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> the change in atmosphere composition over the last 1000 years seems like it would be detectable Interesting to think what conclusions would be drawn in these

by nawgz 5y ago

> the change in atmosphere composition over the last 1000 years seems like it would be detectable Interesting to think what conclusions would be drawn in these scenarios. Obviously atmospheric composition has drastically changed over the eons - I wonder what sort of civilization could detect these kind of longterm changes, and if they wouldn't have better observational capabilities than what we assume here given they have persistent knowledge over "long" timespans

kadoban 5y ago
I _think_ even just seeing Oxygen (in O2 form) should be fairly suggestive, because it's not stable in the presence of a whole bunch of other things.
- perihelions 5y ago
  And the CFC's would be definitive proof. https://arxiv.org/abs/1406.3025 https://arxiv.org/abs/1406.3025
  - RosanaAnaDana 5y ago
    Yeah, but you might not be looking for those specifically. Oxygen however. Just the fact that our atmosphere is as far out of equilibrium as it is.
- nawgz 5y ago
  I wasn’t clear at all, but I certainly agree it would be clear life was on earth from such data. I am less clear how much about our society you could meaningfully conclude from it is all, but perhaps it’d be clear from our pollution exactly what we’re manufacturing/burning
  - dotancohen 5y ago
    Unless the observers' planet also had ancient, non-renewable carbon deposits (which required very specific conditions) then atmospheric pollution might not even be a concept to them. They might notice a change in our atmosphere's composition, but honestly a 200 ppm to 400 ppm change of some trace gas over the course of two hundred years could have many much simpler explanations than "intelligent life dug up all the carbon and burned it".
    - BBC-vs-neolibs 5y ago
      Haha, yes, talk about Occams razor! :-D
RosanaAnaDana 5y ago
It has, but something fundamental to our atmosphere (even before the great oxygen holocaust) is that it has lots of potential for 'exchange'; ie, its not fully reduced. Part of our earth system depends on the reduction side (us, heterotrophs, etc..) and part depends on things being available to oxidize (co2, previously in greater quantities n2). The fact that both are observable and present would indicate that our atmosphere is being maintained at a stable(ish) state far from equilibrium.

by nawgz 5y ago

kadoban 5y ago

I _think_ even just seeing Oxygen (in O2 form) should be fairly suggestive, because it's not stable in the presence of a whole bunch of other things.

perihelions 5y ago
And the CFC's would be definitive proof. https://arxiv.org/abs/1406.3025 https://arxiv.org/abs/1406.3025
- RosanaAnaDana 5y ago
  Yeah, but you might not be looking for those specifically. Oxygen however. Just the fact that our atmosphere is as far out of equilibrium as it is.
nawgz 5y ago
I wasn’t clear at all, but I certainly agree it would be clear life was on earth from such data. I am less clear how much about our society you could meaningfully conclude from it is all, but perhaps it’d be clear from our pollution exactly what we’re manufacturing/burning
- dotancohen 5y ago
  Unless the observers' planet also had ancient, non-renewable carbon deposits (which required very specific conditions) then atmospheric pollution might not even be a concept to them. They might notice a change in our atmosphere's composition, but honestly a 200 ppm to 400 ppm change of some trace gas over the course of two hundred years could have many much simpler explanations than "intelligent life dug up all the carbon and burned it".
  - BBC-vs-neolibs 5y ago
    Haha, yes, talk about Occams razor! :-D

RosanaAnaDana 5y ago

It has, but something fundamental to our atmosphere (even before the great oxygen holocaust) is that it has lots of potential for 'exchange'; ie, its not fully reduced. Part of our earth system depends on the reduction side (us, heterotrophs, etc..) and part depends on things being available to oxidize (co2, previously in greater quantities n2). The fact that both are observable and present would indicate that our atmosphere is being maintained at a stable(ish) state far from equilibrium.