Order of Kilopi
None of what we discuss in this thread has been put into practice! We don't have starships. WE don't have space colonies. We don't have aliens, by signal or discovery or visit. We have no way to determine any feasibility in practice, because there's been no practice.Originally Posted by Colin Robinson
Seems strange to me to focus on that one bit of a possible scenario when the entire thread is blue-sky speculation.
"I'm planning to live forever. So far, that's working perfectly." Steven Wright
Order of Kilopi
Yes, thank you. That is what I meant.
"I'm planning to live forever. So far, that's working perfectly." Steven Wright
Order of Kilopi
Then we are necessarily a one-world species, and so is every alien. If we can't manage an artificial environment that lasts long enough to build a replacement habitat to move into, then space is forever closed to us except as a temporary work place.
But I do not think that's the case. I think an established environment capable of balancing for a long period is an achievable goal. Not forever, so that's why we'd need redundancy; multiple habitats consisting of multiple modules, each capable of supporting their neighbors should one or more fail.
"I'm planning to live forever. So far, that's working perfectly." Steven Wright
Established Member
A lot of topics we discuss in this thread have been demonstrated to be feasible. Just now we were discussing how organisms with brains first emerged on Earth around the pre-Cambrian epoch. That happened, which means it is feasible, surely?
Order of Kilopi
OK, then why is a stable habitat any more out-there than a starship? That's the whole basis of the Fermi paradox after all, that interstellar travel is possible. If not, why not?
"I'm planning to live forever. So far, that's working perfectly." Steven Wright
Established Member
Of course not.... Doesn't mean he can't create an environment that will be stable for 1000's of years though.
Order of Kilopi
The thing about artificial environments is, they can be adjusted by their users. It's in every dwellers' best interest to maintain a working life support system. To re-balance, to monitor constantly for trouble, to replace losses of volatiles, etc. And yes, some will fail, just as societies on Earth sometimes fail and die off. It'll be a long learning curve under deadly conditions.
It's a hard goal. Not impossible, though.
"I'm planning to live forever. So far, that's working perfectly." Steven Wright
Established Member
Paradox schmeridox, wrong question... Of course interstellar travel is possible. Just because WE don't know how to do it yet means nothing, I'm pretty sure plenty of others do! Heck, we're barely civilized yet.
Established Member
It's true that neither has be demonstrated to be feasible.
The reason I think an indefinitely stable artificial habitat may be less feasible than a starship, is that it's a longer-term gamble. The longer you gamble for, the greater the risk that your luck won't hold.
Order of Kilopi
The physics are plausible. But as I said, it has never been put into practice, and does not appear practical in the foreseeable future. It is not part of our experience.
We are the most "civilized" people we've ever met. Any more "advanced" societies have yet to introduce themselves.
Anyway, I was addressing Colin Robinson's question about feasibility. Which we currently have no way to measure for most of these speculative scenarios, beyond "does it violate the known laws of physics". We're just throwing around opinions.
"I'm planning to live forever. So far, that's working perfectly." Steven Wright
Order of Kilopi
As I said, no one habitat needs to be indefinite. Civilizations and cities rise and fall, but the human race continues. So it might be with populations in space; no single point of failure. As long as people have somewhere else to go, they can build lives in new homes. So we'd need multiple settlements with enough surplus life support to take in refugees if needed, and the capacity to build more. A meta-ecosystem of redundant modular ecologies, each one maybe a little different to add the necessary biodiversity.
"I'm planning to live forever. So far, that's working perfectly." Steven Wright
Order of Kilopi
I don’t understand how there could be a starship carrying people without a fairly impressive closed ecology. It strikes me as a large part of what would go into building a successful crewed starship. If it isn’t possible I don’t see how interstellar colonization would be possible.
"The problem with quotes on the Internet is that it is hard to verify their authenticity." — Abraham Lincoln
I say there is an invisible elf in my backyard. How do you prove that I am wrong?
The Leif Ericson Cruiser
Established Member
In the case of a starship, it would be a closed ecology designed to last for a specific time. Not the same thing as a system that would continue to function indefinitely.
Order of Kilopi
There's that word again!
As I've said, no one habitat needs to be indefinite, just long-period stable. It's not like it would be left on its own like a forest. More like a carefully tended garden. Managed, cared for.
Not like Biosphere II. That was a train wreck. We have yet to successfully create such a small cycle ecosystem. IMO developing such a capacity is far more vital to space colonization that bigger rockets.
"I'm planning to live forever. So far, that's working perfectly." Steven Wright
Order of Kilopi
It would be a closed ecology with about the toughest requirements possible. Mass would be at a premium and it would need to operate long term, so closure would need to be extremely high, far beyond what would be needed for a habitat built to work on a world like, for instance, Mars. And it would need a system that could achieve that with limited mass, so lower mass equipment and a smaller ecology than a world based habitat (unless a monster starship is built, which means a far more expensive and slower one). Whether it would last forever isn’t the point. The difficult requirements are.
"The problem with quotes on the Internet is that it is hard to verify their authenticity." — Abraham Lincoln
I say there is an invisible elf in my backyard. How do you prove that I am wrong?
The Leif Ericson Cruiser
Order of Kilopi
Well, it depends on what you want to do. A Mars habitat (where you can get extra air and water from the outside environment and can dump excess oxygen or whatever if it is convenient) doesn’t need much closure at all, and whatever is dumped isn’t actually lost, just going back into the Mars environment. I expect such a habitat is quite doable with current technology.
An interplanetary spacecraft probably needs more closure than a Mars habitat and has harder mass limits, but to get to Mars is well within current technology. Crewed starships are another matter entirely, and if you want to build a Dyson swarm that will last long term but not run out of volatiles, you also need very tight closure. There can be interconnections between the ecologies of the habitats, but in total they would need to work very efficiently . . . or the answer to the Fermi paradox would be resource collapse.
"The problem with quotes on the Internet is that it is hard to verify their authenticity." — Abraham Lincoln
I say there is an invisible elf in my backyard. How do you prove that I am wrong?
The Leif Ericson Cruiser
Order of Kilopi
Yes.
The mass limitations of relativistic travel prevent you from just, say, carrying a spare comet to milk for resources during the trip, since that would greatly increase the already staggering energy needed to accelerate it; a slowboat would have a compounded problem, needing to be sealed for centuries or millennia without refills.
"I'm planning to live forever. So far, that's working perfectly." Steven Wright
Established Member
I get that population explosions filling the galaxy are nonsense. But what about this.
A species, sometime, constructs a few probes to travel ~5 percent the speed of light and sends them to the several nearest stars. This is not psychologically nonsense, spending a couple centuries to build a cathedral was a thing. And the energy should not be preposterous for a planetary system wide civilization.
The probes build sub-probes in situ and explore the new systems. and report back They also use local resources to construct a couple duplicate probes to send onward to the next couple stars. Lather, rinse, repeat. Naturally, extensive work would have to be done to prevent a sorcerer's apprentice problem...I'll leave that as an exercise for the student :-)
The probes are also programmed to search for technological life (radio, etc.) and if detected to initiate communication. Again, this is plausible...everything we have sent beyond the orbit of Saturn tries to do this (Pioneer plaque, Voyager record, and New Horizons Message).
In other words, the love child of a von Neumann probe and a Bracewell probe.
Assume such a probe started out near the Core 5 million years ago (the Milky Way is certainly old enough) and that zigzagging, construction time, etc. slows the wavefront to ~1%c. By now the whole galaxy is filled.
In fact there is time for this to happen numerous times.
Why haven't we been contacted yet?
SHARKS (crossed out) MONGEESE (sic) WITH FRICKIN' LASER BEAMS ATTACHED TO THEIR HEADS
Order of Kilopi
We're in the wrong galaxy. They covered Andromeda.
"I'm planning to live forever. So far, that's working perfectly." Steven Wright
Established Member
So you think that a population explosion of living things filling the galaxy is nonsense, but a population explosion of robot probes filling the galaxy isn't nonsense?
Perhaps because making von Neumann probes is more difficult than you think...Why haven't we been contacted yet?
These hypothetical probes would be self-repairing, self-replicating systems. They'd behave like living things.
Except that living things are adapted to particular habitats, but your scenario implies that the von Neumann probes would be able to consume resources and carry out replication anywhere in the Galaxy.
They're physically possible, in the sense that they don't violate laws of physics and thermodynamics, any more than living things violate laws of physics and thermodynamics.
But does that mean they're an inevitable or likely product of an advanced civilisation, or even a feasible product of one?
Order of Kilopi
A Von Neumann probe is universal grey goo waiting to happen. Like living things, they can "mutate" and evolve. If they can replicate anywhere from commonly available materials, they better be loaded down with some damn good limiters on their reproduction!
"I'm planning to live forever. So far, that's working perfectly." Steven Wright
Order of Kilopi
Interesting, but actually I'm friends with one of the people in the research group featured in the first article (his office is on the floor above me in the same building). And I think you have misinterpreted what they are saying. The PNAS paper is basically saying that the earliest fossils come from a time when life was already fairly developed, so we can only speculate about whether it arose once or more than once. And they are just using a statistical model to say that they think it might have started more than once. But just to be clear, there is no evidence one way or the other, since there is no fossil record.
And the researchoutreach article is kind of saying the same thing. We don't have any evidence about when life started, so they have a model that explains how it might have evolved in a geyser, but that is just a model.
As far as I know there is no evidence available that life ever got extinguished and then started again.
As above, so below
Order of Kilopi
So, there's an op-ed in Universe Today that pretty much reflects my view of the matter of the Fermi Paradox. Interstellar colonization is non-trivially hard due to the physics and energy involved, and there would be little or no continuity of culture and motive among a multi-stellar species (IE, colonies may not be as eager or quick to colonize as their parent civilization). So any spread through the Galaxy would be limited, slow, patchy, and sporadic.
This concept even has a name, the Percolation Theory (actually a hypothesis, as the testing conditions do not yet exist).
"I'm planning to live forever. So far, that's working perfectly." Steven Wright
Order of Kilopi
Interstellar space is also full of Oort Cloud debris, gas, dust, and other things that could damage or destroy a fast-moving interstellar spacecraft.
Do good work. —Virgil Ivan "Gus" Grissom
Order of Kilopi
Hmm. An additional obstacle.
...Or potential ramjet fuel? I suppose it depends on the collection method. Ionize it with a laser broom, maybe?
"I'm planning to live forever. So far, that's working perfectly." Steven Wright
Order of Kilopi
Personally I'd be very surprised if any biological based life came here to visit. If we assume (no other choice at the moment) that alien life, though possibly different, assuming to be biological based, would share similarities to life on Earth. We find that complex life on Earth is not very arduous when it comes to its environment. To do any space travelling presents many difficulties, even assuming the energy requirements have been solved.
If we take ourselves as the one and only example we know of then most would agree that interstellar space travel is unlikely to become a reality. It would be more likely that "machines" are built to do the travelling and probing, we already do this.
Lex Fridman did a recent study and extended the Drake equation further, then based on our most up to date observations and data did a calculation on what he expects to be the distribution of intelligent life in the universe. He concluded that there would be on average 1 intelligent species per galaxy. Obviously the majority of this is based on speculation of course, but it would fit into why we haven't discovered other intelligent life, and may never do. This means of course though that even if you were to be really pessimistic and say he is out by a factor of say a 100 or even a 1000 then the "universe" is still likely to be teeming with intelligent life. Its just that the likelihood of each species ever crossing paths is almost zero.
Personally, I think its more likely that we are indeed the only or at best the first technological form of life to develop in the Milky Way galaxy. I then expect us to develop AGI that becomes far more intelligent than humans and this AGI would then expand and colonise the galaxy. Lets face it, AGI would have the tools required to design and build interstellar space faring machines that would easily stand up to the arduous environments it would face. We as a species would be left behind (or worse - go/forced extinct) as a new dominating intelligence spreads throughout the universe.
There is so much speculating it is impossible to "solve" the Fermi paradox, at least until we happen upon new discoveries that improve or totally change our understanding of the universe.
One other thing to note is: We currently have limited information on around only 5% of the assumed total universe. The other 95% is inferred and speculated on by our limited observation. Maybe we are missing the big picture?
Order of Kilopi
Why expect travel at all?
A true AGI would have its own motives and resulting actions, which may be nothing like those of biological organisms. Without a reproductive urge, it might have no reason to spread itself all over space.
"I'm planning to live forever. So far, that's working perfectly." Steven Wright
Order of Kilopi
If we get evidence off the presence or absence past life on Mars (even with human explorers actually on Mars, this is likely to be non-trivial), we may get some idea of the likelihood of abiogenisis. Once we get that, the argument will get more interesting, as there will be more data.
Positing a considerable period of active searching, there are a few possibilities (I'm ignoring the possibility of a false negative. Until there has been enough examination -- say until at least 15% of Mars' surface is investigated to a depth of a meter or so -- stating life never existed on Mars is likely premature)
1) There's never been life on Mars.
2) There was life, to the approximate equivalent to prokaryotes.
3) There was life, to the approximate equivalent to eukaryotes
4) There was life, to the approximate equivalent of multicellular organisms
5) There are relics of intelligent life (which I think is extremely unlikely)
6) There is remnant life. I don't think this is impossible, as prokaryotes have been found in subterranean strata over a kilometer beneath the surface.
7) There's an active ecosystem including autotrophs and heterophs. While I don't think this is impossible, I think it's extremely unlikely.
The first five give some information to quantify one or two of the factors in the Drake equation (the ones concerned with the number of planets and habitable planets have some quantification due to the discovery of exoplanets. When Drake conceived this equation, even those were largely data-free). Obviously, relics of intelligent life would be the most surprising and could move the Fermi paradox into something interesting from a rather minor question.
Last edited by swampyankee; 2020-Dec-26 at 11:38 PM.
Order of Kilopi
Space exploration as a religious exercise? Interesting, and it certainly fits the attitude of some of the space enthusiasts.
While I think interstellar travel is possible, albeit quite difficult, I remain to be convinced that a rational society would consider massive expansion into interstellar space to be a worthwhile use of resources. The answer to the Fermi paradox may simply be that the expansionist societies, inexorably and rapidly expanding through the galaxy is vanishingly rare.
Order of Kilopi
Massive is as massive does. An society as a whole might consider the game not worth the candle, but would it require the entire society to do so? Would they be such rational actors? God knows we humans are not.
An advanced, populated star system would have access to many orders of magnitude more resources and energy than a one-planet economy. They might not have the same attitude towards large expenditures as we do. And any small colonized system could, eventually, become as fully capable and industrialized as the parent system. Life could be like a virus, infecting star systems, growing and multiplying within them, and then sending out small units that also grow until they can leap to the next star.
But it would not be fast. Developing that capacity and attitude towards resource use, is not something a young newly established population would do. A mature system-wide infrastructure would be needed to support such activity.
"I'm planning to live forever. So far, that's working perfectly." Steven Wright
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