Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

B Impact of Kepler Telescope Findings on the Drake Equation

  1. Oct 28, 2017 #1
    How much more refined are the various variables of the Drake Equation in view of the recent findings by the Kepler Telescope?


    I imagine fp and ne would surely be better estimates.
    Is there a study on this anywhere?
  2. jcsd
  3. Oct 28, 2017 #2


    User Avatar
    2017 Award

    Staff: Mentor

    Wikipedia cites some estimates. The equation is outdated in some aspects, and I think that is more important than trying to estimate the individual factors. We know how different types of stars have different types of habitable zones with different conditions (locked rotation? Stellar flares? ...). We have found liquid water in places the Drake equation didn’t consider, e. g. moons of outer planets. We have found gas giants close to stars, where large moons could be habitable. We have found planets in unexpected orbits in systems with multiple stars. And so on.
  4. Oct 28, 2017 #3
    Great input, thank you.
    The He link is hilarious, I loved it, thanks for sharing that.
  5. Oct 29, 2017 #4


    User Avatar
    Science Advisor
    Gold Member

    Kepler, along with other studies, has pretty much resolved any doubs over how common planets are - at least within our range of observation. However, that tells us almost nothing about the other factors in the Drake equation, nor does it shed much light on their relevancy. A single ancient instance of intelligent life could have spread like fungal spores throughout an entire galaxy within a short span of cosmological time, as many have historically noted, thus rendering the Drake equation pretty much irrelevant. Little more than technology already conceivable to us would be necessary to facilitate seeding almost every habitable nook and cranny within reach of any sufficiently motivated advanced civilization. This realization may well have been what inspired Fermi's ET remarks.
  6. Nov 8, 2017 #5
    The Kepler space telescope's findings affect the two planet-related parameters in the equation: fp and ne. From that telescope's findings, it is evident that fp is close to 1. I won't say equals because of binary-star systems like Alpha Centauri, where the only places that planets can be stable is either close to one of the stars or else far from the two of them taken together.

    But ne is not adequately addressed by that telescope's findings. The Earth around the Sun would be a borderline detection for it, but it has detected lots of planets only a little larger than the Earth, larger by a factor of 1.5 or 2.

    Since it detects transits, the telescope only gets sizes directly. To measure planets' masses, one needs to do a radial-velocity detection with a telescope with a high-resolution spectroscope, or else one has to find Transit Timing Variations (TTV's). Many of these can be modeled as orbit perturbations caused by other planets' gravity, and the effects of their gravity will be enhanced by the planets being in an orbital resonance. The downside is that those effects are only big because they add up over each orbit that each planet does. But Kepler observed several planets long enough to get good TTV data, and that has given us estimates of some planets' masses.

    From a planet's mass and radius, one can get its average density, but one has to be careful, since a large-enough planet will be centrally condensed because of its interior pressure. From Planet Models, I calculate that without compression effects, the Earth would be about 10% larger than it is, and its average density would be around 4.3 g/cm^3 instead of its actual 5.5 g/cm^3.

    So far, only a few Earth-size planets have measured masses, and those measurements have large error bars. But for TRAPPIST-1, that is enough to suggest that some such planets have super oceans of water, or even lots of hydrogen and helium. Having lots of H2O or H/He can be a problem for habitability, by making it hard for organisms to live near the planet's visible surface, even if hydrothermal vents can still exist.

    So ne is up in the air. Many Earth-mass planets may be water worlds, with huge oceans hundreds of mi/km deep, or else they may have very little water and other volatiles, and thus very thin atmospheres.
    Last edited: Nov 8, 2017
  7. Nov 8, 2017 #6
    As to the other parameters, we are gradually closing in on the origin of life, or at least the emergence of the ultimate ancestor of all our planet's present-day biota. So far, we have gotten to a "RNA world", where RNA acted as both information storage and as enzyme. The main problem I've seen for it is the origin of the RNA -- it's difficult to make it nonbiologically.

    As to the emergence of intelligence, we have resolved several puzzles with the help of molecular phylogeny, though developmental biology, genes to shapes, remains difficult. For instance, multicellularity has evolved several times, with plantlike, funguslike, and slime-moldlike multicellularity each evolving more than once. However, animallike multicellularity evolved only once. Does this mean that there could be planets with big forests and lots of mushrooms but no animals? Not even tiny worms?
  8. Nov 8, 2017 #7
    Then the emergence of communicative ability. For humanity, that has involved the emergence of agriculture. For some strange reason, it was not invented at any time before the end of the Pleistocene, at least not persistently. But after that, in the Holocene, agriculture was invented in several places independently. I've seen the theory that this was because the Holocene has had a more stable climate than much of the Pleistocene.

    It has also involved the invention of writing, something that happened in only a few places, but then followed by lots of borrowing and stimulus diffusion. The idea that writing is feasible has provoked some people to invent writing systems. Also the development of theoretical science. It started in ancient Greece and continued in the Roman Empire before it was interrupted by a period of strife called the Crisis of the Third Century. It only got started again in western and central Europe some 1000 years later, but it has been continuous since then.

    Finally, the lifetime of a communicative civilization. That is almost impossibly speculative.

    So in summary, R* is well-understood, fp is likely close to 1, ne is still very uncertain, and fl, fi, fc, and L are even more uncertain.
  9. Nov 8, 2017 #8

    stefan r

    User Avatar
    Gold Member

    How did Kepler increase the uncertainty of the fs and L?
  10. Nov 9, 2017 #9
    It didn't. I was discussing where we are at. The parameters fl, fi, fc, and L are unaffected by the Kepler results.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted