I suspect it would be a compromise; you travel as fast as you can, while maintaining the ship in a functional state.
Anything faster than 0.1c might be too fast, because of the risk of damage from the interstellar medium; but that would mean each voyage would take a hundred years or so. I don’t think that building things that could last a hundred years would be an insurmountable problem.
Send it at it 0.01c, and the ship has to last a thousand years. More difficult, but still not impossible. We aren’t talking Star Trek speeds here, nor geological time periods. The slower you travel, the easier it is to slow down at the destination.
One bizarre criticism about long-duration starships is the presumption that they will be launched with no experience and thus be subject to breakdowns of crew survivability. That seems flatly absurd to me; no one is going to launch a generation ship on a three-hundred year voyage until we have centuries of experience with keeping habitats going at home in our own solar system.
A recent paper says that it’s not just phosphorus, but also nitrogen. It has to do with how much oxygen is present. Too little and the phosphorus attaches to iron and sinks to the core. To much and (I don’t understand the mechanism here) the nitrogen escapes the mantle to the atmosphere and then to space. Turns out the Earth is right in the goldilocks zone for oxygen.
Now maybe there are alternate chemistries that can work for life without either N or P, so this could be too Earth-centric.
Obviously you don’t take one or two humans and drop them on a planet. You take a group of around ten thousand. A group of ten thousand humans can make another group of ten thousand.
Yeah, while the old joke is that it’s been 30 years away for the past 80 years, I’m sure we’ll get it figured out in the next millennium or so. Which is still a mere eyeblink of time.
That was the thinking of the “space happy” crowd (to use Robert Heinlein’s term). They really and truly thought that humanity would be flying off to planets, setting up colonies, and continuing out to the stars, proto-Musks. They all knew about the size of space and the inadequacy of any feasible propulsion system, but they let their fantasies about atomic power overwhelm them on route to an engineer’s dream future.
Space turned out to be a microcosm of all the myriad eternal technological progresses resulting in a recapitulation of British imperialism and colonization rethought as American dominance that was the John W. Campbell Astounding future that permeated both science and science fiction for two decades after the war. WWII taught too many people exactly the wrong lessons. The 1950s were an extreme outlier than people took to be the norm forever and the place to where a nostalgic return must be made. It’s killing us.
There is no longer any reason to assume out of hand the statistical likelihood that extraterrestrial civilizations exist. They may. They may be looking for us. We may someday be in a place to seriously look for them. Anything other than “may” is lying with statistics.
I’m not sure nitrogen is a particularly significant limiting factor; three worlds in our system have significant amounts of nitrogen in their atmospheres (Venus, Earth and Titan) and they couldn’t be more different fom each other.
So it seems there are many routes to a nitrogen-rich environment.
I was struck the other day by a clip from ST:TOS having Spock announce that a class-M (habitable) planet they were orbiting was “too unremarkable” to be worth further investigation at that time(!) The show originally postulated half a dozen intelligent, spacefaring races within a few dozen light-years of Earth. That sort of super-optimism about the prevalence of life, along with the Heinleinian idea that the European colonization of North America would be recapitulated in space (starships transporting settlers who would begin building cabins and clearing fields for plowing) now seems incredibly dated.
Perhaps a modified version can still be supported. I have pointed out here before that there are very few exact Earth-analog worlds among the thousands of exoplanets detected so far. But the methods we use to detect exoplanets are not well-suited to discovering Earth-analogs. Perhaps there are more - many more- than we currently believe.
Within 100 light-years of Sol there are 8000 stars, give or take a few; that means there are 8000 chances that some sort of Earth-analog planet might be found in our own cosmic backyard; several, if we are lucky.
@Lucas_Jackson might be correct; interstellar travel might be impossibly difficult, but the 8000 stars in our backyard might support a decent number of isolated or isolationist civilisations, all blissfully ignorant of each other (and us).
On the other hand, planets with their own life would probably be level-4 biohazard zones. Absolutely no knowing how we’d react to their microorganisms– or what introducing symbiotic microbes from our bodies might do to the native ecosystem. Humanity might have to speciate into lineages genetically adapted to survive exposure to different alien biology.
Agreed. You’re a hell of a lot safer colonizing a dead planet with human-appropriate chemical abundances and a human-compatible insolation / radiation profile. Rather than the same type planet that’s already got a full bore homegrown biosphere of its own.
But those planets being both abundant and dead leans towards aliens being rare. To find aliens, or at least aliens biologically similar to us, we’d want to discover that most Earth-similar planets are not dead, but rather teeming with life at all scales.
That’s kind of a Catch-22 for us trying to expand colonies all over the galaxy. Or even just our 100LY neighborhood as @eburacum45 suggests.
And it just occurs to me now that the same issue affects any putative bio-similar aliens expanding our way. If “Class M” planets are abundant and dead, there’s (probably) darn near nobody out there to talk to. But if “Class M” planets are abundant and full of existing life, they’re (probably) real bio-inhospitable to you colonizing them and trying to coexist amongst the existing biosphere / ecosystem.
And this applies to bio-dissimilar aliens in a parallel fashion. e.g. assume silicon-based life is possible & exists in the galaxy. It’ll be hard for the various silicon-based societies to expand into each other because the kinds of planets hospitable to them are likely to be rare, or to be already full of Si-life. Which life would be more likely to be deadly to them than benign or “edible”, whatever that word means to Si-life.
An interesting mini-paradox in the larger Drake equation.
I liked the premise of Larry Niven’s Known Space setting, that 3.5 billion years ago a galactic empire seeded millions of planets with the bacteria and algae from their home world. So that in our era habitable planets all share the same fundamental biochemistry and so for example the Kzinti find humans tastey* to eat.
*but in the long run suicidal, as humans get quite indignant about this.
Yes almost certainly. It’s very difficult to see earth-sized worlds; I think we can only see ones that transit their parent star. And it has to be a brighter star and/or orbiting much closer than the earth does to sol.
This is not to say that habitable worlds are common. Just to say that our observations so far give no reason to doubt that earth-sized worlds are common, and a bit of reason to suspect they are (the frequency of super earths).
I’d disagree with that. The common ancestor to life on another planet would not have to be very different to ours for all their life to be completely incompatible with all life here. Just some molecules being a mirror image would do it, let alone completely different molecules for storing energy, transcription and oxygen transport (if they breathe oxygen at all). In all likelihood we’d be immune to all microbes however the flip side of the coin is we would probably not be able to digest any plant(-like) matter there either.
I hypothesize that the bottleneck is going from a planet having animals to advanced industrial civilization. On almost all of these planets filled with life, it may be stuff like ants and amphibians all the way down with evolution a lot slower than here.
As far as interplanetary travel, there are lots of reasons why it is an extremely difficult expensive bad idea. And it is such a big project that most of the governments on the planet would usually have to agree to do it. I would vote no.
However, I think that other types of communication would be frequently attempted by any industrial civilization even a little more advanced than ours. Before too long from now (a century?), almost any national government or multi-billionaire-type could try it, so you do not need some impossible planetary consensus.
As far as the alien advanced industrial civilization being so different from us than communication is impossible, every year SETI continues to fail is a year with evidence that the path to advanced industrial civilization is narrow. A whole lot of convergent evolution is required, and I thinks that’s a tremendous bottleneck..
