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The future lifespan of Earth’s oxygenated atmosphere

nature.com

31–40 of 90 posts

Re: The future lifespan of Earth’s oxygenated atmosphere

#31

I wonder if the great filter is not one, but multiple coincidences brought upon by "intelligent" life and the natural lifetime of a planet and/or solar system. If Mars had intelligent life and now it doesn't how does that bode for Earthlings? Can life really adapt given the lack of evidence anywhere? I wonder how will space travel to the next possible habitable planets work. Shoot in all directions and hope that life…

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Re: The future lifespan of Earth’s oxygenated atmosphere

#33
That article really doesn't give a very good explanation at all, it doesn't make sense. When CO2 breaks down it produces oxygen and carbon, so if oxygen gets burned to produce CO2 it's just gonna get converted back into oxygen when the CO2 breaks down. If the oxygen reacts with the atmospheric nitrogen then surely this will also get broken down since AFAIK less energy is needed to break down NO2 than CO2. Currently the amount of oxygen in the atmosphere is over 500x more than the amount of CO2, so where is all that oxygen going to go?

Re: The future lifespan of Earth’s oxygenated atmosphere

#34
post #23

Interesting. Life emerged 4 billion years ago and the window of habitability for complex lifeforms will end in one more billion years. So terrestrial natural selection required 80% of the window of opprtunity to produce human intelligence. That's a tighter margin than I would have guessed.

This is predicted by the hypothesis that the origin of intelligent life requires the occurrence of several hard steps, each of which take at least several billion years (but with no upper bound) in expectation.

If that hypothesis holds, then conditional on all the steps having completed on a given planet, they will have done so roughly equally spaced in the time allotted, regardless of their relative difficulty.

So, for example, if the window on Earth is 5 billion years, and there are four hard steps to complete, then, conditional on all four steps finishing, we expect each step to have taken about 1 billion years, give or take, with about 1 billion years left to go.

(See the Technical Appendix to Robin Hanson's Great Filter essay: http://mason.gmu.edu/~rhanson/greatfilter.html#appendix, or his more detailed discussion of this particular point: http://mason.gmu.edu/~rhanson/HARDSTEP.PS)

Re: The future lifespan of Earth’s oxygenated atmosphere

#35

I wonder if the great filter is not one, but multiple coincidences brought upon by "intelligent" life and the natural lifetime of a planet and/or solar system. If Mars had intelligent life and now it doesn't how does that bode for Earthlings? Can life really adapt given the lack of evidence anywhere? I wonder how will space travel to the next possible habitable planets work. Shoot in all directions and hope that life…

I think we can all but rule out a dead, ancient planet-spanning civilization on Mars now. We have medium resolution imagery of the entire planet and high resolution (meter or submeter) imagery of a lot of the surface, in a wide distribution. Mars hasn’t had enough volcanic activity to hide evidence of a planet-spanning civilization unless it occurred while large asteroid impacts were much more common.

Venus, however, is sheathed in clouds. So we only have low resolution radar images of most of the planet, and we’ve only sent a few very short-lived landers with low resolution cameras to the surface. They could have landed in areas that were once oceans or otherwise uninhabited. And secondly, Venus has been basically completely resurfaced with lava over time. Venus may once have had large oceans before runaway greenhouse effect. (And keep in mind that the Sun has gotten significantly brighter over billions of years, besides the increased greenhouse effect on Venus.) And so we can’t even rule out a planet-spanning civilization like our own. It’d take a lot more exploration and drilling to rule that out.

Re: The future lifespan of Earth’s oxygenated atmosphere

#36

We humans will be able to control everything on earth's climate if we survive even a couple thousand years from now assuming technological advances.

I can imagine a scenario where civilization collapses and humankind exists in a permanent dark age without abundant oil to launch a new industrial revolution.

Edit: Another alternative is technology progresses but political and cultural institutions do not, so the requisite level of global cooperation never materializes.

Re: The future lifespan of Earth’s oxygenated atmosphere

#37

I wonder if the great filter is not one, but multiple coincidences brought upon by "intelligent" life and the natural lifetime of a planet and/or solar system. If Mars had intelligent life and now it doesn't how does that bode for Earthlings? Can life really adapt given the lack of evidence anywhere? I wonder how will space travel to the next possible habitable planets work. Shoot in all directions and hope that life…

As far as your latter point about life spreading, what’s interesting to me is that the most strict interpretation of our “planetary protection” guidelines at NASA actually prohibit life spreading to other worlds.

Red Tape as the real Great Filter...

Re: The future lifespan of Earth’s oxygenated atmosphere

#38

That article really doesn't give a very good explanation at all, it doesn't make sense. When CO2 breaks down it produces oxygen and carbon, so if oxygen gets burned to produce CO2 it's just gonna get converted back into oxygen when the CO2 breaks down. If the oxygen reacts with the atmospheric nitrogen then surely this will also get broken down since AFAIK less energy is needed to break down NO2 than CO2. Currently t…

There’s an immense amount of buried carbon. If you include all burnable carbon sources underground (including under the oceans), there’s approximately enough to burn up all the oxygen in the atmosphere. Plus there are lots of minerals that can be oxidized.

Re: The future lifespan of Earth’s oxygenated atmosphere

#39

That article really doesn't give a very good explanation at all, it doesn't make sense. When CO2 breaks down it produces oxygen and carbon, so if oxygen gets burned to produce CO2 it's just gonna get converted back into oxygen when the CO2 breaks down. If the oxygen reacts with the atmospheric nitrogen then surely this will also get broken down since AFAIK less energy is needed to break down NO2 than CO2. Currently t…

There’s an immense amount of buried carbon. If you include all burnable carbon sources underground (including under the oceans), there’s approximately enough to burn up all the oxygen in the atmosphere. Plus there are lots of minerals that can be oxidized.

burning carbon creates CO2, which would then get broken down back into oxygen (either by plants or directly by sunlight according to the article).

Re: The future lifespan of Earth’s oxygenated atmosphere

#40

Earlier quoted context omitted.

There’s an immense amount of buried carbon. If you include all burnable carbon sources underground (including under the oceans), there’s approximately enough to burn up all the oxygen in the atmosphere. Plus there are lots of minerals that can be oxidized.

burning carbon creates CO2, which would then get broken down back into oxygen (either by plants or directly by sunlight according to the article).

Plants require a certain temperature range to live (and also replenish CO2 slower than digging up and burning the carbon). And the sun directly is not very effective at producing oxygen. No discovered planet or exoplanet has an oxygen concentration like the Earth’s because it takes photosynthesis to be so extremely far from chemical equilibrium. UV dissociation just isn’t enough to get several psi of oxygen.
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