▲ 65 points
back
100 comments
What a timely coincidence. I just finished reading Cixin Lui's "The Dark Forest" (it and the first book in the series "The Three-Body Problem" I cannot recommend enough). I think the central premise of the book is probably the worst of the possible reasons we haven't found anyone else out there...
"The universe is a dark forest. Every civilization is an armed hunter stalking through the trees like a ghost, gently pushing aside branches that block the path and trying to tread without sound. Even breathing is done with care. The hunter has to be careful, because everywhere in the forest are stealthy hunters like him. If he finds other life—another hunter, an angel or a demon, a delicate infant or a tottering old man, a fairy or a demigod—there’s only one thing he can do: open fire and eliminate them. In this forest, hell is other people. An eternal threat that any life that exposes its own existence will be swiftly wiped out. This is the picture of cosmic civilization. It’s the explanation for the Fermi Paradox."
Same premise as Greg Bear's The Forge of God [1] from 1987, where the aliens play mindgames with the civilizations they are about to destroy. His analogy (from memory) is baby birds cheeping in a tree.
Except that we've been pumping radio waves out of this rock as loud as we can for decades. We're the loud cousin who can't keep quiet when hunting.
> Except that we've been pumping radio waves out of this rock as loud as we can for decades.
It's true but there is a possibility that human radio activity does not last that long. We choose to transmit information using electromagnetic waves that propagates in every possible direction when there is no alternative, but it's a massive waste of energy and we may not continue to do so forever.
As a matter of fact, an increasing amount of communications travel through optic fibers, which are not observable from space. (And that's also why they're efficient)
If that's a correct prediction, we won't be pumping radio waves out of that rocks for more than a couple of decades. This is nothing compared to the age of the universe and may very well be missed, even if there's someone to observe.
And, if one civilization found another it would take massive amounts of resources and time to launch an interstellar attack. I doubt humanity's first reaction would be to embark on a giant project to somehow try to destroy the other civilization. This idea makes no sense.
Except that we've been pumping radio waves out of this rock as loud as we can for decades. We're the loud cousin who can't keep quiet when hunting.
The inverse-square law makes this a non-concern, doesn't it?
maybe we're just the crickets
This is how far human radio broadcasts have reached into the galaxy
http://www.planetary.org/blogs/emily-lakdawalla/2012/3390.ht...
Researched Cixin Lui. Wow. Why haven't I heard about him before? I'm downloading The Three-Body Problem on my Kindle tonight.
Because western countries don't tend to get access to Chinese science fiction authors. Totally worth reading.
This is also the premise of David Brin's short story "Lungfish".
The sequel is excellent as well. I'd also recommend it highly. It's great seeing how one's culture affects your writing style and content.
My interest is piqued. Could you elaborate a bit on the writing style and content?
> and since we don’t see any obvious signs of aliens here, searching for their signals is pointless.
That is a huge over simplification. The fermi paradox doesn't really conclude. It is called a paradox because we need to solve the riddle that combined with the drake equation it is awfully quiet in our universe, why is that?
If you have 20 minutes: http://waitbutwhy.com/2014/05/fermi-paradox.html
This is probably one of the best long reads on the internet dealing with this question.
The real issue is not that we haven't been visited (for which read, we exist, because the matter of the solar system wasn't turned into computronium by some group billions of years ago), but that everything we see is a wilderness. All of the observable universe appears natural in every place we can assess whether or not it is natural. No dyson spheres in evidence, no class 3 civilization in any of the nearest 100,000 galaxies, etc, etc.
This makes no sense given that we exist, and the laws of physics show no indications that we are a special case, or that transforming the universe into intelligent matter is impossible. All it takes is one small group in one species to create the self-replicating probes that dismantle every natural grouping of matter to create more efficient arrangements to support more intelligence, and on a small timescale compared to the age of the universe entire galaxies are turned from wilderness to structure.
https://www.exratione.com/2015/05/the-cosmological-noocene/
"Per our present understanding of physics and intelligent economic activity, we will turn every part of that great span into our descendants if not diverted or stopped by some outside influence, stars and all. The cosmological noocene, an ocean of intelligence. That the natural universe remains present to be used by us indicates that something is awry, however, that some vital and important understanding is missing, and as a species we are still just making the first fumbling explorations of the bounds of the possible with regards to what it is that we don't know."
There are two main assumptions in those "where are they?" Scenario. One is that self replicating probes are feasible and the other is that ots practical for them to travel interstellar distances.
I think the problem of designing and building self replicating probes, capable of recreating themselves from asteroidal matter, is greatly underestimated. We currently have little to no idea how to design such a thing, and no real idea what the lower bound on the mass of such a thing might be.
The next problem is nterstellar travel. The difference un scale between traveling to the moon and travelling to a nearby star is about the same difference in scale between throwing a rock down a typical garden and launching astronauts to the moon. The Daudalus project did down good work on this and their very modest proble of just a few tons, doing a flyby of a nearby star, took a large to portion of the mass of Neptune to construct in terms of fuel. The resources available in a typical planetary system might not be up to the job.
I don't honk magic future technology hand waves these problems away. Any future technology will have to work with the same elements on the same periodic table we have now, manipulating the same physical forces we work with now. We can't wish magic unobtainable into existence and the limits of what is achievable with matter and energy are already pretty much computable.
So it really may well be that going sustainably interstellar might be impractical.
The mass number you through out (large portion of the mass of Neptune) seemed really off to me so I looked it up and found some comparisons.
For a flyby: Daedalus mass = 5.0 * 10^7 kg (500 kg of scientific equipment)
With a slowdown to stay in the system: Daedalus mass = 10^10 kg
Mass of Neptune: 10^26 kg
So even for an extended stay, the mass of the Daedalus is no where close to a significant portion of Neptune.
I looked for equivalent mass objects, here is a few:
1.4 * 10^18 = all oceans on earth combined
10^12 kg = 1.4km diameter asteroid (Icarus)
3.5 * 10^10 kg = 0.5 x 0.3 x 0.2 dimension asteroid (Itokawa)
Estimates put the number of asteroids larger than 1km diameter in the belt between mars and Jupiter at 750,000
These are just straight mass conversions, no idea about the real content of fuel. If all those asteroids were straight fuel then you could launch upwards of a million Daedalus class ships that stay in the orbit of their target star.
Maybe they have been turned into structure and intelligence, but we can't see it because it's operating in ways that are invisible to us.
The fallacy is that aliens must be using *technology that can be recognised as technology by early 21st century humans."
I suspect this is a low bar.
For all we know galaxies have already been transformed, and the curious science we're seeing - not least dark matter and/or dark energy - are the result.
Perhaps alien technology is non-material, and probes aren't any more necessary to aliens than head hunting is to us.
If you can manipulate spacetime and quantum phenomena directly, you're probably not going to spend a lot of time turning your star system or your galaxy into a showy megastructure.
One pretty sensible argument is that life/intelligence takes a lot of time to develop. I.e. we aren't the upstart humans encroaching on Ancient Aliens, we are Ancient Aliens. If we are among first intelligence to develop, then of course, we won't see signs of intelligent life.
Except the universe has been around 13 billion years, and our solar system has only been around 3-5 billion, so it seems unlikely we are the first.
> All it takes is one small group in one species to create the self-replicating probes that dismantle every natural grouping of matter to create more efficient arrangements to support more intelligence
The "paradox" ultimately comes down to a lack of data. If the milky way evolves interplanetary civilizations every 5 billion years, it's clear the odds are stacked against ever meeting another living civilization... especially if FTL is impossible and transporting large masses at C is not viable.
The assumption that life naturally lead to computronium and self-replicating structures also seems unfounded.
This is not my understanding of the Fermi Paradox and I've never heard this interpretation before. The paradox is; given the Drake equation, where is everyone? That's all it amounts to, hence the paradox. The author of the article states the paradox differently, that, because we can't see any evidence, we shouldn't look. That is not the Fermi Paradox.
One of my favourite responses involves cryptography: Given a sufficiently advanced civilisation, one might imagine that their ability to encrypt information is perfect, therefore any signal is indistinguishable from noise.
We don't even know how accurate the Drake Equation is - many of the variables are just filled with guesswork. As such, we can't even know whether the "Fermi Paradox" is a paradox or an artifact of our own anthropocentric ignorance.
See Stanislaw Lem: His Master's Voice
https://en.wikipedia.org/wiki/His_Master%27s_Voice_(novel)
That's been recommended to me before, but I'd forgotten about it - I shall act this time. Thanks!
I started to read Solaris, but found the translation stilted and difficult, so gave up. I've just read that Lem himself didn't like the Rnglish translation! It's unlikely I'll be learning Polish this lifetime.
No need for encryption. Sufficiently advanced compression will give signals apparently perfect entropy.
Another possibility is: they never feel like it.
It's possible intelligent species inevitably overcome/loose the desire for infinite self replication.
It's clear other animals will breed to occupy all available habitats. But it seems humans uniquely are developing the idea of the preserve in which environments are intentionally left unoccupied. I have even heard a tiny amount of talk questioning the impact of even a Mars landing. If that question is already coming up centuries before interstellar travel, one wonders what attitudes will be prevalent then.
Just a century ago it was quite desirable to intentionally release new species of bird's into new continents purely for aesthetic reasons. Now such an attitude would be abhorrent.
I suppose if one could demonstrate that the desire to endlessly replicate across the universe is somehow beneficial to individuals currently living then I imagine their values will embrace it. If endless self replication is not beneficial to the exiting population then they will eventually reason their way clear of that instinct and that reasoning will be integrated into their ethical code.
So while I, like most people reading this, am very excited by space exploration, that attitude may not be a permanent cultural characteristic.
Fermi:
> ...technological civilization doesn’t last long enough for it to happen.”
Writer:
> Both York and Teller seemed to think Fermi was questioning the feasibility of interstellar travel—nobody thought he was questioning the possible existence of extraterrestrial civilizations
What happens when a technological civilization 'doesn't last long enough'? It stops existing.
That's assuming a technological civilization's natural progression is towards space travel, which may or may not be true. The Aztecs were way "behind" when explorers first discovered them, but were doing pretty fine.
It might stop existing as a technological civilization, but it might continue existing as a civilization that's lost access to its technology.
> What happens when a technological civilization 'doesn't last long enough'? It stops existing.
But it did exist, which is clearly the point here.
"The other is the so-called Fermi paradox, which claims that we should see intelligent aliens here if they exist anywhere, because they would inevitably colonize the Galaxy by star travel—and since we don’t see any obvious signs of aliens here, searching for their signals is pointless."
Either this is worded wrong or illogical. If this is true, as it's worded now, then we humans either do not exist or are not intelligent, by its very definition. Both are ridiculous conclusions. The assumption is "because they would inevitably colonize the Galaxy by star travel". What if they're not advanced enough to do so yet? Does that make them not intelligent? If so, that would make us non-intelligent. Does that prove aliens don't exist? If so, then we humans are proven to not exist (which is ludicrous).
Finally the stupid conclusion: "since we don’t see any obvious signs of aliens here, searching for their signals is pointless." So as a corollary, other aliens searching for us would be pointless since we humans don't exist since there are no signs of us on other planets.
This is incredibly stupid. No wonder Fermi never wrote it. He would never write something this dumb.
I've heard this before, that Fermi was really questioning interstellar travel, not alien existence. Given all the matter we've found in interstellar space, from dust clouds to brown dwarfs, it seems pretty clear that travelling near the speed of light out there would be perilous indeed. Even a small rock, colliding with your ship travelling at .5c is going to destroy it.
In a universe that is very old and very large, anything that can occur will eventually happen somewhere. This includes the launching of interstellar self-replicating von Neumann probes. All it takes is one civilization somewhere lobbing one sufficiently automated sublight probe, and in a few million years the galaxy is full of them for the rest of time. Either the galaxy is full of interstellar self-replicating probes, or empty of them. Their absence here is strong evidence that nobody, at least in our galaxy, has evolved a technical civilization, and that we are the first or only to approach that level.
Not sure why you wouldn't just manufacture a bunch of probes in one system and then send them out en masse. You wouldn't need to worry about creating self-replication units, you'd get to each system more quickly (you wouldn't have to deal with multiple accelerations/decelerations or manufacturing time), you'd have more control (wouldn't have to worry about drone swarms and could inspect each probe before it's sent to its destination), you'd probably have quicker manufacturing (since it'd be done by specialist machines rather than hybrid manufacturer/probes), could probably give the probes a boost form the home system when you send them out, etc. Self replication doesn't seem to add much, but certainly takes away a lot.
This is also assuming that aliens will want to scout out the universe, and that probes are the best way for an advanced civilization to do so. We might be like someone from the past who comes to the present and determines that we don't have any long distance communication because they don't see any smoke signals.
I see what you are getting at, but in an infinitely large universe, those events may be infinitely distant from us.
The von Neumann probe is an interesting thought experiment, but practically speaking, what reason would there be for anyone to ever create one (assuming it would ever be possible)?
I'm taking a moment to be thankful that today no army of self-replicating probes annihilated life on earth.
On the other hand, we are surrounded by earthly self replicating probes and we seem to be doing fine.
Necessary read for reasonable discussion:
https://en.wikipedia.org/wiki/Rare_Earth_hypothesis
"the Rare Earth Hypothesis argues that the origin of life and the evolution of biological complexity such as sexually reproducing, multicellular organisms on Earth (and, subsequently, human intelligence) required an improbable combination of astrophysical and geological events and circumstances. The hypothesis argues that complex extraterrestrial life is a very improbable phenomenon and likely to be extremely rare."
We already know that there are likely billions of planets which are likely to be similar to Earth in terms of temperature, size and being terrestrial.
The only question here is that even here on Earth, out of the tens of millions of species, only one is capable of creating advanced technology.
I am almost certain life exists elsewhere, but likely not intelligent.
Bottom line is we only have one example. We simply do not know. For all we know the frequency could be less than one per galaxy per billion years, in which case we are likely alone.
Given the sheer size of the galaxy, forget the universe, C is unfathomably slow in comparison.
It's no wonder, at least not to my imagination why we haven't found any other life yet, or visa versa.
c may be slow relative to distances in space, but the universe is incredibly old as well. A civilization a million years ahead of us could have colonized the entire galaxy by now.
And in any case, if there is anyone out there, there should be some evidence. Scientists have looked in various ways for megastructures (e.g. Dyson Spheres) and have found no evidence for their existence, even in the oldest of galaxies.
The picture in my mind is quite bleak. The evidence seems to point to a very limited number of scenarios:
1. We are unique (in existence, in our technology, in our desire to expand, etc.) 2. We are first. 3. Civilizations destroy themselves before they can expand. 4. Civilizations do something else we don't yet understand that doesn't involve gathering more and more energy from surrounding space.
A better measure of whether there is other life in our universe might be the percentage of us which really believe, at our very core, we are the only life in a vast universe we understand less than the soil we tread on each day.
It can't be a paradox if you know you can change the question.
I'm skeptical on looking for radio waves. How could interstellar intelligence use radio waves to communicate anyway, they're traveling at C and are still too slow
All communication is limited to c. Any novel forms which are not limited to c are beyond our ken so we lack even the ability to look.
At this point, scientists are looking for someone who would want to talk to us. (We are very unlikely to intercept anything not intended for us.) Anyone who wanted to talk to a fledgeling civilization is probably smart enough to know to use radio waves.
Interstellar intelligence can still travel at time frames much longer than human life.
It's like complaining that a letter from America to Europe would travel for many months in 1495. There were still incentives for Europeans to go to America.
Our civilization has had radio communication for 100 years but we're well on our way to environmental collapse within the next thousand years. The milky way is over 100k light years wide. By the time our signals reach any other potential civilizations we'll be long gone. If the average civilization broadcasts for a thousand years but they're tens of thousands of light years apart, communication is not be possible within a civilization-span.