The conclusion of this paper is, paraphrasing, "We should stop using point estimates for what should be distributions. When we do that, we get much lower bounds and have a better chance at being more precise, whether or not we are alone." It opens up avenues for more questions, which is the correct stance given how little we know.
Ecosystems are limited by the availability of water, not sunlight. Also there are more "habitable" places in the universe which are underground oceans (the default condition outside the frost line) as opposed to a tiny fraction of rock worlds which have to parametrically fine tuned to have water -- ex. there are 10-20 worlds that have underground oceans in our own solar system.
Why would a spacefaring civilization care about dry worlds inside the frost line? The most absurd thing about "Battle: Los Angeles" is not that aliens would come to Los Angeles (as opposed to Detroit) to steal water, but that they would come to a planet which has a thin layer on the surface as opposed to being just a run-of-the-mill dwarf planet or asteroid or comet or whatever you call it that is closer to 50% water.
If civilizations of the dark had deuterium fusion they might see very little reason to mess around with the puny resources to be found close to a star. It's entirely plausible that a generation "starship" could live off the land and hop from comet to comet to the next star in 10,000 years but probably the crew would lose interest long before the first millenium.
> The most absurd thing about "Battle: Los Angeles" is not that aliens would come to Los Angeles (as opposed to Detroit) to steal water,
Hey, they landed near all major coastal cities; the movie was just following one group of soldiers fighting off one part of the invasion force.
> but that they would come to a planet which has a thin layer on the surface as opposed to being just a run-of-the-mill dwarf planet or asteroid or comet or whatever you call it that is closer to 50% water.
Fair enough.
Disclaimer: I really liked the movie and wish there was a sequel made.
EDIT: My guess would be that the alien military tech was running off water (probably hydrogen/oxygen), so they started the invasion on the coasts to have essentially unlimited supply of water, but the actual purpose for the invasion was something else entirely. The "aliens need our water" hypothesis was AFAIR proposed by some talking head in the movie, not stated as in-universe fact.
I'm going to repost the same comment I made on Reddit:
This is quite interesting. It certainly sounds like this does dissolve the Fermi paradox, as they say. However, I think the key idea in this paper is actually not what the authors say it is. They say the key idea is taking account of all our uncertainty rather than using point estimates. I think the key idea is actually realizing that the Drake equation and the Fermi observation don't conflict because they're answering different questions.
That is to say: Where does this use of point estimates come from? Well, the Drake equation gives (under the assumption that certain things are uncorrelated) the expected number of civilizations we should expect to detect. Here's the thing -- if we grant the uncorrelatedness assumption (as the authors do), the use of point estimates is entirely valid for that purpose; summarizing one's uncertainty into point estimates will not alter the result.
The thing is that the authors here have realized, it seems to me, that the expected value is fundamentally the wrong calculation for purposes of considering the Fermi observation. Sure, maybe the expected value is high -- but why would that conflict with our seeing nothing? The right question to ask, in terms of the Fermi observation, is not, what is the expected number of civilizations we would see, but rather, what is the probability we would see any number more than zero?
They then note that -- taking into account all our uncertainty, as they say -- while the expected number may be high, this probability is actually quite low, and therefore does not conflict with the Fermi observation. But to my mind the key idea here isn't taking into account all our uncertainty, but asking about P(N>0) rather than E(N) in the first place, realizing that it's really P(N>0) and not E(N) that's the relevant question. It's only that switch from E(N) to P(N>0) that necessitates the taking into account of all our uncertainty, after all!
[Note afterward: Over on Reddit, hxka points out that that should be P(N>1), not P(N>0). Or really it should be P(N>1|N>0)...]
I have trouble calling it a paradox, because there is nothing that needs explaining in my view. Just throw in the fact that known fudge factors are important, and throw in the fact that there are more fudge factors that we don't know.
For example the traditional Drake equation doesn't include as a major factor "large moon that stabilizes the axial tilt over evolutionary time". And yet that seems to be needed and at least somewhat rare.
The traditional Drake equation doesn't include as a major factor "life not wiped out by a supernova over evolutionary time". And yet per http://earthsky.org/astronomy-essentials/supernove-distance there are estimates that this might happen on average once per 15 million years. From the Cambrian explosion to the present is around 540 million years. The odds of that forbearance is on the order of 7 billion to 1 against. How much does THAT change the Drake equation?
It doesn't have to include these specifics. They are just sub-factors contributing to higher level factors.
Your first is covered by "fl, the fraction of those planets that actually develop life", and your second is covered by "fi, the fraction of planets bearing life on which intelligent, civilized life, has developed".
What you are saying seems to be the same as OP. It's not a paradox because the chances are insignificant, so we are indeed alone.
I agree, I also can't see a paradox in terms of nature. And I would like to add an aspect of sociology (sociology is rarely discussed at this topic):
Given mankind's industrialization period and decline of the ecosystem is normal it takes longer to get to an exoplanet than to ruin it. - So, what interstellar space travel really would be is this: The living mankind on Earth gives up itself and its home planet to spread the genes of those who plan its demise.
http://www.hashsign.eu/html/blog/dominance/hadfield-hawking-...
My answer to the Fermi Paradox is this: These bastards shouldn't get away with it.
It's "papers" like this by people that are either clueless or malicious that make everyone pine for the pre-arxiv days.
Everyone considered this option. From the very first day the paradox was posed. We don't know the parameters well, it's within our margin of error that no one else is out there, so it's an option. This is such an absurd claim to take as your own that it's literally on the wikipedia page!
It's also extremely shortsighted in order to get media attention. This resolves nothing about the paradox. What about the universe prevents other intelligent species from existing nearby? Sure, it's within our margin of error, but where is this coming from? Too few planets, too little abiogenesis, etc? Many factors or a single one? Is our existence simply a consequence of the fact that we're here therefore the dice must have landed well for us? Or is there something fairly unique about our solar system / planet / species / etc.
That's the real scientific question that keeps people up at night.
I dunno, I kind of doubt that Eric Drexler is clueless or malicious. Maybe if you read the paper and understood their approach you'd have less of a knee-jerk reaction. They are arguing (as pointed out in comments elsewhere) that the math on probabilities should be using distributions, and this is what they do, and they go on to show that the resulting probabilities are far, far lower than the simplistic Drake equation would suggest.
Can you point to a single person making the point previously that even small amounts of uncertainty in the distribution of each variable in the Drake equation often implies a small or near-zero number of ETI even when the best mean point-estimate of the distribution for each variable, when multiplied together, predicts a large mean number of ETIs?
Agreed. This is just picking parameters consistent with no detection of extraterrestrial civilizations. The point of the Fermi paradox is that it's a stretch to assume such parameters. It's not prediction about extraterrestrial civilizations collapsing or whatever. It's just an alternative to consider. And perhaps a warning about shouting at the Universe. Although it's probably too late to fret too much about that.
The paper just says that Fermi estimation method is not applicable in this case. It does not say that there is no life, it says that is not the right way to estimate life existence. You can as well flip a coin, and then be amazed that aliens do not turn up when you guess heads right.
The most interesting option (danger: my dumbass opinions ahead) for why there's no other communicating species in radio range is whether there's a great filter right under our nose.
If we can ever prove that there's plenty of planets and plenty of abiogenesis and plenty of multicellular things out there that just don't know how to make radio waves, then either the leap to technology is exceedingly rare or we are in very big trouble very soon. I could see that keeping some people up at night.
Of course it could just be that, like us, other technological beings don't constantly broadcast super-directional radio transmissions at super-high power into random areas of space. We sent the Arecibo message a couple times for a few minutes, but it was really not enough to ever hope it got noticed by anyone out there. Even if space is bursting with intelligent life. Not even close. Cute project, though. Why do we expect more from others?
There was once a fairly mature plan, back in the 60s I believe, when nukes were still all the rage and people were discussing lots of exciting ways to use them for space exploration, wherein some physicist calculated how much power you'd need to make meaningful, intelligible radio contact a few stars over using an omnidirectional radio source. It involved setting off lots of nuclear bombs somewhere around Jupiter's orbit, in fact modulating the detonations and using the EMP as the signal. Those are the extreme methods needed get a signal out there up and over the noise of our own star, to defeat outrageous inverse square losses, to have it even barely intelligible at a very low baud rate a few light years away. Have we ever actually done that, even once? No.
So that should also tell you that nobody is listening to our old TV broadcasts and it's no surprise we aren't able to pick up anyone else's. No sane technological race is going to do an omnidirectional burst of communications meant for local use at such an enormous magnitude of power. It would be wasteful and destructive. Directed, focused transmissions only reach a billionth of the sky, so that has its own odds against it. SETI is a highly optimistic program considering the physics at work here.
The other argument for Fermi's paradox and why, if there are intelligent beings out there, we should know about it: If there's an advanced race even a couple million years ahead of us--just a blink of an eye in astronomical terms--they should have proliferated through the whole galaxy by now. We wouldn't be listening to their broadcasts, we would be them. Even discounting how unlikely it is that any race will ever be able to get to another star, this assumes that life (or Von Neumann machines) will spread and replicate endlessly, until they fill an extremely large space and convert an astronomically large amount of mass into themselves. We don't really see that with life we have on Earth. Most of our biome is still matter which is not life, and it's been here for billions of years. I don't understand the assumption that life will spread infinitely instead of staking out a reasonably large area that is barely manageable and then cull down, as life does here in our data set.
Even if there's a lot of technological species out there, and they're broadcasting with rational amounts of power, and they've expanded to cover rational amounts of space, it's still no surprise that we haven't found one yet. It's almost impossible to keep in mind just how big it all is. We also haven't been searching exhaustively or for a very long period of time. Would an alien SETI comparable to ours be able to detect our own transmissions? It's actually really unlikely.
How can we be expected to take seriously a probability estimate of life being "out there"? Only 10 years ago we discovered how many Earth-like planets are likely in our galaxy (I didn't see this aspect mentioned in the paper...), and they are also calculating a probability of abiogenesis (emergence of life), which, while I'm not an expert, seems highly speculative.
Why can't you estimate probability of something speculative? Of course it must be speculative if you're talking probabilities; otherwise you'd just know if the life is out there or not.
If the assumptions are very speculative, you just end up with very wide probability distributions, which is exactly what the paper argues for.
The reasoning seem to be "as we don't have enough data, lets conclude whatever I want".
The Fermi paradox assumes that if there are aliens more advanced than us somewhere for a long time, they should be here by now. Maybe more advanced technology enables interstellar travel (maybe not, maybe is not practical at all), maybe they may not have all our motivations (expansion, technological advancement in our own focus, exponential growth, etc), maybe they don't want to expand or announce themselves because they went cyber or try to pass unnoticed in the dark forest, or things that we can't even imagine yet, as we are not advanced enough.
We just don't have enough data to give a meaningful answer. And maybe never will. The only way to decide if we are alone in the universe or not is actually finding someone else. But with so much outside our physical or practical line of sight we can't just say that there is no one else because we didn't see anything.
When talking about the Fermi Paradox it's not about what this or that extra-terrestrial civilization might do. It's about what none of them is doing.
When you say "maybe they don't want to expand", if you want this to explain the paradox, you actually mean "none of them want to expand". Because if just one did, we would see it.
The thesis of the article is not "lets conclude whatever I want"
The foundational assumption is that (a) historically people have just picked the values for the Drake Equation that "felt right", and this is wrong, biased, and stupid, and (b) we should not be surprised if the Drake parameters fall in any order of magnitude. So let's Monte Carlo in a log-scaled distribution (roughly). Thus, given what we actually do know, median civilizations per galaxy is 0.32, average is 27 million.
Interestingly, this suggests that optimistic Drake Equation parameters must be wrong, lest they create an empirically impossibly-populated galaxy.
>Maybe more advanced technology enables interstellar travel (maybe not, maybe is not practical at all)
We have practical interstellar travel today if you don't artificially constrain your thinking to sending blobs of mostly water with lifespans measured in decades.
I would rephrase the question as: What are reasonable bounds on the number of intelligent civilizations, given that we have observed exactly one in the archeological record of our own planet, and no others elsewhere with current technology?
So, tiny sliver of time over billions of years, and communications technology that only reaches to a few nearby stars.
Trying to use probability of certain chemistry is, I think, highly subject to errors and failure to consider some alternative possibilities.
Life itself, however, is a totally different equation because it’s nearly as old as the earth. This might suggest that there is a lot of it out there.
In my opinion, takling the ET existence using the drake equation is not efficient because it boils down to estimate or guessing values.
I favor the following reasonning. For simplification, let consider the universe as homogene. Now, let p be the probability that life emerges in one unit of time and space. (1-p) is the probability that life does not emerge in the unit of volume and space.
If v is the number of volume units in the universe and t the age of the universe in unit of time, then the probability that life never emerges in the universe is (1-p)^(v * t). If p is bigger than zero, this probability will tend to 0 with a growing v and t, regardless of the magnitude of p. This always converges to 0. Soon or later, life will emerge in the universe as long as it can emerge spontaneously.
What is the probaility that our solar system is the only place in the universe where life emerged. Let s be the volume of our solar system. That probability is (1-p)^((v-s) * t). Since s is very small relative to v, that probability is very close to the above probability. And with growing v and t this probability tend to zero. In other words the probability that life emerges elsewere in the universe after removing the volume of our solar system is not much affected. It still tends toward 1.
This should give you the idea. The only unknown variable is p. But even if we don't know it's value, we can draw two important conclusions from this. 1) it doesn't matter how small p is, soon or later life will emerge. 2) the probability that we are alone in the universe is tending toward 0 with increasing t and v.
Could we be the most advanced ? Why discarding the ufological data ? It's time this non-sense and ostrich attitude stops.
If the argument stated above is correct, there is an awful waste of space. (Thanks, Carl!)
There is nothing in physical law to suggest that here is substantially different from anywhere else in the universe. To believe that here is manifestly different from every other place in the universe is a really surprising claim.
First, we know with absolute certainty that here is substantially different from anywhere else: we know there's life here, we haven't found life anywhere else. (And the null hypothesis is that we haven't found it because it doesn't exist.)
Second, it's a waste of space only if 1) it was created on purpose and 2) the purpose wasn't "to allow us space to expand". If either of those is false, I don't see how it can be called "a waste of space".
expectation that the universe should be teeming with >intelligent life<.
It's only a paradox if you're capable of entertaining such an expectation. Based on my life experience, I'd estimate the probability is about the same as finding a bottle of my favorite drink sitting on the doorstep.
I feel like if aliens come they might keep themselves hidden, rather than announce their presence. If so, it could be Fermi was right, we just haven't seen the evidence of it yet, since the Fermi Paradox presupposes that their should be intelligent life and the we actually can point to evidence of it.
To other life forms humans look like H.R. Giger's xenomorph aliens from the movies.
We're obviously intelligent, yet we absolutely refuse to communicate with other life forms. we're not even interested in the possibility.
We consume other organisms with rapacious abandon, converting them into more of ourselves as fast as we can. We are strip-mining the oceans of protein, our chattel livestock out-mass all other land animals by several times, and still we consume. We clearcut forests leaving patterns visible from space.
We cover everything with asphalt and concrete to create huge sprawling nests that are inimical to life other than our own (and a few species that can live with us.) Again, this is clearly visible from space.
From orbit we look just like a disease.
There's a place in Washington (state), a lake, where the UFOs take off and land (underwater) and the cheeky fuckers will wave back at you from windows in the ships.
The time span of human civilization is too small to witness the emergence and extinction of intelligent civilization elsewhere. Universe is really very vast in terms of distance and time.
The Drake equation is the epitome of garbage in garbage out. Trying to draw a line using a single data point.
There was recent news from NASA about the discovery of organic molecules on Mars and the possibility of life there at some point in the past. Discovery that life once existed on Mars would blow up the assumptions in the Drake equation.
As for the Fermi paradox I'm still of the opinion that its solution is simple but depressing: Interstellar travel is so difficult that by the time you're capable of it you don't need it anymore, and even when you're capable of it you still don't get very far outside of your stellar neighborhood. Unlimited power systems, reactionless drives, and FTL travel (or even high-c travel) are depressingly impossible. And then the cold hand of entropy and the aggregate chance of disaster make it extremely dangerous to even attempt. Basically without Sci-Fi propulsion/power you end up traveling at an interstellar snail's pace, and the longer the trip the more likely it is that a random meteorite smashes through your vessel, or you simply run out of spare parts and materials to make them, and the amount of fuel you need to just keep the lights on becomes enormous.
If you can build a starship that can travel between solar systems with our current understanding of physics, then you can build orbital colonies for basically unlimited living space much much easier. For one, they can be powered by solar cells instead of needing to carry fuel. It's not like we are going to run out of raw materials either. Even restricting yourself to the belt the amount of material available would last basically indefinitely. Worst case you can start breaking up moons.
So even in a universe full of life everybody is alone. Especially if you think about how genetic algorithms tend to get hung up on local maxima, so lots of planets waste millions of years with dumb dinosaurs with no space program or radio telescopes.
How did you/they calculate that probability of being alone? Anybody who tries to slap some number on such things as the probability for life to emerge is dishonest at least.
Does anyone else find this question totally uninteresting? There's no discussion to be had about this paradox that doesn't devolve into an N=1 predictive model.
I find it interesting because if N=1, then we're an incredibly statistical fluke, and yet there's no reason to suppose that our solar system or planet is that much of an anomaly.
[+] [-] poppingtonic|7 years ago|reply
[+] [-] PaulHoule|7 years ago|reply
Why would a spacefaring civilization care about dry worlds inside the frost line? The most absurd thing about "Battle: Los Angeles" is not that aliens would come to Los Angeles (as opposed to Detroit) to steal water, but that they would come to a planet which has a thin layer on the surface as opposed to being just a run-of-the-mill dwarf planet or asteroid or comet or whatever you call it that is closer to 50% water.
If civilizations of the dark had deuterium fusion they might see very little reason to mess around with the puny resources to be found close to a star. It's entirely plausible that a generation "starship" could live off the land and hop from comet to comet to the next star in 10,000 years but probably the crew would lose interest long before the first millenium.
[+] [-] TeMPOraL|7 years ago|reply
Hey, they landed near all major coastal cities; the movie was just following one group of soldiers fighting off one part of the invasion force.
> but that they would come to a planet which has a thin layer on the surface as opposed to being just a run-of-the-mill dwarf planet or asteroid or comet or whatever you call it that is closer to 50% water.
Fair enough.
Disclaimer: I really liked the movie and wish there was a sequel made.
EDIT: My guess would be that the alien military tech was running off water (probably hydrogen/oxygen), so they started the invasion on the coasts to have essentially unlimited supply of water, but the actual purpose for the invasion was something else entirely. The "aliens need our water" hypothesis was AFAIR proposed by some talking head in the movie, not stated as in-universe fact.
[+] [-] woodandsteel|7 years ago|reply
[+] [-] Sniffnoy|7 years ago|reply
This is quite interesting. It certainly sounds like this does dissolve the Fermi paradox, as they say. However, I think the key idea in this paper is actually not what the authors say it is. They say the key idea is taking account of all our uncertainty rather than using point estimates. I think the key idea is actually realizing that the Drake equation and the Fermi observation don't conflict because they're answering different questions.
That is to say: Where does this use of point estimates come from? Well, the Drake equation gives (under the assumption that certain things are uncorrelated) the expected number of civilizations we should expect to detect. Here's the thing -- if we grant the uncorrelatedness assumption (as the authors do), the use of point estimates is entirely valid for that purpose; summarizing one's uncertainty into point estimates will not alter the result.
The thing is that the authors here have realized, it seems to me, that the expected value is fundamentally the wrong calculation for purposes of considering the Fermi observation. Sure, maybe the expected value is high -- but why would that conflict with our seeing nothing? The right question to ask, in terms of the Fermi observation, is not, what is the expected number of civilizations we would see, but rather, what is the probability we would see any number more than zero?
They then note that -- taking into account all our uncertainty, as they say -- while the expected number may be high, this probability is actually quite low, and therefore does not conflict with the Fermi observation. But to my mind the key idea here isn't taking into account all our uncertainty, but asking about P(N>0) rather than E(N) in the first place, realizing that it's really P(N>0) and not E(N) that's the relevant question. It's only that switch from E(N) to P(N>0) that necessitates the taking into account of all our uncertainty, after all!
[Note afterward: Over on Reddit, hxka points out that that should be P(N>1), not P(N>0). Or really it should be P(N>1|N>0)...]
[+] [-] btilly|7 years ago|reply
For example the traditional Drake equation doesn't include as a major factor "large moon that stabilizes the axial tilt over evolutionary time". And yet that seems to be needed and at least somewhat rare.
The traditional Drake equation doesn't include as a major factor "life not wiped out by a supernova over evolutionary time". And yet per http://earthsky.org/astronomy-essentials/supernove-distance there are estimates that this might happen on average once per 15 million years. From the Cambrian explosion to the present is around 540 million years. The odds of that forbearance is on the order of 7 billion to 1 against. How much does THAT change the Drake equation?
[+] [-] jobigoud|7 years ago|reply
Your first is covered by "fl, the fraction of those planets that actually develop life", and your second is covered by "fi, the fraction of planets bearing life on which intelligent, civilized life, has developed".
What you are saying seems to be the same as OP. It's not a paradox because the chances are insignificant, so we are indeed alone.
[+] [-] stephenwinter2|7 years ago|reply
[+] [-] light_hue_1|7 years ago|reply
Everyone considered this option. From the very first day the paradox was posed. We don't know the parameters well, it's within our margin of error that no one else is out there, so it's an option. This is such an absurd claim to take as your own that it's literally on the wikipedia page!
It's also extremely shortsighted in order to get media attention. This resolves nothing about the paradox. What about the universe prevents other intelligent species from existing nearby? Sure, it's within our margin of error, but where is this coming from? Too few planets, too little abiogenesis, etc? Many factors or a single one? Is our existence simply a consequence of the fact that we're here therefore the dice must have landed well for us? Or is there something fairly unique about our solar system / planet / species / etc.
That's the real scientific question that keeps people up at night.
[+] [-] titzer|7 years ago|reply
[+] [-] gwern|7 years ago|reply
[+] [-] mirimir|7 years ago|reply
[+] [-] jawns|7 years ago|reply
Confirmed: https://en.wikipedia.org/wiki/Fermi_paradox#Extraterrestrial...
[+] [-] Luc|7 years ago|reply
[+] [-] uniformlyrandom|7 years ago|reply
[+] [-] vertexFarm|7 years ago|reply
If we can ever prove that there's plenty of planets and plenty of abiogenesis and plenty of multicellular things out there that just don't know how to make radio waves, then either the leap to technology is exceedingly rare or we are in very big trouble very soon. I could see that keeping some people up at night.
Of course it could just be that, like us, other technological beings don't constantly broadcast super-directional radio transmissions at super-high power into random areas of space. We sent the Arecibo message a couple times for a few minutes, but it was really not enough to ever hope it got noticed by anyone out there. Even if space is bursting with intelligent life. Not even close. Cute project, though. Why do we expect more from others?
There was once a fairly mature plan, back in the 60s I believe, when nukes were still all the rage and people were discussing lots of exciting ways to use them for space exploration, wherein some physicist calculated how much power you'd need to make meaningful, intelligible radio contact a few stars over using an omnidirectional radio source. It involved setting off lots of nuclear bombs somewhere around Jupiter's orbit, in fact modulating the detonations and using the EMP as the signal. Those are the extreme methods needed get a signal out there up and over the noise of our own star, to defeat outrageous inverse square losses, to have it even barely intelligible at a very low baud rate a few light years away. Have we ever actually done that, even once? No.
So that should also tell you that nobody is listening to our old TV broadcasts and it's no surprise we aren't able to pick up anyone else's. No sane technological race is going to do an omnidirectional burst of communications meant for local use at such an enormous magnitude of power. It would be wasteful and destructive. Directed, focused transmissions only reach a billionth of the sky, so that has its own odds against it. SETI is a highly optimistic program considering the physics at work here.
The other argument for Fermi's paradox and why, if there are intelligent beings out there, we should know about it: If there's an advanced race even a couple million years ahead of us--just a blink of an eye in astronomical terms--they should have proliferated through the whole galaxy by now. We wouldn't be listening to their broadcasts, we would be them. Even discounting how unlikely it is that any race will ever be able to get to another star, this assumes that life (or Von Neumann machines) will spread and replicate endlessly, until they fill an extremely large space and convert an astronomically large amount of mass into themselves. We don't really see that with life we have on Earth. Most of our biome is still matter which is not life, and it's been here for billions of years. I don't understand the assumption that life will spread infinitely instead of staking out a reasonably large area that is barely manageable and then cull down, as life does here in our data set.
Even if there's a lot of technological species out there, and they're broadcasting with rational amounts of power, and they've expanded to cover rational amounts of space, it's still no surprise that we haven't found one yet. It's almost impossible to keep in mind just how big it all is. We also haven't been searching exhaustively or for a very long period of time. Would an alien SETI comparable to ours be able to detect our own transmissions? It's actually really unlikely.
[+] [-] unknown|7 years ago|reply
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[+] [-] not_a_moth|7 years ago|reply
[+] [-] Anderkent|7 years ago|reply
If the assumptions are very speculative, you just end up with very wide probability distributions, which is exactly what the paper argues for.
[+] [-] gmuslera|7 years ago|reply
The Fermi paradox assumes that if there are aliens more advanced than us somewhere for a long time, they should be here by now. Maybe more advanced technology enables interstellar travel (maybe not, maybe is not practical at all), maybe they may not have all our motivations (expansion, technological advancement in our own focus, exponential growth, etc), maybe they don't want to expand or announce themselves because they went cyber or try to pass unnoticed in the dark forest, or things that we can't even imagine yet, as we are not advanced enough.
We just don't have enough data to give a meaningful answer. And maybe never will. The only way to decide if we are alone in the universe or not is actually finding someone else. But with so much outside our physical or practical line of sight we can't just say that there is no one else because we didn't see anything.
[+] [-] jobigoud|7 years ago|reply
When you say "maybe they don't want to expand", if you want this to explain the paradox, you actually mean "none of them want to expand". Because if just one did, we would see it.
[+] [-] mechsquirrel|7 years ago|reply
The foundational assumption is that (a) historically people have just picked the values for the Drake Equation that "felt right", and this is wrong, biased, and stupid, and (b) we should not be surprised if the Drake parameters fall in any order of magnitude. So let's Monte Carlo in a log-scaled distribution (roughly). Thus, given what we actually do know, median civilizations per galaxy is 0.32, average is 27 million.
Interestingly, this suggests that optimistic Drake Equation parameters must be wrong, lest they create an empirically impossibly-populated galaxy.
[+] [-] sulam|7 years ago|reply
We have practical interstellar travel today if you don't artificially constrain your thinking to sending blobs of mostly water with lifespans measured in decades.
[+] [-] carry_bit|7 years ago|reply
[+] [-] jl2718|7 years ago|reply
So, tiny sliver of time over billions of years, and communications technology that only reaches to a few nearby stars.
Trying to use probability of certain chemistry is, I think, highly subject to errors and failure to consider some alternative possibilities.
Life itself, however, is a totally different equation because it’s nearly as old as the earth. This might suggest that there is a lot of it out there.
[+] [-] sbensu|7 years ago|reply
[1] http://rationallyspeakingpodcast.org/show/rs-203-stephen-web...
[+] [-] chmike|7 years ago|reply
I favor the following reasonning. For simplification, let consider the universe as homogene. Now, let p be the probability that life emerges in one unit of time and space. (1-p) is the probability that life does not emerge in the unit of volume and space.
If v is the number of volume units in the universe and t the age of the universe in unit of time, then the probability that life never emerges in the universe is (1-p)^(v * t). If p is bigger than zero, this probability will tend to 0 with a growing v and t, regardless of the magnitude of p. This always converges to 0. Soon or later, life will emerge in the universe as long as it can emerge spontaneously.
What is the probaility that our solar system is the only place in the universe where life emerged. Let s be the volume of our solar system. That probability is (1-p)^((v-s) * t). Since s is very small relative to v, that probability is very close to the above probability. And with growing v and t this probability tend to zero. In other words the probability that life emerges elsewere in the universe after removing the volume of our solar system is not much affected. It still tends toward 1.
This should give you the idea. The only unknown variable is p. But even if we don't know it's value, we can draw two important conclusions from this. 1) it doesn't matter how small p is, soon or later life will emerge. 2) the probability that we are alone in the universe is tending toward 0 with increasing t and v.
Could we be the most advanced ? Why discarding the ufological data ? It's time this non-sense and ostrich attitude stops.
[+] [-] ISL|7 years ago|reply
There is nothing in physical law to suggest that here is substantially different from anywhere else in the universe. To believe that here is manifestly different from every other place in the universe is a really surprising claim.
[+] [-] mdpopescu|7 years ago|reply
Second, it's a waste of space only if 1) it was created on purpose and 2) the purpose wasn't "to allow us space to expand". If either of those is false, I don't see how it can be called "a waste of space".
[+] [-] 8bitsrule|7 years ago|reply
It's only a paradox if you're capable of entertaining such an expectation. Based on my life experience, I'd estimate the probability is about the same as finding a bottle of my favorite drink sitting on the doorstep.
[+] [-] jackconnor|7 years ago|reply
[+] [-] carapace|7 years ago|reply
To other life forms humans look like H.R. Giger's xenomorph aliens from the movies.
We're obviously intelligent, yet we absolutely refuse to communicate with other life forms. we're not even interested in the possibility.
We consume other organisms with rapacious abandon, converting them into more of ourselves as fast as we can. We are strip-mining the oceans of protein, our chattel livestock out-mass all other land animals by several times, and still we consume. We clearcut forests leaving patterns visible from space.
We cover everything with asphalt and concrete to create huge sprawling nests that are inimical to life other than our own (and a few species that can live with us.) Again, this is clearly visible from space.
From orbit we look just like a disease.
There's a place in Washington (state), a lake, where the UFOs take off and land (underwater) and the cheeky fuckers will wave back at you from windows in the ships.
We're not alone. We just suck.
[+] [-] unknown|7 years ago|reply
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[+] [-] taylorswift_|7 years ago|reply
[+] [-] mchahn|7 years ago|reply
[+] [-] tachkotic|7 years ago|reply
[+] [-] jpm_sd|7 years ago|reply
[+] [-] jandrese|7 years ago|reply
There was recent news from NASA about the discovery of organic molecules on Mars and the possibility of life there at some point in the past. Discovery that life once existed on Mars would blow up the assumptions in the Drake equation.
As for the Fermi paradox I'm still of the opinion that its solution is simple but depressing: Interstellar travel is so difficult that by the time you're capable of it you don't need it anymore, and even when you're capable of it you still don't get very far outside of your stellar neighborhood. Unlimited power systems, reactionless drives, and FTL travel (or even high-c travel) are depressingly impossible. And then the cold hand of entropy and the aggregate chance of disaster make it extremely dangerous to even attempt. Basically without Sci-Fi propulsion/power you end up traveling at an interstellar snail's pace, and the longer the trip the more likely it is that a random meteorite smashes through your vessel, or you simply run out of spare parts and materials to make them, and the amount of fuel you need to just keep the lights on becomes enormous.
If you can build a starship that can travel between solar systems with our current understanding of physics, then you can build orbital colonies for basically unlimited living space much much easier. For one, they can be powered by solar cells instead of needing to carry fuel. It's not like we are going to run out of raw materials either. Even restricting yourself to the belt the amount of material available would last basically indefinitely. Worst case you can start breaking up moons.
So even in a universe full of life everybody is alone. Especially if you think about how genetic algorithms tend to get hung up on local maxima, so lots of planets waste millions of years with dumb dinosaurs with no space program or radio telescopes.
[+] [-] dosshell|7 years ago|reply
> we find a substantial probability that we are alone in our galaxy, and perhaps even in our observable universe (53%–99.6% and 39%–85% respectively).
> ’Where are they?’ — probably extremely far away, and quite possibly beyond the cosmological horizon and forever unreachable.
[+] [-] ssijak|7 years ago|reply
[+] [-] amelius|7 years ago|reply
... in the observable universe.
[+] [-] psychometry|7 years ago|reply
[+] [-] goatlover|7 years ago|reply
[+] [-] FreekNortier|7 years ago|reply