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Musings on the Ages of Man

Centauri Dreams takes an optimistic view of the human future, one in which interstellar flight becomes a reality at some point in this millennium. My impression is that we’d all better be optimists. Think about the Drake Equation. Perhaps its most significant variable is the lifetime of a technological civilization, a figure that has implications for any creatures who have developed the tools to go into space. If the lifetime of such a civilization averages a million years, then the ‘where are they’ question Fermi asked becomes more charged. Shouldn’t we be detecting them?

But if the average lifetime of a technological culture is, say, five hundred years, then we may be confronted with a galaxy filled with wreckage, planets where life persists in evolving and forming intelligent beings who bring about their own destruction. Like I say, I’d rather be an optimist, but none of us knows the real answer. I note that Jan Zalasiewicz (University of Leicester) has offered up a new book that assumes at least long-range limits for our own species. Thus this comment:

“From the perspective of 100 million years in the future–a geologist’s view–the reign of humans on Earth would seem very short: we would almost certainly have died out long before then. What footprint will we leave in the rocks? What would have become of our great cities, our roads and tunnels, our cars, our plastic cups in the far distant future? What fossils would we leave behind?”

On the other hand, Zalasiewicz is a geologist. He’s used to working with time measured in eons, and even a million year run for humans would be dwarfed from that perspective. The book, called The Earth After Us (Oxford University Press, 2008), asks what alien explorers might discover if they arrived on Earth one hundred million years from now. Their scientists would find evidence of vast tectonic movements, ice ages and the movement of oceans, a geological history sprinkled with life and its occasional catastrophic collapse. They might also find, in a single layer of rock, signs of cities and the creatures who built them.

The concept of ‘deep time’ was originally developed to encompass the perspective changes induced by geological study (thus 18th Century mathematician John Playfair’s comment upon studying a particular site, “the mind seemed to grow giddy by looking so far into the abyss of time.” We might also consider it in terms of communication, as Gregory Benford does in his book Deep Time: How Humanity Communicates Across the Millennia (Bard, 2001). Or maybe we should think about deep time in the sense of placing human awareness in the broadest possible context.

Those of you who have read Greg Laughlin and Fred Adams’ The Five Ages of the Universe (Free Press, 1999) will readily identify with the concept. Laughlin and Adams look at the history of the universe in terms of ‘cosmological decades,’ each decade being ten times as long as the one before. When I say that the end of stellar burning 100 trillion years from now is only the early part of the story, you’ll understand how interesting is the possibility of intelligent life surviving the entire cosmic history.

As to Zalasiewicz (whose book I much look forward to reading), another question posed by alien archaeologists sifting through the traces of our cities in layered rock is this: If a technological civilization does indeed have a sharply limited lifetime, then how long is enough to ensure survival elsewhere? In other words, if 10,000 years is the technological average, is this long enough for that culture to have spread to space habitats or the nearest stars? An optimist’s answer to that one comes easy: Yes, we’ll have that chance to move outward before the big collapse, but given the uncertainties, we won’t want to wait too long.

Comments on this entry are closed.

  • tacitus September 29, 2008, 15:52

    Although I have no doubt that we still have many dangerous hurdles to overcome, I too am optimistic about the future. Even as weapons technology has become exponentially more lethal, we have made great strides in places like Central and Western Europe, which, within my parents’ lifetime was still embroiled in what was merely the latest war in centuries of almost continuous national conflicts. Sure, there are still a few of hot spots where deep seated enmities of the past (e.g. the Balkans) are yet to be overcome, but even there things are improving.

    Of course, there is still much trouble in other regions of the world, and will be for decades, but Europe for all its past turmoil, is an example of what can be done once the stakes become so high — mutually assured destruction on one hand, and economic stability and prosperity on the other — that to go to war becomes almost unthinkable.

    And I am actually quite optimistic about the Islamic nations in the long run — even the one founded by revolution just 30 years ago. The Mullahs (i.e. the ones who really hold the power in Iran) may be actively seeking nuclear weapons but (a) I don’t believe the fat-cat Mullahs will do anything to risk their lives or their grip on power (b) they will never have anything like enough nukes to sink the world into a civilization-ending nuclear conflict anyway. And look at arch-rivals India and Pakistan who have fought a couple of limited wars and several other skirmishes. They are both nuclear powers these days, but neither side appears ready to use them offensively against the other even though the conflict over Kashmir remains tense and unresolved.

    Nuclear terrorism will probably be a big problem some time in the future, but I can’t see how that could be civilization ending. Global warming may cause great suffering and loss of life, but even in the likely worst case scenario, we will probably be able to maintain our technological progress, even if it is slowed for a time.

    So, apart from a short period where an unanticipated comet/asteroid strike is possible (within the next 50 – 100 years or so) and other possible, but extremely unlikely (in the short term) space-born disasters like nearby gamma ray bursts and supernovae, then I believe the biggest threats to our existence as a species are bioterrorism and (in the future) “nanoterrorism”.

    Advances in genetic manipulation may bring some truly horrendous biological weapons within the reach of individuals at some point in the future. While I do not fear that a rogue government in this regard, there is reason to fear things like apocalyptic cults (of all religions) or insane individuals who want nothing more than to bring forward the end of the world for religious or even just twisted personal reasons.

    Even if we avoid total annihilation from bioterrorism, once nanotechnology is perfected then a similar threat from equally insane individuals wielding nanotech weapons will need to be met. Hopefully, there will also be efforts to introduce nanotech countermeasures that defend our bodies from such attacks, but who knows if they will be effective?

    Anyway, to sum up, I think the greatest threat to our survival as a species in the future, will come from insane individuals or groups who gain access to ever more accessible bio- and nanotechnology. We already have examples of small religious cults plotting terrible destruction to achieve their twisted ends and there are plenty of examples of suicidal maniacs who want to take as many people with them as they can. These people will turn out to be much more dangerous in this regard than religious regimes or brutal dictators who, despite their repressive and murderous ways, still value their own lives and the power they wield.

    On balance, I still think we will survive to see our species leave this solar system. Whether we develop into a multi-system civilization, I think depends more on what’s out there. If Earths are so rare that we cannot find another, then it will be tough-going, but I doubt we will give up, even then.

  • Adam September 29, 2008, 17:38

    Hi Paul

    We might die as a species – certainly we won’t be unchanged by the billennia ahead – but geologists should know better than to write us off as pioneers of a new “life-stream”. Consider the first hexapods on land, or the first tetrapods. Both life-streams are still going strong, with genera essentially like the ancestral forms still in existence. ‘Neoceratodus’, the Australian Lungfish, is not much different to its fossils from c.90 Mya. Likewise for many other species.

    We might well begin a phylum – a life-stream – that will last a billion years or more.

  • tacitus September 29, 2008, 17:50

    On a lighter note, Douglas Adams was convinced that a collapsed civilization would leave evidence behind — in the form of a Shoe Event Horizon

    I would tend to agree that by the time we’re done with Earth, we well have left enough evidence behind for it to be fairly obvious that there was intelligent life on this planet at some time in the past — even millions of years in the future.

    For example, we have greatly enhanced the odds of fossilization of our bones by burying them in organized ranks of graves all over the planet. In many cases we have left granite tombstones right next to them, along with other imperishable artifacts made of precious metals and gemstones. Sure, tectonics and vulcanism will claim the majority of all that given enough time, but I think we’d be looking at time scales approaching billions of years before the evidence is almost gone.

    And don’t forget the stuff we’ve left (and are going to leave) on the Moon and Mars. Barring a solar-system wide calamity, at least some of that will be exactly where we left it for a very, very long time.

  • Benjamin September 29, 2008, 19:47

    I can’t help but think that the interstellar expansion of humanity is likely to come long after the expansion in our own solar system.

    It is easily possible that through chance or some fault of our own – probably the latter, but you never know – technological civilisation could end on earth, for a time or permanently. But the earth has a forgiving environment, in the sense that unarmed, naked humans managed quite successfully for hundreds of thousands of years. The same is not true of Mars. If we can sustain human life on Mars, that is necessarily technological life.

  • Paul Titze September 29, 2008, 20:17

    Tsiolkovsky’s words seem appropriate here:

    “A planet is the cradle of mind, but one cannot live in a cradle forever”, 1911.

  • David September 29, 2008, 23:02

    If humans do become extinct, I suspect that to a visitor from the far future, the best evidence that there was technological life on this planet would be the remains of those spacecrafts on the Moon and possibly still in high orbit. There is almost no erosion, and no plate tectonics so such remains will still be on the lunar surface or in orbit, and in one piece.

  • ljk September 30, 2008, 9:41

    Check out the 2008 book, The World Without Us, by Alan Weisman:


    The National Geographic Channel recently had a program on
    this very subject, if humanity just suddenly vanished. Apparently
    ancient buildings would actually last longer than most modern
    ones, and cell phones would not decay for thousands of years.

    As for preserving some segment of humanity, the Voyager Records
    are estimated to survive in deep space for at least 1 billion years,
    and that’s just on the side exposed to space.

    We used to assume that human society would be wiped out by
    a nuclear war, but now we may be doing ourselves in piece by
    piece. If this financial crisis continues, I have little doubt that
    the general public will not be supportive of anything that isn’t
    about immediate needs on this planet, let alone an interstellar
    mission. People have to be taught to think past their own needs
    of nex week.

  • Elbert September 30, 2008, 10:27

    Maybe its fun to place the drake equation on centauri dreams.
    And keep the equation up to date with current facts and believes

  • Hiro September 30, 2008, 13:35

    Also, if we don’t have any FTL technology or fusion propulsion in the next 200 years, then our future will be within this solar system, our civilization will decay and collapse when fossil fuels are completely used up. Anyway, I think we can survive on Earth several million years, although the population might be less than a few thousand people.

  • Administrator September 30, 2008, 13:41

    Elbert said:

    “Maybe its fun to place the drake equation on centauri dreams.
    And keep the equation up to date with current facts and believes

    Excellent point, and you’re more or less reading my mind. Marc and I have been discussing quite an interesting presentation of the Drake Equation, one that’s in the works now and will find its way onto the Tau Zero site. I’ll post that information as soon as our version of the equation is available.

  • Adam October 1, 2008, 5:54


    Fission power can last for billions of years at current levels of electrical energy use or even modestly increased levels, via extraction from sea-water. Uranium is continually released into the oceans via erosion from the land, and thus so long as there’s erosion there will be fissionables. We have to transition from liquid fossil fuels to electric vehicles, but otherwise matters are pretty straight forward.

    Alternatively clathrates contain many thousands of years of potentially useable natural gas. That can, if oil runs out too soon, power rockets to build sufficient solar power satellites to power the planet. Photovoltaic cells are already over 40% efficient and SPS can easily be built using concentrator arrays to minimise the mass and semi-conductor materials needed.

    What’s lacking isn’t either resources or technology, but will. A slavish devotion to one particular model of a market economy might ruin our chances at switching from fossil fuels to fission/solar. Fusion or something better will only be an added bonus. We can build a better future without them.

  • Benjamin October 1, 2008, 19:44

    I’m curious. Solar satellites are very good for powering space development, but how are you supposed to get the technology to Earth in a safe and efficient way? A cable of present-day materials would collapse under its own weight. How are microwaves supposed to transport energy efficiently without spreading out or attenuating?

  • ljk February 3, 2009, 10:19

    The Future of Man – How Will Evolution Change Humans?

    Contrary to popular belief, humans continue to evolve. Our bodies and brains are not the same as our ancestors’ were—or as our descendants’ will be.

    By Peter Ward