4 ms·

One might assume then that life is inevitable. Seems like too much if a coincidence (although I appreciate the tautology of that thought).

narag 4y ago
The alternative explanation is that seeds from a previous evolution started colonizing the planet as soon as the medium became viable. But that's like cheating.
- lovemenot 4y ago
  Panspermia is not cheating. If we believe abiogenesis to be vanshingingly unlikely on any one planet, panspermia paralelises discovery of a solution.
  - narag 4y ago
    You surely knew I was half joking. Anyway, I'll explain a little further. I said cheating because panspermia, as I understand it, has a very narrow window of usefulness. If surface abiogenesis is unlikely, panspermia is more unlikely because it needs the former, plus a way for the spores to survive in space, the travel of interplanetary, maybe interstellar distances, atmosphere re-entry and developement in a new environment. Another factor is that, if we accept the current estimations for the age of Universe and the fact that some elements only are present in second or third generation star systems (because they were formed inside novas), we could be one of the first guests to the party. Panspermia would place abiogenesis even further in the past. The only scenario in which panspermia would be more likely is that some components that are needed for life can only appear in space and develop on the surface. That's not to say that panspermia is in itself an absurd idea, actually the fact that some elements need to be created inside stars means that we're somehow children of the stars, it just happens that panspermia isn't a great substitute for abiogenesis. An amplifier, maybe.
    - lovemenot 4y ago
      Perhaps we understand panspermia differently. I understand it as a possible answer to the question: how did most of the life in the universe arrive where it is presently to be found? Clearly not all life, since as a matter of certainty abiogenesis has occurred at least once. >> If surface abiogenesis is unlikely, panspermia is more unlikely because it needs the former, plus ... That depends. Panspermia gets a huge multiplier from distributing the number of planets and eons on which abiogenesis might have happened just once. So it depends on the relative impacts of very different factors - neither of which have been well quantified. If panspermia had ever been feasible, it was likely more so in the earlier universe. Personally, I prefer it because it seems to follow the Copernican Principle.
      - narag 4y ago
        So it depends on the relative impacts of very different factors - neither of which have been well quantified. Well, that's... correct. I still think that it's less probable, but I have no way to prove it :)
muyuu 4y ago
Or that "intelligent" life is very unlikely if you consider that our planet will no longer be inhabitable in roughly the next 10% of its total existence and 7% since it's estimated microbial life appeared. If human equivalent creatures had taken just 10% longer to appear the sun would have dried up all the water on the earth and wiped its atmosphere before it happened.
- anonymouskimmer 4y ago
  The satellites of Saturn and Jupiter will still be chugging along. Our star is unusual, as well over 90% of stars are smaller (and thus longer lived). Though if you go small enough you start dealing with planets in the habitable zone being tidally locked.
  - Tuna-Fish 4y ago
    But if a species capable of rocketry had not developed, there is no way complex life would be able to get to those satellites. The increased likelihood of being tidally locked is not the only problem with smaller stars. As a rule, larger stars are more stable and smaller stars are more active. This is made worse by the fact that the habitable zone is closer to the star for smaller stars. Most stars in the universe probably can't support life as we know it because any planet close enough to be warm would get it's atmosphere stripped off by flares.
    - anonymouskimmer 4y ago
      > But if a species capable of rocketry had not developed, there is no way complex life would be able to get to those satellites. I'm talking about continuing evolution of the life that may already be there. Informative points about stars.
- Turskarama 4y ago
  It's hard to say for certain that there has never before been an intelligent species. Over hundreds of millions of years even evidence of cities (even assuming that all intelligent species would even make cities) could be entirely wiped away.

narag 4y ago

The alternative explanation is that seeds from a previous evolution started colonizing the planet as soon as the medium became viable. But that's like cheating.

lovemenot 4y ago
Panspermia is not cheating. If we believe abiogenesis to be vanshingingly unlikely on any one planet, panspermia paralelises discovery of a solution.
- narag 4y ago
  You surely knew I was half joking. Anyway, I'll explain a little further. I said cheating because panspermia, as I understand it, has a very narrow window of usefulness. If surface abiogenesis is unlikely, panspermia is more unlikely because it needs the former, plus a way for the spores to survive in space, the travel of interplanetary, maybe interstellar distances, atmosphere re-entry and developement in a new environment. Another factor is that, if we accept the current estimations for the age of Universe and the fact that some elements only are present in second or third generation star systems (because they were formed inside novas), we could be one of the first guests to the party. Panspermia would place abiogenesis even further in the past. The only scenario in which panspermia would be more likely is that some components that are needed for life can only appear in space and develop on the surface. That's not to say that panspermia is in itself an absurd idea, actually the fact that some elements need to be created inside stars means that we're somehow children of the stars, it just happens that panspermia isn't a great substitute for abiogenesis. An amplifier, maybe.
  - lovemenot 4y ago
    Perhaps we understand panspermia differently. I understand it as a possible answer to the question: how did most of the life in the universe arrive where it is presently to be found? Clearly not all life, since as a matter of certainty abiogenesis has occurred at least once. >> If surface abiogenesis is unlikely, panspermia is more unlikely because it needs the former, plus ... That depends. Panspermia gets a huge multiplier from distributing the number of planets and eons on which abiogenesis might have happened just once. So it depends on the relative impacts of very different factors - neither of which have been well quantified. If panspermia had ever been feasible, it was likely more so in the earlier universe. Personally, I prefer it because it seems to follow the Copernican Principle.
    - narag 4y ago
      So it depends on the relative impacts of very different factors - neither of which have been well quantified. Well, that's... correct. I still think that it's less probable, but I have no way to prove it :)

muyuu 4y ago

Or that "intelligent" life is very unlikely if you consider that our planet will no longer be inhabitable in roughly the next 10% of its total existence and 7% since it's estimated microbial life appeared. If human equivalent creatures had taken just 10% longer to appear the sun would have dried up all the water on the earth and wiped its atmosphere before it happened.

anonymouskimmer 4y ago
The satellites of Saturn and Jupiter will still be chugging along. Our star is unusual, as well over 90% of stars are smaller (and thus longer lived). Though if you go small enough you start dealing with planets in the habitable zone being tidally locked.
- Tuna-Fish 4y ago
  But if a species capable of rocketry had not developed, there is no way complex life would be able to get to those satellites. The increased likelihood of being tidally locked is not the only problem with smaller stars. As a rule, larger stars are more stable and smaller stars are more active. This is made worse by the fact that the habitable zone is closer to the star for smaller stars. Most stars in the universe probably can't support life as we know it because any planet close enough to be warm would get it's atmosphere stripped off by flares.
  - anonymouskimmer 4y ago
    > But if a species capable of rocketry had not developed, there is no way complex life would be able to get to those satellites. I'm talking about continuing evolution of the life that may already be there. Informative points about stars.
Turskarama 4y ago
It's hard to say for certain that there has never before been an intelligent species. Over hundreds of millions of years even evidence of cities (even assuming that all intelligent species would even make cities) could be entirely wiped away.