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I think the really significant term in the Drake equation is the question of time overlap between our civilization and any civilizations in other star systems.

• ldjkfkdsjnv 3y ago
  Reminds me of the failing of the k-nearest neighbor algorithm. It works extremely well in low dimensionality, but given high dimensionality, its astoundingly bad. As you scale up the space and number of dimensions, the distances between individual chunks of data gets so large its hard to draw meaningful conclusions.
  • nmca 3y ago
    I dunno I've done a lot of high-dim knn that were quite pragmatically useful
    • ldjkfkdsjnv 3y ago
      https://en.wikipedia.org/wiki/Curse_of_dimensionality https://en.wikipedia.org/wiki/Curse_of_dimensionality
      • nmca 3y ago
        Maybe we're talking at cross purposes; what I mean is that PCA+KNN or other tricks mean that for high dim and large amounts of data you can get useful results; with the enlarged view of KNN as "anything where the last step is KNN" your statement that it's "astoundingly bad" is wrong. But for the narrow view of just KNN then sure cod applies.
  • natch 3y ago
    How high is high?
    • ohazi 3y ago
      I had a professor who would jokingly say "It's lonely in 128 dimensions"
      • galaxyLogic 3y ago
        Right, nobody's at those other dimensions at the same time as you are.
• TaylorAlexander 3y ago
  The other part of that overlap is whether they are using radio signals. I think a lot about the fact that there may very well be other ways of wireless signal transmission that don’t require radio (gravitational waves are one example though I’m not sure if I would expect those to be used for data transmission). 200 years ago no one knew radio communications were possible. We still don’t understand quantum entanglement. Our understanding of physics, while more advanced than the past, is still clearly limited. We may find that there are better ways than radio to transmit data, and this could explain why our radio surveys have so far not detected extraterrestrial data packets (as far as we can tell).
  • evilduck 3y ago
    Even for radio we went from blasting megawatts into space to keeping a lot of it in the atmosphere. We ourselves are proof that radio's a poor way to detect aliens and our reduction in radio emissions was a natural progression of our technology, not an attempt to hide. What's more telling for those in the neighborhood is the strange amounts of O2 in our atmosphere's spectral lines. That came to be long before us, it will persist long beyond us and it's a clear indicator of a non-geological process that might intrigue aliens.
    • saiya-jin 3y ago
      Spectral lines may be telling about conditions suitable for certain type of life. But as per some theories life itself may be quite abundant in universe, but mostly primitive equivalents of stromatolites so it may not be that interesting for aliens to keep checking every single planet for such life in whole galaxy, especially if speed of light is absolute speed barrier. One other thing I came up with on a long evening walk recently was to check for gravity fields. If you have all bigger pieces of matter mapped well within galaxy, and you grok all physical laws there are, you should be able to predict movements and gravity fields for billions of years with high precision. Kind of make a complex checksum of given galaxy. If this changes for no predicted reason, bingo you just have a very strong candidate of life evolving enough to escape its planet and start moving big chunks of matter around (think big asteroids or changing orbit of planet slightly to ie counter some natural catastrophe like greenhouse effect / ice age, or living near slowly dying star). Obviously this is way ahead of us and maybe even not possible, just a fun thought. But if you start space mining company by any chance in the future, please don't move matter around too much.
• bratbag 3y ago
  As far as I remember, the likelihood of a technological civilization forming before us is rather small. Basically we live in the goldilocks zone of our galaxy. Stars further towards the center are being constantly bombarded by types of radiation that make the formation of structured self-replicators almost impossible.Entropy rules. Stars further towards the rim have not yet gone through enough generations to produce the abundant heavier elements needed. We live in the zone that is both old enough and stable enough for technologically adept life to thrive, and we turned up on the scene about as early as we could. So we are probably just one of the first.
  • GoblinSlayer 3y ago
    We are a late by random 100000000 years since the point of as early as we could, which is a pretty big error.
  • di456 3y ago
    > So we are probably just one of the first. We don't really have any way to know that. Considering that there may be as many stars in the sky as grains of sand on Earth, there are many many unknowns. For another example we don't know for sure if our universe is the only one and it's entirely possible that everything that could ever happen plays out in real time across and infinite number of universes. We don't have any way to physically measure that possibility yet. We only have mathematical theories. Similar to how Copernicus proposed the heliocentric model, maybe our universe is not even the center of existence? It is humbling to imagine.
    • adastra22 3y ago
      All those stars you see in the night sky? That’s an astronomical waste of energy. No technological energy limited civilization would let that waste continue, entirely unhindered. The fact that we don’t see the light of stars, or whole galaxies replaced by dim infrared waste heat emissions means either (1) new physics will point to free energy solutions that circumvent thermodynamic laws [unlikely], or (2) we are the first.
      • 3y ago
• anonymous_sorry 3y ago
  > In other words, the likelihood that they either lived before or (will live) after us is overwhelming, since the time scale of the universe is so vast Not sure this logic makes a whole lot of sense. Imagine a universe similar to ours, but with a lifetime cut short by a doomsday device. Would you expect any difference in the likelihood that mirror humanity coincides with another alien civilisation? Independent of other factors, adding more time doesn't really reduce the number of civilisations existing at any one time, it gives more time for civilisations to emerge. Your logic suggests there is a fixed number of civilisations to distribute evenly across the lifetime of the universe. Now, the number of civilisations may be limited by usable energy for life to consume rather than time - but in that case I'd expect civilisations to cluster at the beginning of time when entropy is low. Edit: in fact Drake didn't actually include any term for age of the universe in his equation.
  • zelos 3y ago
    I think it reduces the lower bound for how many civilisations we'd expect to exist, from our N=1 example? 1 civilisation in (say) 1 million years would suggest they're more common than 1 civilisation in 13.7 billion years?
    • anonymous_sorry 3y ago
      Tricky, but maybe. But I think I was imprecise with my language. By "age" I meant the total lifetime of the universe as a place with planets capable of supporting life, rather than the amount of time between the big bang and now.
• gizajob 3y ago
  I think the most significant term in the Drake equation is the one chosen by users of it to hang themselves on this week. It's an equation that pumps out a number between zero and bazillions dependent on imaginations towards a situation that is nevertheless a paradox. The only thing that can be said right now is that it's perhaps likely that the number is >1.
  • pfdietz 3y ago
    It's >1 over what volume? The galaxy? The observable universe? All the unreachable volumes of space beyond that in our universe? All the many-worlds branches of this universe?
    • gizajob 3y ago
      “Perhaps likely >1” - in whatever volume the Drake equation covers. Until it goes to a certainty of >1 in the volume we can explore then it’s basically =1. I don’t believe the current absence of evidence is much of a useful data point. Until we have scoured other star systems and the rest of the galaxy turning over rocks we can’t really generate useful empirical data to fill in the numbers on the Drake equation. The paradox of “where is everybody” has myriad solutions. A mistake definitely lies in philosophers and theorists believing their sci-fi ideas are better than anyone else’s. Certainly not useful data towards writing papers that form a proof of any number as a solution. It’s hard to prove an absence, particularly when there’s a universe of empirical data that can be potentially gathered but hasn’t been yet. If I was a betting person, I’d put a stake on there being life somewhere like Enceladus. Even life from earth in the form of fungal spores has existed for long enough to escape and float around the galaxy - they’ve had a few hundred million years. Life here could have also landed from elsewhere as easily as terrestrial abiogenesis. There’s just so much we don’t know and haven’t tested. Not being able to pull radio signals out of the noise proves nothing given the mere seventy years of attempts. I’m not sure about many worlds, and how that could be proved either to be a useful part of science. By the same token, in an infinite universe, then literally every single possibility and permutation is being tried, so in that case, yeah there’s life everywhere. Including a universe where I’m out being the first human to find it rather than writing this comment.
• sampo 3y ago
  > I think the really significant term in the Drake equation is the question of time overlap between our civilization and any civilizations in other star systems. universe begins 0.1 Gy first stars 9 Gy our solar system begins 0.5 Gy or less early life 3.5 Gy complex, multicellular, macroscopic life 0.5 Gy sentient, intelligent life I think the important delays are the 9 Gy and the 3.5 Gy. (Gy = billion years) 9 Gy: After first stars, how many generations do you need of large stars, synthesizing heavy elements, going supernova and shooting the heavy elements around, contributing to the condensation of new stars (now with some heavy elements to begin with), until you cal form solar systems and planets like ours, with enough iron and heavier elements to make life chemically possible. Do you need to wait this full 9 billion years, before planets with the chemical composition of Earth appear, or did they already appear sooner? 3.5 Gy: How long does it "usually" take from early microbial life, for evolution to develop complex multicellular life? In our case it took 3.5 billion years, but are we among the fastest, or the slowest?