The astronomers Adam Frank and Woodruff Sullivan have an interesting paper out where they’ve essentially flipped the Drake Equation on its head. If that equation is meant to give us some handle on the probability that there are aliens out there, Frank and Sullivan have used the plethora of exoplanets discovered since the launch of the Kepler space telescope to calculate the chance that, so far, we alone have been the only advanced civilization in the 13.7 billion year history of the universe. I won’t bore you with actual numbers, but they estimate the chance that we’re the first and only is 1 in 10 billion trillion. I shouldn’t have to tell you that is a really, really small number.
Frank and Sullivan’s paper emerges as a consequence of the fact that we now have very clear answers to at least some of the values of the Drake equation. We now know not only how many stars are out there, but also how many of those stars are likely to have planets, and how many of those planets are likely within their star’s habitable zone. It is the fact that this number of potentially habitable planets is, to channel Donald Trump, so huge, which leads to the conclusion that (when plugged into Frank and Sullivan’s rejiggered Drake equation where the requirements that alien civilization exists presently and are within communication distance from us are dropped) the only way we have been the first and only technological civilization would be if we were the beneficiaries of the most extraordinary luck.
We’re not quite at the point, however, where we can make a definitive guess as to just how lucky, or how normal, our civilization is in history the cosmos. To do that we’ll need to find out what the probability is that life will develop on planets that have liquid water, and how difficult the leap is from single celled life to multicellularity. As I’ve written about before these questions are the subject of sharp differences and debate between bio-physicists and evolutionary biologists with some of the former, notably Jeremy England, seeing the laws of physics in a sense priming the universe for life and complexity and the latter seeing evolution as much more contingent and intelligence of our sort a lucky accident.
The historical question, namely, how likely is complex life likely to give rise to a technological species will remain unanswerable as long as the universe continues to be silent or until we discover the artifacts of some dead civilization. Frank and Sullivan’s answer to the silence is that the vast majority of alien civilizations have died, and those that might exist are beyond any distance in which we could observe or communicate with them. Theirs is the ultimate cautionary tale.
Then again, perhaps we’re on the very verge of finding other technological civilizations that either exist now or existed in the very recent past once we start to look in the proper way. That, I think, is the lesson we should take from last year’s observation by the Kepler space telescope of some very strange phenomenon circling a star between the constellations of Cygnus the Swan and Lyra. Initially caught by citizen scientists reviewing Kepler data, what stuck astronomers such as Tabetha Boyajian was the fact whatever it is they are looking at is distributed so widely, and follows such an unusual orbit, that it has lead some to speculate that there is a remote possibility that this object might be some sort of Dyson Sphere.
It seems most likely that some natural explanation will be found for the Kepler data, and yet, whatever happens, we are witnessing the birth of what Frank and Sullivan call cosmic archeology. The use of use of existing tools, and eventually the creation of tools for that purpose, to look for the imprint of technological civilizations elsewhere in the cosmos.
We do have pretty good evidence of at least one thing: if there are, or have been, technological civilizations out there none is using the majority of its galaxy’s energy. As Jim Wright at Penn State who conceived of the recent scanning 100,000 galaxies that had been observed by NASA’s Wise satellite for the infrared fingerprints of a galactic civilization discovered. Wright observed:
Our results mean that, out of the 100,000 galaxies that WISE could see in sufficient detail, none of them is widely populated by an alien civilization using most of the starlight in its galaxy for its own purposes. That’s interesting because these galaxies are billions of years old, which should have been plenty of time for them to have been filled with alien civilizations, if they exist. Either they don’t exist, or they don’t yet use enough energy for us to recognize them.
Yet perhaps we should conclude something different about the human future from this absence of galactic scale civilizations than the sad recognition that our species is highly unlikely to have one. Instead, maybe what we’re learning is that the kind of extrapolation of the industrial revolution into an infinite future that has been prevalent in science-fiction and futurism for well over a century is itself deeply flawed. We might actually have very little idea of what the future will actually be like.
Then again, maybe the silence gives us some clues. Rather than present us with evidence for our species probable extinction, perhaps what we’re witnessing is the propensity of civilizations to reach technological limits before they have grown to the extent that they are observable across great interstellar distances by other technological civilizations. To quote myself from a past post:
This physics of civilizational limits comes from Tom Murphy of the University of California, San Diego who writes the blog Do The Math. Murphy’s argument, as profiled by the BBC, has some of the following points:
- Assuming rising energy use and economic growth remain coupled, as they have in the past, confronts us with the absurdity of exponentials. At a 2.3 percent growth rate within 2,500 hundred years we would require all the energy from all the stars in the Milky Way galaxy to function.
- At 3 percent growth, within four hundred years we will have boiled away the earth’s oceans, not because of global warming, but from the excess heat that is the normal product of energy production. (Even clean fusion leaves us burning away the world’s oceans for the same reason)
- Renewables push out this reckoning, but not indefinitely. At a 3 percent growth rate,even if the solar efficiency was 100% we would need to capture all of the sunlight hitting the earth within three hundred years.
There are thus reasonable grounds for assuming no technological civilization ever reaches a galactic scale whether because it has destroyed itself, or, for all we know just as likely, that all such civilizations run into development constraints far closer to our own than someone like Ray Kurzweil would have you believe.
Energy constraints might even result in the cyclical return of intelligence from silicon back to carbon based forms. At least that’s one unique version of the future as imagined by the astrobiologists Caleb Scharf in a recent piece for Aeon. Silicon intelligence has some advantages over carbon-based, as Lee Sedo can tell you, but you can’t beat life when it come to efficiency. As Scarf points out:
Estimates of what you’d need in terms of computing power to approach the oomph of a human brain (measured by speed and complexity of operations) come with an energy efficiency budget that needs to be about a billion times better than that wall.
To put that in a different context, our brains use energy at a rate of about 20 watts. If you wanted to upload yourself intact into a machine using current computing technology, you’d need a power supply roughly the same as that generated by the Three Gorges Dam hydroelectric plant in China, the biggest in the world. To take our species, all 7.3 billion living minds, to machine form would require an energy flow of at least 140,000 petawatts. That’s about 800 times the total solar power hitting the top of Earth’s atmosphere. Clearly human transcendence might be a way off.
A problem that neither Murphy nor Scharf really deal with is one of integration over a vast scale. A not insignificant group of techno-optimists sees the human technological artifice not just an advanced form of industry-based civilization but as an emerging universal mind in embryo. Personally, I think it more likely that we are moving in the exact opposite direction, towards a balkanization of this global brain, but there might be reasons to think that even if what we’re seeing is the birth pangs of something out of Stanisław Lem’s Solaris or Teilhard de Chardin, that such intelligence wouldn’t occupy a space all that much larger than the earth.
As the physicists Gregory Laughlin recently pointed out in the magazine Nautilus, the speed of light would seem to impose limits on how big any integrated intelligent being can become:
If our brains grew enormously to say, the size of our solar system, and featured speed-of-light signaling, the same number of message crossings would require more than the entire current age of the universe, leaving no time for evolution to work its course. If a brain were as big as our galaxy, the problem would become even more severe. From the moment of its formation, there has been time for only 10,000 or so messages to travel from one side of our galaxy to the other. We can argue, then, that, it is difficult to imagine any life-like entities with complexity rivaling the human brain that occupy scales larger than the stellar size scale. Were they to exist, they wouldn’t yet have had sufficient time to actually do anything.
Since the industrial revolution our ideas about both the human future and the nature of any alien civilization have taken the shape of being more of the same. Yet the evidence so far seems to point to a much different fate. We need to start thinking through the implications of the silence beyond just assuming we are either prodigies,or that, in something much less than the long run, we’re doomed.