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I half expected this article to essentially say "we wouldn't know life if it hit us in the face", but happily the conclusion was that yes, we could see strong e

• marcosdumay 3y ago
  People weren't that bullish on the conclusiveness of those results at the time. (Except for the radio signals.) Even though we know that our atmosphere is maintained by life, nobody did really know if something else could create oxygen and methane. And betting on a specific light absorption spectrum is quite a hard thing to justify. Today we know that those things are rare. And they are orders of magnitude more intense than the unexplained phenomenon we see on other planets. But at the time, we didn't have proof.
  • robomc 3y ago
    And the radio signals are a pretty unhelpful indicator because you could have looked at earth with life on it at any point within the last three billion years and there have only been radio emissions for the last 30-millionth of that time. And they might become pretty rare or completely gone in another 30-millionth. For mammals, the radio-emitting time is still only a 2-millionth of the total.
    • DaiPlusPlus 3y ago
      The thing about radio-waves is inverse-square-law. I don’t understand why we’d expect our nondirectional radio/TV broadcasts to be distinguishable from background radiation once you get past, say, a light year or two from our solar system.
      • goodcanadian 3y ago
        I don't have a reference for you, but I recall a study a decade or two ago that suggested that we would only be able to detect our strongest radio signals out to a distance of about 10 light years with existing telescopes (I may have that number wrong, but it was not large). That said, with new telescopes, particularly things like the Square Kilometre Array, we have higher sensitivity, and more importantly, we have the angular resolution to measure whether an excess of radio emission is coming from a star or from a planet around that star. So, even a weak signal can be detected, and if we were to find such a signal originating from a planet rather than another object, we could make a pretty good guess that it is artificial in origin.
      • andyjohnson0 3y ago
        Earth SETI is basically just looking for directed signals: hypothesised to be either intentional communication attempts directed at us, or signals that we happen to be in line-of-sight of. Omniidirectional signals that could be detectable over interstellar distances would require immense amounts of power at the transmission end, and anyway may even be detected by conventional radio astronomy observations. The popular conception is that our undirected, historical tv/radio signals might be detected by ETIs - and that therefore this is what our SETI efforts are looking for. In practice, the former is unlikely using known scientific principles, and the latter isn't really being attempted for the same reason.
  • billiam 3y ago
    I dunno, one of the slam dunks was the spectrum cliff showing vegetation. What if the energy production system on Planet X wasn't based on Mg-bearing chlorophyll? And plants have only been around for 1/7th to 1/4 of the planet's history, so it's a crap shoot any way you slice it.
• Beijinger 3y ago
  "Life in other places might be radically different from our own, and we might be looking for the wrong things" Very possible. Something behind our imagination (e.g. Energy, Light based life forms etc.). But it is not unreasonable to expect something similar, based out of Carbon or Si that has a metabolism and senses. Once I read a suggestion to look for life: look for an entropy source.
  • thenobsta 3y ago
    I always thought it would be a cool investigation to look at the distribution of entropy signals coming from celestial bodies and group them. I'd bet there is a non-'natural' entropic signal coming from planets with biological processes on them.
    • breezeTrowel 3y ago
      How would you measure entropy signals at astronomical distances?
      • deleted 3y ago
        [deleted]
    • PeterisP 3y ago
      It's interesting that both compression and encryption turn otherwise clearly "engineered" signals into something that's literally indistinguishable from noise, removing any redundancy or regularity.
      • giantrobot 3y ago
        The inverse square law means we're not going to pick up stray radio signals from an alien civilization. If you build an Arecibo-equivalent telescope (AET) in space and flew it out of the solar system our radio noise (uncompressed and unencrypted) would fade into the cosmic background at about half a light year out. Even powerful radars wouldn't be detectable much past Alpha Centauri assuming their beam even happens to sweep the portion of the sky where the receiver will be taking into account proper motion between the systems. The only way alien civilizations will pick up each others' signals is if they're intentionally directed at those systems with highly focused emitters. If you're intentionally sending a signal in hopes another civilization will see it you're definitely not going to encrypt it. Compression also serves little purpose as there's no shared context to decompress the message.
• jandrese 3y ago
  I used to think scientists were being awfully carbon centric in their quest for life. There must be so many other ways for live to exist right? But once you take organic chemistry it seems so likely that other life would also be carbon based. Literally nothing else in the periodic table is as good as carbon for the flexibility that life benefits from so much. Silicon is a distant second. While it is certainly not impossible that there are forms of non-carbon based life out there, they would have to be utterly dwarfed by the number of carbon based ones.
  • rendall 3y ago
    Our body of knowledge derives from intimate familiarity with an environment that is rare in the universe. The extremes here do not compare at all to cosmological extremes. It's not surprising that our chemistry is quite sophisticated and nuanced when the elements involved are abundant here and the temperatures involved are within a range easily achievable here and the gravity is more or less 1G and there is atmospheric pressure and the ambient magnetic field is inside a certain range and the time intervals involved are observable within a human attention span. I think we make a mistake by universalizing our perspective, so to speak. We define life by what we see around us and then assert, correctly and unassailably, that life must be made of the chemistry that we ourselves are made of, without generally understanding that the definitions are circular.
    • jvanderbot 3y ago
      I'm lost. Presumably chemistry would work the same everywhere. So we should be able to recreate or predict some environments that would yield the same magic as 1g, 70deg F, carbon-based life, but with other parameters. Yet the consensus seems to be that there are relatively few other parameter sets that would yield some alien equivalent of organic chemistry. What gives?
      • rendall 3y ago
        It is very difficult for us humans to really grasp that unknown unknowns are real and have an effect. On some level, we assume that if we don't know something, it's not worth knowing, or we confidently make things up not even realizing we have done so. This bias influences us to believe that we know far more than we actually do. ...we should be able to recreate or predict some environments that would yield the same magic... Why should we? Physics and chemistry derive from observation. Theory is descriptive. 1) Our experience with chemistry outside of the Earth environment is almost entirely theoretical. Only very expensive equipment can achieve, for only fractions of a second, in only microliters volume, extremes of temperature, pressure, magnetic fields, and never any environment with higher gravity than our own. We have no experimental access to, not to mention actual intuitive understanding of, the widely diverse environments that exist in the Universe. So, our experimental knowledge is lacking. 2) Were we disembodied minds with no actual experience of the world, could we predict the existence of terrestrial life from first principles if given complete access to current knowledge of terrestrial physics and chemistry? Probably not. We don't know what makes a good environment for life, other than that we look around on Earth and see it everywhere. So, our theoretical knowledge is inadequate. 3) Even what we perceive and define as life, sentience or civilization is limited by our lack of experience. If trees for example had a rich storytelling tradition, epics unfolding over centuries perhaps, how would we even discover that or understand them? Trees are far more relatable than aliens are likely to be given that we share a common ancestor. The concept of, say, wind patterns or waves or nebulae being alive or sentient is easily dismissed, but again, our definition of life is narrowly defined by our single data point, our interests and outlook conferred and constrained by our evolution. Is it useful? Is it dangerous? This is the sort of thing that informs even our ability to perceive something as worthy of attention. Before microorganisms were discovered, the concept of invisible critters was laughable. So, our understanding of what we're looking for is inadequate. I suspect that the evidence of alien life is all around, but it's just too different even to be interesting.