Home > Science > The arithmetic of space travel (crossposted from Crooked Timber)

The arithmetic of space travel (crossposted from Crooked Timber)

May 13th, 2013

There’s been a lot of excitement about the discovery of two Earth-like[^1] planets, a mere 1200 light years away. Pretty soon, I guess, we’ll be thinking about sending colonists. So, I thought it might be worthwhile to a little bit of arithmetic on the exercise.

I’m going to assume (generously, I think) that the minimum size for a successful colony is 10 000. The only experience we have is the Apollo program, which transported 12 astronauts to the Moon (a distance of 1 light second) at a cost of $100 billion or so (current values). So, assuming linear scaling (again, very generously, given the need to accelerate to near lightspeed), that’s a cost of around $100 trillion per light-second for 10 000 people. 1200 light-years is around 30 billion light-seconds, so the total cost comes out roughly equal to the value of current world GDP accumulated over the life of the universe.

Even supposing that technological advances made travel possible over such distances possible, why would we bother. By hypothesis, that would require the ability to live in interstellar space for thousands of years. A civilisation with that ability would have no need of planets.

[joke alert on] On behalf of my fellow Australians, I’m going to make a counter-offer. For a mere $10 trillion, we can find you an area of land larger than a typical European country, almost certainly more habitable than the new planets, and much closer. We’ll do all the work of supplying water and air, build 10 000 mansions for the inhabitants and guarantee a lifetime supply of food. I’m hoping for a spotters fee of 0.01 per cent.[joke alert off]

On a related point, what should we be wishing for here? The fact that no-one has sent a detectable signal in our direction suggests that intelligent life forms similar to humans are very rare. If habitable planets are very rare, then this is unsurprising – interstellar distances preclude both travel and any kind of two-way communication. If on the other hand, the emergence of intelligent life is common, then the evidence suggests that its disappearance, through processes like nuclear war, must also be common.

[^1] Where Earth-like means somewhere between Venus-like and Mars-like.

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  1. Jim Rose
    May 13th, 2013 at 16:25 | #1

    On any mission to mars, at least one of the crew will lose their minds. Space psychiatry is a serious issue.

    Members of the soviet space station stopped talking for months other than for work purposes. Skylab astronauts went on strike for a day.

    There are plenty of strange and territorial behaviours over the winter at the Antarctic bases. People were sent home on separate ships because of death threats and much of that was before women were posted down there. Their arrival made a great contribution to improved male personal hygiene and regular bathing.

    Describe sensory and sleep depravation and you have described life on a space station but with no weekends off too.

  2. Troy Prideaux
    May 13th, 2013 at 16:31 | #2

    That’s probably a conservative costing of the Apollo program in today’s dollars – it’s probably closer to double that [sigh]
    To quote the great Henry Spencer with regards to the funding pumped into the Apollo program between 61-67:
    “1961-1967 was an astonishing anomaly, a freak political accident, that inherently wasn’t going to last and isn’t repeatable.”
    Trivia bit: regarding the the amount of power used to lift the mighty Saturn V – as the 1st stage was lifting off, the entire energy consumption of the United States rose by approximately 7.8%!!!

  3. michaelfstanley
    May 13th, 2013 at 17:31 | #3

    Once we figure out how to open up some good wormholes the universe is ours.

    Although 10,000 colonists is probably a grave underestimation. I remember Charles Stross writing a post where he suggested around a billion people would be needed to maintain our present level of technological sophistication on Earth. I guess we’d have some sweet AI in the future that could do some of the work though.

  4. May 13th, 2013 at 18:25 | #4

    Stress also has a more detailed costing of interstellar colonisation, which JQ’s post reminds me of: http://www.antipope.org/charlie/blog-static/2007/06/the_high_frontier_redux.html

  5. May 13th, 2013 at 19:03 | #5

    We can’t really conclude anything about the likelyhood of intelligent life in space from our observations. And by observations I mean both of the universe and of ourselves. From our observations of space the best we can say is we have not yet detected anything that we can be sure is not natural, although for all we know the stars are actually arranged in patterns that spell, “Drink Facehugger Cola” in alien languages. As for aliens wanting to contact us, well, Charles Darwin loved his earth worms, but as far as I’m aware he never sent any of them a telegram. The fact that we haven’t received a radio signal might be as significant as the fact that we received any message sticks or smoke signals or hand written letters from them either. Why on earth (or where ever) use a method as stupid as radio signals? The reason radio telescopes are so useful in astronomy is because stuff in space gives off radio signals and as a result it’s kind of noisy out there. If there was an exact copy of earth in the solar system closest to our own we’d have trouble detecting its radio signals from here. So we can’t actually conclude anything, apart from the fact that they haven’t destroyed the earth yet. We can only speculate. And that’s okay. Speculation is fun.

  6. May 13th, 2013 at 19:05 | #6

    A number of points:-

    – The minimum size of a viable colony is much lower, particularly if it brought along frozen sperm to boost genetic variety. Fifty would probably be enough to get started, basing that on village sizes in other times and places.

    – The moon effort isn’t a good basis for extrapolation, since that was trying for different things and deliberately used other methods than would be appropriate for interstellar probes. Even with current technology, it would probably be engineeringly feasible to try for nuclear powered ion rockets reaching less than 0.001 of the speed of light. A million plus year passage would make it practical to seed life, but probably not humanity, let alone any particular culture. Enough unicellular life to get going could probably survive lithobraking even at those speeds – artificial panspermia.

    – However, an optimistic project could send out a probe with just cargo mass and sufficient computerisation and primitive peripherals, with the expectation that software upgrades could be developed and sent out during the first few centuries so that what finally arrived would be able to manufacture tools to make tools, and so on all the way to synthetic human beings and an environment for them to grow up and learn in. For instance, frozen embryos could be sent without the means to develop them into functioning adults, if those means could be built during the last decades of the voyage by software updates received a few centuries after starting.

    – Variations of the Fermi Paradox allow a lot more scenarios than just the ones in that conclusion, i.e. “The fact that no-one has sent a detectable signal in our direction suggests that intelligent life forms similar to humans are very rare … If on the other hand, the emergence of intelligent life is common, then the evidence suggests that its disappearance, through processes like nuclear war, must also be common”. For instance, further advances might use other means of communication than the ones we can detect and sometimes look for, maybe tight beam neutrino modulation – or there might really be replicating probes that wipe out competition when they find it, a danger that would not be inherent in the intrinsic nature of intelligent cultures but in their interaction with outside circumstances.

  7. Ron E Joggles
    May 13th, 2013 at 19:08 | #7

    Obviously we couldn’t send actual people, they’d be at each others throats after a few decades, and disastrously inbred after a few generations, and the need to limit acceleration to levels human bodies can tolerate would make for a long journey – once upon a time I had the mathematics to work this out, but sadly, no longer.

    But all is not lost – we could send von Neumann machines capable of withstanding high Gees, with a precious cargo of frozen embryos – or maybe with just genetic information and the facility to assemble DNA and proteins from raw materials.

    Better yet, we could wake up to ourselves and start looking after our unfortunate, abused planet, and not have to look for some other refuge until a little later, when our sun expands in a few billion years.

    Who am I kidding? The first two scenarios are much more likely.

  8. sunshine
    May 13th, 2013 at 19:24 | #8

    We may find new laws of physics that enable a solution to the the problem of distance our current conception of space-time presents . Another problem though is that our bodies are reliant on this messy Earth in so many ways. For example; the total number of bacteria ,fungi and viruses that live on and in us outnumbers our own cells by 20 to 1 ,(there is also worms etc). The Human Bio-genome project is underway to gene map all of them . That is a much bigger project than the Human Genome project already completed. Our health depends on those organisms being there with us . We are soaked in our Earthly environment . It will be hard to remove people from this living soup to a different place .

    P.S. The relationship between ‘our’ cells and all those others is a fine example of cooperation in nature – its not only competition out there .

  9. Robert Merkel
    May 13th, 2013 at 21:38 | #9

    If we were to repeat Apollo today – particularly if we were prepared to expose the crew to similar levels of risk – the costs would be a small fraction of what they were back then.

    However, your argument is like somebody in 1950 claiming that you could never build a computer with more than a few thousand switching elements because you could never have that many valves operating simultaneously for more than a few minutes without a failure. Clearly, for interstellar travel to become plausible, you have to assume some fairly major breakthroughs in technology – nothing that violates our current understanding of physics, but major nonetheless.

    As to why our distant descendants might choose to travel through interstellar space, might I suggest boredom may become an increasingly powerful motivator as utopia becomes increasingly tedious.

  10. Peter Davidson
    May 13th, 2013 at 22:13 | #10

    I know that this is all pretty much tongue in cheek, but a minor point with respect to your calculations – the key variable is surely energy rather than distance (recognising that our colonists are going to be travelling for a long time). Wikipedia tells us that it takes 60 MJ/kg to “leave” Earth’s gravity field, another 900 MJ/kg to leave the Sun’s gravity field. Assuming that we can negotiate a path through the intervening stellar systems, the energy requirement to get to another star seems like it’s only 15 times greater than the energy to get off Earth. Mind you the energy required to accelerate to 0.1c is more of a problem (http://en.wikipedia.org/wiki/Interstellar_travel) – 450 million MJ/kg! Still this only gives us an 8 million multiplier (assuming that the scaling up for extra people is captured by improved efficiencies since the 1960’s). Multiply by $100b to get the much more affordable $800,000 trillion – only 10,000 year’s worth of GDP!

  11. Mark
    May 13th, 2013 at 23:58 | #11

    Sorry to nit-pick ProfQ, but due to relativistic time dilation (http://en.wikipedia.org/wiki/Time_dilation) the colonists would not necessarily experience the full 1200 years in transit, assuming their space-craft could travel close to the speed of light. In fact, as the speed of light is approached, the time they would experience approaches 0! (neglecting the acceleration and deceleration phases). Not saying that makes it any easier or cost-effective, but a fun fact to think about. One of the most amazing things I learnt in undergraduate physics – just thought I’d share.

  12. Troy Prideaux
    May 14th, 2013 at 00:13 | #12

    Robert Merkel :
    If we were to repeat Apollo today – particularly if we were prepared to expose the crew to similar levels of risk – the costs would be a small fraction of what they were back then.

    Given that all of today’s rocket propulsion technology is still 1950’s tech and the fact that electronics provides only a small fraction of a rocket’s input costs and system complexity, then… ahhh nah, I couldn’t see how that could be possible.

  13. May 14th, 2013 at 01:20 | #13

    This makes me scream with laughter.
    These po-faced dolts actually pretend to write back with a straight face.
    Doesn’t anyone remember that episode of ‘Hitchhiker’s Guide’ when the first starship was sent off?

    I won’t bother reciting what was on board.
    But apparently that sorry lot ended up flying through space and eventually populating Earth.
    Apparently the decent people stayed behind and as some sort of cosmic joke were wiped out by some sort of virus.

    Meanwhile some millions of years later – Oh, never mind!

    What a completely stupid subject at this time when our bludger politicians cannot even offer any help for our most disadvantaged in society.

    It is out of mind and beyond belief that their sort carry on the way they do.

    Meanwhile boring, unmindedness comes pouring in from dullards without any clue – to your pages.

    Time loop – quantum loop – round their sort up and put ‘em aboard that ‘Douglas Adams’ starship and without any doubt whatsoever, they’d be back to grind our lives down into boring inanity five years before I was born.

    Hateful nonentities, the bang lot of them.

  14. Paul Norton
    May 14th, 2013 at 06:54 | #14

    Ron @7, you’ve stolen my thunder!

    Even allowing for relativistic effects, biological humans would probably live through several generations on the ship/s before they reached their destination. Quite apart from the logistic difficulties, it would be very difficult to avoid cultural drift and possible degeneration resulting in, among other things, the on-ship population losing interest in and/or capacity for the original aims of the mission. Stephen Baxter works with this theme in several of his stories.

  15. Paul Norton
    May 14th, 2013 at 06:56 | #15

    It will, of course, be interesting to experience the sociocultural and political ripples on Earth when a Chinese woman becomes the first human to set foot on Mars.

  16. May 14th, 2013 at 07:17 | #16

    Biological humans won’t do this, it would be mind uploads or other machines that would find it fairly easy to survive in interstellar space. See also https://en.wikipedia.org/wiki/Self-replicating_spacecraft

    99.99999999999(etc)% of the resources in the galaxy aren’t in the solar system, so eventually we would benefit from leaving here. With sufficiently good technology an altruistically motivated minority might suffice.

  17. Ikonoclast
    May 14th, 2013 at 07:19 | #17

    Take the time to watch or re-watch Kubrick’s “2001 : A Space Odyssey”. This movie was released in 1968 and predicted the following by 2001; commercial space travel, an orbiting “space hotel” above earth and a very considerable moon base, much of it undergound, called “Clavius”. Other off-planet activity was implied plus the ability to build a very large vessel (a sort a space train) in orbit and then send it to Jupiter.

    Of course, 1968 was a time of scientific and space exploration optimism. We are more than a decade past that time of prediction and none of these things have come to pass nor anything remotely like them. The key reason is the energy costs involved. The energy costs of lifting all those materials into space would be far too high and totally unachievable in practice. While J.Q. focuses on financial costs, the real costs are the material and energy costs (plus human costs).

    It is unfortunate that economists focus on financial costs unless they make it crystal clear that financial costs are just a proxy for real costs. Financial costing is for accountants. We need a deeper analysis of the economics of the real economy from economists.

    On an aesthetic note, the video display technology of “2001” still looks less anachronistic than the video display technology of “Alien” now looks. And “2001” at least communicated the facts that sound does not exist in space and “artificial gravity” could only be created by centrifugal forces.

  18. Paul Norton
    May 14th, 2013 at 08:06 | #18

    It’s also notable that many of the sf book and film classics of the C20 missed the Internet and much of the ICT revolution.

  19. J-D
    May 14th, 2013 at 08:22 | #19

    Did a nerd steal your lunch money?

  20. May 14th, 2013 at 08:32 | #20

    Troy Prideaux, one estimate I read put the cost of a US moonshot today at half that of Apollo. Assuming that estimate was correct it should be possible to go even cheaper and increase safety by using Russian launch vehicles instead of American. Computer Assisted Design and improved materials technology allow for cheaper rocket design and building, while anything that reduces the weight of the payload such as using solar panels instead of fuel cells helps reduce the costs. Not requiring a person to sit in the lunar orbiter is a big help. Even greater savings could be obtained if the most useless part of the mission, the remaining two crew members, could be eliminated. (As in they stay behind and supervise the automated lander from mission control, not get murdered by HAL.)

    Of course if the US did get serious about sending humans to the moon again, I wouldn’t be surprised if the project went way over budget and/or resulted in another compromised cludge like the space shuttle. Bush’s ‘moonshot’ (the pretzel vulnerable Bush) wasted a lot of money without getting Americans much closer to the moon again.

  21. May 14th, 2013 at 08:43 | #21

    Ikonoclast, you wrote that nothing remotely like the movie 2001 has come to pass, but we’ve actually done a lot of exploration of the solar system, includng Jupiter, just not by sending people. At this moment there are robotic explorers on Mars. Basically, if we detected a monolith around Jupiter today, we’d send HAL by herself.

  22. Ron E Joggles
    May 14th, 2013 at 08:50 | #22

    IKONOCLAST wrote: “artificial gravity” could only be created by centrifugal forces.

    Gravity can also be simulated by steady acceleration – the shortest journey time is achieved by accelerating (at the optimum for the occupants) to the halfway point, then decelerating at the same rate for the second half – obviously this requires a power source operating the entire journey.

    Of course this discussion is just a bit of fun – though GRIMBISTE..#12 doesn’t seem to get that.

    But seriously, isn’t it a real concern that the very real and urgent problems threatening Earth’s biosphere are just not being addressed with any sense of commitment or urgency? The record high level of atmospheric CO2 announced a couple of days ago has caused scarcely a ripple.

    It’s entertaining to imagine a high-tech colonization of another solar system, but much more likely is an abject struggle to survive on a radically degraded Earth.@Ikonoclast

  23. Troy Prideaux
    May 14th, 2013 at 10:25 | #23

    Iko, it’s not the energy costs that are the killer, it’s more the actual energy. The fuel and oxidizer costs for typical orbital capable launch vehicle (the rocket) is a small fraction of the mission costs (caveat: for liquid rockets). Rockets are so expensive, primarily because they’re expendable ie. not reusable. They’re a one use piece of very expensive and sophisticated hardware that generally carries a payload that can fit pretty much that same broad definition too. Due to the intense energy the rocket is exposed to and has to handle, it’s an incredibly difficult task to design them to be reusable. Many in “NewSpace” will vigorously argue that the US wasted its opportunities with Apollo or Shuttle and should have instead concentrated resources on a “proper” reusable vehicle – not a “pretend” reusable such as Shuttle that requires hundreds of millions in refurbishment between each mission. They also argue that the primary reason why rockets are so unreliable is due to the expendability of them which is a fair argument when examined in detail. Alas, the unreliability of the mission coupled with the value of the payloads relate to high insurance costs which turns out to be a very large fractions of the ultimate mission cost.

  24. Troy Prideaux
    May 14th, 2013 at 10:36 | #24

    Ronald Brak :
    Ikonoclast, you wrote that nothing remotely like the movie 2001 has come to pass, but we’ve actually done a lot of exploration of the solar system, includng Jupiter, just not by sending people. At this moment there are robotic explorers on Mars. Basically, if we detected a monolith around Jupiter today, we’d send HAL by herself.

    I think Iko’s point was that yes we significantly underestimated the advances in electronics, communication and computers, but by the same token, just as significantly overestimated the advances in propulsion and advanced transportation – where’s our flying cars? We’re still using 1950’s rocket propulsion technology; commercial air travel speeds are all subsonic now when there used to be a supersonic option and we were supposed to be at least in the hypersonic regime now! Not even the most advanced military jets operate at hypersonic speeds.

  25. Ikonoclast
    May 14th, 2013 at 10:39 | #25

    @Ronald Brak

    2001 envisioned human exploration, commericial space travel and very significant and large space stations and moon bases. Nothing like that has come to pass. I stand by my statement.

    That is not to devalue unmanned solar exploration. It’s very important even from a pure science point of view. And it’s the only feasible option for the foreseeable future.

  26. Ikonoclast
    May 14th, 2013 at 10:55 | #26

    @Ron E Joggles

    “Centrifugal” force is applied by an acceleration to move an object in a circle so technically I am right. However, I did not think of your point about straight line acceleration creating artificial gravity so that is a very good point.

    Here’s a poser for the physicists. I am not a physicist so I don’t know the answer. “Joggles” gravity is produced by constant acceleration or constant de-celeration of the space ship. In each case energy will be consumed the whole time, maybe from a nuclear or ion drive.

    With centripetal force, to use the correct term, the energy would be used spinning the “centrifuge” space station up to the required rotation speed. Once the space station is spun up, no more acceleration forces are applied so it appears we can then get the artificial gravity free forever for no more energy input. However, there is no such as a free lunch in thermodynamics and energy physics (at least in this era in this universe).

    So, what is the resolution of this seeming paradox? Will the rotating space station suffer gyroscopic precessional forces and orbital decay effects which will both require more energy inputs to correct? That’s my guess but the physicists can tell me. And what about a theoretical space station rotating far out alone in deep space and not orbiting anything? First, what is it rotating in relation to? (All motion is relative motion.) My guess it is rotating in relation to the scalar field of space itself. Pure “empty” space is now known to be not nothing but to be something, namely a kind of field.

  27. Troy Prideaux
    May 14th, 2013 at 11:24 | #27

    You’re confusing gravity with “work” I think. Gravity can be created with no energy input eg. by mass alone. The energy relating to gravity isn’t the gravity itself. but in the object’s location relating to the gravity field and is the “potential energy”.
    With regards to the spinning space station – energy is consumed in creating the torque, but once the station is spinning at the chosen rate, that energy is contained within the rotation of the mass. If the occupants of the station decided to move from the outside rim to the centre of the station, the station’s spin rate should increase to keep with the conservation of energy laws. The energy within the rotating station remains constant unless another torque (or drag) is applied.
    The only orbital decay should stem from external influences like atmospheric drag which is a real issue in low earth orbit (LEO) but not so much an issue in upper bound orbits.
    Yes, it’s totally impractical I think to rely on liner acceleration for artificial gravity as the energy consumption horrendous.

  28. May 14th, 2013 at 11:29 | #28

    No one’s getting a free lunch on a rotating space ship or space station. Just as rotating planets don’t need an energy top up to keep spinning, neither do space stations or space ships. (The earth’s rotation is very gradually slowing due to tidal forces, but that’s another matter.) If I were on a rotating space station and I climbed the ladder to the hub where I would be weightless, my spin would be imparted through the ladder to the rest of the station which would speed up. When I go down again the stations slows down to what it was before I climbed the ladder in the first place. It all adds up, so no free lunch. But I’m not an actual physicist so it might be best not to ask me what would happen if one attempted to run a hydroelectric power plant on a rotating space station.

  29. Troy Prideaux
    May 14th, 2013 at 11:32 | #29

    Replace liner with linear

  30. May 14th, 2013 at 11:39 | #30


    What a coincidence! Watched “2001” on the weekend.

    I agree “nothing remotely like” is probably a bit harsh. There is a space station still up there, but nowhere near the ideas in the movie. I didn’t take the movie as a prediction of the future so much as an analysis of the state of things around the time.

    It was much more realistic than his moon landing effort (yes, I’m joking)!

    Apparently some people interpret the black oblong thing as some religious reference and others take it to be an alien-higher-intelligence-evolved-to-a-form-of-pure-energy thing.

    I liked the fact that (the US) TPTB chose to deceive their (international, Russian?) partners with a fabrication about a disease outbreak so they could have the black oblong thing all to themselves. And then on the long voyage they had also programmed HAL to kill the humans if it “perceived” they were going to endanger the “mission”.

    I find it curious that the well-founded and widespread mistrust of the benevolence of power from the ’60s through to the ’90s appears to have been almost totally obliterated from our society today. How and why did everyone become so trusting of their rulers? My feeling is that the means and methods of propaganda have been advanced massively to bring us to this point. I suppose it would be called propaganda productivity gain.

  31. Ken Fabian
    May 14th, 2013 at 12:06 | #31

    The attractiveness of space as endless frontier feeds into our cornucopian streak – all that abundance just out of reach. But I seriously doubt the ‘just’ part; I suspect a lot of the optimism is misplaced and whilst the role Earth’s abundance has played in allowing us to get to where we are now is much underestimated by those with eyes on the heavens, the expected ease of exploiting off-planet resources is much overestimated. Forget the big numbers; Earth, even facing the problems we do, offers more opportunities and possibilities than the hard vacuum, hard radiation and hard to access resources of space.

    Pr Quiggin, I liked the joke offer – care to build a self supporting habitat in the Simpson Desert, High Altiplano or Antarctica? More essential resources, better climate and the chance to bail out when things get rough.

  32. Lord Foul the Despiser
    May 14th, 2013 at 12:09 | #32

    Of course this entire discussion will be rendered moot when the Worm of the World’s End finishes devouring the Cosmos later this year.

  33. Newtownian
    May 14th, 2013 at 12:13 | #33

    Good to see you indulging in a bit of fluff John though clearly you haven’t read enough science fiction else you would know its speculatively possible and at a much lower price.

    Further if the high frontier people get their way this could actually happen – to a degree.

    To wit:

    – getting into space – we have Arthur C. Clarke’s space elevator sprouting out of the equator starting at Sri Lanka http://en.wikipedia.org/wiki/Space_elevator_economics . It all depends on nanotube technology advances and the support of Richard Branson.

    – alternatively you could blast all the fertilised embryos into orbit you needed in one shuttle mission.

    – economic development of the infrastructure for space travel – the plausible answer here is self reproducing Von Neumann machines also made briefly famous under the term Grey Goo. These will process the solar system into product. As to who would own it, that is currently a topic under consideration by the lawyers. Case W. Res. J. Int’l L. 119 (2009)
    Establishing a Legal Framework for Property Rights to Natural Resources in Outer Space; Coffey, Sarah

    – ready made spaceships? – they are called comets. They are loaded with resources and with a nudge can do the job. http://en.wikipedia.org/wiki/Heart_of_the_Comet

    – who will do all this? John Galt of course. http://en.wikipedia.org/wiki/Atlas_Shrugged http://en.wikipedia.org/wiki/John_Galt

    – chances of success? – as above noted – consider the Fermi Paradox – http://en.wikipedia.org/wiki/Fermi_paradox

  34. Troy Prideaux
    May 14th, 2013 at 12:15 | #34

    @Ken Fabian
    Do you really think there’s that much optimism and appetite for space exploration out there? I can’t see beyond a small core group of believers these days.

  35. gerard
    May 14th, 2013 at 12:28 | #35

    The fact that no-one has sent a detectable signal in our direction suggests that intelligent life forms similar to humans are very rare.

    Hardly. It suggests that technological projects like Active SETI are rare. But nothing about intelligence makes such technologies and projects inevitable or even possible.

    I would guess that the majority of “intelligent” species in the galaxy have probably been something like hunter-gatherers.

  36. Ron E Joggles
    May 14th, 2013 at 12:31 | #36

    Power to maintain acceleration for the entire voyage would be essential for a human-crewed interstellar mission – accelerating for a while at the outset and then decelerating for a while at the end, and just coasting most of the way (with or without simulating gravity) would extend the trip by several millenia, I suspect.

    My understanding of physics is qualitative, and I’d be grateful if anyone could provide the formulae to calculate the duration of a voyage, given the distance (say 1200 lightyears) and acceleration of 1G (approx 9.8 m/s/s) to midpoint and deceleration of 1G to destination – and what would be the maximum velocity reached.

    Back to Iko’s poser – centripetal force to simulate gravity is the great advantage of a toroidal (doughnut-shaped) space station in orbit. Local factors like friction from trace atmosphere may erode rotational velocity, as may contrary movement of internal mass – though I’m sure these would be slight. You’d want to be able to stop the rotation anyway, for maintenance, loading, or for tasks requiring zero G.

    The station in deep space would be rotating in relation to space itself but necessarily also in relation to stars no matter how far away.

  37. Ron E Joggles
    May 14th, 2013 at 12:45 | #37

    PS: I still think we would be much better off concentrating on getting Earth back into a sustainable condition – it’s the only space ship we have!

  38. Ikonoclast
    May 14th, 2013 at 12:46 | #38

    Good points from Troy and Ronald. I don’t think I was confusing gravity with work but I was coming perilously close. Artificial gravity is another issue and there are energy and work involved in setting up a situation to provide artificial gravity.

    I think the true message of the thread is that endless-growth cornucopian optimism is unfounded both on earth and in relation to escaping earth and the solar system.

    My personal view on the distribution of intelligent life through the universe is this.

    (1) The natural laws of the universe have given rise to life on earth thus life could arise anywhere in the universe where the local conditions are conducive. The probability of conducive local conditons is very low and the probabiltiy of life arising in even conducive conditions must also be very low. However, given the vast size of the universe, it is likely that life has arisen in hundreds of thousand of locations in the universe. Then life has to evolve to intelligent life, another low probability event.

    (2) We might reasonably assume that intelligent life has arisen in at least a few thousand places in the universe.

    (3) However, given the size of the universe and its inflation rates early and now, the probability of two sets of intelligent life being even a “mere” 1,200 light years apart is very low.

    The Cosmos, in its “wisdom” has kept intelligent life disparate and well apart so it won’t fight. That might seem almost like conscious wisdom but I reckon it’s blind luck.

  39. May 14th, 2013 at 13:04 | #39

    @Ron E Joggles
    At one g acceleration it would take about 1,500 years for a spacecraft to travel the 1,200 light years to Kepler 62. Or at least it would take that long from the point of view of people left behind on earth. From the point of view of the spacecraft it would be less than 15 years.

    To travel 10 light years to Sirius at one g would take the ship 12 years for people observing from earth or 5 years from the point of view of the ship.

    To reach mars could take as little as three days, but you’d need an atomic clock to notice the time dialation effects at the speeds that would be reached.

    I could give you the equation used to determine this, but I don’t know how to type it in. (I just googled it anyway, so it shouldn’t be hard to find.)

    Unfortunately accelerating at a constant one g and surving at the speeds that would be reached is really tricky.

  40. Jim Birch
  41. Jim Birch
    May 14th, 2013 at 13:13 | #41

    Sorry, the link entry macro didn’t quite work as expected.

  42. may
    May 14th, 2013 at 13:17 | #42

    @Ron E Joggles


    what is mean’t by we?

  43. hc
    May 14th, 2013 at 14:27 | #43

    An implication of the view that we cannot settle on planets other than earth is that the human species is doomed and not only by the inevitable moment in 6 billion years when the earth crashes into the sun. It will occur long before that.

    If there are very low probabilities of catastrophic climate change, scientific experiments going seriously wrong, nuclear or biological warfare that wipes us all out, and if these very low probabilities are sustained over thousands of years then we have had it.

    Economists teach us that because we discount the future that events a few hundred years hence are inconsequential. I disagree. I think most of us assign positive value to the perpetuation of the human species. If that cannot occur we should all feel sadder now.

    Some cosmologists claim that we are soon to disappear. Carter uses Bayesian methods to argue that if you had to guess where we are in the evolution of the human species then, because human populations are greatest now with greatest likelihood, humanity is towards the end of their evolutionary span.

    Even if there are thousands of parallel life forms out there – the most plausible hypothesis – they will face the same survival dilemma. The chances are that fate will extinguish them before they get a chance to communicate with others. This is sometimes advanced as one reason we have not heard from other civilizations.

  44. Ron E Joggles
    May 14th, 2013 at 14:38 | #44

    @may Hi May. By “we” I meant the human occupants of Spaceship Earth. While it may be fun to riff on the remote possibility of interstellar colonization, I have no doubt that dealing with global environmental degradation is a little more pressing.

  45. Ikonoclast
    May 14th, 2013 at 15:20 | #45


    Yes, we are doomed. Individual death followed by species extinction at some point. These events must occur according to all the the known laws of biology and physics. There are series of extinction risk points for homo sapiens. Several of these risk points will occur this century and most of them is this millenium. A couple of “final” ones are a long way away but pretty much totally certain. The main risks are;

    1. Nuclear war
    2. Limits to Growth
    3. Climate Change
    4. Mass extinction event of other species
    5. Massive solar flares
    6. Gradual warming of sun to Red Giant (earth will be a cinder before R.G. stage)
    7. Heat death of the universe. (Or collapse to another singularity).

    Actually, try to imagine existing individually for all eternity until you become omniscient or else fail to grow further in knowledge and wisdom. Each state would actually be a kind of hell. To reach omniscience and perceive an “unchanging all” or to reach a limited stasis and thus be trapped and bounded forever. Be pleased there are ends as well as beginnings, I think.

    If I ever were to entertain a “religious” metaphysic, I would suggest that the “unchanging all”, which is also the same as nothing as there is no differentiation, periodically disinetegrates to create differentiation and thus being and things. It explodes from non-being into being at the singularity. The cycle plays itself out until all differentiation fails and it realises it is “one” and collapses back out of differentiated being into unified being which is also non-being.

  46. J-D
    May 14th, 2013 at 16:38 | #46

    Since this is an economist’s blog, I’m going to quote an economist:
    ‘In the long run, we are all dead.’

    And since this is a science-fictional topic, I’m going to quote a science-fiction writer:

    Only in silence the word
    Only in darkness light
    Only in dying life
    Bright the hawk’s flight
    On the empty sky

  47. Alan
    May 14th, 2013 at 17:35 | #47

    I’d add volcanic eruptions to Ikon’s list. In 1883 Krakatoa ejected 12 cubic kilometres of material. 74000 years ago the Lake Toba supervolcano in Sumatra ejected 2800 cubic kilometres. Humanity has survived at least one supervolcano catastrophe. Humanity would probably survive such an experience again, but I am not at all confident that civilisation could.

    Longterm I think humanity needs more than one planet. I’d be seriously surprised if the Kepler-62 planets are the first chosen. Exoplanets have proved much more common than astronomers expected. For example it was once thought that binary stars could never have planets although we now know that is untrue. Binaries are more common than single stars like Sol.

    One of the weaknesses in the OP is assuming that the nearest habitable planet is 1200 kilometres away.

  48. Newtownian
    May 14th, 2013 at 18:12 | #48

    @Jim Birch

    You’ve overlooked the imaginative idea of the Bussard Ram jet. http://en.wikipedia.org/wiki/Bussard_ramjet. That said the high energy protons etc. are a bit of a worry.

  49. Newtownian
    May 14th, 2013 at 18:30 | #49

    Anybody have opinions on absurdly large telescopes as an alternative to travelling there? These could go a long way toward detecting life and maybe examples of the Fermi paradox via climate change – a CO2 sweatbox in mild earthtype orbit.
    http://en.wikipedia.org/wiki/Extremely_large_telescope. Personally I think they are great value for money – $1 billion or so to find out where life likely exists nearby and many other utterly unforeseeable discoveries – especially given the nonsense and dross, moneys are spent on in this country and elsewhere these days (more casinos football fields and overpriced apartments).

  50. May 14th, 2013 at 18:34 | #50

    I have long thought that a return to the moon to make a permanent base has a lot more sense than going to Mars, at least if you we can get clear confirmation of substantial amounts of ice near the surface at the lunar poles.

    The best justification that I can see for it (yet it seems rarely discussed) is to serve as a biological and technological lifeboat – sort of a souped up version of that Global Seed Bank up in Spitsbergen, as well as a depository of all knowledge needed to rebuild a civilization in the event of near total collapse. (Although I suppose it has to be said that the de-centralisation of knowledge via “the cloud” makes the loss of knowledge less and less likely as the decades roll on. Still, if you run out of electricity, getting information out of the cloud is a major problem!)

    Apart from that, the Moon seems a good place for radio astronomy, and (it seems to me) is really not all much less hospitable than Mars, with its extremely thin atmosphere and extreme distance from Earth in the event of emergency. I think imagery from Mars gives a deceptive impression of its similarity to Earth, although it does have water going for it.

    As for further expansion into the universe: yes, one has to pretty much pin one’s hopes on a breakthrough in fundamental physics, but no one can accuse scientists of feeling they have just about solved everything with only a bit of tidying left, as they are said to have thought at the start of the 20th century. There seems plenty of room for dramatically new stuff to be found yet, and who knows what that may hold for galaxy exploration…

  51. May 14th, 2013 at 18:50 | #51

    Grimbister replies to – J-D at # 19

    You reckon some nerd et me lunch?
    Far from the truth.
    Wrong, so unfortunately wrong. It was that Arthur, the tealad at Calligulashorse.

    Can’t keep his big teeth off anything.
    Lost a few girlfriends that way, has Arthur.
    (Raiding their fridges, I mean.)

    Which causes me to speculate what would happen if a bloke like Arthur ended up signed on as crew on some starship.
    By the time it reached Betelgeuse he’d have eaten everything on board.
    The trail of ‘spacejunk’ along the line of flight would definitely be a navigational hazard for the next ship out.
    They never touched that sore of embarrassing stuff in ‘Startrek’ or ‘Blake’s Seven’.

    But then again; consider that Arthur could be connected to the reverse pointing plumbing and be fed an intense diet of fried beans –
    Admittedly it would still take a while to get up to light speed with such a ‘green’ form of propulsion – and there’s no way I’d pretend it would be ‘clean’.
    And if anyone doubts what I say here – consider DARPA’s help with the American bicycle team at the Olympics (was it Atlanta?) some years back.

    There is, of course, the problem that if the prototype starship ran out of beans that Arthur would unplug himself and search for some other form of tucker.

    But I suppose that is why ‘the immaculate one™’ stretched space out so far as to preclude the loose cannons (like Arthur) of a hunter gatherer species such as homo sapiens from getting too far away from their home planet.

    PS – Arthur – you’ll see him over their on the right hand side of those despicable pages of Calligulashorse . com.

  52. May 14th, 2013 at 19:01 | #52

    On a more serious note – consider Churchill’s summation of the Royal Navy.
    “Rum, bum and baccy.”
    If interstellar navigation ever happens it’ll be accomplished by a standing crew of the psych profile of male airline attendants.

    They’ll assiduously attend the frozen fertilized blastulae of the arriving generation – take risk management to the stage that the entire enterprise will hover in space somewhere mid-path like that apocryphal donkey stuck between two bales of feed.

    Nope. Thankfully the species is subject to exactly the same rules as is the individual.
    Best we make the best of the allotted time we have.

  53. May 14th, 2013 at 19:06 | #53


    I’m quite excited by the prospect of extremely large telescopes. I like to see one in space in a sensible orbit where it could take long exposures of objects of interest. It would be possible to make out the surface features of planets around other stars. But just being able to reliably image exoplanets at all will let us detect markers of life such as oxygen or methane and detecting pollution could indicate technology using intelligent life. (Or would that be technology using stupid life?)

  54. Salient Green
    May 14th, 2013 at 19:17 | #54

    I think this is a great topic to stimulate lateral thinking in an entertaining way and shows John Q’s skill as an educator.
    While I have always had a keen interest in Astronomy I have resigned myself to the inescapeable fact that with our present knowledge of physics, we will never achieve interstellar travel.
    I’m going to suggest that Humanity requires a period of introspection before we set out for the other planets in our solar system, let alone around other stars.
    I think there is much to explore about ourselves, our brains and the way things happen when we really work together for common good.
    If the Human race were technologically able to set off among the stars in our present state of ‘development’, what damage would we do?

  55. May 14th, 2013 at 22:48 | #55

    This is the outer limit of our enterprise –

    Anyone reasonable might suppose that Quiggin has a point.

    The MAJOR point might be not to let anything like Costello oversee even minor projects.
    We are discussing here grand leaps of the imagination.
    The grand problem with the island of Oz is that we cannot find the means to put anyone in charge who can display imagination – or the means to develop their imagination toward any sort of acceptable outcome.
    The acceptable outcome I mean is about providing benefit for all stakeholders within society.
    We seem to be stuck in a blind.
    The masters keep droning on forever about pettifogging stuff that might have bankers, numbercrunchers and all sorts of mindless dolts going back trying to analyse their drivel.
    Perhaps they might find a word, phrase or two encouraging to believe that they are right.

    The next press release will tell ‘em that they were astoundingly wrong..
    Or so it appears on the propaganda pages and in the thirty second grab of the bullshine news.
    But where do the sweaty little buggers who either believe, or take advantage of this sort of crapola – where do they live?
    What corrosive littoral zone of habit do they inhabit?

    And how could any ‘happy band of brothers’ (ask Lord Nelson) ever find a way to escape the clutches of their sort in order to undertake any great enterprise of discovery into space and out toward the stars?

  56. May 14th, 2013 at 23:01 | #56

    PS –
    I’d love to be a fly on the wall at a Costello family barbecue.
    I doubt very much whether Tim, the do-gooder would grumble overmuch when Pete gave him a few hints about how to pick up some extra credits on the fast money market.
    What an incestuous mob of bludgers they all are!

    Rocket science?
    I believe not.

  57. May 15th, 2013 at 00:03 | #57

    I refer you back to Krugman’s paper on the Economics of Interstellar Trade.

    And we in the States will see your Outback and raise you the water-table-less West.

  58. paul walter
    May 15th, 2013 at 05:00 | #58

    It must be a fascinating thing to have the imagination of an economist.

  59. TerjeP
    May 15th, 2013 at 09:47 | #59

    Why is NASA taxpayer funded?

  60. Jim Birch
    May 15th, 2013 at 10:04 | #60

    Because it was discovered a long, long time ago that group objectives are better met by community action. Have you tried building your own sewerage system recently?

  61. May 15th, 2013 at 10:09 | #61

    Because it provides public goods. Unfortunately, while it’s public goods don’t get a lot of attention, it’s public bads do.

  62. May 15th, 2013 at 10:27 | #62

    One prime example of a NASA public good, close to the hearts of all Australians but even closer to their integumentary systems, was them eventually figuring out, “Hey, we’ve made some sort of massive hole in the ozone layer. Maybe we should stop doing that.”

  63. Troy Prideaux
    May 15th, 2013 at 10:57 | #63

    Agreed. Yes, NASA (and its dinospace subsidiaries LockMart/Boeing etc) is/are littered with unparalleled volumes of white collar welfare, but they have done an awful lot of public good IMHO. Companies like SpaceX are game changing the light/medium and heavy lifting markets – a good thing – but you still need a government funded space administration like NASA to manage the science and the missions to gather and analyse the science.

  64. Paul Norton
    May 15th, 2013 at 11:19 | #64

    hc @44:

    Carter uses Bayesian methods to argue that if you had to guess where we are in the evolution of the human species then, because human populations are greatest now with greatest likelihood, humanity is towards the end of their evolutionary span.

    The Carter Prophecy is the jumping-off point for Stephen Baxter’s Time. At one point in the story Baxter has an anonymous blogger circulating arguments against Carter to be used in debate with people, including:

    Appeal to common sense. Look back in time. A human of, say, AD 1000 would likewise have been sitting on top of an exponential curve reaching back to the Palaeolithic. Would she have been correct to deduce she was in the last generations? Of course not, as we can see with retrospect. (You may find Carter proponents countering this one by saying this is a false analogy; humanity today faces far graver extinction threats than in AD 1000 because of our technological advancement, the way we have filled up the Earth, etc. And it took our modern-day sophistication to come up with the Carter argument in the first place. So we have formulated the Carter prophecy at precisely the moment it is most applicable to us. But then you can argue that they are appealing beyond the statistics.)

  65. wilful
    May 15th, 2013 at 11:44 | #65

    Terje, you might possibly in the near future have the beginnings of a point, but if you think that private enterprise would have achieved anything whatsoever over the past six decades in space, you’re deluded. Without NASA, the rest of the US military, the Soviet programs and European government efforts, all by that accursed government, we would not yet have a single satellite in orbit. There is no way whatsoever that Elon Musk’s or Richard Branson’s (barely economic, mostly ego (not that I have a problem with that)) endeavours could have existed without several decades of government investment.

  66. Troy Prideaux
    May 15th, 2013 at 15:16 | #66

    wilful :
    There is no way whatsoever that Elon Musk’s or Richard Branson’s (barely economic, mostly ego (not that I have a problem with that)) endeavours could have existed without several decades of government investment.

    The Branson suborbital venture could be debatable with regards to requiring or even relying on any form of previous government investment. The propulsion system technology was actually from a completely non government base; what’s more, it was from a purely amateur/hobbyist development process. The aircraft (WK2) and spacecraft(?) (SS2) were mostly developed by Burt Rutan (revisions of XPrize winning WK1 & SS1 Combo) who is famous for his unique and out-of-the-box designs. I think it’s safe to say neither was based on or borrowed unique design features from existing craft or design concepts that originated from government ink. It could be argued the turbofan engines that power WK2 are a somewhat distant derivative of government sponsored R&D, but whether that’s enough of a dependence to confidently claim that excluding such a link would be a showstopper is marginal.

  67. John Quiggin
    May 15th, 2013 at 15:22 | #67

    @Salient Green

    Thanks, Salient. Compliments are few and far between in this business, but always appreciated.

  68. John Quiggin
    May 15th, 2013 at 15:29 | #68

    Suborbital space flight is a bit like circumnavigating the world by walking around one of the poles: it satisfies the standard definition, but doesn’t really achieve much. That’s why real space programs skipped that step and went straight to orbital flight, more than 50 years ago now.

  69. Troy Prideaux
    May 15th, 2013 at 15:38 | #69

    Of course, I should have also pointed out that Branson’s VG is probably the only prominent exception to the point you were making (maybe XCOR’s Lynx too), but there’s no true examples of completely private *orbital capable* operations out there with no reliance on both government support and previous R&D.

  70. Troy Prideaux
    May 15th, 2013 at 16:07 | #70

    John Quiggin :
    Suborbital space flight is a bit like circumnavigating the world by walking around one of the poles: it satisfies the standard definition, but doesn’t really achieve much. That’s why real space programs skipped that step and went straight to orbital flight, more than 50 years ago now.

    That’s probably a touch unfair. All previous government orbital capable space programs didn’t skip that step and those at Scaled/Virgin & XCOR would probably argue that their suborbital capability is a steppingstone for orbital aspirations.

  71. May 15th, 2013 at 16:20 | #71

    @Troy Prideaux

    The Soviet Union didn’t bother with sub-orbitals. Unless one defines space as being so low the Nazis got there first, Yuri Gargarin was the first person in space and the first to orbit the earth. He actually holds the record for doing the least number of orbits – one.

  72. May 15th, 2013 at 16:27 | #72

    The year Yuri Gagarin went into space is also easy to remember. In weightlessness there is no up or down and 1961 is the same whether it is the right way up or upside down. (Turn your monitor upside down if you don’t believe me.) But oddly enough this wasn’t the reason the Soviet Union shot a person into space that year.

  73. May 15th, 2013 at 16:40 | #73

    I’ll just second that Burt Rutan is a brilliant engineer. If there is anyone who could build a functioning space ship without the benefit of a century of research and development into heavier than air flight by others it would be him. Or possibly a wizard.

  74. Troy Prideaux
    May 15th, 2013 at 16:48 | #74

    Ronald Brak :
    @Troy Prideaux
    The Soviet Union didn’t bother with sub-orbitals. Unless one defines space as being so low the Nazis got there first, Yuri Gargarin was the first person in space and the first to orbit the earth. He actually holds the record for doing the least number of orbits – one.

    Yes indeed, they did bother with them. After building an entire V2 production capability after the war, they further went on to develop a suborbital program even more extensive than the Americans – R2, R5, R11, R3, R7 etc. You couldn’t just jump straight into orbital capability from nothing.

  75. sunshine
    May 15th, 2013 at 19:11 | #75

    Why the desire to see humanity continue forever ? How to justify this wish ? Where does it come from ? Im not sure I was there when god handed that one out . I do care about those currently living members of the animal world, but if those trillions of unborn future ones didnt get to live ? Not so sure that matters much to me, or for any other reason. The universe may just as well be better off without them , .

  76. hc
    May 15th, 2013 at 19:48 | #76

    Paul Norton @14, Was there a population surge leading up to 1000 AD? I think if there was then it was a pimple compared to the massive increase over the last 200 years.

  77. May 15th, 2013 at 22:02 | #77

    Jim Birch is right. You simply can’t travel at anywhere near the speed of light, because collisions with atoms are too damaging. Just imagine how bad hitting a grain of sand would be. So you are going to be in space for a few thousand years.

    But don’t worry, we’ll have suspended animation by then!

  78. Patrickb
    May 15th, 2013 at 22:41 | #78

    AFAIK there is no empirical evidence for life anywhere in the universe other than here. There may be inferences that we can make that indicate that there should be life elsewhere but sadly up to today we have not been able to detect any intelligent life other than what we find on earth.
    It’s a bit like this book I’m reading on the historical figure of Jesus, its in a small font, it’s well footnoted and it’s a few hundred pages. After reading a third of it the message from the author is plain: there is almost no direct evidence whatsoever for the historical figure of Jesus.
    OK, a bit OT but it fascinating how belief in alien life has become a characteristic of recent western culture to the extent that it is largely unquestioned and unquestionable.

  79. TerjeP
    May 15th, 2013 at 23:07 | #79


    Satellites are fantastic. The rest of the achievements in space seems mostly about nationalistic ego. It’s nice we visited the moon and built a space station, and these feeds our dreams. But they aren’t particularly useful outcomes for humanity in any practical sense. I enjoy knowing about the planets and what they look like and pondering settlements on Mars or terraforming Venus but NASA seems to be a big money pump designed to give engineers big toys. Sure there are spin offs but there are also plenty of other clever things Americans could have done instead. They could have had more missions to the ocean floor. Or better homes. Or rid the world of polio already.

  80. May 16th, 2013 at 00:21 | #80

    A rat done bit my sister Nell,
    With Whitey on the moon,
    Her face and arms began to swell,
    And Whitey’s on the moon,
    I can’t pay no doctor bill,
    But Whitey’s on the moon,
    Ten years from now I’ll be paying still,
    While Whitey’s on the moon…
    -Gil Scott-Heron

  81. zoot
    May 16th, 2013 at 00:21 | #81

    True Terje, but they insist on wasting their money starting wars that they can’t finish.

  82. paul walter
    May 16th, 2013 at 02:28 | #82

    Miscegenation?@Paul Norton

  83. May 16th, 2013 at 05:34 | #83

    In data communications we gain efficiency and security by compressing and encrypting data, which turns the stream of bits into something closely resembling noise. So even if aliens were broadcasting using a technology we could “hear”, we might not be able to tell it apart from the background noise.

    But then consider how much radio communications has changed just in the last 20 years – from analogue mobile phones at 1200bps to LTE at 25+ Mbps. Samsung have just invented a system which essentially sends a tight, point to point radio beam to each terminal (phone) at gigabit speeds – this would be pretty much impossible to detect from any distance, and at the suggested speeds would obviate almost all other radio communication, including radio and TV.

    And this all assumes that we won’t one day soon discover something better than electromagnetic radiation for communication. If for example we were to discover a means of low power, high bandwidth point to point communication over long distances, it’s difficult to believe that radio transmission of any kind would continue for more than a couple of decades after commercialisation. I’m looking forward to someone discovering how to communicate using quantum entanglement – which would have the additional advantage of perhaps being instantaneous.

    Given the march of human technology, it seems to me that we would struggle to identify evidence of even moderately advanced alien technology even if it was right in front of us. Why would we send a space ship when a swarm of nanites equipped with instantaneous long distance low power communications would do the job? These things could easily be everywhere, and yet we don’t have the technology to see them.

    The Fermi paradox is perhaps not a paradox, and the Drake equation is misleading. Perhaps the reason we haven’t seen any little green men just yet, is because they are much smaller than we expect?

  84. Paul Norton
    May 16th, 2013 at 06:19 | #84

    hc @74, I was quoting an imaginary blogger in a work of fiction, and the words quoted shouldn’t be taken as representing my own views.

    As it happens there does seem to have been something of a population surge around 1000 AD, but it was followed by a decline soon after, and in any case, as you say, it was at a much slower rate of growth, from a much lower base, than the current population surge.


    Paul Walter @80, can you elaborate?

  85. Ootz
    May 16th, 2013 at 09:45 | #85

    Why this dream of intergalactic escape velocity, and balanced budgets?

    “If we grant that human existence is the state of damnation, two possibilities follow. Either we can learn to retrace the stages of our fall into matter, and so escape, or we can devise some means of extinction of personality. The pagan art and culture of the world, past and present, is divided in the pursuit of these alternatives. On one hand art is followed as a continuous labyrinth in which by blind, dogged persistence we may struggle upward by means of will power and ethical struggle. On the other hand there is the intellectual course presented by Mr. Eliot, in which we move from one intensity to another, towards a final flash of awareness and extinction. In the one art – that linked with Plato’s cave man – Time, continuity, dialectic, are of the essence. In the other, time is lost in simultaneities and juxtapositions.”

    H. M. McLuhan,
    Eliot and the Manichean Myth as Poetry (unpublished),
    p.3, 1952.

  86. sunshine
    May 16th, 2013 at 09:45 | #86

    I agree . lots of scientific techno goodies have come from space research . But they could sill have come otherwise . Much good could have been done here on earth with that money .

    Space programs are not just nationalistic ego. -Desire to send embryos or digitised human consciousness into space to spread ,save or continue the race I just dont get . Theres been no mention here yet of saving any of the non human consciousness either .I care about the future for humanity because those here now will be living in it tomorrow etc , and because our kids will, and they will probably want to have kids too . So theres a kind of connection that rolls forward like that . But whether we are around in 1 or 50 million years or not doesnt seem vitally important to me .

    I know this is an isolated thought experiment thread of a blog, and some have expressed concern for our earth , but I get the feeling that ,when it comes down to it ,the mere concept of distant future human consciousness is more important than the sum total of all non human consciousness (and possibly a good deal of the human consciousness too ) which is alive here now . Im getting impression that the entire biosphere -all of life – doesnt seem to compare much to the apparent glory of human consciousness or continuation. Humanistic not just nationalistic ego .

    I hope that doesnt sound too unfair to some as I know there are lots of caring souls who read this blog .

  87. Paul Norton
    May 16th, 2013 at 11:04 | #87

    michaelfstan @3 is the only person thus far to mention wormholes. This concept is deployed by, among others, Baxter & Clarke in The Light of Other Days, Peter Hamilton in his Commonwealth Saga, and the Killer Bs in the Second Foundation Trilogy. It would be good to get some comments and/or links to current knowledge on the practicalities of wormholes.

    Wormholes have nothing to do with Frank Herbert’s sandworms, Stephen Donaldson’s Worm of the World’s End, or the Channel Nine election worm.

  88. Troy Prideaux
    May 16th, 2013 at 11:09 | #88

    @Mark L
    This has probably already been mentioned (apologies if I missed it) but if we are relying on electromagnetic based (say radio) communications to detect transmissions from intelligent life, we also must allow for the lag time of the message to reach us. In terms of interstellar communications, we could be talking thousands of (earth) years lag. What’s more, the power of the transmission will need to be really substantial when you factor in inverse-square losses etc.

  89. Mike Smith
    May 16th, 2013 at 11:43 | #89

    I am nervous about suggesting that John Q got his maths wrong, but I think he may have perhaps possibly got his maths wrong.

    Consistent with what has been said by others above eg Peter @ #10, I can’t see that the average cost per light second of a short trip is necessarily the same as the marginal cost per light second: the considerable costs of escaping gravity and initial acceleration apply once per trip, twice in a return trip, but not every klight second, for example.

  90. May 16th, 2013 at 11:54 | #90

    @Paul Norton

    Wormholes are things that we have no good reason to think exist, but which aren’t impossible as far as we know. While interesting to speculate about, the least brain taxing option given the lack of evidence for their existence is to assume they don’t exist, as it seems unlikely that the universe is arranged to make it easy for us to have Star Trek type adventures. If wormholes do exist then it could be possible to arrange it so the entrance and exit are next to each other and you will come out of the exit before you go into the entrance. Whether or not this woudl instill a desire within you to kill your grandparents is unknown. If you don’t think the universe would allow these sorts of shenanigans, then the universe may not allow wormholes.

  91. Nick
    May 16th, 2013 at 12:08 | #91

    @John Brookes

    “Jim Birch is right. You simply can’t travel at anywhere near the speed of light, because collisions with atoms are too damaging. Just imagine how bad hitting a grain of sand would be. So you are going to be in space for a few thousand years.”

    If you’re travelling near the speed of the light, you may as well imagine yourself as particles getting bounced around in an accelerator – hence the massive amounts of radiation produced when you collide with hydrogen atoms…

    OTOH, short of bringing several million tonnes along with you, the energy from colliding with all those hydrogen atoms is probably the only feasible way of fuelling the journey in the first place 🙂

  92. hc
    May 16th, 2013 at 12:16 | #92

    I am interested in the fact that this post has aroused so much interest both here and at Crooked Timber. Apart from being an interesting post – well done John – isn’t it nice to use our brains to think about things that are not defined by politics? (I agree some of the discussion at CT has become political but most isn’t).

  93. paul walter
    May 16th, 2013 at 12:27 | #93

    Worms can be a problem. Had a dose of threadworm as a kid and had to swallow this awful stuff from the chemist. After that, no more itchy wormhole.@Paul Norton

  94. Troy Prideaux
    May 16th, 2013 at 12:32 | #94

    Mike Smith :
    I am nervous about suggesting that John Q got his maths wrong, but I think he may have perhaps possibly got his maths wrong.
    Consistent with what has been said by others above eg Peter @ #10, I can’t see that the average cost per light second of a short trip is necessarily the same as the marginal cost per light second: the considerable costs of escaping gravity and initial acceleration apply once per trip, twice in a return trip, but not every klight second, for example.

    Dunno, you need mass to enable energy to be useful (provide propulsion), alas, an inconvenient and unavoidable fact and for every kg of mass used to propel the craft through the cosmos, many multiples of mass and energy are required to actually lift and accelerate that mass, so you’re constrained to the rocket equation with the added inconvenience of having to lift through a gravity field.
    John’s equations, whilst very simplistic, are probably (maybe^2) not that far off the mark.

  95. may
    May 16th, 2013 at 15:06 | #95

    well the space cadets at the fin have surprised me.

    i expected them to go ballistic yesterday.

    splashed headlines and incompetence everywhere.

    but it was all mealy mouthed.

    i had to hunt around to even find the size of the deficit.

    around 19 thousand million.

    disability cost turns out to be around the same.

    does that mean without helping out the disabled the budget was balanced?

    i don’t know if i’m joking or not.

    yesty also had a heartwarming story of profit taking medical person gifting 85 million dollars to his family.
    isn’t that nice.

  96. May 16th, 2013 at 15:15 | #96

    Many years ago 10,000 people was a number more or less pulled out of a hat for a minimum colony size, based upon how many people would be required to prevent inbreeding. (Given how long ago this was I can’t help but wonder if it was actually how many people of northern European decent were required to prevent inbreeding.) But given that we can now print out DNA and that we’re not likely to shoot anyone into interstellar space before we finish work on developing reliable artificial sperm, inbreeding is not a problem. But DNA is a kind of an old fashioned molecule and it seems likely that our star colonists will have something a bit less shoddy than that in their cells by the time they are ready to shoot themselves across the universe. And cells are a bit squishy too, so they may as well get rid of them as well. After all, it would probably help save on their insurance premiums. It might be safest to send simulated humans in a computer instead of physical ones. According to Ray Kurzweil computers will be able to simulate a human brain in 26 years time, but assuming you don’t buy into his particular brand of nuttiness a much more realistic estimate is that it will take at least 28 years. So just sending a computer instead of squishy people full of water who are addicted to oxygen and food could save a lot of resources. Program people can be switched off to save on energy on the way. (Yes, switching them off will kill them, but they will be ressurected when the power returns. It’s kind of like how electroshock therapy kills us, but then we reboot.) Since there’s no hurry when sending program people there’s no need to try to approach the speed of light to go as fast as possible. And since program people won’t need an earthlike planet we can send them to a nearby solar system instead of some distant place with oxygen. Once they get to their destination they can print out some robot bodies, which is something we’re working out how to do at the moment, and build a “laser” or other communication device to let us know what they’ve found. And if anyone else wants to go there they can send the relevant details down a laser beam and get printed out at the end. Or it might be cheaper to use snail mail and send information in a physical medium. It all depends on how the technology pans out.

  97. Paul Norton
    May 16th, 2013 at 18:30 | #97

    Ronald Brak @46:

    It might be safest to send simulated humans in a computer instead of physical ones.

    But look at what Voltaire and Joan of Arc got up to in the second Foundation Trilogy. 🙂

  98. Mel
    May 16th, 2013 at 19:07 | #98

    @John Quiggin

    “Thanks, Salient. Compliments are few and far between in this business, but always appreciated.”

    If it was up to me you would be named President-for-Life, all school children would be forced to read Zombie Economics and all your enemies would be put to the sword.

    There you go, another compliment 🙂

  99. May 16th, 2013 at 19:29 | #99

    @Paul Norton

    I wish I could, but I haven’t worked out how to buy books off the internet yet.

  100. John Mashey
    May 17th, 2013 at 16:15 | #100

    See #157, #162 and #165 over at that Crooked Timber thread. Some questions are philosophical, but basic physics doesn’t care much. The only signals we’d ever see from nearby aliens would happen only if they are contemporaneous and spend massive amounts of energy beaming at us, at least now and then, over long periods.
    Forget about picking up alien broadcast leakage.

    As for belief in aliens, it is (oddly) included in recent US survey mentioned in National Geographic.
    It is summarized and the actual questions and % are here.

    Q10 (Do you believe aliens exist, or not?) is badly-posed if it was supposed to be a conspiracy-theory question. Actually, it’s badly posed, period, when folks at NASA tell me they wouldn’t be able to answer it.

    A good conspiracy theory question would be:
    Do you believe aliens exist here on Earth, but governments have hidden this fact, i.e., like Men In Black?

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