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> Earth is about 4.5 billion years old, and early forms of life were definitely on the planet by 3.7 billion years ago. That bare fact seems to imply that it w

by placebo 12y ago

> Earth is about 4.5 billion years old, and early forms of life were definitely on the planet by 3.7 billion years ago. That bare fact seems to imply that it wasn’t hard to get life going on Earth; if initiating life was really improbable, then we should have had to wait a long time before its appearance. I think that's a big leap to make in drawing conclusions exactly because of the N=1 problem. If we had managed to reproduce a process by which a bunch of organic compounds turn into a the simplest cell type then we could start talking about probabilities of this process happening elsewhere in the universe. It might very well be true that life would start just as easily elsewhere but that conclusion can't be based on the amount of time it took life to appear on earth. The fact that someone wins the lottery the first time they buy a ticket does not mean its easy to win the lottery...

sampo 12y ago
You sound like you want to believe that the emergence of life is difficult (by comparing it to winning in a lottery). Then the N=1 evidence that we actually have says, the emergence of life was easy (or, at least, quick). But you brush this off by saying blah, it's just N=1. But the evidence for your emergence-of-life-is-difficult is N=0. Granted, N=1 is not much. But it's still more than N=0.
- placebo 12y ago
  I don't want to believe anything until there's evidence for it. My intention was to show there's a problem with the logic that assumes it's easy when there is not enough evidence to support either that it is easy or that it is difficult. The example of the lottery was meant to illustrate how it could be difficult while seeming easy, not to convince anyone that it is in fact difficult. I wouldn't agree with someone claiming that the development of life is difficult for exactly the same reasons.
danieltillett 12y ago
It is a big leap to draw if life has to exist for a long time before intellegence can emerge. Given how close we are to the end of the carbon cycle on Earth (in geological terms) it implies that it takes a very long time for intelligent life to evolve. This requires that life appears early. What I think is better proof that intelligent life is rare is the existence of stars. Stars are like finding gold coins on the street - they both only will be there if intelligent life is not.
- mod 12y ago
  Can you expand on your idea about the stars? I follow why gold coins aren't found in the street, but not how intelligent life would scoop up stars.
  - danieltillett 12y ago
    It is not my idea (I wish it was), but the basic idea is that any intelligent life a little more advanced than us would build Dyson spheres [1] around each star to capture the energy being released. This would shift the stars EM spectra heavily into the red. Combine these with von Neumann machines [2] and the stars soon cease to shine. Interestingly while we are not really capable of searching for such stars right now we have found few possible candidates [3]. I personally think these are likely to all be false positives because any civilisation capable of building a Dyson sphere will be able to capture all the energy being emitted and so the black body temperature of the sphere will be only be a little above 2.73K. These we would not be able to detect. 1. http://en.wikipedia.org/wiki/Dyson_sphere http://en.wikipedia.org/wiki/Dyson_sphere 2. http://en.wikipedia.org/wiki/Self-replicating_machine http://en.wikipedia.org/wiki/Self-replicating_machine 3. http://home.fnal.gov/~carrigan/infrared_astronomy/Other_searches.htm http://home.fnal.gov/~carrigan/infrared_astronomy/Other_sear...
    - mod 12y ago
      Awesome, thanks for writing this up for me. I wonder if there's reason to think that all or many stars would need capturing. Also, is there perhaps an alternative situation, where, put simply, there power needs can be sufficiently met without capturing all that available? (Lower power tech, or some very efficient power capture / production?)
      - danieltillett 12y ago
        Once you have von Neumann machines spreading they will take over each new star system pretty much as soon as they reach it. Assuming the von Neumann machines are small and are being powered by an energy source (i.e lasers) from their origin star system they will spread through the galaxy at close to the speed of light. This spread method creates an interesting effect in that we would not see the stars go out until the von Neumann machines had almost reached us if the origin star was within our galaxy - basically the von Neumann machines would be traveling only a little behind the light front from the origin star system (this would make a good science fiction story). If the origin star system was far enough a way, then the slightly slower speed that the von Neumann machines would travel at should allow us to see them progressing though a distance galaxy. Such a galaxy would look to us like part of the galaxy had a chunk taken out of it. It would be worth looking through the galaxy classification data set [1, 2] to see if there are any galaxies like that out there that look like this. My feeling is we won't find any as I think intellegent life is near unique within the visible universe, but it is at least a testable hypothesis. 1. http://www.galaxyzoo.org http://www.galaxyzoo.org 2. http://en.wikipedia.org/wiki/Atlas_of_Peculiar_Galaxies http://en.wikipedia.org/wiki/Atlas_of_Peculiar_Galaxies
throwaway_yy2Di 12y ago
"Earth is about 4.5 billion years old, and early forms of life were definitely on the planet by 3.7 billion years ago. That bare fact seems to imply that it wasn’t hard to get life going on Earth; if initiating life was really improbable, then we should have had to wait a long time before its appearance." I think it's a significant observation that there's just a single origin of life -- that after a 4.5 Gy sample time, we only observe one type of biochemistry. If you predict abiogenesis happens easily, you should expect it to have happened again independently, many times, and expect to find distinct classes of radically different, "alien" life on earth.
- cLeEOGPw 12y ago
  Not necessarily. It might have happened that different types of chemistry appeared, but as life evolved, one type pushed out the other. So we can't really tell if life happens easily or not from the fact that there's one type of biochemistry here.

by placebo 12y ago

sampo 12y ago

You sound like you want to believe that the emergence of life is difficult (by comparing it to winning in a lottery). Then the N=1 evidence that we actually have says, the emergence of life was easy (or, at least, quick). But you brush this off by saying blah, it's just N=1. But the evidence for your emergence-of-life-is-difficult is N=0. Granted, N=1 is not much. But it's still more than N=0.

placebo 12y ago
I don't want to believe anything until there's evidence for it. My intention was to show there's a problem with the logic that assumes it's easy when there is not enough evidence to support either that it is easy or that it is difficult. The example of the lottery was meant to illustrate how it could be difficult while seeming easy, not to convince anyone that it is in fact difficult. I wouldn't agree with someone claiming that the development of life is difficult for exactly the same reasons.

danieltillett 12y ago

It is a big leap to draw if life has to exist for a long time before intellegence can emerge. Given how close we are to the end of the carbon cycle on Earth (in geological terms) it implies that it takes a very long time for intelligent life to evolve. This requires that life appears early. What I think is better proof that intelligent life is rare is the existence of stars. Stars are like finding gold coins on the street - they both only will be there if intelligent life is not.

mod 12y ago
Can you expand on your idea about the stars? I follow why gold coins aren't found in the street, but not how intelligent life would scoop up stars.
- danieltillett 12y ago
  It is not my idea (I wish it was), but the basic idea is that any intelligent life a little more advanced than us would build Dyson spheres [1] around each star to capture the energy being released. This would shift the stars EM spectra heavily into the red. Combine these with von Neumann machines [2] and the stars soon cease to shine. Interestingly while we are not really capable of searching for such stars right now we have found few possible candidates [3]. I personally think these are likely to all be false positives because any civilisation capable of building a Dyson sphere will be able to capture all the energy being emitted and so the black body temperature of the sphere will be only be a little above 2.73K. These we would not be able to detect. 1. http://en.wikipedia.org/wiki/Dyson_sphere http://en.wikipedia.org/wiki/Dyson_sphere 2. http://en.wikipedia.org/wiki/Self-replicating_machine http://en.wikipedia.org/wiki/Self-replicating_machine 3. http://home.fnal.gov/~carrigan/infrared_astronomy/Other_searches.htm http://home.fnal.gov/~carrigan/infrared_astronomy/Other_sear...
  - mod 12y ago
    Awesome, thanks for writing this up for me. I wonder if there's reason to think that all or many stars would need capturing. Also, is there perhaps an alternative situation, where, put simply, there power needs can be sufficiently met without capturing all that available? (Lower power tech, or some very efficient power capture / production?)
    - danieltillett 12y ago
      Once you have von Neumann machines spreading they will take over each new star system pretty much as soon as they reach it. Assuming the von Neumann machines are small and are being powered by an energy source (i.e lasers) from their origin star system they will spread through the galaxy at close to the speed of light. This spread method creates an interesting effect in that we would not see the stars go out until the von Neumann machines had almost reached us if the origin star was within our galaxy - basically the von Neumann machines would be traveling only a little behind the light front from the origin star system (this would make a good science fiction story). If the origin star system was far enough a way, then the slightly slower speed that the von Neumann machines would travel at should allow us to see them progressing though a distance galaxy. Such a galaxy would look to us like part of the galaxy had a chunk taken out of it. It would be worth looking through the galaxy classification data set [1, 2] to see if there are any galaxies like that out there that look like this. My feeling is we won't find any as I think intellegent life is near unique within the visible universe, but it is at least a testable hypothesis. 1. http://www.galaxyzoo.org http://www.galaxyzoo.org 2. http://en.wikipedia.org/wiki/Atlas_of_Peculiar_Galaxies http://en.wikipedia.org/wiki/Atlas_of_Peculiar_Galaxies

throwaway_yy2Di 12y ago

"Earth is about 4.5 billion years old, and early forms of life were definitely on the planet by 3.7 billion years ago. That bare fact seems to imply that it wasn’t hard to get life going on Earth; if initiating life was really improbable, then we should have had to wait a long time before its appearance." I think it's a significant observation that there's just a single origin of life -- that after a 4.5 Gy sample time, we only observe one type of biochemistry. If you predict abiogenesis happens easily, you should expect it to have happened again independently, many times, and expect to find distinct classes of radically different, "alien" life on earth.

cLeEOGPw 12y ago
Not necessarily. It might have happened that different types of chemistry appeared, but as life evolved, one type pushed out the other. So we can't really tell if life happens easily or not from the fact that there's one type of biochemistry here.