Gwynne Dyer: Panspermia and the Drake Equation

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      One by one, the empty boxes in the Drake Equation are being filled in with actual numbers, and it’s looking good. So good that Yuri Milner is spending $100 million of his own money over the next 10 years to fund the search for non-human civilizations orbiting other stars.

      But it’s a pity that the Philae lander from the European Space Agency’s Rosetta mission didn’t have more time to look for life on Comet 67P/Churyumov-Gerasimenko.

      Yuri Milner is a Silicon Valley billionaire who was working on a PhD in theoretical physics at the Russian Academy of Sciences before he moved to the United States and got rich. His money will buy thousands of hours of radio-telescope time each year to look for radio transmissions from other star systems.

      This represents at least a tenfold increase in the amount of work being done on finding intelligent life elsewhere in the galaxy, and Yuri Milner is no fool. Why does he think it’s worth spending this money now?

      Probably because the Drake Equation is finally coming into its own. It has seven terms, and American astronomer Frank Drake could not give a value to any of them when he first wrote it in 1961. It was just a formula that would let us estimate the number of civilizations in the Milky Way galaxy when the relevant data eventually became available.

      To fill in the first three terms, we needed to know how many stars there are in the galaxy, how many of them have planets, and how many of those planets are in the “habitable zone” where liquid water can exist.

      In 1961 the estimate was 100 billion stars. Now it is 400 billion, of which 300 billion are essentially similar to our Sun.

      Until 1992, we didn’t even know if other stars had planets circling them. Now we can estimate that at least 40 percent of them do, although the real answer may be almost all of them. (We still cannot detect planets much smaller than Earth.)

      As for how many planets are in the “habitable” zone, not too close or too far from their parent star, the answer is probably one or two per star.

      Using the data acquired in the past 20 years, NASA now estimates that there are 144 billion habitable planets in our galaxy. Not all of them will harbour life, of course, but that is a very encouraging number.

      Other questions remain, however. How many “habitable” planets will actually have life on them? On how many of those planets will an intelligent species appear? How many of those intelligent species will build civilizations that use electromagnetic communications? And how long, on average, would those high-tech civilizations last?

      We don’t yet know the answers to any of those questions, but we do know that organic compounds are common even in interstellar space, and that they are continuously raining on our own planet. So the standard assumption is that they somehow combined on Earth to form the first single-celled creatures, and evolution did the rest.

      But if it were easy for those organic compounds to combine into complex microbes and viruses, then you would expect it to have happened here a number of times. There would be several or many unrelated genetic lineages on Earth—and there aren’t. All life here has a common ancestor.

      So it must be very rare for life to develop spontaneously. If it actually happened here, it would mean that we are a miracle, and pretty much alone in the galaxy. But maybe the miracle happened on another of those 144 billion planets, billions of years ago, and life been spreading through the galaxy ever since— not as alien beings on starships, but as microbes and viruses on meteorites and comets.

      This is the “panspermia” hypothesis, first proposed by astronomers Sir Fred Hoyle and Dr Chandra Wickramasinghe in 1974. Dissatisfied with the notion that Earth was unique, they suggested that not only organic compounds but actual microbes and viruses could travel through interstellar space, dormant but still viable in the liquid water that they suspected was present in the interior of many comets.

      It sounds weird, but it is just as plausible as the rival hypothesis of an independent origin of life on Earth. Comet 67P/Churyumov-Gerasimenko was the first-ever opportunity to see if this hypothesis holds water (so to speak). The Philae lander did detect 16 different organic molecules as it bounced along the comet’s surface, but it ended up in the shadows without power to pursue its investigations further.

      Pity, but there’ll be another comet along in a while. And if it turns out that Hoyle and Wickramasinghe were right, then most of those 144 billion planets will have life on them. The history of evolution on earth tends always to greater complexity, so a fair proportion of them would have intelligent life on them.

      How many of them have high-tech civilizations on them at the moment, of course, depends on how long the average technological civilization survives. Our own high-tech civilization has survived, so far, for about one century.



      Lots of Aliens

      Aug 12, 2015 at 3:18pm

      The Math / Physics dictates that there are lots of "Aliens" out there.

      Some of them must be advanced enough into Type 2 or Type 3 Civilizations.

      Since we are almost a Type 1 civilization sooner or later we will detect something.

      S H

      Aug 12, 2015 at 8:35pm

      Richard Dreyfus knows, but he's been gone since 1979.

      Seriously though, this is the reason life is too short - we'll never know.

      But, future generations will. What a freak out that will be.

      R. Lindsay

      Aug 12, 2015 at 10:40pm

      The likelihood of us finding intelligent life elsewhere is pretty slim. Confounding additional 'unique' criteria about the earth's history that have been discovered since the formulation of the Drake equation include :
      - the destruction of the first generation of the sun's rocky inner planets by the wandering of the planet Jupiter into the inner system and the subsequent formation of the current smaller rocky planets from the debris remaining that wasn't either thrown into the sun or out of the solar system. The fact that this happened at all and the timing of the event is a function of the number, size and orbital dynamics of the large gas giant planets that formed in our solar system. The timing of the formation of rocky planets and how long they survive will affect the likelihood of the development of complex, intelligent life.
      - the later collision of the earth with a mars-sized planetoid that resulted in the Moon's formation. This collision added a lot of thermal energy to the Earth. In the absence of this added energy, the Earths' core would already have cooling sufficiently to reduce the strength of it's magnetic field to a level that would no longer protect its surface from ionizing cosmic radiation that would sterilize the earth's surface.
      - the relatively large size of Earth's moon results in tides that likely played a significant role in the eventual colonization of land by plants and animals. In earth's history, land dwelling has been essential for the development of pretty much all complex technology.

      So not only is it necessary for a planet to be in the 'Goldilocks zone'. It also needs to have a hot enough core to maintain a magnetic shield against cosmic rays for sufficient time for a complex civilization to arise, have liquid water seas for life to begin in, land for a life to develop technology on and an impetus to encourage life to colonize the land quickly enough to allow time for this all to work.

      There will likely be more 'unique' things that we will learn about Earth's history in the future that will add more confounding variables to the likelihood of other complex civilizations existing during a period of time where a complex civilization exists on Earth to observe evidence of their existence.

      And one more thing... Homo Sapiens almost went extinct at one point tens of thousand of years ago, long before we had civilization.

      Kai Anne

      Aug 13, 2015 at 12:53am

      Problems are that :
      1)-the distances between stars are so vast,
      2)-in comparison, radio signals are so slow,
      3)-our experience is that civilizations blink on/off so rapidly,
      4)-our high-tech civilization has kept ancient hates while developing earth-destroying technology/weapons,
      5)-such that it is highly unlikely that two high-tech civilizations are close enough together AT THE SAME relative time to exchange signals. Best we could hope for would be to receive a faint signal from a long dead civilization.

      Martin Dunphy

      Aug 13, 2015 at 12:57am

      All of the above cautionary criteria apply, of course, to only one planet out of, potentially, hundreds of quadrillions.

      Stellar's Jay

      Aug 13, 2015 at 1:37am

      "So it must be very rare for life to develop spontaneously."

      Yeah, no, that doesn't follow. Bacteria swap DNA amongst themselves all the time, which makes analyzing their deep heritage murky at best. And it's fairly common for one line to fill an ecological niche so well that it wipes out all its competitors in that niche. For example, currently all large terrestrial carnivores belong to one order of mammals. If Dyer's logic were correct, that would mean that it's very rare for large terrestrial carnivores to evolve. But paleontology shows us the fossilized bones of large carnivores from many orders of animals, extinct hooved carnivores, extinct marsupial carnivores, and even extinct giant flightless carnivorous "terror birds" - and that's just the recent ones. Bzzt, invalid logic.

      A better estimate would be that since bacteria showed up on Earth's surface within a couple of hundred million years of conditions becoming plausible for life or for us to find it in the fossil record, bacteria-like organisms can be expected to develop, given the right conditions, pretty much automatically.


      Aug 13, 2015 at 5:48am

      Yes, it's good to know that Yuri Milner is spending $100 million of his own money over the next 10 years to fund the search for non-human civilizations orbiting other stars. And it's a pity that the Philae lander from the European Space Agency’s Rosetta mission didn’t have more time to look for life on Comet 67P/Churyumov-Gerasimenko. Yes, if it weren't for saintly folk like Milner, who knows what would happen?


      Aug 13, 2015 at 7:45am

      "our experience is that civilizations blink on/off so rapidly,"

      Once you develop the printing press, civilization don't collapse like they used to because knowledge is spread far more widely and is much harder to lose.

      I suspect the limiting factor is how many of those intelligent species will build civilizations . We often see ourselves as violent, but we aren't that bad. Chimpanzees will try and kill any male from another troop they encounter. Humans formed tribes the united villages allowing peace between them and exchanges that multiplied the benefits of new technology and ideas because they could be shared and combined more widely.

      Jonathan Cressman

      Aug 13, 2015 at 10:44am

      Spoiler alert - Mr Dyer might be planning a second part of article

      Finding the constants in this Drake equation is the most important question of the human race. Yuri Milner isn't doing this out of curiosity, he is doing it for the survival of future generations. We know the value of the Drake equation, it's one. We are the only civilization we see. That means each time we discover one of the first constants (the ones that come before intelligent life transmits signals into space) and that constant turns out to be large then we unfortunately have to lower our estimates for the remain constants. Which is depressing because those constants how long a civilization lasts and how far it spreads are before us.

      The Math
      So far we have 150 billion possible planets that life could evolve on. If over the course of 6 billion years everyone of those planet develops a civilization that's a rate of 25 civilizations a year. If each lasts 10 000 years and sends signals to 1/25th of the galaxy we should see 10 000 civilizations. So if Yuri Milner doesn't find lots and lots of civilizations it means either intelligent life evolving on any one of those 144 billion worlds is very low (good for us) or that civilizations only leave a mark on a small portion of the galaxy (unlikely), or civilizations last a very very short time (very bad for our future).

      So let's hope Yuri Milner finds lots of civilization and if he doesn't we better start considering that there is something that will like end our civilization quite soon.

      Martin Dunphy

      Aug 13, 2015 at 1:56pm

      Not sure why everyone seems to think that human characteristics such as greed, vanity, aggression, gluttony, etcetera, can be applied across the board to all other possible nonhuman
      life forms.
      Survival, reproduction, society, and "civilization" might mean entirely different things to a silicon-based being that has evolved "consciousness".
      How many angels can dance on the head of a pin again?