Three possibilities:
(i) many humanly habitable extra-solar planets, as in many sf works;
(ii) many humanly uninhabitable biospheres, as in Poul Anderson's Question and Answer;
(iii) many planets but almost no life, as in Anderson's Genesis.
I think that (ii) is the most likely.
Foundation and Dune share a variant of (i) (a): no other intelligent species. Thus, humanity alone is free to colonize all those planets.
Perhaps the most likely scenario is (ii) (a): planets that remain humanly uncolonizable even though they are not already inhabited.
Life is likely to be common because all that it requires is an energy source, complicated chemistry and enough time for energized complex molecules to change randomly until one becomes self-replicating but how often will natural selection generate multicellular organisms, then central nervous systems, then intelligence? And how often will intelligence develop civilization, then technology? Maybe we are the first.
10 comments:
Kaor, Paul!
And I simply don't believe ours is the only planet with intelligent life in the Milky Way galaxy! We already know billions of planets are likely to exist, so I believe there are many worlds with life on them. And I also think it's reasonable to think many planets are both uninhabited and capable of being colonized by humans.
Ad astra! Sean
"humanly uninhabitable biospheres"
I can easily imagine planets with life that would be uninhabitable for *unmodified* humans unless the planet was modified.
Eg: an earth size world that gets about half the heat from its star that earth gets from the sun. The carbonate-silicate cycle would probably result in a planet with plenty of liquid water because there is enough CO2 to warm the planet above 0 C.
https://en.wikipedia.org/wiki/Carbonate%E2%80%93silicate_cycle
However, that much CO2 would be lethal for humans to breath, even with O2 levels adequate for human life.
Could genetic engineering make humans that can live just fine in such a high CO2 atmosphere?
Would humans finding such a planet instead do something to reduce the amount of CO2 and add other greenhouse gases like CF4 and SF6 to make a breathable atmosphere while keeping the planet mild? Would that harm existing native life? Would humans do that anyway?
Then there would be planets like Diomedes where the life is inedible.
There are earth plants that must be processed to remove toxins before eating. eg: Cassava.
Perhaps settlers on an other planet could develop ways to process more exotic life to make it edible.
Perhaps the processing would be feeding the native biomass into vats with microbes that would ferment it to something nutritious for humans.
There are lots of possibilities that make 'uninhabitable' a sliding scale.
Kaor, Jim!
To me, the real moral issue would be whether such a planet had intelligent life. If not humans should go ahead and make it breathable for our species.
Ad astra! Sean
How intelligent?
If it has an ecosystem of complex life, but nothing at human level intelligence, I would still be very reluctant to cause a mass extinction of that life. Van Rijn could get lots of valuable biological products from it. ;)
Kaor, Jim!
I would still at least mostly disagree. If such a planet has no intelligent races I see nothing wrong with modifying it to suit human needs. If such modifying leads to mass extinction of merely animals, so be it.
That said, I have no objection to taking a good long time to study that kind of planet. And I like your suggestion about Old Nick! (Smiles)
Ad astra! Sean
Actually, I don't valorize humans because of their intelligence. I do it because they're my relatives -- shared species and DNA.
Kaor, Mr. Stirling!
A perfectly good and legitimate reason for favoring out own species!
Ad astra! Sean
Note that when it comes to the habitability of extra-solar planets, we're essentially wheel-spinning. There is no data, and it's a non-falsifiable hypothesis either way.
Right. I think it's a pretty fair bet that we are so precisely adapted to Terrestrial conditions that even "terrestroid" planets would harbour many either overt or subtle death traps. However, anyone who crosses an interstellar distance has to take his life support system/environment with him and therefore is not dependent on finding a habitable environment in any newly entered planetary system. Maybe we can just go beyond the need for planetary surfaces? As Niven's Belters ask: Why live at the bottom of a gravity well? Anderson's Lunarians show that energy and technology can be used to create colourful and voluminous living spaces even in the outer Solar System.
Kaor, Mr. Stirling and Paul!
Mr. Stirling: I have to agree, for now all we can do is speculate. We know many planets exist, and some are in the "Goldilocks zone," and that's it.
Paul: I have nothing against O'Neil habitats or humans excavating and making asteroids and moons habitable. But I still believe most humans would still prefer to settle planets, if that ever became feasible.
Ad astra! Sean
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