Two is faster. If every system makes two you can exponentiate.
That explains why we didn’t leave Africa or reach the Americas until the development of reliable sea travel in the 1800s
I think an episode of Star Trek: TNG did that. A probe made Lt. Barclay super intelligent and Barclay made the Enterprise jump exceptionally far in almost no time. When the Enterprise arrives they learn that some aliens were exploring the galaxy by bringing stuff to them and making Barclay super smart was a means to that end (upon arrival they made Barclay normal).
Nah, you could fit the entire galaxy within a third of a lightyear radius and not make a black hole.
Still pretty big, sure, but not galaxy spanning big.
Or ten or a hundred. By the time we can make self replicating excavators, it’s not like there’s going to be a human hand that touched any part of it anyway.
Now there’s an idea. Instead of sending out self replicating excavators, we send out Bracewell probes. The probes contain all the information they need to bootstrap their technology to the point where they can start building self replicating probes. Which then are used to send stuff to us.
I know; I’ve written about that possibility elsewhere. All that concentrated mass does funny things to time, though.
The rest have to be made out of something.
I only assume they might head here if they thought there was intelligent life here. But the resources they need are not that easy to find or they wouldn’t be searching the universe for them. The resource they can’t simply make is a fertile world they can exploit.
Yes. Michael Hart in 1975 suggested that these devices could be built in distant systems from local materials, by colonists; in other words by humans who have travelled to distant systems.
In 1980 Tipler refined this by replacing the humans with autonomous robots; something not everyone might be happy about.
Realistically planets are a red herring. They are where you evolve, but they are a cradle.
Once we are committed to being in space, planets stop being interesting because they are a massive gravity well. You spent your entire history as a species clawing your way out of that well. Why would you want to go back into one?
Most of your population and capital should be in space, on airless bodies with very low gravity, or in entirely artificial habitats in orbit.
Yeah, the asteroids or planets that they dismantle
Why?
Do we only mine coal in places where we think there is intelligent life?
They are plenty easy to find. They aren’t searching, they are exploiting. Stuff is literally just floating around in space.
But they don’t need a fertile world to exploit.
If such probes came to our solar system, and they were programmed with enough intelligence and ethics to leave inhabited worlds alone, they wouldn’t miss anything by not visiting Earth, and instead contenting themselves to mining out the rest of the solar system, leaving us as just a single planet orbiting a star.
Maybe they hang out and wait for us to die off, then finish the job.
Let me posit a possible explanation. Go back in time just 100 years, and think about our capacity at that time to detect evidence of alien intelligence. The galaxy could have been full of aliens building giant mega-structures, beaming signals at us from all over, and we’d have been completely oblivious to anything that wasn’t figuratively right in front of our noses. Scientists of the day had no capacity for building powerful radio telescopes, or putting up a Hubble or a Webb space telescope, or detecting gravity waves. In fact I recall reading an article from sometime in the 1920s in the archives of Popular Mechanics that seriously speculated on what various forms of exotic life on Mars might look like, and the author was convinced that the existence of such creatures was more likely than not. We simply had no idea.
Now go back to the present. We are only 100 years removed from that time. Is it not perhaps rather arrogant to assume that we know what to look for, and that even if we did, that we have the appropriate technology to detect it? We think we’re pretty technologically sophisticated, but the whole zeitgeist of the 20s was “modernity” and the miracle of “modern” technology. Searches like SETI are necessarily based on the implicit assumption that radio waves will be the preferred means of interstellar communication. But is that valid? Perhaps, or perhaps if it was valid at all, it was only for a very short period in the evolution of a civilzation.
Today we are just barely on the cusp of maybe – with the most advanced instruments we know how to build – maybe being able to use the Webb telescope to detect for the first time the potential biosignatures of life on some exoplanets. Who knows where we’ll be in another 100 years, or 1000, and what we might then be able to detect. It might completely revolutionize our views of alien life and alien intelligence.
I don’t know why I need to say this almost every post but here we go again: I am assuming nothing about alien life.
So, sure, perhaps once we can detect “quasitron waves” or whatever, the sky will light up with the evidence of thousands of civilizations. Maybe, I wouldn’t rule that out.
But we’d still be curious why none of these civilizations has absolutely any tech that radiates detectable EM radiation currently in operation. Or has extant, visible mega structures.
As for how wrong our notions of ETs might have been 100 years ago, that’s exactly the point: the Fermi paradox is entirely about our known and unknown unknowns. It’s not about claiming we somehow already know and understand ETs and extra solar ecosystems already.
I’m not saying that you are. I’m saying that the very question of why we are not seeing evidence of alien activity when we “should be” if they’re really out there does carry the implicit assumption that we know what to look for.
As far as EM radiation is concerned, I would suggest that the vast majority – almost certainly all – hypothetical advanced aliens monitoring our solar system would reach the same conclusion: there’s nothing there. Either because we’ve only been emitting EMR for about a century and it hasn’t reached them yet, or more likely because they are far too weak to be detectable against the background noise of the galaxy and the CMB, and most likely because of both.
As for megastructures, it’s highly speculative with regard to why they would build them, or what they might look like, so it gets back to my original point.
We have reason to believe some things must be true about any alien life.
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Liquid water is necessary.
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They are most likely carbon based.
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Life will produce things in an atmosphere that would not be there otherwise (and we can detect that).
We may not know any details but there is good reason to think we can tell if a planet has life on it from some telltale signs.
oops… Popular Science, not Popular Mechanics, just to set the record straight. Not sure what year it was, but definitely 1920s.
Firstly, as I say it’s debatable whether most discussions of the Fermi paradox are in the context of positing that there “should be” evidence. I don’t think it is, I think it is usually just about discussing all the various unknowns here.
Secondly, no, it’s not about claiming to know what aliens would do. Who knows what my gamma ray helix is for? The point is simply we have seen no evidence of ETs so far, and that’s an important data point. Not something to be ignored.
Sure. A civilization as primitive as ours would be hard to detect using only technology as primitive as ours.
This isn’t really relevant to the Fermi paradox though, as the gap between a civilization as primitive as ours and one that can expand across the galaxy is, well, an eyeblink. Galactically-speaking.
Again: I’m assuming nothing. I’m pointing out that we see no mega structures yet.
If someone wished to speculate that advanced species are common, then we can ask the question why none of those advanced species ever built anything visible across the galaxy. For any purpose whatsoever.
One potential answer to this of course, is that there is no benefit to ever making such structures. But we can already disfavor such an explanation given that we can already posit megastructures that could potentially be useful, like Dyson swarms.
we already have multiple theoretical methods of reaching maybe 20% of the speed of light.
nuclear pulse engines, solar sails, fusion reactors.
The galaxy is 100,000 light years in diameter. in theory we could colonize it in under a million years at 10-20% of light speed even without new interstellar technologies.
Also mass doesn’t really start to increase until you go past 60% of the speed of light. so perhaps even less time if they can accelerate more
That’s kinda the point of discussing the Fermi Paradox and the Drake Equation, it helps us to know where to look, what unknowns we don’t know about yet.
But, we can only base things on what we do know, or at least what we can speculate about. Things beyond our ken aren’t all that useful.
Overall, however, the whole idea is not that there may be life out there that we cannot detect, it’s that signs of life should be out there that we can.
I don’t think that anyone has really hypothesized that there are aliens monitoring us. At least not specifically us. They may have sent probes/excavators/colonies all over, but they probably would not have sent them specifcally for us.
OTOH, Earth has been showing signs of life for billions of years, and even more so in the past few hundred million. That’s not something that we can hide, and it’s something that we may be able to detect on relatively close planets with JWST. IF we put up a much bigger instrument, we’d be able to find life on planets dozens or hundreds of light years away.
If habitable worlds are uncommon, but not super rare, I could certainly see why an alien carbon based civilization would be interested in our planet, and could have been for a very, very long time.
They would build them for the same reasons that we will build them, to increase power, resources and living space. Will all of them do so? Maybe not. But why would none of them do so?
I don’t know that your list is all that accurate. We don’t know that there aren’t super intelligent gas clouds living on gas giants, or complex self reproducing chemical reactions on asteroids. Or a world may have developed carbon based life, created artificial intelligence, got wiped out, and the planet scoured of any form of life.
However, we do know that carbon based life, like ourselves, is possible, and really seems like a pretty good way to go.
I would not say that, if life is common in the universe, all of it is carbon based, but I would say that at least some of it should be, and that’s what we are looking for.
I’m not sure that anything short of anti-matter is going to get a self propelled craft at anything close to those speeds. Laser sails, maybe, especially if an interstellar civ is cohesive enough to build interstellar laser highways.
But fission and even fusion are not going to get you there, and a solar sail, if only powered by the light of a star, isn’t going to get you anywhere at all(interstellar speaking, they may have use in interplanetary transport).
I don’t think we’re really much in disagreement. I believe that life exists throughout the galaxy where conditions are favourable – and there are likely millions of such planets – and that some of it has evolved to at least our level of intelligence and some of that likely very far beyond. And I think that the Fermi “paradox” is not so much a paradox as a statement that begs for an explanation, some of which I’ve hypothesized.
However, my statement about detection of our incidental EM radiation from routine earth-based transmissions is based on something much more fundamental – basic signal theory, like the Shannon-Hartley theorem. No amount of sophisticated technology is going to tease out a signal that consists of just a few occasional photons from the background noise of the universe. So aliens from Kepler 442b are not going to be able to watch I Love Lucy original broadcasts weekly on CBS from the 1950s no matter what technology they have, and we are likewise not going to be able to watch their domestic entertainment, if they ever had any.
I agree here.
This part, I don’t. If we manage to visit other life bearing worlds in the galaxy, I expect to find a bunch of single celled prokaryotic life, and very little any more advanced than that.
That’s what a paradox is. Two statements that lead to different conclusions cannot both be true. So, the debate is how to resolve the assumptions so that that contradiction no longer exists.
I don’t see why this is true. A larger receiver will get a stronger signal. A large enough receiver would pick up incidental transmissions of that nature. The Starshot people think that we can detect a radio transmission from a one gram probe from four and a half light years away. I see debate on the engineering challenges of such a feat, but I don’t see claims of physical impossibility.
Plus, there are other signs. As I said upthread, we have been advertising our status as an oxygen rich world with liquid water on the surface for a very long time, something detectable with sufficient resources from most of the way across the galaxy. In somewhat more recent years, the chemistry of our atmosphere has changed in ways that are hard to explain naturally, and any species that went through a similar industrial revolution would recognize.
And it’s not just “I Love Lucy” out there. Television signals are weak compared to radar and other avionic related transmissions that are deliberately directed towards the sky. They may not get a picture show, but they would certainly notice their coherent and unnatural nature.
Well, we have one example of a life-bearing planet and we have good reason to think that life wants water and would be carbon based and so on. It just makes sense chemically. Other possibilities may exist but are less likely. We could look for the Hooloovoo which are a super-intelligent shade of blue but that’s probably harder to do.
And, there is no need for intelligent life. Algae could leave a telltale sign.