I think the simplest explanation for the absence of alien communication is that development of technological civilization is very rare and the universe is very big. The idea that any technological civilization will set out to colonize the universe seems to me highly implausible. The aliens will have evolved and that implies they have a reproductive, and death, cycle. So the alien life span is not going to be enough to travel to even nearby exoplanets and return. Colonizing exoplanets will not be of interest. They might develop artificial beings with much longer "life" spans, intelligent exploratory probes, which might visit other planets and send back data, as we do with the outer planets. But even this would be very limited. Would we send probes to exoplanets to send back data ten generations hence? Brent On 11/22/2018 10:29 AM, Keith F. Lynch wrote:
D J Makin <makinmagic@tiscali.co.uk> wrote:
Not really ?Mathematics? as such - but how do we do it when the part or parts of the electro-magnetic and/or chemical and/or even base quantum or other physical manifestations of existence the aliens use to communicate or just plain sense, is unknown ? We have to make assumptions. For instance to assume that the aliens think somewhat similarly to how why do. This seems plausible if they evolved on a planet similar to ours. We have the experience of lots of very different cultures here on our planet, albeit all of the same species. And of knowing how differently individuals in our own culture think from each other, including beliefs (I know a guy, otherwise apparently sane, who believes everything Alex Jones says), ethics, ways of learning, decisions about what to learn, and time preference. For instance I find choosing to smoke cigarettes incomprehensible. And I continue to be baffled by why anyone would append a complete copy of the message they're responding to to their reply to it (doing that may be useful in SETI, but it's annoying here).
I am not a visual thinker. Many of my dreams are non-visual. I was able to learn SQL in less than an hour, but was unable to learn OpenGL at all, except by rote memorization of a few things that worked. I am routinely beaten at rapid visual pattern-matching games such as Jungle Speed by small children.
We also have an enormous variety of animals with very different senses and behaviors we can study. We can think about what their society might be like if they were to evolve intelligence.
I'm very close to believing that "intelligence" is an incoherent concept, and that there are only skills at various tasks, not an overriding Spearman's G. There certainly appears to be little correlation, except at the very low end, between skill at taking IQ tests and success in life.
We don't yet have the technology to detect interstellar signals of plausible strength in any form but electromagnetic. For instance the weakest gravitational wave events that LIGO can detect are powerful enough that if they were visible light, we could read by them. Our best neutrino detectors are better, but not by much. And of course there may be forms of radiation (or non-radiation means of long distance communication) which we haven't discovered yet.
It's an interesting question whether our progress in math, physics, and technology took the only possible path. For instance could aliens discover branches of math we never thought of, but completely fail to discover counting, addition, and multiplication? Could there be an alien OEIS with no overlap with Sloane's OEIS?
In Harry Turtledove's 1985 short story "The Road Not Taken," aliens attempt to invade our planet with muskets and other technology that's about what we had around 1500 -- except that they do have a star drive, based on principles that we never stumbled into, since those principles are so different from the ideas of Newton, Watt, etc., and their successors. And in Poul Anderson's 1960 novel _The High Crusade_, aliens with advanced technology attempt to invade Earth in the 13th century, but English soldiers end up stealing their starship and taking over the whole galaxy, since the English were much better than them at leadership and the non-technological aspects of warfare, and since the galactic civilization had a major organizational problem which feudalism was a good solution for.
Probably neither of those stories is plausible. But if there are creatures living in very un-Earthlike environments, they are likely to learn physics in a different order, and to come up with very different technologies. For instance in _Incandescence_, a 2008 Greg Egan novel, non-technological aliens living in a hollow asteroid in a close orbit around a black hole figure out general relativity with some very simple experiments.
The good news is that advanced technology means we can simultaneously scan a large part of the EM spectrum for a large number of ways in which a signal might plausibly differ from noise. Not in every possible way, of course, but certainly the two most obvious, a very narrow band with modulation or very short regularly-spaced pulses with gaps, and maybe a hundred others. (Well, the most obvious to *me*, maybe not to them.)
Of course the aliens would have to be intending to be understood. For one thing, unless they're using utterly enormous amounts of power, their signal must be aimed at our solar system rather than being omnidirectional. For another, the most efficient way to use spectrum, i.e. maximum channel capacity for a given bandwidth and power, results in a signal indistinguishable from noise to anyone who doesn't know the details of the modulation. For instance compare the size of the specifications for NTSC (the analog television standard formerly used in the US) and ATSC (the digital television standard that replaced it). I think there's little doubt that aliens could have figured out NTSC given nothing but a very strong and persistent signal in that format. Even now, aliens on a planet around Aldebaran may be watching I Love Lucy, though there's an even chance they have the image flipped left-to-right. But I doubt anyone, even here on Earth, could make any sense of an ATSC signal unless they read the manual (or, obviously, used a television built by someone who read the manual).
Actually, there's one obvious alternative to a signal aimed directly at us. The aliens could put one or more giant opaque rotating rings around, and perpendicular to, their star, with patterns of immense holes in them. Their star would then appear, from vast numbers of other solar systems (though not nearly to all of them) to be blinking in specific patterns. Such rings could be extremely thin, hence not need much matter. To nearby solar systems, it could even be read by eye. It's an interesting question what the ancient Greeks would have made of Sirius blinking in a prime-number pattern.
There is a star which is blinking in an unexplained way, though not with any obviously intelligent pattern. See https://en.wikipedia.org/wiki/KIC_8462852 (Perhaps we're in an unfortunate direction in which the star is blocked by two such rings, which is why we can't make any sense of the pattern. If so, further observations should allow us to deconvolve the two signals.)
Another possibility, which I posted about here on April 1, 2015, is that instead of transmitting non-stop for perhaps billions of years (we've had radio for only one of the 45 million centuries that our solar system has existed) the aliens would leave a message. I suggested they might plant a tuning-fork-containing titanium or tungsten sphere in bedrock on our planet, sound from which could be detected after an earthquake by a phased array of microphones embedded in the top of the bedrock. Has anyone tried listening for such a thing? Or working out whether such a sphere could survive for long?
On the other hand, if the aliens could come here long ago, would they have bothered to leave a message and go away, or would they have colonized the place? The Fermi paradox says that if aliens exist in our galaxy, and neither progress nor capital accumulation ends, that even if they're only a tiny fraction of the age of the galaxy older than us, they should have reached everywhere already, and their presence should be as blindingly obvious as the presence of Pilgrims at the (alleged) first Thanksgiving was to the Indians there.
One obvious answer, albeit one that tends to be unpopular with my fellow science fiction fans, is that there are no intelligent aliens, never were, and never will be. It's possible that some step in the formation of intelligent life is so extremely unlikely that it only happened once in our entire universe. If it's true that our universe is one of a vast number of universes with different laws of physics, and that most sets of laws of physics are incompatible with the evolution of intelligent beings, and that there are many different ways in which such a universe can fail to be compatible with the evolution of intelligent beings, one would expect that most habitable universes would be near the edge of habitability. (Most points inside an N-dimensional sphere are very close to the surface if N is large.)
Perhaps "habitability" is the wrong word. I don't mean to imply that it's very difficult for life to exist in our hypothetical lonely universe. Indeed, it may someday spread from Earth to fill billions of galaxies. I mean that the laws of nature have to be such that intelligent life has to not merely be capable of persisting once it exists, but has to be capable of evolving or in some other way coming into existence in the first place.
There are of course countless other possible explanations for the Fermi paradox. Perhaps technological progress always levels out not much beyond where we are now. It may already be happening here. The world of 2018 is much more like the world of 1968 than the world of 1968 was like the world of 1918. Except in computers and communication, there's really been rather little progress in the past fifty years, at least compared to the previous fifty, or the fifty before that.
At the other extreme, we may have already long since reached the omega point, and may be living in a simulation, perhaps as an experiment to learn what our distant ancestors were like.
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