Just bouncing some things around inside my head. Feel free to join in.
'Visible light' is an anthropocentric term. There's nothing inherent in those particular wavelengths that makes them visible, it is our ability to perceive them that makes them visible. Had we evolved around a dimmer sun, the range that we call 'visible' could easily be shifted into longer wavelengths. Had there been an evolutionary advantage to being able to see by microwave radiation, we would call that the visible spectrum, and many species on Earth do have different ranges of what they would call 'visible' -- bees seeing into the ultraviolet, or snakes into the infrared, or even some birds that can sense the magnetic field of the earth. Were any of them the dominant species, they would call their particular range 'visible light', and it would not be the same as ours. By the same token, we can't assume that other intelligences in the universe would consider the same stretch of radiation 'visible light'.
...but...
There are some good physical reasons that the vicinity of what we call 'visible light' should be the electromagnetic range of choice for any entity evolving organs of detection. First and foremost, stars with the kind of stable life span that gives time for evolution to do its thing emit strongly in this range. Our own sun emits most strongly at around 500nm (green, oddly enough), which is smack in the middle of the spectrum we've evolved to perceive, and comparably long-lived stable stars also peak in that vicinity (or longer in the case of red dwarfs). So it's not unreasonable to suggest that on average, species that evolve the ability to detect electromagnetic radiation will tend to detect this particular range from the infrared to the ultraviolet. Also, the wavelengths involved are short enough that they tend to reflect off atoms (okay, okay, are absorbed and re-emitted by them) rather than ionize them like shorter wavelengths do, or slip past them with barely a whisper (or only induce heating) like those with wavelengths larger than the atomic scale.
So I don't know. Is the phrase 'visible light' unnecessarily anthropocentric, or are there good reasons that evolution would favor development of detection of that range of electromagnetic radiation?
As you say, it's right at the range produced by our local star. Any life out there should perceive, in the same way, the light that their particular star emits. So you're right, the term "visible light" is only so in relation to us and the light we perceive.
Actually, though, the sun is larger than about 95% of stars, so if life can evolve in systems with smaller stars, their visible range would be toward the longer wavelengths, so most life would probably have a visible range toward the redder end of the spectrum.
Yeah, there's been an amazing turnaround in the last couple decades about what does and does not constitute a habitat. When I was small, the best speculation about life elsewhere in our own solar system was limited to lichens on Mars, and Sagan and Salpeter's ingenious ideas about life in Jupiter's clouds (http://www.daviddarling.info/encyclopedia/J/Jupiterlife.html), and that was pretty much it. Everywhere else was too hot or too cold or too airless.
Now just in our own solar system, we not only consider those two, but also the clouds of Venus and the subsurface oceans of Ganymede, Enceladus, Europa and Titan as potential habitats. Eight habitats (one confirmed, seven hypothetical) in just one solar system certainly forces us to think more broadly when looking for extrasolar life.
I'm not sure what I think about the chances of complex life on a tidally-locked world around a red dwarf. They're certainly long-lived enough to allow enough time for biological evolution, but I wonder if the relatively fixed environment would encourage development beyond simple multicellular life. The weather on such a world would be constant, within limits -- there would be no seasons and no tides, and the effects of those on evolution must be profound.
So now I think I'm leaning towards an argument that intelligent life would probably mark the range of 'visible light' as roughly similar to ours, because I suspect you're going to need a variable environment to keep pushing speciation, and that means a star that's large and bright enough to have a habzone sufficiently distant that the planet (or planets) orbiting therein does not rapidly become tidally locked.
That is going to generally rule out red dwarfs as hosts for intelligences, but they are probably going to be the most common hosts for simple life just because there are so many of them.
Evolution seems to revolve around DNA or some similar mechanism, so I'm wondering how likely it is that DNA or some similar mechanism is bound to occur. Is it likely or not? If it isn't, evolution is not going to happen. As for life itself, I have the same question. It seems that atoms have a propensity to combine in many ways. We know that the possible combinations are not infinite. Certain atomic combinations appear to be impossible. Did the combinations that lead to life on Earth just occur as an unlikely fluke, or are they of the nature that given time they are likely to happen? Life isn't a miracle, unless you believe it is. There isn't anything remarkable about life, unless you think it's remarkable. All it seems to be is a certain combination of atoms. Different combinations produce substances with different characteristics. Life is just one characteristic of certain combinations, and there may be more combinations that are possible than the combination we know of. It just hasn't happened on Earth.
Is that a loose enough thought to be in keeping with this thread?
Quote from: SGOS on June 04, 2017, 10:41:54 AM
Evolution seems to revolve around DNA or some similar mechanism, so I'm wondering how likely it is that DNA or some similar mechanism is bound to occur. Is it likely or not? If it isn't, evolution is not going to happen. As for life itself, I have the same question. It seems that atoms have a propensity to combine in many ways. We know that the possible combinations are not infinite. Certain atomic combinations appear to be impossible. Did the combinations that lead to life on Earth just occur as an unlikely fluke, or are they of the nature that given time they are likely to happen? Life isn't a miracle, unless you believe it is. There isn't anything remarkable about life, unless you think it's remarkable. All it seems to be is a certain combination of atoms. Different combinations produce substances with different characteristics. Life is just one characteristic of certain combinations, and there may be more combinations that are possible than the combination we know of. It just hasn't happened on Earth.
Is that a loose enough thought to be in keeping with this thread?
Good question. It would seem, post facto, that genes are a great idea in biology. But this is in two stages ... with genes, nuclear and mitochondria ... one can conserve successful design. The early Greek idea of random body parts combining with various reasonable success in the environment ... is an early version of evolution. Turns out the real combinations occur at a level below eyesight, but which manifests in ways that can be seen in megafauna/flora. But change is only thru mutation, and most mutations are deleterious. The second great stage is sex ... the semi-random combination from two different individuals, exponentially expands what life can do, an innovation that happened early, before plants and animals became separate life forms. Can you propose any other mechanism, that both conserves and innovates so well?
Quote from: SGOS on June 04, 2017, 10:41:54 AM
Evolution seems to revolve around DNA or some similar mechanism, so I'm wondering how likely it is that DNA or some similar mechanism is bound to occur. Is it likely or not? If it isn't, evolution is not going to happen. As for life itself, I have the same question. It seems that atoms have a propensity to combine in many ways. We know that the possible combinations are not infinite. Certain atomic combinations appear to be impossible. Did the combinations that lead to life on Earth just occur as an unlikely fluke, or are they of the nature that given time they are likely to happen? Life isn't a miracle, unless you believe it is. There isn't anything remarkable about life, unless you think it's remarkable. All it seems to be is a certain combination of atoms. Different combinations produce substances with different characteristics. Life is just one characteristic of certain combinations, and there may be more combinations that are possible than the combination we know of. It just hasn't happened on Earth.
Is that a loose enough thought to be in keeping with this thread?
Works for me. That's the nice thing about loose thoughts, they point in all sorts of directions and you never know where you'll end up when you follow one.
I would love to see other kinds of data-bearing molecules, just to see what's possible. Given the ease with which the basic amino acids form, I wouldn't be surprised to see DNA-
like molecules in extra-terran life, but I would be surprised if the overall basic chemistry is the same. Certainly the principle of mediocrity leads us to assume that there must be more efficient ways to store, replicate and evolve biological data than the way DNA does it.
Of course, a
perfect replicator would be an evolutionary bottleneck, with changes limited to the genetic shuffle of sexual replication and the stray cosmic ray causing damage.
And I agree, there's nothing special about life insofar as the rest of the universe goes -- excluding non-reactive helium, we and the universe are made of the same things in the same order of abundance. That tells me we're a product of the universe, not an insertion into it.
Well
Quote from: trdsf on June 06, 2017, 03:42:44 PM
I would love to see other kinds of data-bearing molecules, just to see what's possible.
Well, there's XNA (
Xeno Nucleic Acid (https://en.wikipedia.org/wiki/Xeno_nucleic_acid)), but that's artificial. Could be possible for a self-replicating molecule to form naturally, made of things other than A, G, C and T.
Quote from: Unbeliever on June 06, 2017, 05:18:15 PM
Well
Well, there's XNA (Xeno Nucleic Acid (https://en.wikipedia.org/wiki/Xeno_nucleic_acid)), but that's artificial. Could be possible for a self-replicating molecule to form naturally, made of things other than A, G, C and T.
Did paper level experiments in college regarding xenobiology. DNA is tricky, it is a series of 4 kings of pairs, but really are just two (A/T) and (C/G) in order to keep the helix in line ... (so it is a binary code if you don't care which way the pair is going, but a quaternary code when it is de-helixed. You pretty much have to use carbon, not silicon, and the (zipper teeth) base pairs have to have the same size, to keep the helix in line.. There is DNA Origami ..
https://en.wikipedia.org/wiki/DNA_origami
Quote from: Unbeliever on June 06, 2017, 05:18:15 PM
Well, there's XNA (Xeno Nucleic Acid (https://en.wikipedia.org/wiki/Xeno_nucleic_acid)), but that's artificial. Could be possible for a self-replicating molecule to form naturally, made of things other than A, G, C and T.
Ooo, that's new information to me. Neat!
One wonders what other data-bearing molecules there might be, ones that don't look like DNA/RNA/XNA, though. Why only four types of base pairs, for example?
And the flip side, as usual, is that the molecules that make up the nucleic acids are very easy to form naturally, so we might be better served looking for other ways to combine them than for completely different structures.
Another loose thought.
The estimated spontaneous remission rate of cancer is about 1 in 100,000.
The Vatican has confirmed 69 "miracle cures" out of about 200,000,000 visitors to the shrine at Lourdes, among all maladies.
That calculates out to random chance being at least 29 times better at miracle cures than faith -- alas, I only have cancer's remission numbers, so I can't get more exact.
Quote from: trdsf on June 08, 2017, 01:59:55 PM
Another loose thought.
The estimated spontaneous remission rate of cancer is about 1 in 100,000.
The Vatican has confirmed 69 "miracle cures" out of about 200,000,000 visitors to the shrine at Lourdes, among all maladies.
That calculates out to random chance being at least 29 times better at miracle cures than faith -- alas, I only have cancer's remission numbers, so I can't get more exact.
Only matters if you are a cancer victim, and if cured, who you blame the cure on.
Well, it might just matter to the families and loved ones of cancer victims, as well.
Quote from: Unbeliever on June 09, 2017, 05:32:59 PM
Well, it might just matter to the families and loved ones of cancer victims, as well.
As to causation ... two people, three opinions ;-)
Another loose thought. Let's take 25 years as the average length of a generation.
If you go back 30 generations, around 1200-1250CE, on average you have more ancestors than there were physically alive at the time.
If you go back 38 generations, around 1000-1050CE, on average you have more ancestors than the total number of human beings that have ever existed.
Never let anyone tell you we are not all related.
I have a distant cousin who converted to Mormon back in the 70s or 80s and did a huge genealogical thing that happened to sweep my family up in it, so I have a family tree back to the 1400s in southwest England for that one line. At the same time, I had about half a million other direct ancestors in the same generation that I have no idea who they were. I find that sobering. I would like to know who they were, and where they were.
Usually regular genealogy is only good back 10 generations or less ... because of adoptions and fostering (in Ireland). Most people didn't have a family name before 1500, and some not before 1800 (Jewish folks).
DNA checks are on autosomal DNA (good back 300-500 years), Y chromosome (good back 5,000 - 10,000 years) and Mitochondrial DNA (good back 5,000 - 10,000) years. That is because the autosomal DNA is shuffled every generation, the other two only change slowly by mutation. So we can have a little knowledge about our Neolithic ancestry. The other stuff, does show where in the world my ancestors were living, in general (basically NW Europe as of 300 years ago). Back then I had 4,000 ancestors (some of which may be the same person, due to over counting). Of course in longer time frames, there is inevitable over counting ... but presumably not much impact due to inbreeding. Having any knowledge prior to 300 years ago, only happens if you have noble ancestry, of the kind of people who kept genealogical records. Because I am part noble ... I have some family related history (but no direct connection) going back to Roman times. Of course the closer you are related to recent noble ancestors, the more inbreeding you suffer from.
And just to follow up on those roughly half-million ancestors from 500 years ago: that's actually half a million positions on the family tree, not half a million individuals. It's statistically certain that individuals occupied multiple positions in my ancestry, and probably even across multiple generations.
Of course, to throw a little further perspective on this, I can do no better than to quote Robert Anton Wilson:
QuoteMost of our ancestors were not perfect ladies and gentlemen. The majority of them weren't even mammals.
According to this:
http://bigthink.com/paul-ratner/how-many-people-have-ever-lived-on-planet-earth
There have been 108.2 billion people that have lived on Earth. That's a lot of ancestors, considering I have no idea who either of my parents were!
Quote from: Unbeliever on June 15, 2017, 03:46:49 PM
According to this:
http://bigthink.com/paul-ratner/how-many-people-have-ever-lived-on-planet-earth
There have been 108.2 billion people that have lived on Earth. That's a lot of ancestors, considering I have no idea who either of my parents were!
Your genes know, approximately, who your biological parents were. But the really important parents are the one's who raise you.
There's a term for the phenomenon of finding a single person in multiple places in your ancestry: Pedigree collapse. (https://en.wikipedia.org/wiki/Pedigree_collapse)
Quote from: Hakurei Reimu on June 15, 2017, 10:18:26 PM
There's a term for the phenomenon of finding a single person in multiple places in your ancestry: Pedigree collapse. (https://en.wikipedia.org/wiki/Pedigree_collapse)
And it's something we all have -- that we
must have, in fact, since it's not possible to have more distinct ancestors than there were/are total people that have ever lived.
Parallel to that, if you're European or of recent European stock, you're descended from Charlemagne (http://www.nature.com/news/most-europeans-share-recent-ancestors-1.12950). Congratulations, Your Highness. :)
Quote from: trdsf on June 16, 2017, 07:55:30 AM
And it's something we all have -- that we must have, in fact, since it's not possible to have more distinct ancestors than there were/are total people that have ever lived.
Parallel to that, if you're European or of recent European stock, you're descended from Charlemagne (http://www.nature.com/news/most-europeans-share-recent-ancestors-1.12950). Congratulations, Your Highness. :)
More recently, King Charles II of GB really got around a lot ;-) Most US Presidents are descended from him. Obama is a cousin of Cheney. Inbreeding.
Quote from: Baruch on June 15, 2017, 08:10:03 PM
Your genes know, approximately, who your biological parents were. But the really important parents are the one's who raise you.
Well, I was adopted when I was 3, then those folks got divorced when I was 10, and I went to a boy's camp for a couple of years. Then I went to a foster home for four years, then I was in an orphanage for a couple of years, then got in trouble with the law and was "encouraged" to join the service when I was 17.
So, who raised me?
Quote from: trdsf on June 16, 2017, 07:55:30 AM
And it's something we all have -- that we must have, in fact, since it's not possible to have more distinct ancestors than there were/are total people that have ever lived.
Parallel to that, if you're European or of recent European stock, you're descended from Charlemagne (http://www.nature.com/news/most-europeans-share-recent-ancestors-1.12950). Congratulations, Your Highness. :)
And if not him, then Genghis Khan:
1 in 200 men direct descendants of Genghis Khan (http://blogs.discovermagazine.com/gnxp/2010/08/1-in-200-men-direct-descendants-of-genghis-khan/#.WURS7TqrP9o)
Quote from: Unbeliever on June 16, 2017, 05:50:25 PM
Well, I was adopted when I was 3, then those folks got divorced when I was 10, and I went to a boy's camp for a couple of years. Then I went to a foster home for four years, then I was in an orphanage for a couple of years, then got in trouble with the law and was "encouraged" to join the service when I was 17.
So, who raised me?
It could even be the favorite authors/characters you read before you were 21. Have any real or fictional heroes you take after? My situation was more stable, so I was able to imprint off my adoptive parents (their good points only). But I have had many real and fictional heroes, because of all I have read. I am still growing ... over 12 feet tall now.
I didn't spend much time reading in those days. So no idols, no heroes, role models. It was purely an act of self-creation.
Quote from: Unbeliever on June 16, 2017, 06:23:21 PM
I didn't spend much time reading in those days. So no idols, no heroes, role models. It was purely an act of self-creation.
Sorry, but psychotic individualism ... isn't a good thing. I am sure you took after some musicians, movie stars or sports stars. Are you sure you weren't kept locked in a basement for 40 years and dreamt the rest of it?
Not at all sure...
The whole idea of the comoving distance (https://en.wikipedia.org/wiki/Universe#Size_and_regions) to the edge of the universe hurts my brain. But it's a good kind of hurt, like chiles. Those quasars 13 billion light years away are actually 46 billion light years because space has expanded since then. Ow. Mentally yummy, but ow.
Quote from: trdsf on July 06, 2017, 01:07:59 PM
The whole idea of the comoving distance (https://en.wikipedia.org/wiki/Universe#Size_and_regions) to the edge of the universe hurts my brain. But it's a good kind of hurt, like chiles. Those quasars 13 billion light years away are actually 46 billion light years because space has expanded since then. Ow. Mentally yummy, but ow.
Even worse, THOSE quasars have the same distance on the other side from us. And so to those.
When "they" say the universe is 13 billion years old, they only mean the part we can see. It logically spreads further.
Quote from: trdsf on July 06, 2017, 01:07:59 PM
The whole idea of the comoving distance (https://en.wikipedia.org/wiki/Universe#Size_and_regions) to the edge of the universe hurts my brain. But it's a good kind of hurt, like chiles. Those quasars 13 billion light years away are actually 46 billion light years because space has expanded since then. Ow. Mentally yummy, but ow.
You have to get into projective geometry ... weirder than Riemannian geometry (of GR). In higher math, you can't visualize, you have to make up a symbolic game, and play out the game. Like tick-tac-toe with yourself, all legal moves being allowed.
Quote from: Cavebear on July 06, 2017, 01:49:41 PM
Even worse, THOSE quasars have the same distance on the other side from us. And so to those.
When "they" say the universe is 13 billion years old, they only mean the part we can see. It logically spreads further.
I'm not sure if there's a meaningful difference between something being 92 billion light-years away in a universe with a 13.8 billion light-year horizon, and that something just being in another universe.
Which kind of leads to the idea of the multiverse being really overlapping universes rather than parallel ones... ow again.
Quote from: trdsf on July 06, 2017, 03:25:48 PM
I'm not sure if there's a meaningful difference between something being 92 billion light-years away in a universe with a 13.8 billion light-year horizon, and that something just being in another universe.
Which kind of leads to the idea of the multiverse being really overlapping universes rather than parallel ones... ow again.
That would be the case for the level one multiverse, I think, since each point in space-time has its own observable bubble (a Hubble Bubble) around it. For the other kinds of multiverse, though, there may be more definite separation, I guess.
The main problem with the Fermi Paradox is that it assumes an eternal, steady-state universe in which time is ultimately not a consideration and civilizations can be arbitrarily old. In the universe we live in that is closed in time at one end, there are some good -- not necessarily convincing or definitive, merely in accord with our current understanding -- reasons why we shouldn’t be surprised no one’s come calling yet.
The first is, as Douglas Adams said, space is big. Really big.
The maximum range at which any ETI might be able to look at our world and think there’s something sentient going on is about 200 lightyears. That’s because about 200 years ago, we started pumping pollutants into our atmosphere as the Industrial Revolution started up. Now, first of all, there needs to be another intelligent life form within that sphere that has sufficient technology not only to detect the Earth from underneath the much larger optical/gravitational signals of the four big outer worlds, but also can resolve it enough to permit spectrographic analysis of our atmosphere. Detecting oxygen is about as dead a giveaway as there is for life, because so far as we can tell, oxygen atmospheres are unstable and something needs to continually replenish the oxygen supply and there aren’t any good candidate non-living physical systems that can do that.
Finding oxygen only says life, though, and doesn’t imply there has to be anything more complicated than algae. The industrial byproducts -- air pollution -- are what indicate the presence of a technological civilization. Fundamentally, gunk in the air implies intelligence. Not necessarily wisdom, but intelligence.
So, worst case, let’s posit there’s one other world at the 200LY marker that just discovered there might be someone here. How abundant does intelligent life have to be to make that more likely than not?
Well, the volume of the Milky Way galaxy is about 3.3×1061 cubic meters. The volume of our 200 light year sphere is around 2.8×1055 cubic meters -- not quite one-one millionth the volume of our home galaxy, so we would expect a bit over a million sentient species in the galaxy to have a better than 50% chance of having one only 200LY away. I’m leaving out some refinements for now, like uninhabitable areas towards the galactic core, but it’ll do within an order of magnitude, and I’ll come back to those later.
We’ll take an average of 250 billion stars for the total in the galaxy, since the range is 100-400 billion -- and again, I’m not going to get into the details of which stars theoretically can and cannot host life-bearing planets, this is all back-of-the-envelope, order-of-magnitude stuff. Around one million sentient life forms spread among around 250 billion stars is around one per 250,000 stars -- and as it turns out, there are known to be some 260,000 stars within a 250 light year radius of Earth (http://www.atlasoftheuniverse.com/250lys.html). So we’re in the right ballpark as far as the numbers go.
Now, that count of stars in our galaxy is all stars, not just the F, G, K and M stars that are long-lived enough to permit the slow process of biological evolution to unfold. And I am strongly skeptical of the ability of M-class stars -- red dwarfs -- to host intelligent life, because these are worlds that will both be very close and rapidly become tidally locked and therefore not have great variability in weather over the course of their very short years. And M-class stars make up 80% of all stars in the galaxy. F, G and K stars make up only 13.5% of the stars in the galaxy, and that cuts our number of available stars from 250 billion to just shy of 34 billion. And of those, the current estimates are that of those 34 billion roughly sun-like stars, there are 2-3 billion with planets in habitable zones -- call it 2.5 billion, or 1% of the total stars in the galaxy.
Now, we still need those million civilizations to get one near enough, volumetrically. But now they need to be not one in every 250,000 stars, but one in every 2,500 habitable stars. And that tallies close enough to 1% of all the stars within our detectability radius, since we know there are 260,000 within 250LY, we're actually doing much better than just staying within an order of magnitude. We calculated that we need 2,500 within 200LY radius, we know there are 2,600 within 250LY radius, and that's much closer than an order up (25,000) or down (250).
So now we can dispense with part of Fermi’s objection: we are only just now at the very beginning of entering an era in which, statistically, we can expect to have been detected only and not yet replied to, and that’s if intelligent life is common enough that there are a million ETIs in this galaxy. So we should not be surprised that we haven’t heard from anyone yet, and the Fermi Paradox fails spatially.
And for the record, while I’m bullish on ETIs in our galaxy, I’m not bullish to the tune of a million. I always seem to come up with 5-10 total when I plug my numbers into the Drake Equation. And that means on average the nearest one would be a long, long way away. I think life is easy, complex life is tricky but do-able, and intelligent life is even trickier, but obviously still do-able.
I suggest that the Fermi Paradox also fails temporally.
It’s pretty clear that complex life could not develop in the earliest days of the universe, since the only elements available in any quantity were hydrogen and helium, and vanishingly small traces of anything bigger. Isolated individual stars going supernova won’t turn the trick either -- you need galaxy-scale masses so that the heavier elements can collect and condense over time, and it takes a long time to collect enough to build metal-rich stellar systems.
I don’t say that it’s necessarily probable, but I think that it’s possible that we’re entering the first epoch of the universe in which complex life can have evolved all the way to intelligence, simply because you need a few generations of exploding stars to enrich the interstellar medium with heavy elements before you can even start a potentially life-bearing stellar system, much less start the process of biological evolution. So several billion years had to pass before things could even get started, and then a few billion years more to just barely get to the point where we can look up and go, “Hey, where is everyone?â€
It’s possible that a species might be millions of years more advanced than we, but I think it’s highly unlikely in terms of both stellar and biological evolution that there would be anything out there billions of years more advanced. And given the distances involved, the expense in both materials and sentients, and the speed limit of light, that’s the kind of time frames we’re talking about to fully explore and/or colonize a galaxy. In the steady-state universe -- which was still a plausible theory with the evidence at hand when Fermi proposed his paradox -- you have the time. In a Big Bang universe, you don’t. So, no paradox temporally either -- we haven’t seen anyone yet because there hasn’t been the time for anyone to randomly stumble across us.
Lastly, I think it fails from sheer perspective. First of all, to the question of “Where is everyone?â€, it’s perfectly legitimate to answer, “I don’t know!†And not only that, it’s appropriate to counter, “Why should they come here in the first place?†As indicated above, no one outside 200 light years can know we’re here (and the radius was less than 150LY in Fermi’s day) -- and if you want to go by our radio bubble, it’s barely 100LY today. Fermi’s assumption that they should come to Earth to see us is nothing more than latter-day geocentrism, the assumption that we’re special somehow that the rest of the galaxy should come to us because we’re the Earth.
And there’s no reason to think that. At least half the galaxy can’t even see our star, and of the remainder that can, they have no particular reason to think we’re anything special. We’re just a catalog number, a boring little yellow dwarf that maybe they can devote a little telescope time to some day, but there’s no hurry.
And when they do, even if they can detect the presence of the Earth, even if they can resolve it just enough to do an analysis of our atmosphere -- all that will tell the vast majority of them is that at least some sort of microbe that excretes oxygen exists here.
I’m all for extraterrestrial life, but even I would question sending a probe hundreds or thousands of light-years to look at pond scum. You save those for the big finds, because of the extreme times and resources involved to get even a small ship across interstellar distances. There’s no reason to assume that ETIs have unlimited resources to fling out probes -- much less staffed survey ships -- to every little speck of light they see.
tl;dr: “Where is everyone?†“Who knows?†:D
The easiest answer to "where is everyone" might just be that long-distance inter-stellar travel is just impossible for intelligent life. Lack of speed, no hibernation works, cosmic rays are unstoppable, etc.
I don't especially like the idea that no problem is unsolvable, but it might be the case.
To get more esoteric, we might be the first. Or only. Or it could be that every intelligent species causes an individual universe around itself by existing.
Do I think that? No, not really, but it's possible. And maybe we don't want to meet a space-faring species. Our history suggests that less-advanced cultures don't do very well when confronted by more advanced ones.
"The easiest answer to "where is everyone" might just be that long-distance inter-stellar travel is just impossible for intelligent life."
Thank goodness we are unintelligent life! The possibilities are endless for us ;-)
I tend to see in the x-rated portion of the spectrum.
Quote from: Gawdzilla Sama on July 11, 2017, 07:47:50 AM
I tend to see in the x-rated portion of the spectrum.
Whatever your um "spectrum" is, it is yours to enjoy.
Quote from: Gawdzilla Sama on July 11, 2017, 07:47:50 AM
I tend to see in the x-rated portion of the spectrum.
But "The Man With The X-Ray Eyes" ... a 1950s B movie ... the protagonist goes insane. Not enough to just see beneath people's clothing. He starts seeing everyone as skeletons!
In cosmic terms, the universe has just begun. We are living at the dawn of time, with hundreds of billions of years to go before things get completely unsuitable for life. We may well be the first of our kind in our Hubble bubble. But looking is fun, and so why not?
Quote from: Cavebear on July 11, 2017, 04:55:22 AM
The easiest answer to "where is everyone" might just be that long-distance inter-stellar travel is just impossible for intelligent life. Lack of speed, no hibernation works, cosmic rays are unstoppable, etc.
I don't especially like the idea that no problem is unsolvable, but it might be the case.
To get more esoteric, we might be the first. Or only. Or it could be that every intelligent species causes an individual universe around itself by existing.
Do I think that? No, not really, but it's possible. And maybe we don't want to meet a space-faring species. Our history suggests that less-advanced cultures don't do very well when confronted by more advanced ones.
Well, sure.
Someone has to be first. It could as reasonably be us as anyone else. Of course, there's just no knowing at this point in time. By the principle of mediocrity, we assume that on average we are not, but we could be.
On the other hand, it's unlikely we're a latecomer to the party. If there were a millions-year-old species in the universe, we should have detected it by now, even given the half-assed way we've gone about SETI -- and by half-assed, I mean in terms of governmental support, not in terms of the science.
Quote from: trdsf on July 11, 2017, 11:17:26 PM
Well, sure. Someone has to be first. It could as reasonably be us as anyone else. Of course, there's just no knowing at this point in time. By the principle of mediocrity, we assume that on average we are not, but we could be.
On the other hand, it's unlikely we're a latecomer to the party. If there were a millions-year-old species in the universe, we should have detected it by now, even given the half-assed way we've gone about SETI -- and by half-assed, I mean in terms of governmental support, not in terms of the science.
Well, as mentioned elsewhere here, signals seem to deteriorate faster than we thought. Our original TV signals have spread out 60-70 light years, but apparently they are merely static after a few stars away.
Quote from: Cavebear on July 14, 2017, 06:28:36 AM
Well, as mentioned elsewhere here, signals seem to deteriorate faster than we thought. Our original TV signals have spread out 60-70 light years, but apparently they are merely static after a few stars away.
Oh, definitely. The limit for direct detection of our radio and TV signals appears to be Proxima Centauri. But a deliberate broadcast is another matter entirely. Using the Arecibo dish as a transmitter rather than as a receiver, we could be 'heard' clear to the center of the Milky Way. Radio detection will probably be of species *wanting* to be heard, barring discovery of any refining technique that would allow picking up such fantastically weak signals and separating them from the other sources of radio noise.
Quote from: trdsf on July 14, 2017, 10:54:07 AM
Oh, definitely. The limit for direct detection of our radio and TV signals appears to be Proxima Centauri. But a deliberate broadcast is another matter entirely. Using the Arecibo dish as a transmitter rather than as a receiver, we could be 'heard' clear to the center of the Milky Way. Radio detection will probably be of species *wanting* to be heard, barring discovery of any refining technique that would allow picking up such fantastically weak signals and separating them from the other sources of radio noise.
The most exciting AND scariest moment of my life would be the reception of a signal of a series of prime numbers (or anything equally unnatural) not created by humans. I probably would live to see it, but I suspect some humans will. What will happen then?
Will it be Nightfall, or Utopia? Alpha or Omega?
Quote from: Cavebear on July 14, 2017, 01:53:25 PM
The most exciting AND scariest moment of my life would be the reception of a signal of a series of prime numbers (or anything equally unnatural) not created by humans. I probably would live to see it, but I suspect some humans will. What will happen then?
Will it be Nightfall, or Utopia? Alpha or Omega?
I can't think of a better attention-getter than a sequence of primes; that's what you send if you
want to be heard.
I can imagine a fear reaction to the definite discovery of an alien signal. I would be overjoyed, personally. I think I would be, anyway.
Quote from: trdsf on July 14, 2017, 04:13:03 PM
I can't think of a better attention-getter than a sequence of primes; that's what you send if you want to be heard.
I can imagine a fear reaction to the definite discovery of an alien signal. I would be overjoyed, personally. I think I would be, anyway.
Well, in a sense, I suppose we might as well be thrilled if we contacted an alien intelligence. We would have much choice if detected.
I can imagine the greatest human debate of all time if we received a signal. Respond or not. But I know the answer. Someone would respond.
Then we would wait a few generations to find out if we are the Incans or the Europeans.
If it is beneficent, great. If not, we are out of luck. There wouldn't be any equivalence. If they come here, we're behind.