything.  So far most plastics have proven resistant.  I am not even sure that we would want plastics to be digestible unless designed to be so.  I am reminded of the British SciFi tv series “Out of the UnknowN” and the episode Beach Head where metal-eating bacteria strand a starship crew on an alien world.

        • Charley December 22, 2019, 15:32

          Alex Tolley
          ´´If the local biology used right-handed amino acids, it would be indigestible by any Earth organisms´´ ?

          Simple solution here; take whatever. Amino acids are present or whatever is the compounds present and put them through a furnace converting them to CO2. Now you don’t have a problem with your organic chemistry, not do you?

  • Antonio December 19, 2019, 17:36

    I know this will not convince the doomsayers, but anyway, here it goes:


  • Charley December 19, 2019, 20:22

    In conjunction with all the speculation that has been entailed in this article and in the comments. I would like to say that there was a very, very interesting article that appeared in the new issue of the January 2020 issue of scientific American. It’s too hard to go into it here, but it has to do with the idea of how ‘alien’ races would in their own manner spread among the stars and how that might be something that would happen in the same way with us. Check it out is quite good.

    I am a little surprised here that nobody took up the idea that the way in which humankind might actually go forth and settle exso planets could be not in the form of a biological type of organism, but in in the form of an uploaded consciousness into a silicon substrate inside a computer. Has everybody forgotten about the expected singularity? Not only would this take care of all kinds of issues with regards to the need to nourish the biologic, but also to it would take care of the problems regarding longevity. Sound like a much better solution than going there in person

    • wdk December 27, 2019, 19:53

      Hello, Charley.
      At the local grocery store news rack I did see that article you mentioned. I had hesitated to buy it, but now that it’s part of this topic, but since you brought it up, it pushed me over the edge.

      Caleb Scharf fits in rather well with “Will Humans Ever Walk on Exoplanets?” Beside that it pursues Fermi’s question, “Where is everybody?” In addressing these two questions, it brings up a couple of corollaries to this reasoning. One is the so-called Fact A, in which it is posited that there is no evidence of aliens having visited this planet.
      At least not in the sense that dinosaurs left evidence of their existence or we leave evidence of our existence every day.

      So given that, it would seem that star hopping aliens do not appear to be abundant, and if there are aliens, some of them might appreciate the issues we confront in trying to do interstellar flight, if they are aware of interstellar gulfs at all.

      Reading the article, it makes me wonder if the Drake equation should be further “fractionated” with other likelihood factors:
      Once you get past the factor related to life sustaining planets, one could well ask how many have some of life features like our own and the facets that lead us to consider hopping over to another star. What if aliens are conscious, but do not sense the sky because their planetary atmospheres are more oceanic than ours? Or what if they build cities and hives and use tools, but have little awareness? Bees, for example, have flown for millions of years but remain concerned with pollinating flowers…

      Several months back, I ran into a diagram indicating the changing relative distances of nearby stars – and I passed an observation or two about that to an earlier Centauri Dreams topic. But both then and with Scharf now, perhaps tangentially, it is noted that the best world ship available for interstellar travel are the original one we sail through space on right now.

      If it is a question of human kind propagating out to the stars, the best opportunity might be when the sun has a close passage with another star. How long do we have to wait? Well, it looks like about another 60,000 years before one of our near neighbors comes down to 3.0 light years. Now in the scheme of things, how long would we (?) have to wait before the distance is brought down to about 1.0?

      It could be like waiting for crossing an asymptotic line in this part of the galaxy. Maybe it will be half a million years. Either way, generations after this discussion group adjourns. For interstellar travel, we would probably be better off in another part of the galaxy, maybe in a cluster where stars are more tightly packed, but not destructively so.

      And that might be where everybody is, passing as Scharf says in analogy, like Polynesian migrants in the Pacific, paddling their canoes.

      While “laboratory” results from the Biosphere II, the ISS and previous space stations give us some credits for closed cycle life support, we are
      by no means ready for the closed life support contemplated for ships going out for centuries far from any sun. The article spoke of interstellar “empires” because aliens in theory had moved from one star or another. But I can’t see how they would constitute an empire in the context shown. Maybe, perhaps seeding, unless some other type of transformative technology is involved.

      We do speak of sticks and carrots. For one, the Earth as it exists now will be difficult to sustain over geological periods – even if we can solve the immediate ecological warming crisis. Yet solar systems could
      sustain billions of humans and the concomitant living spaces. Maybe orders of magnitude more than the current single planet system. And
      if so, if human psychology remains the same, it might want to devote some of its resources to interstellar ventures. Perhaps as a hedge against extinction, foreseen or unforeseen catastrophe.

      But an important inducement to doing anything interstellar would be an evaluation of available real estate around other stars. We are obviously just in the initial stages of that. There have been surprises and some anxieties about what the low hanging fruit revealed about the varieties of planets, though we are re- assured about the numbers. Yet already Venus is a forewarning of how uninviting a terrestrial planet can turn out to be.

      My guess is that we can walk on Mars – and even settle it to some degree, but not with an expectation of supporting many millions. I would also suspect that we could identify exo-planets even more hospitable than Mars – eventually – In near term in comparison to prospects for traveling to them. But say we identify an intermediates between Mars and Earth at 20 light years distance… More likely with means of measure, a target would be larger than Earth, but not so much it seems like Neptune. Is that incentive enough to launch? And launch what? As a real estate market, this transcends buyer or seller.

      The assumption of the Scientific American article is that something akin to this slow, incremental migration could be going on in other sections of the galaxy. So far off in time and space, we have not been able to detect it thus far.

      A remaining issue touched on was re-examination of Fact A. We don’t have evidence of alien landing on Earth, but going back millions of years in time, how would we know? It would even be hard to tell whether the dinosaurs themselves had a civilization, or that the Earth were settled for thousands of years by visitors. My answer to that is that objects such as the Moon probably give a better record of visitations. Not that I am saying that they are there. It’s just that the tire tracks remain to be viewed longer. I don’t think we have identified anything like that – yet.

  • Alex Tolley December 19, 2019, 20:55

    A completely bonkers star drive as a thought experiment.

    Imagine an engine that works like an anti-Cavorite. It assumes gravity can only be attractive, and not repulsive. To avoid violation of the conservation of energy, it must generate the energy needed to achieve its results. When the drive is turned on, the ship and all its contents are subject to the same freefall conditions as if they were under normal gravity. The drive just changes the gravitational strength acting on the ship. Think of it just steepening the local curvature of space.

    We want the ship to reach 0.2c. To do so it must accelerate towards some large body such that its terminal velocity reaches that value. By increasing the local attraction to the sun to about 1200g the ship will reach 60,000 km/s at perihelion. The crew will experience no acceleration forces, just as if they were falling into a neutron star or black hole. At perihelion, the engine is turned off and the ship now travels towards it target star at close to 0.2c. The ship is aimed to a close approach to teh star, and at perihelion, the drive is turned on, resulting is a rapid deceleration calculated to reach orbital velocity at the desired HZ planet.

    The journey time for the ship to fall from Earth orbit to skim the sun is about 90 minutes. The same time is needed to decelerate at teh target star. So the trip time is simply the 5x the distance to the star in light years, no long acceleration and deceleration phase.

    The energy demand is certainly high. Assuming that we need to account for the kinetic energy of the ship, the energy source needs to be antimatter. This requires about 5% of the ship’s initial mass to accelerate. Worst case a trip to another star and a return to Earth would require perhaps 20% of the ship to be antimatter fuel and another 20% normal mass to be annihilated. This seems like a very low mass ratio compared to almost any rocket propelled ship. If the energy needed at the solar system could be beamed to the ship, the mass ratio could be doubled. Of course it assumes that only the terminal kinetic energy of the ship must be paid for and that maintaining the curvature of spacetime is costless.

    Assuming I have run the numbers correctly, this would make interstellar travel for robotic craft extremely feasible. The principal cost would be the manufacture of the antimatter which would be extremely high even with several orders of magnitude improvement over current methods. If we wanted just flybys and used beamed energy, such craft could be sent to the nearer stars with power of the order of a TW per kg applied over the acceleration period. Using solar panels, a 1 kg probe would require an array of perhaps 100 km on a side. A 100 kg probe would need an array 1000 km on a side.

    That is my believing in 6 impossible things before breakfast today. ;)

  • Geoffrey Hillend December 20, 2019, 1:37

    That’s an interesting thought experiment Alex Tolley. The only way to increase the gravity on a ship would be to have gravity control. The ship would have to be able to emit gravity waves to create a gravitational field in front of the ship. In theory this is possible and a new type of gravity would not have to be made. It is impossible to increase the local attraction of the Sun without making it more massive. Gravity follows an inverse square law so if you get closer to a large body like the Sun the gravity gets stronger. One can however increase one’s local gravitational field with a gravity control device by increasing the energy of the field and intensity of the waves, but since physicists don’t know how to make gravity waves yet the gravitational wave rocket is limited to the future.

    • Antonio December 20, 2019, 11:23

      Look, a gravity wave device!!


      • Robin Datta December 21, 2019, 0:40

        Been in the US Army & US Navy centrifuges in the course of flight surgeon training. Quite an experience when the “up” and “down” moves 90°! And everything becomes so much heavier!

  • Geoffrey Hillend December 20, 2019, 1:51

    The problem with making colonies on Mars and other planets was already addressed on another Centauri Dreams post; People can live on Mars and other lower gravity environments, but not indefinitely without bone loss. Bases can still be made for temporary living on other planets, moons and asteroids, but not from birth to old age.

    • Daniel December 25, 2019, 8:07

      Centrifugals habitats that create 1g acceleration in the surface of Mars and others objects of solar systems like the Jupiter moons would do the Gravity problem job, until if we not invented better way to create artificial gravity.

  • Project Studio December 20, 2019, 11:04

    “Always listen to experts. They’ll tell you what can’t be done, and why. Then do it.”
    “If it can’t be expressed in figures, it is not science, it is opinion.”
    “When a place gets crowded enough to require ID’s, social collapse is not far away. It is time to go elsewhere. The best thing about space travel is that it made it possible to go elsewhere.”
    “Pessimist by policy, optimist by temperament — it is possible to be both. How? By never taking an unnecessary chance and by minimizing risks you can’t avoid. This permits you to play out the game happily, untroubled by the certainty of the outcome.”
    “What are the facts? Again and again and again — what are the facts? Shun wishful thinking, ignore divine revelation, forget what “the stars foretell,” avoid opinion, care not what the neighbors think, never mind the unguessable “verdict of history” — what are the facts, and to how many decimal places? You pilot always into an unknown future; facts are your single clue. Get the facts!”
    – The Notebooks of Lazarus Long by Robert A. Heinlein

  • Geoffrey Hillend December 20, 2019, 18:14

    A centrifuge can’t be used to make a rocket, i.e,, placing a centrifuge on the front of a rocket won’t take it anywhere since the gravity waves are being made from the kinetic energy of acceleration from the resistance or inertial mass. Acceleration equals gravity so moving at 0.2 c will also increase gravity.

    I meant a theoretical gravity wave emission device which works by converting one kind of energy force into another like the bosons into gravitons; the photon of electromagnetism or the gluon of the strong nuclear force into gravitons or maybe collisions of high energy fermions into gravitons . This would allow gravity control. The graviton is supposed to couple to energy momentum so the graviton potentially could decay into leptons, quarks or bosons. https://atlas.physicsmasterclasses.org/en/zpath_graviton.htm

    My idea was to reverse that process so if one combines two gluons, two photons or two quarks one might make gravitons? I am not a physicist, but I do think like some former NASA physicists that manipulating gravity has many propulsion applications and a propellant less propulsion which can be manipulated electronically just like turning on a laser or light. Also the discovery of the graviton will win a physicist a Nobel prize and a gravity wave particle emission device from the energy conversion of one of the other four forces etc. will also win a Nobel prize.

  • Geoffrey Hillend December 20, 2019, 18:39

    Alex Tolley. I am not saying that we can’t settle on exoplanets, only that robots can do lot work for us especially when we become a type of civilization which has half a million years of technological and scientific evolution. Also if we have FTL, we won’t need to settle on other planets until maybe over one hundred million years in the future. The sun’s brightness increases 10 percent every billion years so in 100 million years it will increase one percent and there will be point when humanity will have to leave the Earth and our solar system. I think by then, our technology will be more than equal to the task. We will have FTL propulsion.

    There is also the ethics of settlement on an exoplanet It seems to me that it is easier to settle on a planet that already has life and an environment which favors it like our Earth than one that has to be terraformed. We we will have to be in harmony with that environment and life and we can’t even do that with our own Earth, but we will become in harmony with the biosphere since we have the technology. This is not pessimism but optimism so by the time we have fast interstellar travel we should have long since solved our own problems of getting along, clean, efficient power, etc I don’t see what the hurry is to settle on another Earth like exoplanet when we can extrapolate and hypothesize everything over there must be the same due to the invariance of scientific first principles and their universality of application, i.e. everything we can learn about the forces of nature here applies on another world so we can’t escape learning it here.

    • Alex Tolley December 21, 2019, 12:27

      If we delay exoplanet settlement for a millions of years into teh future, then even with slow ships we could terraform sterile planets over 10,000-100,000 years in advance of human [or whatever passes for biological humanity] colonization.

      While I don’t think FTL drives will be possible (but never say never), within a millennium we should have enough knowledge to build suitable living space in a variety of places – from space habitats, to inflated asteroids, to planetary surfaces like Mars.

      I am not sanguine about maintaining a large population living sustainably on Earth in harmony with nature. I tend to think this will reinforce Cabal’s “All the universe or nothingness? Which shall it be, Passworthy? Which shall it be? …”.

  • Thomas Hair December 20, 2019, 21:41

    I get tired of the pessimistic meme that we will self annihilate because it’s just too easy to succumb to such nihilistic thoughts. A rational mind wants to keep thinking the thoughts that it has been thinking and will usually cooperate (a hallmark of humanity) to ensure that those thoughts keep occurring. Consciousness may prove to be the most powerful force in the universe. With that said, we can utilize this planet and the rest of the solar system for geologic epochs of time. We may never reach the stars in our current form, but as an optimist (and optimism takes work and is in no way naive) I see the intelligence in our minds spreading through the cosmos (in some form or another) in difficult steps that can be ultimately attained. To use our six thousand year recorded history as a guide to a possible mega/giga/tera-year (?) future history is to my feeble mind the ultimate temple of sophistry.

  • Gary Wilson December 21, 2019, 16:25

    Anyone should be free to make any statement they wish on this blog as long is it is not defamatory or demeaning in any way. I do object to people making unsupported statements about climate change and other serious matters however. When you make unsupported statements you perpetuate incorrect ideas which are then spread in various communities. I encounter the same problem in my everyday life and it worries me a great deal. Opinions matter because they can interfere with or support positive actions going forward. The data available on climate change and its causes and inevitable effects are readily available. Taking dangerous attitudes based on unsupported opinions is in my opinion deeply dangerous to our survival. If we are eventually going to inhabit other worlds we had better start by learning how to live in a peaceful, sustainable manner on this one.

    • hiro December 22, 2019, 16:15

      Good luck with that, we can’t even agree whether the Earth is flat or not, maybe it’s Ricci flat.

  • Gary Wilson December 21, 2019, 17:10

    Here is a good article to begin with. It cites many other important articles with actual data, not opinions. It’s important that people understand the difference. Opinions, by themselves are essentially worthless unless supported by facts which have been agreed upon by many experts (essentially the peer review process). It is vital that people understand this. Climate Scientists Virtually Unanimous:
    Anthropogenic Global Warming Is True
    James Lawrence Powell1 Bulletin of Science, Technology & Society
    2015, Vol. 35(5-6) 121–124

    • Project Studio December 21, 2019, 23:03

      Climate Scientists Virtually Unanimous:
      Anthropogenic Global Warming Is True
      James Lawrence Powell1 Bulletin of Science, Technology & Society
      2015, Vol. 35(5-6) 121–124, free to public:

      • ole burde December 23, 2019, 5:21

        Why is it that the debate about climatechange never enters into the reality of what CAN be done about it ? is the purpose of it limited to creating blame and division ?

        • ProjectStudio December 24, 2019, 7:55

          They say the first step is admitting there is a problem. But yes, what ‘can be done’ is a difficult concept across the board.
          Here in our Australia summer, air conditioned department stores leave their doors open to the street, and the crowds passing along outside feel the cool refreshing breeze blowing out. In the winter time, cafes and restaurants fire up huge gas burners to warm their al fresco tables on the sidewalk. These are simple examples of self-defeating comfortable habits that need to change. Automobile ownership seems an unavoidable necessity, particularly to those living far from city centres. Perhaps with better civic transport and more electric vehicles charged from renewables. Seems a puff compared to the releases of uncontrollable bush fires that could have been better planned for – like allocation of more 737 water bombers. Again, the first step is admitting there is a problem.

        • Alex Tolley December 24, 2019, 12:40

          Why is it that the debate about climate change never enters into the reality of what CAN be done about it ?

          While there is still those denying climate change, the “debate” cannot get further than arguing the evidence. However, if you want to know what can be done, then there is a wealth of information on solutions. The question then becomes which solution or solution mix, and how is the transition to be done. There is plenty of argument there from techno-fixes like geoengineering to decarbonizing energy – renewables or nuclear, and changing practices in transport, agriculture, and general energy use. We have kicked the can down the road for 30 to 40 years at least, and the failure of the last COP25 meeting is disheartening. Even if we fully decarbonized our energy tomorrow, we would still have some warming “baked in” due to reservoirs of CO2 and current feedback processes that will continue. We may even be reaching an irreversible tipping point due to our inaction.

          It is instructive to read Collapse: How Societies Choose to Fail or Succeed by Jared Diamond on historical societies that did and didn’t collapse in the face of environmental change.

          • ole burde December 26, 2019, 13:33

            And these ´´technofixes´´ CAN fix the problem in an any realistic scenario ?
            OK. lets take them one by one :
            1.Renewables can at best suply 20-30 % without becoming impossibly expensive ….in Denmark windpower-electricity costs drive up the general cost of power 3 times more than it would have been with fossil fuels only , and thats only for 40% renewables
            2 . Nuclear , the only LOGIC alternative to fossils ,are beeing HATED fanacticly by the very same people who are supposed lead the fight aganist climate change….and no change in sight
            3. ´´Change in practises´´ (reduction in the energy consumption) ….energy consumption is directly proportional to general growth in the world-economy , so without this growth , the poorest half of the global population will just accept to STAY poor ….right… and the same is true about (1) , because higher cost of alternatives wil similarly lead to reduction of energy consumption
            4 .Geoengineering : can best be imagined as a neanderhal trying to fix a broken computer with his stone ax.
            5 . CO2 deposition : go to (4)
            …..so now we know why nobody really wants to talk about what we realisticly CAN do about preventing global warming ….so perhaps time has come to start talking about how to live with its consequences in the foreseeable future

            • Alex Tolley December 26, 2019, 20:21

              As with antonio, provide references for your assertions.

              But here are some off-the-cuff responses.

              1. Countries and % renewable power. The %ages are for electrical generation. Some countries are already at 100%, e.g. Iceland. Do you hear about the “impossible” cost from the Icelanders?

              2. Nuclear: HATED fanacticly. Hmm, Stewart Brand, argued for nuclear. Nuclear may be a solution for some countries, but in teh US it is now too late to stave off global heating with nuclear power as it takes far too long to get a plant operational. Nuclear is also more expensive than renewables. There is also still no way to ensure that waste can be kept away from people for thousands of years. Nuclear stations require cooling water, which is why they tend to be sited on coastlines. Rising sea levels make the folly of this obvious, even without the unexpected events like a tsunami.

              3. Change in practices: (reduction in the energy consumption) ….energy consumption is directly proportional to general growth in the world economy. Actually changes in practices includes transport options, building LEED ratings, substituting materials,, e.g. reducing cement use, farming methods to reduce nitrogen use, telecommuting…The list goes on and on. Economies do not have to grow by producing only high energy consumption manufactures. Look at figure 2 in this report about historic energy consumption and GDP in the US. You might reconsider the coupling.

              4 & 5. Geoengineering. Vox’ Ezra Klein has been doing some podcasts interviewing experts on climate change. This link is about geoengineering. I will say that at this point we know next to nothing about how geoengineering will work. We should do experiments to see what might work to buy us some time as we decarbonize the economy.

              It isn’t all gloom and doom. If we can move towards building interstellar spacecraft, won’t it will be easier to keep the Earth habitable with known technologies. Unless you have your head in the sand and believe global heating is a hoax, preventing its mitigation is going to take that future away from us.

              • ole burde December 27, 2019, 5:19

                1. Renewables : Iceland , Norway and Canada is an examble of relatively small populations living in countries with unproportionally big hydroelectric potential , the only costeffektive renewable powersource. Thats why I choose Denmark , which I know well, as an examble. In Denmark they have now build an almost DOUBLE powersupply -system : one workin on windpower and another one working mostly on fossils when the wind dont blow . … this has only been possible because Denmark is a very , very windy place and because the country has an very high GNP and an exeptionally obedient population willing to accept an extreemely high electrity price .Another factor enabling the denish examble , is the fact that denmark has no heawy industries . Like most of the world i can by cheap raw matrials like steel produced using coal in some fra away low-cost-country.
                All the other countries with a high % of reneewables , are poor countries with a low energy consumption and no heawy industries.
                2. Nuclear : No matter what we do , it will take generations to reduce the CO2 back to a ´´normal´´ level , so nuclear i still relevant from a timing-perspective. As for the waste problem , read the MIT report back from the 80´s advovating for deposition spaced out in drillholes under the seebed , in the widespread layers of clay which ave an extremely low diffusion -capacity .
                3.developing countries will no-matter-what have to increase their powerconsumption , but perhaps a little less so whith better tecnology .
                4 Pie in The Sky !
                Doom-and Gloom : Not at all ! humans have always been MUCH better at doing the right thing in the last posible moment than anything else , but we newer know what the right thing is before it REALY kicks us in the face ….if we had continued the 1970´s pace of building nuclear powerplants up until today , there would have been no serious CO2 problem

                • Alex Tolley December 27, 2019, 17:14

                  Cost of power. U.S. Energy Information Administration | Levelized Cost and Levelized Avoided Cost of New Generation Resources AEO20191 February 2019Levelized Cost and Levelized Avoided Cost of New Generation Resources in the Annual Energy Outlook 2019. Also, the argument that the sun doesn’t shine at night and other red herrings are being dealt with by smart grids and a huge investment in battery and other storage technologies to supplement reservoirs.

                  If the need is to decarbonize rapidly, why would one want to add nuclear plants? If renewables can meet the demand, then that is the best way to go, with no waste or proliferation issues. Nuclear may be part of the mix where appropriate, but making it the core energy supply is just inviting unnecessary problems. Safe designs and thorium reactors are all experimental, delaying even further any power obtainable from these newer gen4eration plants.

                  humans have always been MUCH better at doing the right thing in the last posible moment than anything else , but we newer know what the right thing is before it REALY kicks us in the face

                  As I said, read Diamond’s Collapse as an example. When the Easter Islanders cut down their last tree, it was rather too late to change course! Britain discovered coal before all the forests were cut down, but it is no longer the forested land it once was, and where Sherwood Forest was large enough for Robin Hood to have hidden.

                  if we had continued the 1970´s pace of building nuclear powerplants up until today , there would have been no serious CO2 problem

                  Maybe. OTOH, we would probably have had several serious accidents, possibly on teh scale of Chernobyl. Certainly on the scale of Fukushima. We would also have a lot of nuclear waste, lots of NIMBYism about how and where to dispose of it (the Irish Sea is an example of what not to do), and probably a lot more authoritarian policing to prevent theft of fissile material and the attendant nuclear threats. But at least the world would not be warming so quickly… ;)

  • Geoffrey Hillend December 21, 2019, 18:24

    I don’t think that world ships and interstellar colonization will come anytime soon for a number of reasons, but that does not mean we should not think about it, and do the quantitative physics, designs etc. The problems we already have here on Earth are going to take precedence over world ships and I do include climate change which is just one of them. Maybe when we get these problems under control, there might be an increased interest, especially if found some exoplanets without biosignature gases.

    I do believe in being realistic about our future which is not pessimism, and the movie “Things to come, ” is obsolete because the events it explains did not happen since the movie precedes the nuclear family, atomic age and post world war II, and what I’ve understood from the post nuclear experts and viewpoint of the world powers is that we can’t have a third world war since the power of the hydrogen bomb in a full nuclear exchange could end all life for the fear of total annihilation is a deterrent, so I don’t see us ending up in some kind of negative alternate world future like on Matrix or Terminator where there are some survivors and everything has been destroyed. It’s just not realistic.

    It also takes a knowledge of science, quantum field theory and atomic physics to understand just how powerful the hydrogen bomb really is. The temperatures in the center an atomic bomb explosion can range for 50 to 100 million degrees, the core center of the Sun is 27 million degrees F., and the center of a hydrogen bomb can reach ten billion degrees equal to the core of the hottest stars. Hawking, a Brief History in Time, p. 147.

    I am not against world ships, but they run into the problem that a certain time later in the future a faster ship and propulsion will be available and one’s ship gets passed by a faster moving ship. I also don’t like the doomsday idea that only a select few escape the Earth and everyone else dies which is too apocalyptic. I used feel it to be fun science fiction like something from Twilight zone or Outer Limits and I would still watch such a thing, but with a matured scientific outlook which is not what I had when I was a young man. I liked the science fiction more at that time, but I still do like it.

    I am not against the idea of terraforming, but there are limits to what one can do with it. It will be much more possible to terraform an Earthlike exoplanet in the future when we have fast interstellar travel especially FTL. There are problems that can’t be solved with terraforming. For example an exoplanet the same size of our Earth without a Moon would have a large axial tilt and wobble so it would experiene huge changes in climate over 50,000 years, a problem that terraforming can’t fix. One could seed the planet with oxygen producing life, but that would take time. One could make oxygen, but that would be more expensive and with the solar wind stripping, so we would have to replace the lost atmosphere over time which would could be done in a number of ways. It seems to me that it is easy to find a living planet without those problems, but on the other hand we would not have to worry about the ethics or interference with another ecosystem if we made our own from a sterile planet as Alex Tolley has mentioned.

    No matter what kind of interstellar technology we get in the future, there will always be a use for drones and automated probes because they can explore hostile environments like cliffs, underwater and volcanoes which are difficult for people. I do prognosticate we will have interstellar travel in the future and humans will walk on exoplanets, but they won’t have to. It will be optional.

    • Charley December 24, 2019, 11:33

      ” … and the center of a hydrogen bomb can reach ten billion degrees equal to the core of the hottest stars. Hawking, a Brief History in Time, p. 147. ”

      temperatures in the center of a hydrogen bomb …

  • Geoffrey Hillend December 24, 2019, 20:22

    I don’t know how Hawking came up with 10 billion degrees for hydrgogen bombs since I am not an expert in atomic physics. Wikipedia says the temperature of a hydrogen bomb reaches 300 million kelvin which is still is very hot. https://en.wikipedia.org/wiki/Thermonuclear_weapon

  • max December 25, 2019, 11:31

    the extinction danger for mankind is very high. i doubt if we even get back to the moon much less another star system.