Anything big enough for an interstellar colony is big enough to be spun.
I'm sure you can't--the question is whether you can make the recycling good enough that the reserves needed are reasonable to carry.
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Do you think any aliens exist in the universe?
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Anything big enough for an interstellar colony is big enough to be spun.
In one sense I'm sure you're right--I very much doubt there will be anything around we would call "homo sapiens" in a million years. However, if we don't destroy ourselves it's quite reasonable to think there might be something human-derived around at that point.
And note that the only thing on your list that could harm a Mars colony also is war. Earth is a case of putting all our humans in one basket.
We will not evolve. We might very well remake ourselves, though.
Here we disagree. If we have viable interstellar colonies it would be very hard to wipe us out.
So?
Except Antarctica has nasty weather. Mars doesn't. The Martian environment is far more hostile but it's far more passive, also.
bilby
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Meh, only half of that is a problem; The Solar Wind would take a vast amount of time to strip away enough of Mars’s atmosphere to make a difference (and when it does, you can just replenish it - which brings us back to the main problem).
Finding enough of the right mix of gases, and transporting them to Mars would be challenging, to coin a massive understatement.
Indeed, O2 is basically found nowhere in the Solar System, apart from Earth, where the tendency of this highly reactive molecule to break down is counterbalanced by its photosynthetic production.
To give Mars an Earth-like atmosphere, it’s probably going to be necessary to import a metric shitload of Carbon Dioxide and Water, add phytoplankton, and wait. Likely for a very long time.
CO2 isn’t hard to find (perhaps it could be harvested from Venus). And comets are mostly water, though getting it into the proto-atmosphere without making big craters in the surface might be tricky.
Can't exist? That means we can't, either.
Super rare? This is the notion that we have been incredibly lucky. Due to the observer effect it is a viable answer.
We are first? Why are we so lucky?
ETs too far away--they don't travel? Somebody would!
ETs not interested in communication? We would see their works.
ETs hidden? We would see their works.
ETs not noticed? We should notice K2 civilizations, period. A K2 civilization will not produce a spectrum like any known star.
lpetrich
Contributor
Life - fl
The origin of life continues to be an unsolved problem. One can approach it in two directions, from the known biota and from prebiotic-synthesis experiments.
There is still a gap between the two, it must be noted, a gap that we still don't have much clue about how to fill.
On the prebiotic-synthesis side, one can make a lot of building blocks, like the simpler amino acids, some nucleobases, porphyrins, etc. but sugars are very hard to make, meaning that one can't easily make the (deoxy)ribose part of nucleic acids. One also has difficulty going further than that.
On the known-biota side, when one works out what the Last Universal Common Ancestor, was like, one finds an impressively complex organism, one much like present-day methanogens.
The main criticisms of the RNA world that I've seen are about how it originated, since it's hard to make RNA prebiotically. Was there something that preceded ribose? Like amino acids, making peptide nucleic acids, and polycyclic aromatic hydrocarbons, making PAH nucleic acids.
I note in passing that PAH's are a late stage in the thermal decomposition of organic materials, with the final stage being graphite sheets: super PAH's. So prebiotic chemistry can end up in a dead end.
The origin of life continues to be an unsolved problem. One can approach it in two directions, from the known biota and from prebiotic-synthesis experiments.
There is still a gap between the two, it must be noted, a gap that we still don't have much clue about how to fill.
On the prebiotic-synthesis side, one can make a lot of building blocks, like the simpler amino acids, some nucleobases, porphyrins, etc. but sugars are very hard to make, meaning that one can't easily make the (deoxy)ribose part of nucleic acids. One also has difficulty going further than that.
On the known-biota side, when one works out what the Last Universal Common Ancestor, was like, one finds an impressively complex organism, one much like present-day methanogens.
- DNA genome
- DNA-to-RNA transcription and RNA-to-protein translation
- The 20 canonical protein-forming amino acids
- ATP used as an energy intermediate
- Lipid-bilayer cell membrane
- Chemiosmotic energy metabolism: pumping hydrogen ions across the cell membrane out of the cell, and making them assemble ATP when they return
- Electron-transfer energy metabolism, ending with nitrogen oxides instead of with oxygen
- Carbon fixation, incorporating the carbon from CO2 into its molecules
- Combining CO2 and H2 for energy, giving methane or acetic acid
- Numerous protein enzymes, including a complete set of biosynthesis enzymes, likely making the organism autotrophic, able to make all its biological molecules
The main criticisms of the RNA world that I've seen are about how it originated, since it's hard to make RNA prebiotically. Was there something that preceded ribose? Like amino acids, making peptide nucleic acids, and polycyclic aromatic hydrocarbons, making PAH nucleic acids.
I note in passing that PAH's are a late stage in the thermal decomposition of organic materials, with the final stage being graphite sheets: super PAH's. So prebiotic chemistry can end up in a dead end.
skepticalbip
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But Antarctica's winds (pretty much Antarctica's only weather) would be an energy source for a colony using wind turbines. Wind turbines would be worthless on Mars and solar panels would be poor at providing power during the global dust storms.
lpetrich
Contributor
Intelligence - fi
This can be broken down into several steps. The first step is using the planet's star's light for energy, thus making it possible to live on much more of a planet's surface. Photosynthesis evolved twice, with one form being very limited and little-known.
The chlorophyll kind is done over the Bacteria, the ordinary bacteria / prokaryotes. Its evolution is rather complicated, with many organisms having only some of the complete photosynthetic apparatus of cyanobacteria ("blue-green algae"). But cyanobacteria use water as a hydrogen / electron source, and they release molecular oxygen. Cyanobacteria are not just free-living; they also live inside some eukaryotic cells as chloroplasts.
Turning to multicellularity, it evolved numerous times: plantlike, funguslike, slime-moldlike, but only once in animallike fashion. So might there be some world with lots of trees and mushrooms and the like but no animals?
Bodies of water are poor places to work with fire and electricity, so we must consider colonization of land. Animals have done so several times:
Something helpful for being large on land is an internal skeleton, and that’s evolved once in animals (vertebrate skeletons), and at least once in plants (wood). Curiously, most animal skeletons are either external (shells), skin-surface (arthropod skins), or just under the skin (echinoderm skeletons). So it may be hard for an animal internal skeleton to evolve.
Grasping limbs and jaws have evolved multiple times, however.
Among land vertebrates, grasping with digits has evolved at least twice, in primates and in perching birds (Passeriformes). Arthropods have evolved pincer limbs at least twice (scorpions, various crustaceans). Tentacles have evolved at least twice, in cnidarians and in cephalopods, and arguably a third time in proboscideans (the elephant’s trunk).
Turning to jaws, vertebrate ones are modified front gill bars, while arthropod ones are modified limbs. Some polychaete worms also have jaws.
About sense organs, vertebrates and cephalopods have independently evolved high-resolution lens-camera eyes, and vertebrates and arthropods have independently evolved color vision.
This can be broken down into several steps. The first step is using the planet's star's light for energy, thus making it possible to live on much more of a planet's surface. Photosynthesis evolved twice, with one form being very limited and little-known.
- Rhodopsin (purple) - addition to chemiosmotic energy metabolism
- Chlorophyll (green) - addition to electron-transfer energy metabolism
The chlorophyll kind is done over the Bacteria, the ordinary bacteria / prokaryotes. Its evolution is rather complicated, with many organisms having only some of the complete photosynthetic apparatus of cyanobacteria ("blue-green algae"). But cyanobacteria use water as a hydrogen / electron source, and they release molecular oxygen. Cyanobacteria are not just free-living; they also live inside some eukaryotic cells as chloroplasts.
Turning to multicellularity, it evolved numerous times: plantlike, funguslike, slime-moldlike, but only once in animallike fashion. So might there be some world with lots of trees and mushrooms and the like but no animals?
Bodies of water are poor places to work with fire and electricity, so we must consider colonization of land. Animals have done so several times:
- Arthropods: insects, pillbugs, land crabs, arachnids, myriapods (centipedes, millipedes)
- Mollusks: land snails
- Annelids: earthworms, leeches
- Vertebrates: tetrapods, starting with real-life “Darwin Fish”
Something helpful for being large on land is an internal skeleton, and that’s evolved once in animals (vertebrate skeletons), and at least once in plants (wood). Curiously, most animal skeletons are either external (shells), skin-surface (arthropod skins), or just under the skin (echinoderm skeletons). So it may be hard for an animal internal skeleton to evolve.
Grasping limbs and jaws have evolved multiple times, however.
Among land vertebrates, grasping with digits has evolved at least twice, in primates and in perching birds (Passeriformes). Arthropods have evolved pincer limbs at least twice (scorpions, various crustaceans). Tentacles have evolved at least twice, in cnidarians and in cephalopods, and arguably a third time in proboscideans (the elephant’s trunk).
Turning to jaws, vertebrate ones are modified front gill bars, while arthropod ones are modified limbs. Some polychaete worms also have jaws.
About sense organs, vertebrates and cephalopods have independently evolved high-resolution lens-camera eyes, and vertebrates and arthropods have independently evolved color vision.
bilby
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Or that there is something completely unique about our local region of space that makes life possible here, and here alone.
How? We can’t travel between stars; Maybe nobody can.
A hypothetical exact copy of the Earth, ten or twenty light years away, would be almost impossible for us to detect, much less identify as life-bearing, unless we knew exactly where to look. Even then it would stretch our capabilities.
They can’t see ours; How would we expect to see theirs?
There’s a BIG gap between ‘ETs exist’ and ‘K2 civilisations exist’.
lpetrich
Contributor
Turning to intelligence proper, it sometimes seems annoyingly lacking in our species, but what's lacking is high-level reasoning. Consider a creationist stating “Evolution can’t be true because dogs don’t give birth to cats.” The hole in that reasoning is rather obvious: no reputable evolutionary biologist claims that evolution works like that. But it is expressed in language that is far more complex than anything that nearly every other species can do.
The most successful language learning outside our species has been by chimpanzees, but while they can learn a lot of sign-language signs, the most that they can do in stringing signs together is two-sign phrases (duck: "water bird") and one three-sign phrase (radish: "cry hurt food").
Most animal species have only single "words", like a vervet monkey's calls meaning “Leopard!”, “Snake!”, and “Eagle!” Their fellow monkeys then do the predator-evasion strategy suitable for each kind of predator.
That leaves bottlenose dolphins and other toothed cetaceans, and the extent of their linguistic capability is still murky. Dolphins can make imitations of objects' sonar reflections, like us calling a dog a "woof-woof". They also prefix their whistles with their names, like a chatroom transcript.
Another criterion is self-awareness, like being able to recognize oneself in a mirror. Human children become able to do that at about 18 – 24 months old, and a few other species seem to have this ability: (other) great apes, dolphins and orcas, elephants, and European magpies.
Most others don’t, and to a dog or a cat, the dog or cat in the mirror is another one.
The most successful language learning outside our species has been by chimpanzees, but while they can learn a lot of sign-language signs, the most that they can do in stringing signs together is two-sign phrases (duck: "water bird") and one three-sign phrase (radish: "cry hurt food").
Most animal species have only single "words", like a vervet monkey's calls meaning “Leopard!”, “Snake!”, and “Eagle!” Their fellow monkeys then do the predator-evasion strategy suitable for each kind of predator.
That leaves bottlenose dolphins and other toothed cetaceans, and the extent of their linguistic capability is still murky. Dolphins can make imitations of objects' sonar reflections, like us calling a dog a "woof-woof". They also prefix their whistles with their names, like a chatroom transcript.
Another criterion is self-awareness, like being able to recognize oneself in a mirror. Human children become able to do that at about 18 – 24 months old, and a few other species seem to have this ability: (other) great apes, dolphins and orcas, elephants, and European magpies.
Most others don’t, and to a dog or a cat, the dog or cat in the mirror is another one.
lpetrich
Contributor
Then what would keep a big brain going. Dolphins do a lot of sonar, and doing good interpretation may require having a lot of brainpower.
For our species, anthropologist Robin Dunbar has proposed the "social brain theory", noting a correlation between brain size and size of social group in our simian relatives. The larger the brain, the more group members we can track. For us, "Dunbar's number" is 150, and we have succeeded in getting around that limit with large-scale societies.
So we have one example of human-scale intelligence, ourselves, and some species that come close – some of the toothed cetaceans.
So while some steps involved in the evolution of intelligence have happened several times, other steps have happened only once. It’s not clear whether the latter sort of step tends to pre-empt other instances or whether it does not often happen. So fi is up in the air.
For our species, anthropologist Robin Dunbar has proposed the "social brain theory", noting a correlation between brain size and size of social group in our simian relatives. The larger the brain, the more group members we can track. For us, "Dunbar's number" is 150, and we have succeeded in getting around that limit with large-scale societies.
So we have one example of human-scale intelligence, ourselves, and some species that come close – some of the toothed cetaceans.
So while some steps involved in the evolution of intelligence have happened several times, other steps have happened only once. It’s not clear whether the latter sort of step tends to pre-empt other instances or whether it does not often happen. So fi is up in the air.
lpetrich
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Communication - fc
Some sentient species may be incapable of that, because they live in oceans. Dolphins are obvious, and they have very limited manipulation abilities. They can grab stuff with their mouths, but they don't have hands or pincers or tentacles.
So we must look to our history.
The first step along the way is agriculture, since it enables larger population densities and larger-scale societies than foraging can. What is curious about this is that present-day humanity did not have it for most of its some 100,000 years of its existence. But in the Holocene, after the end of the last ice age, humanity invented agriculture independently in several places in the world.
Vavilov center - "Vavilov centers of origin: (1) Mexico-Guatemala, (2) Peru-Ecuador-Bolivia, (2A) Southern Chile, (2B) Paraguay-Southern Brazil, (3) Mediterranean, (4) Middle East, (5) Ethiopia, (6) Central Asia, (7) Indo-Burma, (7A) Siam-Malaya-Java, (8) China and Korea."
I have seen a speculation that this curious timing is due to the climate being more stable in the Holocene than in the time since the previous interglacial about 100,000 years ago. An unstable climate makes it difficult to get started with agriculture, since the weather can turn bad for it too quickly. There were a lot of Dansgaard–Oeschger event - warming by some 5 C over a few decades, then cooling back down over the next few centuries.
In this connection, Jared Diamond has made a strong case that Eurasian people got ahead of the rest of humanity because they could exchange crop plants across the length of their continent. Also because it had some conveniently domesticatable animals. By comparison, it was difficult to get potatoes and llamas from the Andes to the North American Rockies, where they can thrive, because of the tropical-climate places in between.
Some sentient species may be incapable of that, because they live in oceans. Dolphins are obvious, and they have very limited manipulation abilities. They can grab stuff with their mouths, but they don't have hands or pincers or tentacles.
So we must look to our history.
The first step along the way is agriculture, since it enables larger population densities and larger-scale societies than foraging can. What is curious about this is that present-day humanity did not have it for most of its some 100,000 years of its existence. But in the Holocene, after the end of the last ice age, humanity invented agriculture independently in several places in the world.
Vavilov center - "Vavilov centers of origin: (1) Mexico-Guatemala, (2) Peru-Ecuador-Bolivia, (2A) Southern Chile, (2B) Paraguay-Southern Brazil, (3) Mediterranean, (4) Middle East, (5) Ethiopia, (6) Central Asia, (7) Indo-Burma, (7A) Siam-Malaya-Java, (8) China and Korea."I have seen a speculation that this curious timing is due to the climate being more stable in the Holocene than in the time since the previous interglacial about 100,000 years ago. An unstable climate makes it difficult to get started with agriculture, since the weather can turn bad for it too quickly. There were a lot of
Dansgaard–Oeschger event - warming by some 5 C over a few decades, then cooling back down over the next few centuries.In this connection, Jared Diamond has made a strong case that Eurasian people got ahead of the rest of humanity because they could exchange crop plants across the length of their continent. Also because it had some conveniently domesticatable animals. By comparison, it was difficult to get potatoes and llamas from the Andes to the North American Rockies, where they can thrive, because of the tropical-climate places in between.
lpetrich
Contributor
I now turn to persistent information storage: writing. It can easily outlive its creators, and it does not need the memory cues that are convenient for memorizing large amounts of content. Rhythmic poetry has the function of jogging the memory of its reciters, and not surprisingly, it was a very valued art in some societies.
The Internet Classics Archive | Phaedrus by Plato - Plato imagined someone objecting to writing because it would make people’s memories atrophy and make people only appear to be learned.
Writing was only invented in two or three places: Sumer, Central America, and maybe also China. But once it was invented, it was widely copied, and many people invented writing systems out of awareness that it was possible: stimulus diffusion.
After that was development of science, but that was difficult and slow. It started in classical Greece and continued into the early Roman Empire, where it was interrupted by the “Crisis of the Third Century”: strife and civil war. It did not restart until over a millennium later in western and central Europe, and even then, it was slow going at first.
There is a further problem. The social-brain theory of intelligence suggests that sentient species may prefer to be concerned with social relations and gossip and the like; that sometimes seems rather evident in our species. That extends to anthropomorphizing nonhuman species like pet species, like making LOLcat pictures.
However, some of us have Asperger’s syndrome, which may help its sufferers understand impersonal things and features and relations. Not many, but enough to be useful for the rest of us. So might other sentient species have Asperger-like variants?
The Internet Classics Archive | Phaedrus by Plato - Plato imagined someone objecting to writing because it would make people’s memories atrophy and make people only appear to be learned.
Writing was only invented in two or three places: Sumer, Central America, and maybe also China. But once it was invented, it was widely copied, and many people invented writing systems out of awareness that it was possible: stimulus diffusion.
After that was development of science, but that was difficult and slow. It started in classical Greece and continued into the early Roman Empire, where it was interrupted by the “Crisis of the Third Century”: strife and civil war. It did not restart until over a millennium later in western and central Europe, and even then, it was slow going at first.
There is a further problem. The social-brain theory of intelligence suggests that sentient species may prefer to be concerned with social relations and gossip and the like; that sometimes seems rather evident in our species. That extends to anthropomorphizing nonhuman species like pet species, like making LOLcat pictures.
However, some of us have Asperger’s syndrome, which may help its sufferers understand impersonal things and features and relations. Not many, but enough to be useful for the rest of us. So might other sentient species have Asperger-like variants?
lpetrich
Contributor
So fl, fi, and fc are very much up in the air, and I now turn to L, which is even worse.
There are several possible limiting factors:
(2) That is a bit farfetched, but not impossible with suitable genetic engineering, like creating a time-bombed microorganism that spreads without causing symptoms, and then starts attacking its hosts.
(3) These include various ways of impairing the habitability of one’s homeworld, like ruining farmland and altering the climate.
(4) This includes running out of fossil fuels, metal ores, and the like, without developing good substitutes. I think that energy resources are especially critical, since without energy, you can’t do anything else. So it is important to learn how to use long-lived energy sources like the light of one’s homeworld’s star.
(5) There are several ways that this can happen.
There are several possible limiting factors:
- Wars
- Diseases
- Environmental problems
- Resource depletion
- Loss of interest
(2) That is a bit farfetched, but not impossible with suitable genetic engineering, like creating a time-bombed microorganism that spreads without causing symptoms, and then starts attacking its hosts.
(3) These include various ways of impairing the habitability of one’s homeworld, like ruining farmland and altering the climate.
(4) This includes running out of fossil fuels, metal ores, and the like, without developing good substitutes. I think that energy resources are especially critical, since without energy, you can’t do anything else. So it is important to learn how to use long-lived energy sources like the light of one’s homeworld’s star.
(5) There are several ways that this can happen.
- Reversion to a lower level of technology
- Turning inward
- Feeling threatened by the possibility of intelligent entities elsewhere in the Universe
- Deciding that such entities cannot exist
- Quitting after failing to discover such entities
- Considering self-advertisement too dangerous or too expensive
- Considering searches likewise too dangerous or too expensive
DBT
Contributor
The apparent rarity of phosphorus may be a limiting factor for life in the universe.
Jarhyn
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I mean they have *A* specific prehensile tentacle they can manipulate things with...
steve_bank
Diabetic retinopathy and poor eyesight. Typos ...
More basic. LOT and entropy. Can O2 and H2O be recycled indefinitely without loss. Can you recycle 1kg of water and always get back 1kg of water.
The Biosphere experiment in the 80s was an attempt at an isolated self sustaining habitat.
Biosphere 2 - Wikipedia
Simply saying anything can be spun is more a scifi approach.
steve_bank
Diabetic retinopathy and poor eyesight. Typos ...
We can look at the Earth's biodiversity and only ]one species devoloped science.
Humans in teh Americas did not develop science as humans did elsewhere.
If evolution is a constant then if conditions exist for life it will come to be. Discovering EMR and building radios is anoter matter.
As to communications.
You can calculate the transmitter energy required for a radio transmitter at a distant planet to be above minimum detectability here on Earth.
The distant transmitter with a directional antenna radiating power in watts with a beam divergence. Ignoring deflection and absolution in the path the transmitter radiates into a sold angle where the energy density of the wavefront decreases by 1/r.
A 1st order approximation for radio reception is the noise in a 50 ohm resistor, the typical radio input impedance.
Variables
transmit power
transnit solid angle or beam divergence
receiving antenna diameter
receiver noise floor(50 ohms)
An ET transmitter here on Earth looks like a point source. The solid angle is a cone with the peak at the transmitter and the base the with a base of an area at the plane of the Earth.
Total received energy is the energy density of the base of the solid angle times the area of the receiver antenna. Engry rescibed has to be at least at the noise floor represented by the 50 ohm resistance.
Basic trig, a right triangle with the base in the plane of the Earth.
The WOW signal, one can always hope.
en.wikipedia.org
Humans in teh Americas did not develop science as humans did elsewhere.
If evolution is a constant then if conditions exist for life it will come to be. Discovering EMR and building radios is anoter matter.
As to communications.
You can calculate the transmitter energy required for a radio transmitter at a distant planet to be above minimum detectability here on Earth.
The distant transmitter with a directional antenna radiating power in watts with a beam divergence. Ignoring deflection and absolution in the path the transmitter radiates into a sold angle where the energy density of the wavefront decreases by 1/r.
A 1st order approximation for radio reception is the noise in a 50 ohm resistor, the typical radio input impedance.
Variables
transmit power
transnit solid angle or beam divergence
receiving antenna diameter
receiver noise floor(50 ohms)
An ET transmitter here on Earth looks like a point source. The solid angle is a cone with the peak at the transmitter and the base the with a base of an area at the plane of the Earth.
Total received energy is the energy density of the base of the solid angle times the area of the receiver antenna. Engry rescibed has to be at least at the noise floor represented by the 50 ohm resistance.
Basic trig, a right triangle with the base in the plane of the Earth.
The WOW signal, one can always hope.
Wow! signal - Wikipedia
Bomb#20
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Your futility arguments are temporally provincial. Picture Leif Ericsson in 11th-century Spain trying to interest El Cid in founding the Spanish Empire. Picture Columbus sailing south instead of west and trying to establish McMurdo Station. Elon Musk's fantasies notwithstanding, let's table the Mars colony question and revisit it in 500 years.
"(aside) He little thinks how eloquently he has pleaded his rival's cause!"
All the more reason to seek out Planet B. You've shown it's something we need to get right on, and not wait 400,000,000 years for the threat posed by boiling oceans to become immediate.
That seems a feeble reason to stop caring about future generations.
Hey, just because you don't care to plan beyond the next quarterly earnings report is no reason for the rest of us to share your discount rate. I'll be dead in forty or fifty years -- so why should I care more about our successors a hundred years from now than about our successors a billion years from now? None of them are me; none of them are my friends; all of them are my people.