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Necessary read for reasonable discussion: https://en.wikipedia.org/wiki/Rare_Earth_hypothesis https://en.wikipedia.org/wiki/Rare_Earth_hypothesis "the Rare Ea

by acqq 11y ago

Necessary read for reasonable discussion: https://en.wikipedia.org/wiki/Rare_Earth_hypothesis https://en.wikipedia.org/wiki/Rare_Earth_hypothesis "the Rare Earth Hypothesis argues that the origin of life and the evolution of biological complexity such as sexually reproducing, multicellular organisms on Earth (and, subsequently, human intelligence) required an improbable combination of astrophysical and geological events and circumstances. The hypothesis argues that complex extraterrestrial life is a very improbable phenomenon and likely to be extremely rare."

api 11y ago
Bottom line is we only have one example. We simply do not know. For all we know the frequency could be less than one per galaxy per billion years, in which case we are likely alone.
- cdelsolar 11y ago
  There are hundreds of billions? of galaxies though.
  - api 11y ago
    Intergalactic travel or communication is exponentially harder than interstellar.
    - acqq 11y ago
      Exactly. As far as I know, except for the Andromeda galaxy, which will collide with ours, all other galaxies zoom further away. https://en.wikipedia.org/wiki/Andromeda%E2%80%93Milky_Way_collision https://en.wikipedia.org/wiki/Andromeda%E2%80%93Milky_Way_co... Far enough in the future, even if we survive, we won't see any other galaxy -- they will zoom out of our observable universe! The expansion of the Universe accelerates, according to our last estimates.
      - skc 11y ago
        Wouldn't this imply that future generations may actually lose this history? There would be no way to prove that another galaxy ever existed.
        acqq 11y ago
        The universe is still "young enough" for galaxies to be close enough to each other for a while. But yes, based on the current knowledge of the constants that drive the universe, in some very distant future we can imagine some potential civilizations that will be able to learn dramatically less about the Universe than we already know now, their model will be: What's the Universe? Only the stars around us, all in the group. What's behind them? Nothing. In even more distant future, eventually the supply of gas needed for star formation will be exhausted: https://en.wikipedia.org/wiki/Future_of_an_expanding_universe https://en.wikipedia.org/wiki/Future_of_an_expanding_univers... In the exponentially distant future the Universe is going to get always more and more boring.
        skc 11y ago
        It's actually fascinating. When future civilizations read "old" science texts it will be virtually impossible for them to not think of them as crackpot science or fairy tales. The idea of other galaxies ever having existed will have about as much verifiable scientific evidence as the tooth fairy
        acqq 11y ago
        The "Big bang" can't be proved anymore then too -- not billions of galaxies all flying away from us, but just: nothing.
- acqq 11y ago
  The universe exists just some 14 billion years, Earth some 4.5 billion. For all we have on the Earth the older generations of supernova stars and their explosion were needed. Then the timeline of the life on Earth spans almost 4 billion years: https://en.wikipedia.org/wiki/Timeline_of_the_evolutionary_history_of_life https://en.wikipedia.org/wiki/Timeline_of_the_evolutionary_h... But we're "intelligent" enough for space travel only the last 50 years. But notice how the backward ideologies even got significantly stronger during the last 30 years and add to that that we've also probably spent a half of all oil in the last 100 years, which was probably produced during hundreds of millions of years, and that the awareness of that simple fact and its effects is also low. There's nothing that guarantees that "it's always going to be better for us" no matter what we do. "More than 99 percent of all species, amounting to over five billion species, that ever lived on Earth are estimated to be extinct." We initiated the last wave of extinctions. Or as Taleb would write: "Consider the turkey before and after Thanksgiving." Every day the hypothesis "it's going to be better" is confirmed again and again. Until... http://4.bp.blogspot.com/-qok3PSFR6NU/Ug4_QOjDUZI/AAAAAAAAA6w/g1F3pJT4HFI/s1600/turkey+graph.jpg http://4.bp.blogspot.com/-qok3PSFR6NU/Ug4_QOjDUZI/AAAAAAAAA6... "This naive projection of the future from the past can be projected from anything."
- jcranmer 11y ago
  Well, the best way to put it is that, with n=1, the posterior distribution is going to be the same as the prior distribution, so any attempt to "explain" the Fermi paradox is dominated more by what you want to be true than what you can evidence to be true. This is particularly clear when you think of it in terms of the Drake equation. We can devise reasonable estimates for parameters in terms of "number of habitable planets," but we know so little about how life works or how it starts that any later variable turns out to be complete guesswork. It's also sobering to learn that even our own ability to discover the history of life for which we have physical evidence turns out to be rather poor--being able to decipher Mayan script showed us that a fair amount of what we thought we knew about the Mayan civilization was just projection of archaeologists' opinions.
IndianAstronaut 11y ago
We already know that there are likely billions of planets which are likely to be similar to Earth in terms of temperature, size and being terrestrial. The only question here is that even here on Earth, out of the tens of millions of species, only one is capable of creating advanced technology. I am almost certain life exists elsewhere, but likely not intelligent.
- x1798DE 11y ago
  How similar is similar? Mars and Venus are "similar to Earth" in nearly every way that we could detect if they were exoplanets, but neither is capable of sustaining Earthlike life. I think it's far from a solved question how likely life is, given we have exactly one example of it arising.
- acqq 11y ago
  My position is: even the intelligent life doesn't have to reach what some assume can be reached (Dyson spheres and stuff). We can't be sure we'll reach it until we reach it. Don't forget, there's enough nuclear weapons to roll us back to the prehistoric levels of existence. Don't forget the climate, etc. Before we land on any planet around any other star or have some other kind of proof, don't assume others do trivially. And, even if the advancement is probable enough, be aware that the other civilizations don't have to have good intentions. Better avoiding signalling around.

by acqq 11y ago

api 11y ago

Bottom line is we only have one example. We simply do not know. For all we know the frequency could be less than one per galaxy per billion years, in which case we are likely alone.

cdelsolar 11y ago
There are hundreds of billions? of galaxies though.
- api 11y ago
  Intergalactic travel or communication is exponentially harder than interstellar.
  - acqq 11y ago
    Exactly. As far as I know, except for the Andromeda galaxy, which will collide with ours, all other galaxies zoom further away. https://en.wikipedia.org/wiki/Andromeda%E2%80%93Milky_Way_collision https://en.wikipedia.org/wiki/Andromeda%E2%80%93Milky_Way_co... Far enough in the future, even if we survive, we won't see any other galaxy -- they will zoom out of our observable universe! The expansion of the Universe accelerates, according to our last estimates.
    - skc 11y ago
      Wouldn't this imply that future generations may actually lose this history? There would be no way to prove that another galaxy ever existed.
      - acqq 11y ago
        The universe is still "young enough" for galaxies to be close enough to each other for a while. But yes, based on the current knowledge of the constants that drive the universe, in some very distant future we can imagine some potential civilizations that will be able to learn dramatically less about the Universe than we already know now, their model will be: What's the Universe? Only the stars around us, all in the group. What's behind them? Nothing. In even more distant future, eventually the supply of gas needed for star formation will be exhausted: https://en.wikipedia.org/wiki/Future_of_an_expanding_universe https://en.wikipedia.org/wiki/Future_of_an_expanding_univers... In the exponentially distant future the Universe is going to get always more and more boring.
        skc 11y ago
        It's actually fascinating. When future civilizations read "old" science texts it will be virtually impossible for them to not think of them as crackpot science or fairy tales. The idea of other galaxies ever having existed will have about as much verifiable scientific evidence as the tooth fairy
        acqq 11y ago
        The "Big bang" can't be proved anymore then too -- not billions of galaxies all flying away from us, but just: nothing.
acqq 11y ago
The universe exists just some 14 billion years, Earth some 4.5 billion. For all we have on the Earth the older generations of supernova stars and their explosion were needed. Then the timeline of the life on Earth spans almost 4 billion years: https://en.wikipedia.org/wiki/Timeline_of_the_evolutionary_history_of_life https://en.wikipedia.org/wiki/Timeline_of_the_evolutionary_h... But we're "intelligent" enough for space travel only the last 50 years. But notice how the backward ideologies even got significantly stronger during the last 30 years and add to that that we've also probably spent a half of all oil in the last 100 years, which was probably produced during hundreds of millions of years, and that the awareness of that simple fact and its effects is also low. There's nothing that guarantees that "it's always going to be better for us" no matter what we do. "More than 99 percent of all species, amounting to over five billion species, that ever lived on Earth are estimated to be extinct." We initiated the last wave of extinctions. Or as Taleb would write: "Consider the turkey before and after Thanksgiving." Every day the hypothesis "it's going to be better" is confirmed again and again. Until... http://4.bp.blogspot.com/-qok3PSFR6NU/Ug4_QOjDUZI/AAAAAAAAA6w/g1F3pJT4HFI/s1600/turkey+graph.jpg http://4.bp.blogspot.com/-qok3PSFR6NU/Ug4_QOjDUZI/AAAAAAAAA6... "This naive projection of the future from the past can be projected from anything."
jcranmer 11y ago
Well, the best way to put it is that, with n=1, the posterior distribution is going to be the same as the prior distribution, so any attempt to "explain" the Fermi paradox is dominated more by what you want to be true than what you can evidence to be true. This is particularly clear when you think of it in terms of the Drake equation. We can devise reasonable estimates for parameters in terms of "number of habitable planets," but we know so little about how life works or how it starts that any later variable turns out to be complete guesswork. It's also sobering to learn that even our own ability to discover the history of life for which we have physical evidence turns out to be rather poor--being able to decipher Mayan script showed us that a fair amount of what we thought we knew about the Mayan civilization was just projection of archaeologists' opinions.

IndianAstronaut 11y ago

We already know that there are likely billions of planets which are likely to be similar to Earth in terms of temperature, size and being terrestrial. The only question here is that even here on Earth, out of the tens of millions of species, only one is capable of creating advanced technology. I am almost certain life exists elsewhere, but likely not intelligent.

x1798DE 11y ago
How similar is similar? Mars and Venus are "similar to Earth" in nearly every way that we could detect if they were exoplanets, but neither is capable of sustaining Earthlike life. I think it's far from a solved question how likely life is, given we have exactly one example of it arising.
acqq 11y ago
My position is: even the intelligent life doesn't have to reach what some assume can be reached (Dyson spheres and stuff). We can't be sure we'll reach it until we reach it. Don't forget, there's enough nuclear weapons to roll us back to the prehistoric levels of existence. Don't forget the climate, etc. Before we land on any planet around any other star or have some other kind of proof, don't assume others do trivially. And, even if the advancement is probable enough, be aware that the other civilizations don't have to have good intentions. Better avoiding signalling around.