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This is a very optimistic view, but there are plenty of theories claiming otherwise. Check out the Fermi Paradox [1], or the Rare Earth Hypothesis [2] for a mor

This is a very optimistic view, but there are plenty of theories claiming otherwise. Check out the Fermi Paradox [1], or the Rare Earth Hypothesis [2] for a more detailed view on the problem. To be honest the easiest explanation for the Fermi Paradox is that we are indeed alone as an inteligent civilization. If we were just an average civilization there should be plenty of evidence of more advanced civilizations across the galaxy, because probabilistically they would be millions of years more advanced than us. [1] https://en.wikipedia.org/wiki/Fermi_paradox https://en.wikipedia.org/wiki/Fermi_paradox [2] https://en.wikipedia.org/wiki/Rare_Earth_hypothesis https://en.wikipedia.org/wiki/Rare_Earth_hypothesis

Razengan 8y ago
Honest question: Do we have the means to detect conclusive evidence of life on Earth itself from even "only" as far as, say, Pluto, without knowing exactly what to look for?
- adrianN 8y ago
  You'd be able to detect radio waves from Earth. We can still communicate with the Voyager probes that are further out. We probably can't detect life on Earth from Alpha Centauri with our current technology.
  - Razengan 8y ago
    > We can still communicate with the Voyager probes that are further out. This is what I mean by "knowing exactly what to look for." Can we place something at Pluto and have it listen to radio waves from the direction of Earth, and compare it to the background "noise" at that location? How different is it? How much of that perceived difference would be our own bias? How much evidence about life on Earth is available to our own instruments from this range? -> https://www.bing.com/images/search?q=Pale+Blue+Dot https://www.bing.com/images/search?q=Pale+Blue+Dot
    - simonh 8y ago
      That's a cosmically trivial distance. Yes we could absolutely detect vast amounts of transmissions at that range, and even figure out how to decode a lot of them. For example video transmissions clearly have a tabular data structure, pixel data structure, timing encoding, serial frames, etc. Theres no way they could be natural. You could even see differences over time as video standards evolve and update. That's just one example. Bear in mind in wartime we manage to extract useful meaningful data from deliberately obscured and encrypted data, so determining useful data from vast ranges and quantities of non-encrypted transmissions would be comparatively easy.
      - Razengan 8y ago
        > Bear in mind in wartime we manage to extract useful meaningful data from deliberately obscured and encrypted data Yes, but data created and encoded by other humans. We would likely not even know where to begin when encountering data (assuming we even recognized it as such) from beings who may perceive reality completely differently.
        patejam 8y ago
        99.9999999999999999% of radio waves we get from the rest of the universe is absolute garbage. There would be some kind of pattern with purposeful radio communications. Recognizing purposeful radio communication is a much easier task than interpreting the data. But we don't need to interpret the data to know it came from someone/something we should go and check out, because it could be intelligent life.
        ohyes 8y ago
        Maybe it’s encrypted.
    - adrianN 8y ago
      The Voyager probes emit less radiation than your typical cell phone, so the Megawatts of emissions we produce would be very bright on typical radio telescopes on Pluto, I presume.
- simonh 8y ago
  We can detect atmospheric water and oxygen[1] on planets round other stars, so yes. Although your last qualifier is flexible enough to kill almost any possible answer. [1] https://uanews.arizona.edu/story/oxygen-and-carbon-discovered-exoplanet-atmosphere-blowoff https://uanews.arizona.edu/story/oxygen-and-carbon-discovere...
  - adrianN 8y ago
    I wouldn't say that water and oxygen are conclusive evidence of life. Neither are organic compounds (space is full of them).
    - RosanaAnaDana 8y ago
      Neither is the detection of those elements requirements for life. We know for a fact that for 2 billion years our earth had very very low levels of oxygen, but was in-fact full of life.
- MichaelMoser123 8y ago
  If you have a species of intelligent squids then there will not be much of a radiation background - radio waves are no good in water. That would be a false negative.
bena 8y ago
I've never liked the Fermi paradox. It seems terribly contrived. It assumes way too much. That space colonization is inevitable and/or that strong AI is also inevitable. What if it's not? What if it's an intractable problem? What if technological advancement isn't exponential? What if it's more of an inverse tangent? A slow start, an explosive middle, then a long finish with an upper bound. We have absolutely no other examples to base any assumptions of technological societies on, so why do we get "space colonization" and "independently thinking machines" for free?
ChrisBland 8y ago
To the single cell organism; the worm looks to be advanced and complex. To the worm; the human looks to be advanced and complex. Its possible we are still way down on the intelligence chain and too dumb to realize that we are in fact the worm in the scope of the universe
- babuskov 8y ago
  > To the single cell organism; the worm looks to be advanced and complex. To the worm; the human looks to be advanced and complex. I don't think either of those is advanced enough to have a concept of anything "looking complex" to them. A cat or a dog would be a much better for comparison.
  - sandworm101 8y ago
    But we arent fundimentally more complex than the cat or dog. The only real difference is the relative size of various structures. We are both as complex as creatures come on this planet.
    - wallace_f 8y ago
      Probably there is some limiting factor to complexity, such as either the naivety to advertise existence, or the inevitably to halt creative destruction once we figure out how to not die.
    - JackFr 8y ago
      > We are both as complex as creatures come on this planet. Gaia says: Whatever, buddy. You're like a neuron comparing yourself to liver cells.
    - perl4ever 8y ago
      It is said that the wheat genome is five times the size of the human one...
- Rattled 8y ago
  A cell has no way to conceive of a worm, and worms probably can't conceive of humans. But they probably have some conception of birds, and birds can perceive humans. Where are our birds? As you go up the intelligence chain the ability to see beyond seems to increase, but we don't see anything beyond us.
gldalmaso 8y ago
Maybe the oldest and most advanced civilizations decided to go tribal. Maybe they are so advanced that they can hide their trail so belligerent civilizations like ours do not encounter them. I don't think the easiest explanation is to assume that there is any sort of naturally occurring event in the universe that is one of a kind, save maybe for the big bang.
SmellyGeekBoy 8y ago
There are civilisations on earth (uncontacted tribes) who are completely unaware of the existence of modern society. With this in mind your view seems incredibly naive.
- Razengan 8y ago
  Yes, https://en.wikipedia.org/wiki/Uncontacted_peoples https://en.wikipedia.org/wiki/Uncontacted_peoples And we collectively decided to leave them alone, ostensibly for their own good.
- mihaifm 8y ago
  True, but all these assumptions are probabilistic. What are the chances of us being one of those uncontacted tribes. We have found thousands of other tribes, leaving only a handful hidden. The probability of a tribe to remain hidden is almost 0. And this probability decreases more and more with time.
cthalupa 8y ago
There might simply be no way to travel at, or even near, and much less faster than, the speed of light, in which case the universe could be full of life that we will never contact or meet. Life might be rare enough that it's unlikely in any single galaxy.
- mihaifm 8y ago
  Even at very low speeds, a civilization with a 10 million year "head start" (which is nothing on the timescale of the universe) would be able to send autonomous robots across the galaxy. At least that what we would do if we had sufficient enough technology. This is essentially the paradox.
  - DmenshunlAnlsis 8y ago
    So many assumptions here. Maybe they’d be able to, but why would they want to? What’s the point of probing a galaxy that you can only ever explore below the speed of light, at the cost of ungodly amounts of energy and eons of time? Why wouldn’t that same civilization stick within 1-100 light years instead? There is only a paradox if an advanced civilization with high tech is so irrational that they can’t control their breeding and doesn’t care about time dilation and efficient use of resources. It also assumes that it’s safe to broadcast your presence to the whole galaxy that way. It assumes a lot of unproven ideas and then hand waves at a “sufficiently advanced” species that has only apparently enjoyed technological advancement rather than personal or social advancement. Maybe humans as we know them would spread unmanned probes across the galaxy for the sake of doing it, but I have doubts that humans capable of th feat would do it. I suspect we’d be wiser, or we’d be dead.
  - Razengan 8y ago
    That so-called paradox takes the following assumptions: • That it is possible for a region as large as even a single galaxy to ever be "full" of one species or their creations. • That anything can keep spreading indefinitely, and remain intact, not only across the gargantuan distances involved but also over potentially millions of years for other species to encounter them. • That intelligent life wants to keep spreading or exploring indefinitely. As opposed to, say, creating VR universes of its own and attaining contentment within them. • That there are only a few "directions" into which species or machines can spread across the universe, for them to run into each other. • That there are no "stabilizing" forces – natural or adversarial – which counter rampant expansion.
WilliamEdward 8y ago
That theory doesn't account for the fact that the laws of physics prevent anything from traveling faster than the speed of light. because our galaxy is 100000 lightyears long by itself, it would take 100000 years for an advanced civilization just to get to us let alone cross their own galaxies. It's highly possible other life doesn't exist but the reason we can't see them is because space is way larger than you think it is and takes a long time to travel across.
- elboru 8y ago
  It's easy to speculate when there are infinite "what-ifs". If AGI (artificial general intelligence) development is technically possible and if they're really able to recursively self-improve themselves to become semi-gods and if there are really N number of civilizations out there, then there should be N number of AGIs too, it would make sense that we should be able to see their traces of existence across the universe.
  - Razengan 8y ago
    This makes a lot of cherry-picked assumptions: https://news.ycombinator.com/item?id=17829840 https://news.ycombinator.com/item?id=17829840
- travisoneill1 8y ago
  Which is a very short amount of time for a species to be in existence. Alligators have been around for 2000x that amount of time. If you take a max speed of 0.01c which is possible with technology that we will probably have in the next 100 years (fusion power) that means the galaxy could be colonized in 10 million years. If 200 million years ago humans had evolved instead of alligators (can’t see any reason this is not possible on some alternate earth) then we could have colonized the galaxy 20 times over by now.
  - Razengan 8y ago
    "Unrestrained colonization just because we can" relies upon a lot of assumptions: https://news.ycombinator.com/item?id=17829840 https://news.ycombinator.com/item?id=17829840 For example, we could have begun building a base on the Moon by now if we wanted to, but we have decided not to.
MichaelMoser123 8y ago
The Fermi paradox assumes that there is infinite progress, what if going interstellar is just too hard? (Warp drive too hard and going such distances directly just impossible) What are the incentives to go interstellar once a species has colonised it's solar system?
- thatguy0900 8y ago
  The incentive would be to escape the eventual heat death of their sun or insure their race against any other solar system wide extinction event, I guess
  - MichaelMoser123 8y ago
    This assumes that the civilization would be able to prevail for an extremely long time.
amf12 8y ago
The universe is 13.8 Billion years old, so we can only observe the universe 13 Billion light years away. However the universe is practically infinite and much larger than the observable universe. It's not possible for us to detect a galaxy and a civilization (if it exists) in the said galaxy outside the observable range. Similarly, for the said civilization we lie outside that observable range and they can't detect us because nothing can travel faster than the speed of light. Now imagine, how huge the unobservable universe is. Probabilistically, it is quite possible for a civilization (or multiple) more or less advanced than us to exist far, far away, or may have existed some point in time. But none can detect each other. Its even possible for a civilization to exist in the spheres of observation of other civilizations but so far away that its almost impossible to make contact. 13.8 Billion years is not a long time on the scale of the universe, but it is also a long time on evolutionary scale for a civilization to have existed and have been extinct.

Razengan 8y ago

Honest question: Do we have the means to detect conclusive evidence of life on Earth itself from even "only" as far as, say, Pluto, without knowing exactly what to look for?

adrianN 8y ago
You'd be able to detect radio waves from Earth. We can still communicate with the Voyager probes that are further out. We probably can't detect life on Earth from Alpha Centauri with our current technology.
- Razengan 8y ago
  > We can still communicate with the Voyager probes that are further out. This is what I mean by "knowing exactly what to look for." Can we place something at Pluto and have it listen to radio waves from the direction of Earth, and compare it to the background "noise" at that location? How different is it? How much of that perceived difference would be our own bias? How much evidence about life on Earth is available to our own instruments from this range? -> https://www.bing.com/images/search?q=Pale+Blue+Dot https://www.bing.com/images/search?q=Pale+Blue+Dot
  - simonh 8y ago
    That's a cosmically trivial distance. Yes we could absolutely detect vast amounts of transmissions at that range, and even figure out how to decode a lot of them. For example video transmissions clearly have a tabular data structure, pixel data structure, timing encoding, serial frames, etc. Theres no way they could be natural. You could even see differences over time as video standards evolve and update. That's just one example. Bear in mind in wartime we manage to extract useful meaningful data from deliberately obscured and encrypted data, so determining useful data from vast ranges and quantities of non-encrypted transmissions would be comparatively easy.
    - Razengan 8y ago
      > Bear in mind in wartime we manage to extract useful meaningful data from deliberately obscured and encrypted data Yes, but data created and encoded by other humans. We would likely not even know where to begin when encountering data (assuming we even recognized it as such) from beings who may perceive reality completely differently.
      - patejam 8y ago
        99.9999999999999999% of radio waves we get from the rest of the universe is absolute garbage. There would be some kind of pattern with purposeful radio communications. Recognizing purposeful radio communication is a much easier task than interpreting the data. But we don't need to interpret the data to know it came from someone/something we should go and check out, because it could be intelligent life.
        ohyes 8y ago
        Maybe it’s encrypted.
  - adrianN 8y ago
    The Voyager probes emit less radiation than your typical cell phone, so the Megawatts of emissions we produce would be very bright on typical radio telescopes on Pluto, I presume.
simonh 8y ago
We can detect atmospheric water and oxygen[1] on planets round other stars, so yes. Although your last qualifier is flexible enough to kill almost any possible answer. [1] https://uanews.arizona.edu/story/oxygen-and-carbon-discovered-exoplanet-atmosphere-blowoff https://uanews.arizona.edu/story/oxygen-and-carbon-discovere...
- adrianN 8y ago
  I wouldn't say that water and oxygen are conclusive evidence of life. Neither are organic compounds (space is full of them).
  - RosanaAnaDana 8y ago
    Neither is the detection of those elements requirements for life. We know for a fact that for 2 billion years our earth had very very low levels of oxygen, but was in-fact full of life.
MichaelMoser123 8y ago
If you have a species of intelligent squids then there will not be much of a radiation background - radio waves are no good in water. That would be a false negative.

bena 8y ago

I've never liked the Fermi paradox. It seems terribly contrived. It assumes way too much. That space colonization is inevitable and/or that strong AI is also inevitable. What if it's not? What if it's an intractable problem? What if technological advancement isn't exponential? What if it's more of an inverse tangent? A slow start, an explosive middle, then a long finish with an upper bound. We have absolutely no other examples to base any assumptions of technological societies on, so why do we get "space colonization" and "independently thinking machines" for free?

ChrisBland 8y ago

To the single cell organism; the worm looks to be advanced and complex. To the worm; the human looks to be advanced and complex. Its possible we are still way down on the intelligence chain and too dumb to realize that we are in fact the worm in the scope of the universe

babuskov 8y ago
> To the single cell organism; the worm looks to be advanced and complex. To the worm; the human looks to be advanced and complex. I don't think either of those is advanced enough to have a concept of anything "looking complex" to them. A cat or a dog would be a much better for comparison.
- sandworm101 8y ago
  But we arent fundimentally more complex than the cat or dog. The only real difference is the relative size of various structures. We are both as complex as creatures come on this planet.
  - wallace_f 8y ago
    Probably there is some limiting factor to complexity, such as either the naivety to advertise existence, or the inevitably to halt creative destruction once we figure out how to not die.
  - JackFr 8y ago
    > We are both as complex as creatures come on this planet. Gaia says: Whatever, buddy. You're like a neuron comparing yourself to liver cells.
  - perl4ever 8y ago
    It is said that the wheat genome is five times the size of the human one...
Rattled 8y ago
A cell has no way to conceive of a worm, and worms probably can't conceive of humans. But they probably have some conception of birds, and birds can perceive humans. Where are our birds? As you go up the intelligence chain the ability to see beyond seems to increase, but we don't see anything beyond us.

gldalmaso 8y ago

Maybe the oldest and most advanced civilizations decided to go tribal. Maybe they are so advanced that they can hide their trail so belligerent civilizations like ours do not encounter them. I don't think the easiest explanation is to assume that there is any sort of naturally occurring event in the universe that is one of a kind, save maybe for the big bang.

SmellyGeekBoy 8y ago

There are civilisations on earth (uncontacted tribes) who are completely unaware of the existence of modern society. With this in mind your view seems incredibly naive.

Razengan 8y ago
Yes, https://en.wikipedia.org/wiki/Uncontacted_peoples https://en.wikipedia.org/wiki/Uncontacted_peoples And we collectively decided to leave them alone, ostensibly for their own good.
mihaifm 8y ago
True, but all these assumptions are probabilistic. What are the chances of us being one of those uncontacted tribes. We have found thousands of other tribes, leaving only a handful hidden. The probability of a tribe to remain hidden is almost 0. And this probability decreases more and more with time.

cthalupa 8y ago

There might simply be no way to travel at, or even near, and much less faster than, the speed of light, in which case the universe could be full of life that we will never contact or meet. Life might be rare enough that it's unlikely in any single galaxy.

mihaifm 8y ago
Even at very low speeds, a civilization with a 10 million year "head start" (which is nothing on the timescale of the universe) would be able to send autonomous robots across the galaxy. At least that what we would do if we had sufficient enough technology. This is essentially the paradox.
- DmenshunlAnlsis 8y ago
  So many assumptions here. Maybe they’d be able to, but why would they want to? What’s the point of probing a galaxy that you can only ever explore below the speed of light, at the cost of ungodly amounts of energy and eons of time? Why wouldn’t that same civilization stick within 1-100 light years instead? There is only a paradox if an advanced civilization with high tech is so irrational that they can’t control their breeding and doesn’t care about time dilation and efficient use of resources. It also assumes that it’s safe to broadcast your presence to the whole galaxy that way. It assumes a lot of unproven ideas and then hand waves at a “sufficiently advanced” species that has only apparently enjoyed technological advancement rather than personal or social advancement. Maybe humans as we know them would spread unmanned probes across the galaxy for the sake of doing it, but I have doubts that humans capable of th feat would do it. I suspect we’d be wiser, or we’d be dead.
- Razengan 8y ago
  That so-called paradox takes the following assumptions: • That it is possible for a region as large as even a single galaxy to ever be "full" of one species or their creations. • That anything can keep spreading indefinitely, and remain intact, not only across the gargantuan distances involved but also over potentially millions of years for other species to encounter them. • That intelligent life wants to keep spreading or exploring indefinitely. As opposed to, say, creating VR universes of its own and attaining contentment within them. • That there are only a few "directions" into which species or machines can spread across the universe, for them to run into each other. • That there are no "stabilizing" forces – natural or adversarial – which counter rampant expansion.

WilliamEdward 8y ago

That theory doesn't account for the fact that the laws of physics prevent anything from traveling faster than the speed of light. because our galaxy is 100000 lightyears long by itself, it would take 100000 years for an advanced civilization just to get to us let alone cross their own galaxies. It's highly possible other life doesn't exist but the reason we can't see them is because space is way larger than you think it is and takes a long time to travel across.

elboru 8y ago
It's easy to speculate when there are infinite "what-ifs". If AGI (artificial general intelligence) development is technically possible and if they're really able to recursively self-improve themselves to become semi-gods and if there are really N number of civilizations out there, then there should be N number of AGIs too, it would make sense that we should be able to see their traces of existence across the universe.
- Razengan 8y ago
  This makes a lot of cherry-picked assumptions: https://news.ycombinator.com/item?id=17829840 https://news.ycombinator.com/item?id=17829840
travisoneill1 8y ago
Which is a very short amount of time for a species to be in existence. Alligators have been around for 2000x that amount of time. If you take a max speed of 0.01c which is possible with technology that we will probably have in the next 100 years (fusion power) that means the galaxy could be colonized in 10 million years. If 200 million years ago humans had evolved instead of alligators (can’t see any reason this is not possible on some alternate earth) then we could have colonized the galaxy 20 times over by now.
- Razengan 8y ago
  "Unrestrained colonization just because we can" relies upon a lot of assumptions: https://news.ycombinator.com/item?id=17829840 https://news.ycombinator.com/item?id=17829840 For example, we could have begun building a base on the Moon by now if we wanted to, but we have decided not to.

MichaelMoser123 8y ago

The Fermi paradox assumes that there is infinite progress, what if going interstellar is just too hard? (Warp drive too hard and going such distances directly just impossible) What are the incentives to go interstellar once a species has colonised it's solar system?

thatguy0900 8y ago
The incentive would be to escape the eventual heat death of their sun or insure their race against any other solar system wide extinction event, I guess
- MichaelMoser123 8y ago
  This assumes that the civilization would be able to prevail for an extremely long time.

amf12 8y ago

The universe is 13.8 Billion years old, so we can only observe the universe 13 Billion light years away. However the universe is practically infinite and much larger than the observable universe. It's not possible for us to detect a galaxy and a civilization (if it exists) in the said galaxy outside the observable range. Similarly, for the said civilization we lie outside that observable range and they can't detect us because nothing can travel faster than the speed of light. Now imagine, how huge the unobservable universe is. Probabilistically, it is quite possible for a civilization (or multiple) more or less advanced than us to exist far, far away, or may have existed some point in time. But none can detect each other. Its even possible for a civilization to exist in the spheres of observation of other civilizations but so far away that its almost impossible to make contact. 13.8 Billion years is not a long time on the scale of the universe, but it is also a long time on evolutionary scale for a civilization to have existed and have been extinct.