Alien life, probabilities, and interstellar propagation of human life

[DaveC426913]

It's a fundamentally different project to a) build a city on Earth; b) build a city on Mars; c) build a city on an exoplanet.

That is not what started this particular discussion. What started this discussion was BWV's assertion that we would not be venturing beyond our current circumstances untl we knew our babies were not at risk.

 

[PeterDonis]

The problem is that we have made so little progress since the Moon landings.

In half a century or so. That's an extremely short time on the scale of human history.

At the moment, we have little idea of the feasibility of any of this.

Sure, but the time frames you're giving for when we might are on the order of a century or so. Which is still an extremely short time on the scale of human history.

On a time scale of thousands or millions of years, the things you're concerned about simply aren't going to be constraints. The constraints on that time scale will be the laws of physics and whether we humans manage to survive that long at all, which is not a matter of engineering or technology.

 

[BWV]

That is not what started this particular discussion. What started this discussion was BWV's assertion that we would not be venturing beyond our current circumstances untl we knew our babies were not at risk

North American settlers risked their families for a payoff of a better life they and their immediate descendants could experience - way different to condemn yourself and your succeeding 6-10 generations to a lifetime in what is effectively a prison for a hope that your great-x grandchildren could benefit

 

[PeroK]

In half a century or so. That's an extremely short time on the scale of human history.


Sure, but the time frames you're giving for when we might are on the order of a century or so. Which is still an extremely short time on the scale of human history.

On a time scale of thousands or millions of years, the things you're concerned about simply aren't going to be constraints. The constraints on that time scale will be the laws of physics and whether we humans manage to survive that long at all, which is not a matter of engineering or technology.

There are also biology and human psychology to take into account.

 

[BWV]

North American settlers risked their families for a payoff of a better life they and their immediate descendants could experience - way different to condemn yourself and your succeeding 6-10 generations to a lifetime in what is effectively a prison for a hope that your great-x grandchildren could benefit

To quantify this - settling the new world had a risk but a positive expectation- once you discount the payoff past your great-grandchildren’s lifetime there is no way to discount it to justify the risk and suffering entailed

 

[PeroK]

My point is that generally given how little we've done in the past 50 years, it's a bit rich to claim the inevitability of indefinite technological progress, space exploration and explanet colonisation.

It's a bit like someone who went to the climbing gym once and never went back again claiming that inevitably they'll solo El Capitan one day!

 

[PeterDonis]

There are also biology and human psychology to take into account.

On a time scale of thousands or millions of years, those things are highly changeable. To the extent they're constraints on that kind of time scale, I would say that's because they affect the probability of our surviving at all for that long.

 

[javisot]

The constraints on that time scale will be the laws of physics and whether we humans manage to survive that long at all, which is not a matter of engineering or technology.

The possibility of facing mass extinctions, such as a meteorite impact, wars, viruses, etc, presents a technological challenge. I doubt we will survive long enough for technology not to be a problem, without having previously developed enough technology.

I mean, if we survive long enough for technology not to be a problem, we'll still have impressive technology (limited by the laws of physics, of course).

 

[PeterDonis]

The possibility of facing mass extinctions, such as a meteorite impact, wars, viruses, etc, presents a technological challenge.

That's true, but I think the technological aspects of those challenges are already well within our capability. The aspects we still have problems with are political and social, not technological.

I mean, if we survive long enough for technology not to be a problem, we'll still have impressive technology (limited by the laws of physics, of course).

Of course we will. I think it's safe to predict that, as long as we continue to exist as a species, our technology will continue to advance. On a time scale of thousands or millions of years, that means we are very likely to have technology limited only by the laws of physics, if we survive that long.

 

[DaveC426913]

North American settlers risked their families for a payoff of a better life they and their immediate descendants could experience - way different to condemn yourself and your succeeding 6-10 generations to a lifetime in what is effectively a prison for a hope that your great-x grandchildren could benefit

Sure but that's your personal preference. It's not an opinion you can reliably count on for others.
It is pointless to rule out possibilities based on what you think people in the future might not be game for.

 

[Ken Fabian]

Coming in on this a bit late to manage a point by point discussion, but I am of the pessimistic persuasion in this. At the most basic level of motivations I think sufficient 'need' has not been demonstrated. If saving humanity from major disasters were a priority I expect we would start with bunkers. Few nations have ever committed to that for the population at large rather than reserved for the few - Switzerland? Defending Earth from eg big impactors makes more sense in a near term sense than expansion to space, which simply does not look feasible. It would also support ongoing space technology development.

If meteorite defense isn't feasible I expect self reliant survival out there would be a LOT harder and much less feasible. It has to be feasible first, technologically, economically, socially and it isn't. And sites like this will give a very skewed sense of popular opinion about it.

I think technologies will always have hard limits - no endless 'exponential' development that bypasses them; we are getting better at identifying those limits. Even where a technology is possible it won't necessarily be viable. Like supersonic passenger jets. For space travel even hypothetical fusion drives will need huge amounts of reaction mass - much more than any payload.

I also think historical explorations and colonisations bear only superficial resemblance - far more different than similar. Other lands, abundant in readily usable resources using existing technologies in widespread use were a powerful attractant. Voyages of exploration were not funded by curiosity; there were strategic and economic motivations. Those doing so hoped for fortunes and fame (which counts as fortunes).

It would be rare to take families (and probably women) anywhere that was not already known to exist and known to have suitable resources other than out of dire desperation; whilst the risks of such voyages was real there had to be reasonable expectation of arriving intact. I doubt many did so lightly, without other more pressing motivations, like escaping overpopulation, resource depletion (poverty), conflict (arising from those), oppression. In the European colonising times moving to a colony already successful was possible because they were successful; not unusual for the journey to be aboard worn out ships slated for scrap, at low cost. At least one group of Scottish colonists sailed to Australia in an open fishing boat. Those colonies traded. It was possible to saw lumber into boards with your own labor and export them back to the mother country at a profit.

All the knowledge required was in the heads of those and other early colonisers - for Polynesians, all the resources to replenish their tools and boats would be there along with suitable places to plant their crops and build. For Euro colonisers, there was trade to provide the technologies they used but couldn't make themselves. Water and food might be scarce by journey's end but the possibility of fresh water falling from the sky and for trailing fishing lines to catch food was there too. Air too of course.

The extraordinary abundance of readily exploitable resources - and knowing they were there - made those colonisations possible.

I think generation ships are not reasonable - less reasonable than Mars colonies, which I think are not feasible for some of the same reasons; a comprehensively capable advanced industrial economy built on sufficient abundance of raw resources is needed for the barest basics of survival. Advanced economies can make the harder things because there is sufficient demand to make making them cost effective. They can draw on specialised resources and capabilities from around the world.

I think the most reasonable approach to human habitation/expansion beyond Earth is space habitats exploiting asteroid/comet resources - bypassing planets. Achieving that threshold - a sufficient diverse economy from such resources with the addition of reliable controlled fusion energy (and the ability to reproduce such technology - makes it hypothetically possible to leapfrog from deep space object to deep space object, where resources for refueling and re-supply can be found... after a sufficient local economy is established. Possibly depending on trade between existing stepping stones and the new.

If a sufficiently capable economy can be built at each stop then travel to the next one becomes possible. That still looks extraordinarily difficult - far beyond current technological and economic capabilities.

 

[javisot]

A civilization that colonizes other planets with its spaceships—can't that be called panspermia?

If we succeed (colonizing other planets), we would be living proof that panspermia is possible, but in our case, it will have taken longer than the entire current age of the universe to generate this type of panspermia.

 

[256bits]

A civilization that colonizes other planets with its spaceships—can't that be called panspermia?

If we succeed (colonizing other planets), we would be living proof that panspermia is possible, but in our case, it will have taken longer than the entire current age of the universe to generate this type of panspermia.

That is considered directed panspermia.
The original question of abiogenesis still remains.

The assembly clean rooms for spacecraft have been found to contain bacteria resistant to UV, cleaning agents, and whatever else is thrown at then. Whether these new species of bacteria are 'space resistant' remains to be seen, but these little life form has the ability to adapt quickly to environmental conditions. Some probe eventually will have a space-ready stow away taken along for the ride.

26 Resilient Microbes Found In NASA Cleanrooms Spark New Fears Of Mars Contamination​

Scientists discovered 26 new bacterial species inside NASA’s cleanrooms, raising concerns about microbial survival during space missions.
https://dailygalaxy.com/2025/12/26-resilient-microbes-in-nasa-cleanrooms/

Disregard the bio-film and spore over exaggeration in the article, as that is nothing new for 'regular' bacteria as a mechanism for survival under less than optimum conditions - they either wait it out, or group together as a slime. The emphasis should be in that clean rooms are not completely free of contamination, no matter what is done, at least with what is being done currently.

 

[BWV]

Humans are bacterial colonies - everywhere we go they will follow

 

[BillTre]

Humans are bacterial colonies - everywhere we go they will follow

This is correct.
Not only does it just happen, but is to some extent required for human health and proper development. Guts of mice without a gut biome do not develop properly and their efficiency of food utilization is reduced.
That is just wrt to human body.

However, the easiest way to achieve human success on other planets with no native life or a chemically different kind of life would be to bring the species of a\one or more successful earth ecosystems with them. Chemically different planets might require a lower level of lithotrophs or whatever is appropriate to the environment's available resources. From the lower ecological levels the energy and nutrients found flow up to higher trophic levels in the ecosystem by being eaten by less specialized (to the weird available resources) organisms.
For each species brought on a generation ship, optimally their associated microbiomes would also be intentionally along.

This of course would be in conflict with planetary protection rules that want to prevent introduction of earthly microbes to other planets.

 

[256bits]

For each species brought on a generation ship, optimally their associated microbiomes would also be intentionally along.

Biomes are rarely discussed for generational ships, at least I have not seen much.
Organically its all about what crops to grow.

Who knows, might need the swamp and marsh creatures including the dreaded mosquito to be included in the food chain, or the whole ship or colony collapses.
That's why I say a humungous ship is necessary to contain all the elements of a sustainable ecosystem.
The unicorn would have to be left behind once more, - poor thing, space limitations - no pun intended.

 

[BWV]

Here is a ‘real’ example of plans for a generation ship to Proxima B - 58x6 km and several billion tons. It would take 400 years for the 1000-1500 passengers to reach their destination.

https://www.universetoday.com/artic...neration-ship-competition-have-been-announced

 

[Filip Larsen]

Here is a ‘real’ example of plans for a generation ship to Proxima B - 58x6 km and several billion tons. It would take 400 years for the 1000-1500 passengers to reach their destination.

https://www.universetoday.com/artic...neration-ship-competition-have-been-announced

It is instructive to see how much effort and complexity it realistically takes to simply transport a population of 1500 humans to the nearest star in a generation ship when attempting to address a realistic set of risks. The level of required engineering is absolutely huge. Almost all of the presented complexity arise from having to support a living crew, with all the "other" complexities of building a spaceship capable of interstellar travel on top of that (and barely mentioned or referred to as TBD).

And this project even assumes that there are pre-made facilities at the destination ready to take over once they arrive, so it is still a requirement have to build and transport some kind of robotic mission, likely of comparable size, to establish those facilities ahead of crew arrival. And all this again only makes sense if Proxima Centauri b is revealed to be hospitable enough that it can actually be colonized with a realistic effort, i.e. that it from local resources is possible to produce and expand support for a growing population.

I still claim the idea of using generation ships for interstellar colonization is a wet sci-fi dream that speaks well to the human drive for exploration and story telling but likely never will be "feasible" compared to other potential colonization mechanisms you more or less need anyway.

 

[sbrothy]

It is instructive to see how much effort and complexity it realistically takes to simply transport a population of 1500 humans to the nearest star in a generation ship when attempting to address a realistic set of risks. [...]

Moving even just a subset of the population of a planet is a logistical challenge which we will be close to undertaking when we can build a self-sufficient biome here on Earth. I don't see it in the near - of for that matter, far - future.

Moving the complete population is a logistical impossibility what with new babies being born all the time and whatnot. A pipe dream.

I still claim the idea of using generation ships for interstellar colonization is a wet sci-fi dream that speaks well to the human drive for exploration and story telling but likely never will be "feasible" compared to other potential colonization mechanisms you more or less need anyway.

Using hollowed out asteroids is probably the most feasible method, but finding yourself trapped there, with just a picture of what your home looked like once is bound to invoke some antagonism. And then there's the Island Rule. And if everyone want's to be a baker or artist and no one wants to learn about fusion power or whatever the vehicle requires for propulsion, or life support, you're more or less boned.

EDIT:

Kim Stanley Robinson wrote a "hardish" sci-fi story on this very theme called Aurora. I can recommend it even though it has it's weaknesses.

Ship [the onboard computer which've become more and more self-aware] is therefore forced to decelerate by means of gravity assist [as the laser who accelerated them at the beginning is turned on for deceleration too late, as Earth - surprise - has its own problems] between various planets, a process which takes twelve years. During this time, with the full communications data of humanity available to it, it learns more about why it was launched in the first place—simply for expansionism—and denounces its builders as "criminally negligent narcissists".

 

[pinball1970]

Gosh this thread has moved on a bit!
I do not think anyone has mentioned Drake yet? Worth a citation, on the chance of life being else where, the topic of the thread ;)

@PeroK post # 5 worth a watch.

 

[sbrothy]

I admit a serious topic drift has obviously taken place. My comment was meant specifically and locally for @Filip Larsen 's last post.

 

[256bits]

Gosh this thread has moved on a bit!
I do not think anyone has mentioned Drake yet? Worth a citation, on the chance of life being else where, the topic of the thread ;)

@PeroK post # 5 worth a watch.

The Drake equation is in the wiki reference in Post, as part of the writeup explaining what the Fermi Paradox.

 

[pinball1970]

The Drake equation is in the wiki reference in Post, as part of the writeup explaining what the Fermi Paradox.

So it is, one just has to scroll down a bit, then a bit more.

 

[javisot]

It is instructive to see how much effort and complexity it realistically takes to simply transport a population of 1500 humans to the nearest star in a generation ship when attempting to address a realistic set of risks. The level of required engineering is absolutely huge. Almost all of the presented complexity arise from having to support a living crew, with all the "other" complexities of building a spaceship capable of interstellar travel on top of that (and barely mentioned or referred to as TBD).

And this project even assumes that there are pre-made facilities at the destination ready to take over once they arrive, so it is still a requirement have to build and transport some kind of robotic mission, likely of comparable size, to establish those facilities ahead of crew arrival. And all this again only makes sense if Proxima Centauri b is revealed to be hospitable enough that it can actually be colonized with a realistic effort, i.e. that it from local resources is possible to produce and expand support for a growing population.

I still claim the idea of using generation ships for interstellar colonization is a wet sci-fi dream that speaks well to the human drive for exploration and story telling but likely never will be "feasible" compared to other potential colonization mechanisms you more or less need anyway.

As you rightly say, the part where humans travel to another planet—the simplest part to calculate, dependent on the laws of physics, distances, the speed of light limit, etc—would only be the end of a much longer story, a story that will have required the entire age of the universe to reach this day. We also need millions of years to send unmanned spacecraft to confirm the destination, prepare for our arrival, and return with the information. Last but not least, we have a long journey ahead of us.

(This problem could be mitigated if we also included experimentation with genetic material, embryos, etc., in the automated reconnaissance and preparation missions)

I want to point out another problem: even if we have the perfect plan organized from Earth before departure, even if we manipulate the laws of physics optimally, a meteorite could destroy the habitable planet moments before our arrival, leaving us adrift.

 

[256bits]

Using hollowed out asteroids is probably the most feasible method

Cameflage would guard against the Cylons mistaking you for a copy of the Battlestar Galactica. And confuse them to no end, as you are leaving Earth rather than returning.
Had to throw that in as a breather for all the seriousness going on.

 

[256bits]

I want to point out another problem: even if we have the perfect plan organized from Earth before departure, even if we manipulate the laws of physics optimally, a meteorite could destroy the habitable planet moments before our arrival, leaving us adrift.

As they say, the only sure thing in life is death and taxes.

 

[256bits]

So it is, one just has to scroll down a bit, then a bit more.

And in line with your thought of unknowns, navigation.

Light might take a straight path from A to B.
A space ship on the other hand ....

 

[javisot]

Gosh this thread has moved on a bit!
I do not think anyone has mentioned Drake yet? Worth a citation, on the chance of life being else where, the topic of the thread ;)

@PeroK post # 5 worth a watch.

It's true that the thread has veered off course quite a bit. Initially, I interpreted the main topic as "probability of abiogenesis?"

But everything has changed.

Furthermore, the person who raised the question is not participating, so moderation is still necessary.

 

[DaveC426913]

Humans are bacterial colonies - everywhere we go they will follow

Absolutely. There will come a day when we see humans (and any other living thing) more accurately viewed as a cloud of interdependent microflora and microfauna several metres (or more) in diameter.

 

[DaveC426913]

Here is a ‘real’ example of plans for a generation ship to Proxima B - 58x6 km and several billion tons. It would take 400 years for the 1000-1500 passengers to reach their destination.

https://www.universetoday.com/artic...neration-ship-competition-have-been-announced

"At present, the only method for travelling from one star system to the next within a human lifetime is directed-energy propulsion, where gram-scale watercraft equipped with lightsails are accelerated by laser arrays to relativistic speeds (a fraction of the speed of light)."


Watercraft?