Pretty much my line of thinking. I once joked that the search for intelligent life will be concluded when we do some spectroscopy using more advanced techniques and find evidence of smog and hydrocarbons in the atmosphere.
The least probable thing about Star Trek wasn’t any of the technology, except perhaps transporters, but the fact that you had multiple alien species, and us too, existing in a state of rough technological parity. Unlikely in the extreme. So any existing alien species are either so far ahead of us that they’d be here visiting us (presuming that they’re the traveling sort), or so far behind us that they’re undetectable with our existing capabilities.
Gerard O’Neill once posited the existence of a species he called the “Primans”, the first emergent technologically adept intelligence. He postulated that they would eventually create self-replicating probes that would expand out from their parent solar system but would, and fairly quickly as the universe reckons these things, be in place orbiting every star in the galaxy. Maybe the Primans are out there, maybe they’re us.
Is there a case to be made for Earth being the home of the first technologically adept intelligence? Maybe there is. There is another theory, and I’m uncertain as to whom to credit for it, that Earth gained an evolutionary advantage due to the nearby presence of a really big moon, relative to the size of it’s primary. That the moon, through tidal actions, “stirred the pot”, in the primordial seas, resulting in earlier combinations of materials that brought about in life.
The issue with the Fermi Paradox is that there’s so many assumptions baked into it that it’s impossible to even begin to know which one is incorrect and by how much. Chances are many of the assumptions are off, and some probably by a lot. As some pointed out, we have a sample size of one for what life looks like, it’s possible it might have arisen in ways very different from ours to the point that we’d have difficulty recognizing it as life. Or maybe just because it’s common on Earth doesn’t mean that there isn’t some odd cosmic coincidence of factors that make our form of life fairly easy to arise and evolve on Earth but difficult or impossible outside that narrow window of precise factors. It’s also possible that life might even be fairly common, but intelligent life, the type that could actually create technology to communicate or travel across interstellar space is extremely rare. After all, we’re not even sure exactly what factors were involved in why human brain size changed so drastically compared to our ape cousins.
Or maybe there are other intelligent species comparable to ours, but various other factors just never got them to develop advanced technology, perhaps cultural or religious or economic or ecological reasons. Or maybe they did, but they chose not to leave their planet. Or maybe they died out before they could from changes in climate or impacts or star variances; Earth has been remarkably stable in that regard. Or maybe their technology wiped them out.
Or maybe they’re out there and we just haven’t run into them yet. After all, our earliest radio signals are on the order of a century old, which means they’ve only traveled as far as about one tenth of one percent of the distance across our own galaxy. Or maybe they just have no interest in communicating with us any more than we do with random wildlife we pass by, they just see us as primitive. Or, perhaps as part of that primitiveness and some idea along the lines of the Prime Directive from Star Trek, they’re not interfering with our progress. Or maybe they’ve seen us and find our culture repulsive for some reason. Or maybe they’ve TRIED to communicate with us and we weren’t able to realize it, either because our technology isn’t advanced enough or we just weren’t clever enough to decode it.
Consider, a civilization similar enough to us biologically and culturally and technologically that we could theoretically communicate, and they could even be less than 100 light years away, and we’d still have not had enough time for them to have received a signal from us, if they could even detect it against all the background radiation, and and even send a simple “hi” back to us.
Really, I think probablistically, if we exist, even if it’s a ridiculously rare event, as unimaginably large as the universe is, it’s almost a certainty that other life, even intelligent life exists, it’s just impossible to really guess whether life is common enough that we should expect millions or billions in our own galaxy and it’s odd that we haven’t run into any of them yet, or if it’s so rare that we may never encounter them even if we do develop FTL technology and explore our own and adjacent galaxies.
When he expressed his perplexity at the lack of observed alien activity, Fermi did not mean to doubt the existence of alien life or civilizations, but to suggest there’s something wrong with our approach to the issue.
I don’t want to beat about the bush.
If we put our faith aside and look at the facts, what do we have?
- A 15-billion-old homogeneous universe, where nature follows its course.
- The nearing end of star formation & galaxy regeneration.
- Dark energy thinning out the remaining structures & eventually destroying them.
- Intelligent life on Milky Way’s Earth, a small planet in a peripheral solar system.
- Absence of alien contact.
- No evidence of extraterrestrial life.
What can we infer?
- There must be alien life somewhere else in the universe.
- There must be alien civilizations contemporary to our own (and there might have been others in the past).
- Chances of future alien life and especially of future alien civilizations are decreasing dramatically.
- Life in the universe is typically assimilated by the general context of natural phenomena and fails to stand out.
- Intelligent life fails to control large-scale environments, such as solar systems, galaxies and so on.
- Life will be almost impossible to find and there will be no alien contact.
In what way was it homogeneous? The Universe has already proceeded through many different stages, with different areas being in different states.
Star formation will continue for about 100 trillion years. We are currently near the very beginning of the ‘Stelliferous’ area. We are nowhere near the end.
The major effect of expansion from our perspective will be that somewhere between 100 billion and 1 trillion years from now, we will no longer be able to interact with anything in the universe outside of our local group of galaxies. But these are effects so incredibly far into the future that they are essentially irrelevant to any discussion of the Fermi Paradox.
Nothing you’ve stated requires this.
Again, you’re making a claim that is exactly what the Fermi paradox is calling into question.
Only if your curve stretches out over 100 trillion years. For any reasonable timeframe relevant to human existence, we can treat the universe as static and un-evolving.
Sounds like a flowery way of saying, “there’s a lot of noise, which makes it hard to discover tiny signals.”
Are you assuming that we should have already spotted civilizations capable of controlling their solar system environment?
I’m not sure where this conclusion comes from. Nothing you’ve stated leads to this.
The fact is that the time we have actually spent looking for alien civilisations is just a blink of an eye on the time scale of the universe. The number of star systems we have examined is a tiny fraction of a tiny fraction of our own galaxy, and our examination of them consists of views of small portions of their visible light spectrum. It is way, WAY too early to make any declarations about the likelihood of extraterrestrial life or our likelihood of finding them.
We still have not ruled out the existence of life within our own solar system. Seems a wee bit early to giving up on the entire galaxy, much less the universe.
One conclusion that seems to jump out of the facts as we know them today is that there will never, ever be FTL travel. All the evidence we have suggests that the universe is essentially infinite in size. The part that we can see, our ‘light bubble’ is an infinitesimal part of the entire universe.
The thing about infinities is that anything that has a probability > 0 must be certain. So not only must there be other planets with life, there must be an infinite number of them. If FTL travel exists, then this becomes a serious problem for the Fermi Paradox. But if FTL travel is impossible, we are insulated from the infinite universe by our ‘light bubble’. And furthermore, we are isolated from other civilizations that developed in our own light bubble but which developed insterstellar travel too late to allow them to get to us. So for example, if some civilization has developed Von Neumann replicating probes that travel at the speed of light 2 billion years ago, they could only conceivably reach our galaxy if the ET galaxy is less than 2 billion light years away. If we assume that the early universe was unsuitable for life for, say the first 5 billion years, and if it takes 4 billion years for intelligent life to arise, then we could theoretically only ever have contact with a civilization less than 4 billion light years from us.
To make the problem even more tractable, we can ignore other galaxies as we don’t have the ability to spot life in another galaxy unless it’s a Kardachev Type III civilization. We’ve scanned for these in the nearest globular clusters and galaxies, and found no evidence for them. But they are highly speculative anyway. For any other civilization type, our only hope for detection is within our own galaxy. And realistically, probably only the part of our galaxy nearest us and not obscured by the galactic center.
Narrowing down the problem even more, with our current technology we might be able to detect life spectroscopically or by direct detection of large structures like Dyson Spheres out to perhaps 5000 light years. That gets us down to about 600 million stars, of which only a fraction are ‘G’ type stars. Of those, we have only looked at a tiny fraction of them - about 70,000 stars with Kepler, for example. And, we’re just starting to develop the capability to look at the atmosphere’s of planets spectroscopically.
I believe this is the region that Seth Shostak is talking about when he says he thinks it’s likely that we will discover life by 2040. It’s in this time period that new space and ground-based telecopes will be able to identify planets and their atmospheric signatures at that scale.
Traditional SETI has been focused on picking up radio signals. This is a much more dicey proposition, as no reasonable radio signals could be picked up unless the stars are very close. SETI has only scanned a few thousand systems, so it’s not that surprising that nothing has been found.
They might stop breeding, but Von Neumann machines aren’t just about breeding. Self-replicating probes would be an obvious solution to any species that is even half as curious as human beings. If it ever becomes remotely possible, I suspect humans will try sending probes to other galaxies even if millions of years have to pass before any data is returned.
But even more important that that: all you need is one species that does want to keep breeding. As long as we’re playing with percentages, you can plug in a factor for that as well and still come up with a number that suggests the galaxy should be overrun by now, even at sub light speeds and even if most species have no interest in doing.
UY Scuti writes:
> . . . A 15-billion-old homogeneous universe . . .
13.8 billion.
Where are the tourists? Same place as the tourists going to Egypt - we’re too violent to want to visit.
O2 will indicate the presence of life. Once we find pollution in an atmosphere we’ll know that we’ve found intelligent life. And I agree finding intelligent life that way is much more likely than by them dropping in.
I think many in this thread have misunderstood the Fermi Paradox.
It’s not saying “Assuming aliens are humanoid, communicate using radio waves, and exploit FTL…”.
It makes no such assumptions.
All it’s saying, is that on the basis of what we know, it seems strange we have not detected any evidence of extraterrestrial life. We can speculate on why that is, and that’s largely the point.
e.g. Maybe aliens have visited us but they are so advanced they can do so without us even realizing? Fermi’s paradox does not declare such speculation wrong, but we have no data to support such an idea at this time. Hence the paradox – and speculation – continues.
Even if you create a few billion machines and send them all over the universe, how would we detect them?
I assume each probe would be the size of one of our satellites, or maybe the size of the space station. (or maybe the size of a monolith, like in the movie 
)
It could come visiting, take some pictures, and keep on going, and we’d never know.
It could fly by the earth along with the millions of asteroids which we can’t detect. (or don’t bother detecting?.)
If they’re self-replicating machines, then one copy could remain here, monitoring events. When it detects signs of intelligent life, it would make another copy to send back home to report the news.
If it wants to make contact, we’d know!
Ahh…but what if:
After monitoring us for a couple million years, it detects something interesting, and reports back to ask for further instructions…only to get no answer, because its home civilization no longer exists ?
We’d never know we’ve been spotted!
(hmmm…has anybody ever written a sci-fi story like this? )
Two necessarily speculative points:
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As far as we know, we are the only species in billions of years of life on Earth that is capable of advanced civilization. Life in the universe may be common but intelligent life may be much rarer.
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Advanced industrial civilization may not be stable because it tends to create technologies which threaten itself. We have already created one such technology, nuclear weapons, and have experienced at least one close shave during the Cuban missile crisis. In a few decades we may face another existential threat with climate change and there could be yet others with biological weapons and out-of-control AI. These threats don’t have to complete destroy the species, just destroy the kind of advanced civilization which can travel and communicate through space. For all we know, the universe may be full of post-apocalyptic societies which are really hard to detect.
If intelligent life persists once it has emerged, then it could be just as common as non-intelligent life. Multicellular life emerged about 0.5 gigayears ago; our civilisation is only ten thousand years old, but if it persists for a gigayear, then the duration of intelligence on our planet would be twice as long as that of non-intelligent life.
This may be true of intelligent species which closely resemble humans in development, but if life turns out to be very diverse in our universe, we can’t assume that their civilisation would follow a similar path. What crises would be faced by a civilisation made up of intelligent sea-snakes, or slime-molds, or bacterial mats? What climate changes would occur on a planet with supercritical water for an atmosphere? What weapons would a race of intelligent computers be vulnerable to?
Any sentient species would likely find itself in the same position (with maybe one or two very closely related subspecies).
A sentient species is unlikely to be among the simpler, earlier species to arise and a sentient species’ learning and exchange of ideas is almost-certainly going to be orders of magnitude faster than slower-than-trial-and-error natural selection (so in the time it takes sentient species #2 to evolve, #1 is probably already exploring the galaxy).
- Advanced industrial civilization may not be stable because it tends to create technologies which threaten itself.
[snip]
These threats don’t have to complete destroy the species, just destroy the kind of advanced civilization which can travel and communicate through space. For all we know, the universe may be full of post-apocalyptic societies which are really hard to detect.
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I think it would have to be 100% destruction, because post-apocalyptic scenarios are unlikely to be stable.
With the recent memory of technology, millions of artifacts lying around, and recalling how fast humans can multiply if we want to, I think we would likely be back to skyscrapers and iPhones in virtually no time at all.
Certainly not the timescales required for it to make a noticeable difference to the fermi paradox.
Obviously it would depend on the nature of the apocalypse. In the event of a major nuclear war you would not only have the initial destruction but the subsequent climate change which would probably lead to a collapse of the world food supply and probably most governments. After that there would probably be brutal wars around world for the limited resources that are still available. There is no telling what the ideologies of the survivors would be. I would guess many of them would be extreme religious cults along with brutal military dictatorships neither of which may have much of an interest in reviving industrial progress which could undermine their power. Even if they did, much of the world would be uninhabitable and you couldn’t simple revive the very complex and interconnected economic system we have today.
Idunno. Checking out more interesting locales, maybe.
Kinda-sorta.
See Red Dwarf.