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Fermi Paradox: If the Universe Is Teeming with Aliens, Where Is Everybody? (books.google.com)
51 points by obblekk 1258 days ago | hide | past | web | 75 comments | favorite



To preempt some of the usual thought on this topic: no solution to the Fermi Paradox can rely on every civilization taking a certain direction. It doesn't matter how strong the incentives are for any particular course of action, the numbers (of stars, planets, etc) even in just our galaxy are so very large that even under rare life assumptions there are still going to be an enormous number of civilizations at any given time, never mind over all history.

Some of those will have (or will have had) subcultures that generate self-replicating colonies, probes, or whatever. Those visit every stellar system in the galaxy in a very short time frame.

Possibly viable solutions include:

- We are simulated.

- Stochastic colonization leaves long-lasting uncolonized voids at all scales.

- Wolves. (Ecological wolves intent on making everything look natural, but since they get to be unitary, they can be as odd as they want to be).

But non-wolf Great Filter arguments have the same issues as arguing that all civilizations sublime, or leave, or whatever. There is always going to be someone who doesn't.


the numbers (of stars, planets, etc) even in just our galaxy are so very large that even under rare life assumptions there are still going to be an enormous number of civilizations at any given time, never mind over all history.

The problem is we have no way of estimating the probability of life emerging given favourable conditions. It could be 1x10^-100 for all we know.


Life emerged very early in the geological history of Earth. The probability of this happening is greater under the "P(life|conditions)≈1" model than under the "P(life|conditions)≈0" model. Our historical observations give the "P(life|conditions)≈1" model greater likelihood. It's not exactly proof, but it's enough to convince me.


So that brings up the question, if life happens so readily given the right conditions, how come it only happened once on earth? And I don't buy the explanation that one form out-competed all other forms -- given the diversity that we have now, there can be millions of forms of life all existing at the same place/time. But all instances we have now originated from one single biogenesis event.

So, how do we know that there was only one biogenesis, and not multiple ones that happen to resemble each other (i.e., that DNA-based life is the only thing that ends up working, and it occurred multiple times)? From what I gather, there are many markers in biological molecules, such as the direction certain molecules form (left vs. right, etc), and that multiple biogenesis events would have gotten these in random positions (i.e., your heart on the right side instead of the left side of the body).


> given the diversity that we have now, there can be millions of forms of life all existing at the same place/time.

Sure, each niche favors a different specialist, but why do you think that whichever process led to the emergence of life will be any good at producing competing specialists? I'd think that evolution of existing organisms would be infinitely better at this task, as existing organisms have both a numerical advantage and the strategic advantage of DNA (a "playbook" of previous successful strategies to draw inspiration from).

Very few niches are available for the emergence of life, even though there are clearly many available for the evolution of existing life. The available niches require a level of sophistication that spontaneous process cannot achieve but that evolution can achieve (e.g. photosynthesis).


Actually, given that our star is a third-generation star, you could even ask the question : why wasn't there life in our very own solar system before earth even existed ? Before sol started burning or even coalesce ?

The first generation stars wouldn't have had anything but hydrogen clouds surrounding them, but second generation stars would have had similar amounts of other elements to what we have today floating around them.

Given that "our" biogenesis event happened only the second time it could happen (here and in billions of other solar systems in our galaxy), where the hell are the second generation societies ? Didn't they survive the supernovas ? (possible, I suppose, but not exactly hopeful for our own chances of spreading across the stars). Was there some kind of large scale disaster ? But the question is worse than that, because they should have been spacefaring ... if they had anything like our numbers of satellites, we should have been able to find something, somewhere, right ?


Selection bias.


> Selection bias.

Elaborate. If you're referring to the anthropic principle, I don't see how it's relevant to my argument.


Historical observations of sample size 1?


Not strictly relevant. If your hypothesis is extreme, a single observation can make its posterior probability small. For instance, suppose that Alice gives you a coin and says "it lands on heads 99% of the time" (hypothesis A) but Bob calls BS and says "it looks like a regular quarter, so it should land on heads 50% of the time" (hypothesis B). You assign prior probabilities of 50% to A,B because on one hand you can't imagine how anyone could engineer a coin to land on heads 99% of the time, but on the other hand Alice is a great engineer, so you don't know what to believe. If you flip the coin a single time and get tails, your experiment strongly supports hypothesis B over A. OTOH, if it landed on heads, A would be weakly supported over B. We started with an even prior, so the posterior probability of A,B are proportional to their likelihoods: P(A|t)≈2% and P(B|t)≈98%, while P(A|h)≈66% and P(B|h)≈33%.

Let's say that a typical planet remains habitable for 8b years and it takes 4b years from the emergence of life to the emergence of intelligent life, so according to the anthropic principle life had a 4b year window in which to emerge. Under the model where P(emergence)/time is tiny, the probability of life emerging in the first billion years is ~.25. Under the model where P(emergence)/time≈1, the probability of life emerging in the first billion years is 1. With even priors, the posterior of P(emergence)/time≈1 is 80% and the posterior of P(emergence)/time≈0 is 20%.

It's not scientific proof of anything, but it's enough to make me consider alternative explanations for why life is rare.


Interesting points here: http://www.gwern.net/Colder%20Wars

If there's no FTL, but civilizations can accelerate massive projectiles to near light speed, there's basically no defense against devastating surprise attack. And there's little accountability to allow retaliation.

Basic game theory says either they all destroyed each other, or the survivors are staying very, very quiet.


Planet bust should be visible to our technology. We'll spot one soner or later if colder war is still waged. Plus, it's much harder to cook the entire solar system and planet death isn't the end of the game.


Didn't a rather large asteroid pass between the Earth and the moon recently, and no one even noticed it until it was on the way out?

Just because something should be visible doesn't necessarily mean we'll happen to be looking at the right place at the right time within the right spectrum. There could be a lot we simply don't see.


I mean that we should spot other homeworlds being busted across the galaxy.


There are billions of galaxies, though, and my point is we may still be half-blind, since we've only recently even able to detect exoplanets smaller than Jupiter IIRC. And, if we did see something, we would likely interpret it as a natural event.

It would probably be in the best self-interests of whatever species launched an attack to make it appear like a natural event in any case, so as not to draw attention to their existence from unknown parties (like us.) And a collision that could wipe out a civilization is clearly within the realm of natural possibility since it's happened on Earth in the past (without the civilization part..) so it need not necessarily draw attention to itself.


"Wolves" is a new term to me and I'm having a hard time googling for more reading. Can someone give me a link?


I was puzzled by this as well. I'm not familiar with a "wolf hypothesis" and a google search doesn't turn anything up.

I'm pretty sure he's talking about the Zoo Hypothesis. i.e. our presence is known to other intelligent civilization(s), and for whatever reason they've decided to hide themselves and not engage. Like a village would refer to wolves in the surrounding forest.

For this to work though, you have to have one advanced civilization that has either absorbed the others ("unitary") or powerful enough enforce the rules. Otherwise it would be pretty inevitable that out of a hodge-podge of civilizations one of them would say screw it and engage.


Wolves aren't known for taking other animals, putting them in cages, and staring at them. Wolves are known for eating other animals.


So a prime directive of sorts, perhaps?


I legitimately think we are living in some sort of holographic simulation created by consciousness. I think Thomas Campbell's work is most accurate model of reality I have seen. Check it out:

https://www.youtube.com/watch?v=fT8LaMrn_MM


There's a depressing non-wolf Great Filter argument. What if this sort of scenario is unavoidable for fundamental reasons... possibly involving a combination of thermodynamics, evolutionary dynamics, and game theory.

http://en.wikipedia.org/wiki/Olduvai_theory

For this to be an explanation it would have to be that this "great filter" is so hard to avoid that someone escapes it maybe once per few thousand galaxies per many billions of years.


>We are simulated.

Actually there is a way to tell if the world you're living in is not a simulation. Our world fails this test.


What test?


If these civilisations find some way to communicate or interact at all you can't treat them like independent variables.


Why does everyone assume that if life has existed on another planet for a billion or two years, it must necessarily be similar to life on our planet and be intelligent with some sort of civilization? Why could it not be a planet filled with brainless jellyfish and green algae?

People forget that our planet has been through several catastrophic events that happened at certain times in our planetary evolution, and on other planets those events did not happen, or happened at different points in their evolution, or those events had a more severe impact. Things like the snowball earth phase, and the comet that triggered the die off of most dinosaurs. Maybe most planets are inhabited by symbiotic colonies of advanced trilobites 20 meters long crawling the ocean floor eating the abundant sponges. Have a look at the wierd and wonderful pre-cambrian life forms that somehow combined to create the kind of animalia that we know today. What triggered that? And earlier, what triggered the abundant bacterial mats to start forming mobile colonies?

Sure, life is everywhere in the universe but the trajectory that life took on earth will be exceedingly rare and we may never encounter another such planet even if we develop advanced star travel.


> Why could it not be a planet filled with brainless jellyfish and green algae?

It could be even worse. Maybe we're not finding "life" because the only thing we have to compare to is life on Earth. Maybe there is life at different physical / time scales that we completely miss. Maybe what we call life, and specially intelligent life, is nothing special at all.

I find amusing that the general expectation is to find slightly different humans, with civilizations and communication and interstellar ships.


We should take your idea and push it farther: We're not looking for life.

If we found an advanced civilization of intelligent robots, would we shrug and say "too bad they're not alive?" Of course not. So it's not life we hope to find.


Part of the Drake equation is multiplying by the probability that intelligent life evolves. Of course we only have one data point, but it seems like intelligence is a pretty good response to many evolutionary pressures and so is likely to come about over time.

Of course, this depends on how frequent you think intelligence is. I think most people assume it's very frequent.


Why does everyone assume that...

They don't. They really don't. Do you honestly think you're the first person to ever think of this?


The question is pretty specifically about intelligent aliens. SETI, all of that stuff.


What if it's easier to build a utopia than a starship?

We already have way more money going into entertainment than into space exploration, it's not that hard to imagine that all sentient species eventually learn how to hack themselves into permanent happiness, and then conclude they have no reason to risk death on the final frontier.


A lot of human, throught humanity's history, had the material means to live a pretty pleasant, labor-free life, and yet chose a different path, away from hedonism. I suppose this will still be true many centuries from now.


Pretty much any organism that manages to develop the intelligence to build a starship will have a long history of evolution. Their mindset will presumably be guided by ancient evolutionary pressures. For us humans, we're partially motivated by a desire to explore and understand our surroundings. I think it's realistic to assume that at least some subset of aliens should be motivated by the same exploration drive.


What is the probability of such a utopian society going its entire existence without at least one group of individuals with the resources to go out into the universe pulling the trigger on the decision to risk their lives?

This ofcourse requires some projection of our ideas of happiness onto unknown alien beings, but then why not also project boredom? If anything, we have seen that nothing in nature really stays the same. It is ever changing and evolving.


When I predict that VR will trump reality I never mean to imply a virtual happy Utopia or that such a thing was inevitable. Our future might be a virtual dystopia for all I know, but virtual reality is my bet where most intelligent beings end up going. I think virtual worlds > reality would explain the Fermi paradox nicely.


So religious conservatives who don't like VR will be the ones to go into space, or whatever you'd like to imagine. Just by sheer probability there should be at least a few individuals who don't end up sticking around the sun.


Interstellar probes will get to be pretty cheap with sufficient economic growth. We should be able to easily afford >0.1c probes in 100 years or so on our current economic trajectory. And if our civilization advances for another 1000 years they'll be a piece of cake.

If those probes are Von Neumann machines they can spread throughout the entire galaxy in as little as a few million years. That's the crux of the Fermi Paradox - on galactic timescales any sufficiently advanced civilization should be able to expand its presence to the entire galaxy pretty easily and quickly.


Enjoying the virtual reality world they made, which is probably better than the real world. If you are smart enough to create a virtual world in which you can do almost anything you wanted, why would you give two shits about the real world.

Modern day gaming is the beginning of something much more significant in my opinion.


Because, for some reason, people (myself included) see some value in the idea of legitimate experiences over fabricated ones, although I'm not sure why. If you could be placed in a virtual reality, and not be aware you were in one, would you do it? As much as I would like to live in a perfect world, it's hard to say that I would. It just feels wrong. There's no unknowns. It's not an adventure.

Furthermore, perhaps there's value in things going wrong, and taking risks? I mean, sadness is necessary to happiness. In Brave New World, to create a Utopia free of negative emotions, it is necessary to remove sources of misery- relationships, family, and so on, because when you lose a lover or family, you are miserable. How could you have a perfect reality without these things? No family and no relationships in the first place? Immortality?

But then, perhaps happiness is only relative as well? If nothing ever went "wrong" in your virtual reality, would you really ever feel happy?

Interesting psychological and philosophical questions.


That may be true for some (many? most?) people, I could think of a couple of reasons:

a) Desire to explore nature's imagination instead of that of another human or AI. Perhaps we never hit a limit of computation, but there is an entire expanding, constantly growing in complexity universe out there to understand!

b) Even with artificial penalties, I doubt any virtual world could carry the same perceived risk as going out into the real world and risking getting eaten by a black hole or burned by an exploding supernova (assuming of course, you knew of/could tell the difference).


In the future, I think that even when we end up interacting with the real world we'll have a virtual one mapped over it, ala alternate reality stuff. Check out Rainbows End for what I mean there.

We can't stop interacting with the real world, but I imagine in the future most people wont. Current boredom is a reflection of our current technology and creative state in virtual worlds, not indicative of what the future will hold, it's only going to get better and while nature is amazing is so many ways human imagination trumps it. Whenever we do see something new we take it and add to it.


Human imagination cannot "trump" billions of years of random interaction of an untold amount of matter and the pressures of natural selection on self replicating organisms. The natural world may not have such high a density of activity as any created virtual world, and so it is different, but the universe makes up for its relative homogeneity by being big. Very, very big. So big that we can do no more than helplessly invent the exponent to help us cope with the size of it all.

Until we have the computational ability to simulate all possible permutations of the universe there will always be much to explore because no matter what technology you create, its own creativity is bound by the culture which gave birth to it. If intelligent life and advanced civilizations are even remotely likely, there will be many different forms of imaginations and virtual worlds created around the universe, each born of a distinctly different culture or artificial intelligence shaped by a distinctly different history (unless there is a global optimum towards which all greater intelligences converge on, essentially a global optimum for natural selection).

If you were born on earth and learned an earth language as your first, how do you come up with a language that is entirely uninfluenced by the culture you grew up in, a brand new protolanguage? How do you even confirm that anything you created is so new that it stands entirely outside of your culture's previous ingrained assumptions and interpretation of reality? If your imagination (and thus the collective imagination of the civilization) is bounded, as it is by language, your education, etc., how do you know it can ever "trump" everything this big, big universe has to offer?


Gaming is fun until it bores you. I play from time to time and I certainly would not like to replace more of my life with games. I'm in it not for pleasures but to see what's next and to affect it.

Some individuals will remain active in the virtual society. Active and with lots of technical ability.


Because the real world has surprised for us (and them) to discover. In search of the unknown, humankind has discovered a lot...


https://www.google.ca/url?sa=t&rct=j&q=&esrc=s&source=web&cd...

Edit:

I'll add one to the above: it might be that there are enough hostile forces, or at least the possibility of enough hostile forces, to make every technologically capable civilization conclude to travel near the speed of light to protect themselves from relativistic bombs. (Objects going very close to the speed of light. Impossible to detect in time to deflect, a form of advanced weaponry.)

Each alien civilization sees that there are no observable civilizations and decides that the ones that have existed either died or fled into near-the-speed-of-light vehicles. They rationally conclude to do the same, at least while they advance their technology and search for life. The unfortunate part is that time goes by much faster for us than it does for them, (which negates the advantage that many early civilizations would have had).


I would say the highest probability is that we're in a zoo. We'd be pretty interesting to watch as a blossoming civilization.


Given that there are many stars that are far older than the Sun with Earth-like planets, this is not that far-fetched. We have already started setting aside regions of our own planet as nature preserves, so it's not hard to imagine someone incredibly more advanced than us reaching similar philosophical conclusions and doing so on a solar system or star cluster scale.

This might also involve an element of self-interest on their part. Perhaps intervention has been shown to produce dangerous results.


> Where Is Everybody?

That might not be the right question, or at least is isn't the only pertinent question. Other quesitons: "why can't we see the ones that are around now" and/or "what happened to the ones that aren't around now".

If we are detecting civilisations feom the RF output, then consider how quicly we went from no RF output to nearly blowing ourselves to bits. Many civilisations could have committed suicide in a short space of time too. Many millions of them could have shone breifly and vanished millions of years before we even started looking. That is a tad fatalistic: we haven't managed to wipe ourselves out even though we threatened it to an extent. But there is another good reason why an older civilisation would be difficult to detect: efficiency. As a civilisation's technology improves, unless they find an effectively unlimited energy source, it is likely that they will leak less and less out: communicating point-to-point methods most of the time rather than by broadcast, containing and reusing what would otherwise be waste products of enery production/use. Of course they would never be 100% efficient, but they only need to be efficient enough that by the time the side-effects of their activity reach us they are not descernable amongst the background noise from the stars, black holes and other parts of the cosmos.

Evidence of other life could be passing us by right now and our attmepts to detect it are simply insufficient, in fact the more civilisations there are out there the harder the problem could become: the signals from each would interfere making the attempt to spot any one signal amongst the background noise (in part natural noise and in part that from the other signals) that but harder.

It is all moot at the moment of course: unless they are on our doorstep, to the point where we couldn't miss them, meaningful communication in our lifetimes is very very unlikely.

Of course there are other equally possible explanations, such as us being in a simulation of sorts.


I find the argument that we're in a simulation rather compelling: http://io9.com/5799396/youre-living-in-a-computer-simulation...


I think you would enjoy Thomas Campbell's work :) https://www.youtube.com/watch?v=fT8LaMrn_MM


I really liked his definition of consciousness:

"Consciousness is the only thing that is fundamental. Everything else is derived from consciousness, including this physical reality."


Wow, really enjoyed reading the great thoughts on this thread.

Similar to what others have said, I think the spectrum of 'intelligence' might be exponentially larger than anything the human mind can comprehend at this point in our development.

Since we're at the top of our planet's bio-hierarchy I think we tend to marvel at our own cleverness, yet wonder 'Where are the others like us?"

If other lifeforms are around us, they don't necessarily have to attempt to contact us or make themselves known to us in a way we could understand. There are millions of microorganisms around you right now, but they could never 'contact' you or even observe you in any meaningful way.


"Now my own suspicion is that the Universe is not only queerer than we suppose, but queerer than we can suppose." [1]

[1]J. B. S. Haldane. Possible Worlds and Other Papers (1927), p. 286


Not long ago I read a fiction piece (linked here in HN)that would imagine the world (and universe) in 10^1, 10^2, 10^3, 10^4, 10^5, 10^6... years.

In this tale, Earth would have several species achieving intelligence, all of them failing on interestelar colonization, and the last one, the wisest, figured out from the basic physics knowledge they develop, that this kind of travel would be impossible.

This basic assumption is very strong for me. Even if one civilization can travel at light speed, the multiple civilizations on our universe right now could be at millions of years of distance one of other.



Personally I think civilizations tend to undergo a singularity or destroy themselves eventually and the exceptions to those two cases are rare enough that communication becomes exceptionally rare.


By singularity, you mean the creation of artificial intelligence?

If so, then shouldn't we be encountering these AIs?


No, they would become addicted to pleasure stimulus, their version of digital heroin and become "unproductive"


That is as depressing as it is plausible. Nice that its such a simple theory, but rings more true than any other.


Another possibility is that intelligent life is relatively common, but highly technological civilizations are rare. How would human civilization have panned out if we had not been lucky enough to discover huge, easily accessible reserves of petrochemicals? We might have continued to enjoy a population and standard of living comparable to the 1700s, but not progressed to become the energy intensive civilization we are today. One could argue that would not necessarily be a bad thing in the long run.

It's also worth remembering that for 99.9% of our existence as a species, we lived on a much smaller energy budget. So maybe that's the norm, and planets where Saudi Arabia scale reserves of free energy are just sitting there for the taking are quite rare. Then, of those that do, what percentage successfully make the transition to become long-term spacefaring civilizations?

For a good read on the Fermi paradox, be sure to check out David Brin's The Great Silence.


Any sufficiently advanced civilization will have encrypted communications, and thus their broadcasts will appear to be noise.


I posted this comment on an older thread about the same topic: "If radio signals is the best way for us to detect alien intelligent life, and vice-versa, aren't we doomed to keep quiet then? I mean, how long until we phase strong radio signals almost completely? I mean, has there been any growth in the quantity and power of radio signals since, say, the 80's? It's an honest question, since I don't know, but I see radio declining everywhere, except for, I guess, airplane and naval communication. What else am I missing here? Probably a whole lot, maybe someone could fill me/us in?"


A good overview of the "Great Filter" in the context of the Fermi Paradox: http://en.wikipedia.org/wiki/Great_Filter


My personal theory is that dark matter is the great filter. We can't see them because they've taken it to a whole another level.


I think the mostly likely reason we don't see evidence for intelligent life in the universe is simply because we don't realize how unlikely it is to evolve intelligence.

Maybe there are a lot more evolutionary paths life can take on a world than just something similar to what happened here on Earth. Maybe typically it's unlikely for life to evolve to become much more than plant-like life forms.

I'm sure there are species in the universe which have evolved intelligence but I think they're much rarer than we would assume here on our perfect example world, Earth.


"Now, everything we know about terrestrial life tells us that life has a natural tendency to expand into all available space."

At the same time, it makes sense that more advanced life will try to be more efficient with its use of resources. This is a lot easier to do when you're smaller. Perhaps, they would try to minimize their size, allowing them _expand_ into _smaller_ space.

I'm sure this thought has been considered (e.g., see Men in Black 1), but I felt like sharing it anyway.


There isn't a paradox. The universe is teeming with life.

I've always believed that there was no evidence for ETs and life out there. I thought it was fiction. Then I spent all of last year trying to find legitimate proof of their existence. I just kept my mind open yet skeptical and looked at all the evidence I could find and simply analyzed the data. I was shocked that my conclusion was that ETs exist, they have been visiting us for quite some time, and they are generally benevolent.

You don't have to believe anything I say, in fact I wouldn't want you to. All I can ask is that you also spend some legitimate effort doing your research. Here's something to start your path down the rabbit hole: https://www.youtube.com/watch?v=7vyVe-6YdUk


I believe we are it. That said, if there is alien life it could be at the same stage of industrial development that we are and it will be a long long long time before we meet.


"Page xx is not part of this book preview"

Sigh, I hate crippleware.

I do love this paradox though, it makes for enjoyable conversation over a bottle of wine with just about anyone.


The universe is teeming with intelligent mimes. They can't wait for us to gesture silently to them through the cosmic void. Oh, the horror.


Thank you, everyone! This is probably the best thread I've read on hacker news in years!


Reading their equivalent to HN.


I'll toss another one in:

What if net-positive-EROEI controlled fusion is impossible?

We have only succeeded in producing nuclear fusion in two ways: atomic bomb primers and net-negative-EROEI reactors. Atomic bombs are technically usable as space propulsion (Google Project Orion), but the max velocities reachable are only on the order of 4-8% the speed of light. At that rate, interstellar travel is severely curtailed to only the closest groups of stars. We're talking over a hundred years to Alpha Centauri if you leave time (and reserve extra mass) for acceleration and deceleration.

Net-positive-EROEI controllable fusion is the only power source I know of that could allow anything near practical interstellar flight, so if it's not possible for fundamental physical reasons I'd conclude that interstellar flight is either impossible or nearly so.

If net-positive-EROEI fusion is impossible you could get very large, very complex, and very long lived intelligences but they'd be confined to their own solar systems.

--

For completeness I'll throw in two more, though they're ones I often see discussed:

(1) They're here, and that's what (some) UFO sightings are. They choose not to make explicit contact for some reason that we are not aware of, and that all visitors have so far shared. This could include an altruistic prime directive (intervention may harm us) or a selfish prime directive (intervention has been shown in the past to produce dangerous results, like post-singularity medieval warrior kingdoms or Nazis). A second reason for lack of explicit contact might be extreme alien-ness. Perhaps they are making contact but are doing so in ways that are so goddamn bizarre that we do not recognize it or culturally process it as such. The UFO literature is full of really wacked-out tales. Maybe some of them are true?

http://www.ufoevidence.org/cases/case708.htm

Sounds like a joke, right? Or the guy was insane? But imagine a "post-singularity" (for lack of a better term) intelligence that is utterly alien trying to comprehend our TV transmissions and then trying to make contact. Might the attempt not look something like that? Like some kind of weird dada-ist staged imitation of scenes from "I Love Lucy" and "Father Knows Best" with a dash of "The Outer Limits"?

Might you not also choose an isolated subject for safety reasons? Like a farmer in a field?

Sometimes I wonder if the weirdest most "dada" UFO cases are the most compelling. I would not expect alien contact to look as rational and methodical as meetings between human cultures. We're talking about an intelligence from another biosphere here, or a machine intelligence built by intelligences from another biosphere. Their thoughts might not even be translatable into English outside of the most objective domains like mathematical physics. Consequently unless they staged an undeniably dramatic contact event, we might be likely to dismiss their attempts to communicate as episodes of madness on the part of witnesses.

(2) The theists are right. We are the special creations of (or evolution was guided by) a supreme being and are unique. This is actually a variation on the "we are living in a simulation" hypothesis when you think about it.


I'm pretty ignorant of these details, so: why do atomic bombs only take us to 8% of the speed of light? What happens if we're at 8% and explode a couple of more bombs?


Freeman Dyson did the math, and I am not a physicist. I am assuming some sort of mass/energy trade-off.

http://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsi...

He figured 133 years to Alpha Centauri but without carrying extra mass to slow down. I assume you'd have to double that at least if you carried bombs to decelerate.




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