Thread: Fermi Paradox

The Fermi Paradox: Modern estimates often place hundreds or thousands of intelligent civilizations among our galaxy's hundreds of billions of stars. So why are the airwaves silent?



But where's everyone else? Maybe...

There is no one else

Maybe we are the only or one of the only civilizations in this part of the galaxy. It's a disheartening thought, to me at least. There are a number of more specific scenarios. Just a couple:

Intelligent life is very rare in general. Maybe we vastly underestimate the obstacles keeping an intelligent civilization from evolving on a given planet.

Intelligent life is very rare in our neighborhood. Maybe for some reason our neighborhood is a rural one with few advanced civilizations around. Maybe everyone just got really unlucky with gamma ray bursts or something. Still, this leaves the question, if advanced life is common elsewhere in the galaxy, why haven't they sent us an army of von Neumann probes? Maybe the engineering behind them is just too damned hard. Maybe exploring the galaxy doesn't appeal to them (but you would expect it to appeal to at least one of them, if there were many).

There really are lots of aliens

But maybe they don't want to talk to us. Maybe we're in a zoo owned by a powerful race that tries very hard to keep us ignorant of what's going on elsewhere. Maybe all races just get addicted to extremely advanced forms of electronic entertainment and don't care about anything else.

The universe isn't real

Maybe we live in a computer or some other engineered system. In this case, of course, there might be no aliens or there might be lots of them, but the engineers for some reason want to keep us apart from them.

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Occam's Razor makes me tend to believe that our predictions about how common life is are simply way too optimistic. That seems like a simpler explanation than any I've heard that posit there being lots of aliens.

The "universe isn't real" possibility is an interesting one as well since it's difficult to imagine how likely or unlikely it is, though some disagree pretty compellingly.

Hmm very interesting indeed. I've been thinking about these things as well for quite a while. In my opinion it's an extension of an existential question. That doesn't make it any less interesting though!

Perhaps it's just very unlikely for a race to go galactic before killing themselves off. Maybe it's simply impossible travel between stars for some still unknown reason. Maybe our goverments are hiding the aliens for us. Who knows?

Nice thread!

The universe being a simulation (not being real) can be reasonably discounted by considering Occam's Razor. It has much too many assumptions behind it compared to the other options.

I would tend to gravitate more toward an explanation that claims interstellar travel or even communication is very difficult, resulting in a quiet sky.

Originally Posted by Descensus

The universe being a simulation (not being real) can be reasonably discounted by considering Occam's Razor. It has much too many assumptions behind it compared to the other options.

I would tend to gravitate more toward an explanation that claims interstellar travel or even communication is very difficult, resulting in a quiet sky.

I'm sorry, but how can occam's razor discredit a simulated world? At this very point in time, with what we can currently achieve with technology, we should be able to place people in a convincing simulated reality within the next 100 years.

Occam's razor is great for eliminating extremely unlikely explanations. This world being a simulation is not unlikely at all.

It is pretty simple. Stellar distances when measured in light years are crazy big. The Milky way is something like 100,000 LY across. Now radiowaves do not travel even that fast (close to light speed). We have been making large amounts of radio wave communications for only 100 years or so. For us to recieve another worlds radio waves they must have been transmitted in the past at roughly as many years ago as the distance in light years. Assuming in a straight line across the Milky way intelligent radio using life exists on 1000 worlds, it would only be the ones broadcasting at the right time we could hear. We would be undetectable to all of them except any within 100 light years, which may be roughly 1 or 2 if there are that many (and that is 1000 in a straight line, not in the galaxy)

Originally Posted by sivason

Now radiowaves do not travel even that fast (close to light speed).

Radio travels at exactly light speed. Not slower.

As to the question:

Even if intelligent life is fairly common, and you use liberal estimates in Drake's Equation, you're still only talking about hundreds to thousands of civilizations in the galaxy. There would still be an average separation measured in hundreds to thousands of lightyears, which ultimately means you need to be listening for hundreds of years to have a good chance of picking something up. And that's assuming you even know what you're listening for. So far, programs like SETI have been absolutely retarded in how they listen for radio. They're not even listening on the right frequencies. And that's assuming aliens won't figure out directional communication (like lasers), which is highly unlikely.

As for von Neumann probes, we aren't even remotely close to being able to determine if such a probe has landed on Earth. These probes could be composed of nanobots, or even DNA computers. To us, such advanced technology would appear little more than dust. Or even worse, our own DNA could be the probe itself. It is absolute hubris and, frankly, ignorance, to think that we are equipped to even ask a question such as "Fermi's Paradox".

Originally Posted by cmind

Radio travels at exactly light speed. Not slower.

It may not be important, but that is only true in a true vacuum. Space is far from a true vacuum.

Originally Posted by sivason

It may not be important, but that is only true in a true vacuum. Space is far from a true vacuum.

You're thinking of radio waves as being like light waves travelling through glass or something. That's not a good analogy. There aren't any materials that refract (in other words, slow down) radio waves nearly as much as visible light going through glass or water. It so happens that almost nothing in the universe really impedes radio that much. That's one of the reasons why much of modern astronomy is done in radio -- it passes through dust like it's not even there.

Originally Posted by Dthoughts

Interesting what you said about microbe evolving to attack certain species. Would be bizarre to find one attacking humans. If so, it would certainly, as you may have suggested ,would mean we are somehow distant relatives.

Well if you do the math, it turns out that on evolutionary timescales, you get a LOT of microbes being exchanged between Earth and Mars. And there was an epoch about 3 billion years ago when both planets had warm oceans. It's highly unlikely that life arose at exactly the same time on both planets. More likely is that life arose on one or the other first, then asteroid impacts ejected it to the other. It would only take a few million years for this to happen.

Originally Posted by cmind

Well if you do the math, it turns out that on evolutionary timescales, you get a LOT of microbes being exchanged between Earth and Mars. And there was an epoch about 3 billion years ago when both planets had warm oceans. It's highly unlikely that life arose at exactly the same time on both planets. More likely is that life arose on one or the other first, then asteroid impacts ejected it to the other. It would only take a few million years for this to happen.

The math is controversial.

Your implicit assertion that life ever existed on Mars is extremely controversial.

Personally I think another option is that civilization in this area of the milky way is evolving in a similar fashion. they would have invented the radio perhaps only at the same time as we did.

I don't believe that the large distances are a significant problem. The fact that our radio waves haven't travelled very far is not important. If life is common it would have been common a million of years ago, too—that's a cosmic blink of an eye—and that's plenty of time to send probes (von Neumann probes) to every corner of the galaxy, which seems like natural behaviour for intelligent life.

I'm also highly sceptical that such long-distance transportation is inherently impossible. Civilisation's only been around for a few thousand years and things have started moving extremely rapidly in the last few centuries. In that tiny blip of cosmic time we've been able to send the Voyager 1 probe, still functioning and communicating, outside of our solar system. Given millions of years more, I find it implausible that we'll never master the technology to send probes to neighbouring stars.

My pet solution to the Fermi paradox is the obvious one: life is very rare, and there's little if any intelligent life in the Milky Way. Anybody who doesn't at least accept this as a potential answer is, I think, being a little disingenuous and falling victim to wishful thinking. We have absolutely no idea how likely life is, nor how likely it is that life becomes intelligent. Abiogenesis is a particularly obvious bottleneck, because in current theories, it requires a self-replicating strand of genetic material to come into being by sheer chance. The smallest such molecule may be a hundred chemical units long: we have no idea. If so, life could be extremely unlikely.

We have absolutely no idea how likely life is, nor how likely it is that life becomes intelligent. Abiogenesis is a particularly obvious bottleneck, because in current theories, it requires a self-replicating strand of genetic material to come into being by sheer chance.

Imo, current theories are wrong.

This ted talk goes into that, it's the best format and the quickest to explain this concept; it basically shows chemical blobs considered lifeless showing basic signs of life. At the very least this amazing evidence may postulate that 'random' is an unlikely explanation for life since even chemicals show that they have the same needs. Not that it HAS to be strands of genetic material that arise, that could have been chance but life itself is at the very least subject to less than sheer chance because basic materials behave in the same way we do. They eat they fuck they multiply. Martin Hanczyc: The line between life and not-life | Talk Video | TED.com

Originally Posted by Dthoughts

Imo, current theories are wrong.

This ted talk goes into that, it's the best format and the quickest to explain this concept; it basically shows chemical blobs considered lifeless showing basic signs of life. At the very least this amazing evidence may postulate that 'random' is an unlikely explanation for life since even chemicals show that they have the same needs. Not that it HAS to be strands of genetic material that arise, that could have been chance but life itself is at the very least subject to less than sheer chance because basic materials behave in the same way we do. They eat they fuck they multiply. Martin Hanczyc: The line between life and not-life | Talk Video | TED.com

Thanks for the interesting video. But none of those blobs really showed all of the prerequisites for life: in particular, it doesn't look like there was any mechanism for heritability. If he'd demonstrated blobs which could copy themselves using materials in the environment, and also mutate and form variant strains which copied themselves, that would have been something. But as it stands, it seems that storing genetic information in a molecule is the only way to do this, so we're back to the RNA problem.

A second point: no matter what forms life can take, it's certainly a fact that the life we observe is based on heritability via information in genetic molecules, so a self-replicating RNA strand must have emerged at some time in the past. If there are other far simpler ways for complex life to emerge, the question is raised as to why the complex life we observe is of a vastly more unlikely variety. The vastly more likely forms of life should overwhelm RNA-based life. It seems to me that the only way to resolve this discrepancy, other than admitting a colossal coincidence, is that complex life only emerges due to processes like RNA replicators.

I agree with Denziloe in a way. I feel the chances of intelligent life is very low. Given however an infinite universe, I assume it does happen many times, just not as often as a show like Star Trek makes it appear. Later in Star Trek we find out that life was intentionally spread from world to world, rather than developing randomly. I imagine that it would be pretty natural for space fairing life to spread the seeds of life, if only by accident. However, in regions where this intentional seeding has not happened life may be very rare.

I am just guessing based on nothing, but I could picture there being less than 12 worlds in the Milky way with highly intelligent life at a point where they could use radio, and perhaps 0-3 with the ability to travel between stars at any reasonable rate. None of the broadcasts those imagined 12 cultures make now would enter into the picture for perhaps thousands of years. We would be looking for broadcasts made long ago. I agree the chance of this was the same long ago as now. However, what is the viable life span of an industrialized culture. We have been industrialized perhaps 300 years and are starting to see clear risks, such as starvation, warming, nuclear and so on, plus realizing natural risks, such as gamma ray bursts and frequent super-volcanoes. The point is that the culture may cease to be industrialized at some point due to disaster. So if say a culture broadcast for 2000 years and did so 80,000 years ago, we would miss it unless they were located almost exactly as far away from us in the Milky way as it is possible to be. Then after traveling across the entire galaxy for 80K years, we would have to be in the radiowave path in a time frame stretching only 2.5% of the time it took to travel here. Radio waves from longer ago than that would not matter as they would have passed us.

Next, how degraded would the signal be after traveling so far? Space is not a vacuum as once thought. It is full of high energy particles and dust. I do not get good reception even twenty miles away from the nearest broadcast tower.

The final thought I have is that perhaps advanced cultures do not relie much on radio waves, replacing it fairly quickly with fiber optic cables and other advanced techs.

One nice thing for those of us who like to fantasize. Even if we say intelligent life is overwhelmingly rare, we know it can happen. If we say it happened 1 time in a system with 100+ billion stars and give odds of 1 intelligent culture per 100+ billion stars, we have 100+ billion cultures existing in the known galaxy. Crazy stuff.

As an unrelated side note, one of the papers I read for my Invasion Ecology class was about the effects of invasive microbes. It included an aside about how humans will have to be careful in the future as we begin to explore other planets because we may introduce microbes to the ecosystems in our solar system.

I understood the point, though it was funny that the author assumed there are even ecosystems on other planets/moons to begin with. Aside from Mars, the only real places where there could be ecosystems seem to be below the surface of some of Jupiter's moons. I suppose you could make a case for extremophiles living on Venus or something too.

Well we certainly can be careful when going to one of Jupiter's moons and come back (unlikely at this point but we may at some). There's the possibility of microbes actually already here that have come from asteroids. We've been fine! ^^

Yes, panspermia blows fears of microbe cross-contamination out of the water. Also, as Zubrin has pointed out in Case for Mars, microbes evolve to specifically attack certain species. As he said, humans don't get dutch elm disease and trees don't get the flu. Even more bizarre would be a Martian microbe infecting any species on Earth, or vice versa, assuming that we're not all related anyway (back to panspermia).

microbes evolve to specifically attack certain species As he said, humans don't get dutch elm disease and trees don't get the flu. Even more bizarre would be a Martian microbe infecting any species on Earth, or vice versa, assuming that we're not all related anyway (back to panspermia).

Interesting what you said about microbe evolving to attack certain species. Would be bizarre to find one attacking humans. If so, it would certainly, as you may have suggested ,would mean we are somehow distant relatives.

He's likely talking about transportation of life via rocks blasted off the planet of one surface and landing on another -- if you do the math you find that many of these events will take place over evolutionary time scales. Of course, it's not really an issue of mathematics; it's an issue of science. Such rocks are subjected to huge forces and temperatures, and there is simply no consensus on whether life could survive those conditions.

The tartigrade could survive for a period of time. From mars to earth is quite feasible. It seems to be specifically evolved to live in space. I see no other reason for an organism to evolve a condition to withstand UV-rays, just above 0 temperatures, no oxygen etc. for possibly decades. It's insane. But sane for a space-traveler. Not a microbe though. Yea im having loads of fun thinking about this

Panspermia isn't controversial. I've heard of experiments showing that bacteria can survive the trip.

Well that sorted that out. An uncited experiment of vague description.

You refer to "the trip". Does that just refer to surviving the conditions of outer space? Or did they actually subject the bacteria to the intense conditions involved in blasting a piece of rock off the surface of a planet?

Originally Posted by Denziloe

Well that sorted that out. An uncited experiment of vague description.

You refer to "the trip". Does that just refer to surviving the conditions of outer space? Or did they actually subject the bacteria to the intense conditions involved in blasting a piece of rock off the surface of a planet?

Panspermia - Wikipedia, the free encyclopedia

Read to your heart's content. This was controversial 10 years ago, but it's really not controversial today. It's really more of a question of if it did happen, not if it can happen.

Anyone interested in the Fermi Paradox will enjoy this interactive visualization, which allows you to tweak the parameters of the Drake Equation and calculate the number of civilizations in our galaxy capable of communication.


The most interesting perspective related to the Fermi Paradox that I've ever come across has to be this article by Nick Bostrom. To summarize very briefly, Nick argues that if we find life on Mars, or some other planet, this would be very bad news for the human race, as evidence of the distinct emergence of life elsewhere in our solar system would suggest that life is not rare at all in our galaxy, which in turn suggests that the asnwer to the Fermi Paradox probably has something to do with advanced civilzations inevitably destroying themselves before they develop the technology to traverse the galaxy.