1. aliens spread at a certain speed after developing spaceflight
2. they're not here
3. there are no spacefaring aliens in the galaxy currentlyAnd at that point, where is the incentive to colonize other star systems? You're still probably not going to be able to move a meaningful part of your population, and if you can produce energy that cheaply you can sustain a large population in comfort at home.
It's not inconceivable that there are advanced aliens all over the place, but that interstellar travel is basically limited to probes for pragmatic reasons.
I think when the Fermi Paradox was brought in, there was still some lingering Malthusian idea that geometric population expansion was inevitable. We now know it very much isn't, at least for us. That changes things.
If reactionless drives remain science fiction this mode of travel is flat impossible. There literally isn't enough mass in the solar system.
Should we want a colony on another planet? In another star system? Absolutely. It doesn't take much expansion for us to achieve the goal of having a 'redundant backup' for humanity.
Beyond that, there has to be some sort of economic incentive to drive it. Given there is little chance we can economically trade between planets, much less between star systems, I don't think that incentive is there.
Let's consider extinction mitigation as a luxury? I posit that sooner or later, as technology improves, the relative cost of such projects will go down to a point where some group of people think it is a good idea.
I don't think new discoveries suddenly change the physics of escaping gravity wells. I question whether interplanetary trade will ever move beyond intellectual property.
Basically, colonization will have to be altruistically funded without any expectation of economic return. We've proven we have limited capacity for that.
Currently.
In a system where resources are allocated not to cover the needs of all, but instead to ensure that the victor gets their spoils, this is true.
But IF a civilization makes it to a point where self-sustaining planet settlement is even a real possibility, I think you just have to assume they are post-scarcity and post-currency. Economic return isn't really a thing, if everyone can get what they want whenever they want it.
Therefore, any species with a natural propensity to exploration and curiosity as an individual is going to necessarily seek out new places as a whole. The individual will drive the societal, I guess is what I mean there. Because I want to see something new, and there is no scarcity of resources, society as a whole gets to see something new.
>I question whether interplanetary trade will ever move beyond intellectual property.
Honestly, I don't think so. Because, again, I'm of the firm belief that once a society is able to establish off-world colonies successfully, economics stops meaning anything at all, really.
You might _explore_. You're less likely to _colonise_. The only way you get the sort of geometric expansion people love to talk about is if there's a very strong imperative to colonise, and it's just not clear that it exists.
But humanity is not doing that. The current trend is world population will peak at just over 9 billion in about 30 years. Trends can change, but that is the current one.
And notice that people from different star systems in the same civilization will very likely only have extremely rare direct encounters due to the brutally long distances involved... it's highly likely the civilization will split up into completely separate "star nations", with their own internal issues to keep them busy and at some point may lose interest even in communicating with other star systems... without any incentive at all to expand further as the species survival is guaranteed... curiosity wouldn't be strong enough, probably, because after getting to know several star systems, you may decide they are look more or less the same, and to find anything really interesting might take multi-million year journeys and no one would be able to embark on something like that just for curiosity.
I can't think of any phenomena that could come close to doing such a thing. But if there was one, why couldn't it be like gamma bursts?
If you're scared of nasty aliens, the best defence is to conquer the whole galaxy before them.
There is no way to hide from an interstellar civilization.
Nasty or not, they could always produce self replicating probes and keep track of the whole galaxy.
Also, if you were able to colonize a couple of Star Systems, there's no way you are an anxious/scared species,
It's easy to know where to go next when we only have one option to pursue (such as travelling to the next nearest planet or star). This is a lot like the early web when there were only a handful of interesting sites and discovering new cool sites was a goal in and of itself.
Today, I think we intuitively understand that there's no longer any value in trying to visit every website on the internet. Most sites offer zero value or even net negative value. The entire problem space pivots to one of knowing which 0.00001% of websites are valuable to a given situation.
When a civilization gains the ability to visit any planetary system, the problem shifts to one of filtering choices and information to minimize the amount of unnecessary travel or world-settling.
I assume this is a well-known concept. I'd love to read more if anybody knows what it's called.
Don't see the reasoning here.
For example, we currently can feed the whole Earth population "cheaply". But the wars didn't end. Same with cheap energy.
E.g. we can try to install vast amounts of mirrors to direct Sun's light towards an accelerating ship. But that won't bring us here more comfort.
An example:
We have 1000 stars within the 30 light year radius neighborhood. Traveling at Voyager 1 speed, it takes half a million years to do a 30 light year trip. [1]
Given another half a million years for bootstrapping at the destination for ten more probes, we can send ten more probes, 1 million years from the launch of the first one. At two million years we get 100 probes.
How many probes do we get in a 11 million years? 10^11 probes. We have 10^11 stars in the galaxy.
Dinosaurs roamed the earth aleady 200 million years ago, and died in the mass extinction 65 million years ago. 20 to 5 million years ago was the Miocene, when life was pretty close to modern already. [2]
It's really the nature of exponential growth that makes things seem instantaneous compared to celestial phenomena or evolution. Colonizing the galaxy, even with abysmally slow speeds, is possible, because of the magic of exponentials.
(Certainly this has a lot of assumption, like that you can bootstrap, or that the probe survives the trip. Anyway, optimal probes would be a lot faster and bigger, and there would be more of them. This was just to tie in with something concrete that we know we can do, as Voyager 1 really is out there traveling at 15 km/s, as are Voyager 2, Pioneers and New Horizons probes.)
1: https://www.wolframalpha.com/input/?i=+30+light+years+%2F+vo...
So to explain the fact that the aliens aren't swarming everywhere because they can't afford it means accepting that either they launching a single generation-ship every 5000 years is a huge expenditure (which IMHO it wouldn't be even with our current economy size, definitely not an issue with the tech of 2100 or 2200 assuming at least some growth because at that point a Musk-type figure with a wish to "make humanity interstellar" would be able to afford it from private funds) or that we're the first (only?) life in galaxy or that all the aliens before us didn't try to expand, like, at all - because getting just one single rich eccentric every 5000 years (like a bunch of billionaires here are) would be sufficient to make the galaxy swarm with juuust a bit higher tech level than ours now.
I'm sure we are absolutely not capable to do that now. Maybe with AI.
But we haven't done that with our Moon and that's not even a few lightseconds away.
Just to put this out there, unless every advanced civilization becomes a hive mind with one unified will, some individual or splinter group or just hodgepodge of determined individuals would probably do it even if there were no incentive, and that's not to point out that incentives are somewhat subjective and differ between individuals and groups. If there are enough individuals on a civilization and the capability exists, some crazy person will do it.
1b. Assuming you can solve 1. with some kind of magical alchemical spares-generating technology that never fails, the technology also has to be politically and philosophically stable, with reliable and persistent goals. Otherwise you'll get offshoots competing with each other. Which may mean undermining and perhaps even destroying previous settlements. How much independence is enough? How accurate are your initial models going to be?
2. We don't know that for sure. Absence of evidence is not evidence of absence. (We do know weird things happen, but we're not putting any serious effort into researching them, so we don't know what they are.)
3. There's no need to think about this after 1. and 2.
Edit: to put this in context, you don't need to launch a probe. You need to launch a complete perfectly self-reproducing error-free space program. Which can also adapt to local resources.
This seems... difficult.
Certainly no-one would make the claim that "there are (definitely) no aliens in the galaxy" when we can't disprove the idea that aliens traveling at the speed of light just reached the galaxy (with our current understanding of physics). That doesn't mean you can't make the claim "there are (almost definitely) no aliens in the galaxy (because I just created the most amazing telescope ever and looked at every particle of matter in the galaxy and there were no aliens there)". The principle of charity demands that understand the bare claim that "there are no aliens in the galaxy" to mean something that is plausible, such as "there are almost certainly no aliens in the galaxy".
Well, what matters is expectation. The fact that some people win the lottery doesn't prove that playing the lotto is profitable. In fact it isn't money-profitable. The fact that people sometimes win doesn't change the nature of reality, that even for them, the win is unexpected and playing was negative expectation for them.
You seem to be confusing expected value with results.
Do you revise your decision process every time you get unlucky? On a meta level, sure, paying attention to unexpected failures is important to look for systematic errors. But randomly getting unlucky on 99% certainties does not automatically disprove your decision method.
For example, when asked to be more granular, the turtle could say 'I reason that there is only a 1 in 10 chance that seafaring civilizations exist'. The existence of seafaring civilizations doesn't make the turtle wrong in this case.
If the turtle concluded that 'there can not possibly be any seafaring civilizations, because I don't see any' then you could accuse it of bad reasoning.
The hypothetical turtle did exactly that, loyally following suit with the commenter who I replied to.
Also, since he’s a turtle, he doesn’t, presumably, yet actually know how hard it is to make a boat. The argument for determining whether or not you are the only seafaring species depends, first, on you having attained the ability to travel the seas…
All of that seems necessary before he can conclude whether or not he should consider it ‘surprisingly late’ for his island not to have been reached yet by any seafarers.
But the interesting part of the analogy is maybe that the turtle might fool himself into thinking he understands the parameters well enough to estimate this probability - after all, he’s paddled around off the beach and even made it to a nearby rock - so he reckons he’s got a pretty good handle on how hard it must be to travel between islands.
Ignorance and misestimation of the true underlying factors isn't a trait unique to these hypothetical turtles.
Or, perhaps you have a much higher confidence than I do in humans' assessment of the factors involved in your questions.
I'm saying we are over-confident in the underlying premises of our understanding, just like the turtles would be. The more of the questions you pose that go partly unsolved, the more unsubstantiated the conclusion. Their probability calculations are pointless -- garbage in, garbage out. As demonstrated by the patent wrongness of their conclusion.
If you are confident that we've got solid answers to the interstellar corollaries of all your questions with the evidence we can gather at this point, then we aren't on the same page at all.
This idea, that our observations of the universe are a properly representative sample from which to form conclusions about the unobserved universe, makes as much sense to me as the thinking-turtles assuming you need a small green island to and a thick shell to enable sentience because that's what their observations show.
The limitation could be doubling time not travel time. Sure double every 100,000 years or less and in 4 million years you’ve run out of stars in the Milky Way which is an eye blink on cosmic timescales. But, a civilization that’s remote terraforming worlds that might greatly slow things down. How long does it take Cyanobacteria to create an oxygen atmosphere for example?
Assuming FTL isn't possible, the fact that dark energy makes large sections of the visible universe fundamentally inaccessible is probably a good thing.
Otherwise that is a lot more of the universe that may be ahead of us and would stomp us like ants.
You could make the argument that it does appear that life is fundamentally adversarial, seeing as in our one example all life feeds on other life, and to sustain life a creature must kill. I believe that's simple a circumstance of limited biomass in a closed system and so not fundamental, but you could argue that all civilizations probably get bootstrapped in this way and so it doesn't need to be fundamentally adversarial, but that all civilizations are accustomed to it so the distinction "fundamental" does not really matter. I'd disagree with that also, because a change in conditions to post scarcity changes conditioning and therefore behavior.
You might also come up with a prisoners dilemma type scenario where a civilization doesn't want to be adversarial, but it doesn't know the intentions of others and so to protect itself, as a rule, destroys any that it finds. This is somewhat plausible but I don't really think likely because civilizations that evolved from abiogenetic origins separate from one another would likely have very very different behaviors that might not even overlap in many cases, so even if they were aware of each other they may not even be capable of interacting.
It just does not make sense for a space faring civilization to be hostile. A requirement for space faring and a result of it is post scarcity; resources abound in the vast swathes of dead universe. There is no reason to even think competitively, barring some as yet undiscovered unobtanium so rare and so powerful that civilizations fight to extinction over it, but I doubt it. If anything, I'd think that a space faring civilization benefits the more it understands the universe, and learning about biospheres and civilizations with completely different evolutionary paths from abiogenesis would be more valuable than destruction of them.
What is "volume appearance" BTW?