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Question is to people who say if universe is teeming with life, then why is it not visible close by: We don't know how large the universe is. If say life is "te

• dsq 3y ago
  Life every million parsecs means less than one life form per galaxy, so hardly teeming.
  • zaphirplane 3y ago
    FWIW there are 2 trillion galaxies in the universe So says Wikipedia
• ryandrake 3y ago
  And it's not just the size of the distance we can see, it's the size of the slice of time when we are looking. We've had the tools to sorta-kinda detect life signatures for what, 10-20 years? Maybe we can keep that up for another (at best) 100-1000 years until we destroy ourselves? The universe is on the order of 10^10 years old. Star formation will end ~10^14 years from now The last black holes will evaporate ~10^100 years from now. So our temporal search window is astronomically small, too.
  • smegger001 3y ago
    Why do you assume we distroy ourselves? If we can make spacecolonies at somepoint between now and your 1000 year figure why kill ourselves when we can leave for another star. It doesn't even have to be a popular strategy just one that a nonzero number choose to take rather that self distruction.
    • peddling-brink 3y ago
      How long can we teeter on the knife edge of global annihilation without someone pushing the wrong button?
      • smegger001 3y ago
        We made it through the cold war without turning any cities into molten glass and it was more tense than the world right now.
        • peddling-brink 3y ago
          But, let’s look forward through the next hundred years, do we seem to be going in the right direction?
        • Nevermark 3y ago
          "We haven't died yet" is the most selection biased evidence you could possibly invent. 10 on a scale of 10. It also has no predictive value given the nature of catastrophic threats continues to evolve rapidly in quantity and quality, and the elements of past threats (the cold war -> nuclear war), continue to be threats (autocratic regimes -> fighting or planning wars that could become existential to their leaders -> nuclear war).
          • smegger001 3y ago
            Given we have a sample size of one, its hard to make argument not based on past experience as that's all we have to go on, and we a reasoning about use of weapons that haven't existed for a century yet it hard to make strong argument either way bit MAD seems to have worked so far and most leaders of nuclear armed States are to egotistical to commit suicide when they are living the good-life at the top and that's what launching WMD s, is its is suicide .
    • mdekkers 3y ago
      > Why do you assume we distroy ourselves? Seveneves, by Neil Stephenson, discusses the human penchant for self-destruction much better then I can in an HN comment, it is worth a read. In short, though, we cannot, unfortunately, escape our humanity, and pretending we don’t take it with us wherever we go is wishful thinking. As a group, we are ruled by incredibly base instincts that no longer apply to our situation, but they still largely determine our trajectory.
      • smegger001 3y ago
        You mean the book where the nations of the world put everything aside to preserve the human species from distruction by space based natural disaster by throwing almost all their resources at various space programs?
        • mdekkers 3y ago
          Yeah, that one. Where those people then go on with their stupid, petty, political infighting and senseless scheming thereby nearly bringing about the end of human species anyway. You’ve clearly read the book, I am curious what would drive you to make such an obviously incomplete representation of the story. Being edgy? Contrarian for contrarian’s sake? Since you offer no additional context besides a vague (and uninteresting) insinuation that im somehow wrong, I suspect you are just trolling, smegger001
    • shiroiushi 3y ago
      >Why do you assume we distroy ourselves? Have you not been paying attention to the news? We have a major nuclear power constantly threatening nuclear war, and several very likely conflicts between major nuclear powers.
    • didntcheck 3y ago
      Putting aside the more sociological arguments about (non-)human nature for a second - roughly speaking, technological development = ability to wield greater amounts of energy. The easier it is to put a satellite in orbit, the easier it is land a missile on another country. The easier it is to harness virtually free energy, the easier it is to rain unimaginable destruction on your enemies. Robot workforces enable robot armies (directed by malicious humans, not Skynet) The more widely accessible a technology becomes, the more damage a single person or faction can do, and therefore the probability of someone causing mayhem tends to 1. And it's basically always less effort to destroy something than (re)create it We can hope defensive counterparts to all these risks develop at a greater rate, but I don't think that's a given at all Also remember that from a SETI/Fermi/Great Filter perspective it doesn't matter whether the species completely kills itself off. It could instead just repeatedly reset itself to steam age technology, and therefore never be stable enough for long enough to become seriously spacefaring
• yungporko 3y ago
  it's also not only a question of distance but also a question of time. there could be/have been several alien species that would be our next door neighbours but just not at the same time as us.
• hnlmorg 3y ago
  There’s a few problems when hunting for life: Distances are immense: 1. Our view of the galaxy is very limited. We know almost nothing about our closest neighbouring solar system, let alone anything further afield 2. And because the distances are so far, we are effectively seeing those distant events hundreds or thousands of years in the past. 3. Where to look? We cannot search everywhere. We can only hope to get lucky that we are searching the right corner of the sky at the right time. Alien life is completely alien: 4. We can only make assumptions of what to look for. Any sufficiently encrypted signal might genuinely appear like white noise to us. They might be so advanced that we simply cannot detect them 5. Early communication systems on Earth were noisy in that they were broadcast 365 degrees. Later systems could be targeted, focused in a specific direction. As technology advances, noisy classical methods of broadcasting become less common. This in turn reduces the amount of noisy any extraterrestrial eavesdropper could spot. And that’s assuming they’re not intentionally “cloaking” themselves. Putting aside Star Trek style fantasy for a moment, there is an advantage to remaining hidden. Whether you’re a predator like a burrowing spider or stealth bomber, or prey like bugs that camouflage themselves as plants; being hidden gives you a massive tactical advantage.
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  • smegger001 3y ago
    Cloaking probably isnt possible without discovering someway to violate the laws of conservation of energy. Any work done by a system will produce heat hiding the heat signature of an advanced technological society is probably impossible.
    • hollerith 3y ago
      Every planet, every rock emits heat (thermal EM radiation) so why can't the civilization willing to forgo most of its potential computing and industrial capacities choose to emit a heat signature indistinguishabe from a rock by observers at other star systems?
      • 3y ago
• echelon 3y ago
  If the next "hard step" is aliens going from biological to artificial, how can we be sure what sorts of signals they might leak? We're not even there yet ourselves.
• contravariant 3y ago
  I think you can ignore that second number, best we know the universe is infinite. Though the visible universe is limited.
• username135 3y ago
  Our definition of life is based on 1 single element.
  • dylan604 3y ago
    But why do we think that life would be based on a different single element anywhere else?
    • accrual 3y ago
      Here are some alternative theories of possible types of life. The thought of silicon-based life swimming in oceans of ammonia or other hydrocarbons fascinates me. https://en.wikipedia.org/wiki/Hypothetical_types_of_biochemistry https://en.wikipedia.org/wiki/Hypothetical_types_of_biochemi...
      • safety1st 3y ago
        It's super fun to consider, but one problem with ammonia-based biochemistry is that everything would be so cold. In temperatures that are cold enough to liquefy ammonia you just have a lot less energy going around, and life requires energy to thrive. We can see this principle at work on earth where the tropics have the most biodiversity and the interior of Antarctica is almost totally barren of life. So it seems to me that while an ammonia-based biochemistry might be plausible, it may be a sort of evolutionary dead-end where nothing can progress beyond being simple and microscopic. Or maybe it can at the bottom of an ocean where the pressures are higher and the ammonia is warmer due to geothermal effects...? but then it has no access to energy from the sun, and it's very hard for us to detect something that lives at the bottom of our sea, let alone an extraterrestrial one
        • bee_rider 3y ago
          It seems like there ought to be a sweet-spot where life will consume the right amount of energy for an environment. Consume too much energy, you starve. Consume too little, you are out-competed by other life forms which consume more, and move faster as a result. But that’s environment-specific, maybe it is possible that ammonia life evolved on a lower-energy planet everybody just moves slower?
• xeromal 3y ago
  I don't know anything about anything but I can imagine a society of bacteria saying the world is teeming with life but they're sadly sitting at the bottom of the ocean in a lava tube and they can't manage to find any life.
• deleted 3y ago
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• ineedaj0b 3y ago
  We could just be early. We’re one of the first civilizations to ‘wake up’ perhaps. So it’s teeming, but not much to see with our eyes yet
• somenameforme 3y ago
  I'm fairly sure you know this already, but you just described the Fermi Paradox. [1] And the answer to this paradox is that there is no answer, though there are a million hypotheses. [1] - https://en.wikipedia.org/wiki/Fermi_paradox https://en.wikipedia.org/wiki/Fermi_paradox
• seventytwo 3y ago
  The real answer is that we don’t know. We know with 100% certainty that life exists on the universe, we just don’t know where else besides earth it exists.
• seanhunter 3y ago
  The first exoplanet was only detected in 1988 and confirmed in 2002. These are things we were really really sure were there and are absolutely huge relative to a vital sign. It would be surprising indeed were we to already have found a biosignature given it's got to be a lot harder than finding a gigantic chunk of rock. Astronomy is hard.