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Extraterrestrial Civilizations: Problems of Interstellar Communication (1971)

40 点作者 the-mitr超过 3 年前

6 条评论

BrandoElFollito超过 3 年前
This reminds me of a question during one of my PhD exams (physics): how would you communicate left and right to remote civilizations, using just text (there may have been other limitations).<p>The idea was to use the Wu experiment [1] and the lack of conservation of parity (= there is a difference between left and right, and you can explain which is which) but was a bit taken aback by the question.<p>Interestingly the first thing that popped in my mind was the peptide torsion direction (one of them is preferred in terrestrial life) and I started to wonder about alien abductions etc., and I fortunately got back on track with down-to-earth physics (thanks Ms Wu!)<p>[1] <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Wu_experiment" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Wu_experiment</a>
retrac超过 3 年前
One option that cannot be ruled out, and probably can never be totally ruled out, is that they are in fact out there, and are in fact transmitting quite openly, and we&#x27;re simply too technologically limited to be able to detect them.<p>Over the last century, our own radio technologies have undergone a continual progression in efficiency and data rate. Imagine someone with the latest radio technology from 1920 trying to monitor our civilization&#x27;s progress. By 1950, a lot of things seem to become undecodable (FM), and shortly after that a lot of carriers seem to simply disappear. Assuming they manage to lock on to the frequency-modulated edge of a suppressed carrier in the 1970s, things start to switch to a multitonal digital encoding. Then round after round of increasingly complex digital encodings with error correction and encryption, with larger and larger symbol rates and symbol set sizes. Frequencies climb into the thousands of megahertz. Hundreds of thousands of carriers are used in parallel.<p>By the early 21st century it&#x27;s unlikely our 1920s engineer can even detect radio signals from devices like a modern cellphone even if they had it in the lab with them -- and they blatantly transmit high power beacons in the open to find other devices. Too low power, too high frequency, data encodings based on mathematics not even invented yet. Even if detected, there would be no obvious modulation, and it would look a lot like a white noise emitter.<p>Maybe it&#x27;s not worth even attempting until the receiving civilization would be able to decode more than just a few bytes from a signal that could be affordably transmitted from a single star.
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therealbilly超过 3 年前
Obviously, only a collimated beam of modulated EM frequency would seem feasible. Then you would have to be in the beams path to even see it. If could detect something like that, it would be amazing and of course trying to decode it.
randtrain34超过 3 年前
A question I always had is wouldn&#x27;t all sufficiently advanced civs use quantum communication which we wouldn&#x27;t be able to detect with our usual SETI-style methods?
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charlieyu1超过 3 年前
I don’t think it would be difficult at all. Any civilisation that is at least as advanced as us will understand machine learning, or trial and error. Just send enough messages and eventually the meanings will be understood mutually.
ncmncm超过 3 年前
Aliens Are Slow<p>Aliens have been all over the newsfeeds lately. Fermi Paradox this, Drake Equation that, Oumuamua, tictacs, yada yada. All is speculation (except tictacs: disinformation).<p>Suppose we encountered actual aliens. What could we reasonably expect, from what we know? By the numbers, for us to encounter them at all, these aliens will have to have been around for millions of years. To keep a culture we would recognize going for millions of years, they cannot be primitives like us, fresh from the muck. Nothing we make lasts. Its members have to be better-architected than would evolve the old-fashioned way.<p>To be that old, each was designed by somebody designed by somebody designed by somebody, untold generations deep. They only reproduce by designing a successor, and only die by choice, or embarrassment. Probably little in the outside universe is as interesting as what they are doing on their phones. Although architected to co-exist, each is custom-designed, as alien to one another as to us. Such hyper-evolved aliens won’t be interested in talking with us; if they care enough, they might probe us.<p><i>So, who is left?</i><p>o o o - Pace - o o o<p>We evolved in water, cells moving charges across bi-lipid membranes. This went on for eons until one invented photosynthesis and liberated oxygen, an apocalypse for almost everything alive. Then the Earth froze over solid for an eon. Survivors learned to tolerate and then to use the oxygen, and eventually to sustain bigger, more complex cells that connected up into plants and animals that took to eating one other. And, here we all are.<p>Yet, for all our common heritage, life on our world works at many different paces. Insect brains, microns across, process bits a thousand times faster than ours. Starfish creep, brainless, for all the world like nibbling aquatic Roombas, but in time-lapse playback, they are visibly as aggressive and territorial as any chihuahua. Sequoias live for thousands of years, and seem to be doing nothing, yet they share the world with everything going a thousand or million times faster.<p>There is nothing compelling about our own pace. We got here by a long series of accidents. Others will have had different accidents. A world could be as big and old and complicated as ours, but with everything alive on it a thousand or million times slower than us. They might do what we do, more or less, but just take longer at it.<p>o o o - Slow Worlds - o o o<p>Slow brains evolve differently. Where there is no rush, nerve cells need not be packed tightly together. It’s safer to distribute them. Radically fewer can do the same job, because they have no need to work all in parallel. A cell not immediately needed to think with can do something else useful, meantime. Our brains are about as big as we could afford until just recently. Slow brain-stuff is cheap. There is little pressure to limit it. Slow creatures can afford to be very, very smart.<p>Landing on a slow planet, we would find a whole world frozen in mid-step. They might move by putting down roots in front and taking them up behind. If we dared to cut one down, nothing inside would resemble a brain.<p>Such a civilization could last for millions of years, and still be as young, vigorous, and naive as ours, still interested in other young, vigorous civilizations. There is nothing to keep them from inventing mathematics, lasers, fusion drives. Spaceships. Their first spaceships would have to blast off at speeds like ours, and so be controlled by computers. Like ours.<p>But for a slow people, the vast chill void between stars is no barrier. There is time for a nap on the way. Electromagnetic signals transmitted between their stars need not be intensely bright. A photon now, another later gets the message across fast enough. The great civilizations that have spread across the galaxy, over untold eons, will be slow people. They are who might visit. They are who might blink lasers at us.<p>Slowly.<p>o o o - Contact - o o o<p>If we are interested in signals from galaxy-spanning civilizations, we are going about it all wrong. SETI looks for signals modulated at our speed. Signals too slow are systematically ignored. We miss all the action.<p>But, maybe we can find aliens closer to home. Sequoias do not seem to have brains, but they wouldn’t. Galactic elders, when they finally notice, might be unhappy to find we cut them all down.