Let's create an alien biosphere!

[Schiaparelliorbust]

So in that case, I believe that atmospheric volume will be proportional to the planet's mass—unless the atmosphere would be more dense in planets with higher surface gravity.

Do you think density will matter much?

[MathAndCode]

Do you think density will matter much?

Yes. For organisms that need to get oxygen from the atmosphere, making the atmosphere twice as dense will have the same effect as doubling the proportion of the atmosphere that is oxygen; for organisms that need to get carbon dioxide from the atmosphere, making the atmosphere twice as dense will have the same effect as doubling the proportion of the atmosphere that is carbon dioxide; etc….

[Schiaparelliorbust]

Yes. For organisms that need to get oxygen from the atmosphere, making the atmosphere twice as dense will have the same effect as doubling the proportion of the atmosphere that is oxygen; for organisms that need to get carbon dioxide from the atmosphere, making the atmosphere twice as dense will have the same effect as doubling the proportion of the atmosphere that is carbon dioxide; etc….

I could only find a single physics stack exchange thread about gravity and air density. Do you think that the air density will be 20% higher (because of 20% higher gravity)?

[MathAndCode]

I could only find a single physics stack exchange thread about gravity and air density. Do you think that the air density will be 20% higher (because of 20% higher gravity)?

That makes sense. In that case, the alien planet's atmosphere will be slightly over twice as massive as Earth's.

[Schiaparelliorbust]

That makes sense. In that case, the alien planet's atmosphere will be slightly over twice as massive as Earth's.

Did you multiply its surface area by gravity to get that?

[MathAndCode]

Did you multiply its surface area by gravity to get that?

We would have to multiply by surface gravity (or radius) twice in order to get that because more surface gravity makes the atmosphere both thicker and denser.

[Schiaparelliorbust]

We would have to multiply by surface gravity (or radius) twice in order to get that because more surface gravity makes the atmosphere both thicker and denser.

Then did you multiply by it twice or something else?

[MathAndCode]

Then did you multiply by it twice or something else?

Yes, or one could simply raise the radius relative to Earth to the power of four.

[Schiaparelliorbust]

Yes, or one could simply raise the radius relative to Earth to the power of four.

Ok, thanks. What should we do now?

[MathAndCode]

Ok, thanks. What should we do now?

That tells us that the oxygenation of the alien planet will likely take about twice as long as the oxygenation of Earth, so we can resume working on the timeline.

[Schiaparelliorbust]

That tells us that the oxygenation of the alien planet will likely take about twice as long as the oxygenation of Earth, so we can resume working on the timeline.

Is around 620 million years good?

[MathAndCode]

Is around 620 million years good?

Yes, that sounds good—although keep in mind that oxygen won't start accumulating in the atmosphere right away because it will be absorbed by other things first.

[Schiaparelliorbust]

Yes, that sounds good—although keep in mind that oxygen won't start accumulating in the atmosphere right away because it will be absorbed by other things first.

620 million years is the time between when oxygen starts accumulating in the atmosphere and where it reaches an end point. Actually where should we define that end point?

[MathAndCode]

620 million years is the time between when oxygen starts accumulating in the atmosphere and where it reaches an end point. Actually where should we define that end point?

Let's define it at 20% concentration, like on Earth.

[Schiaparelliorbust]

Let's define it at 20% concentration, like on Earth.

There's are at least two problems with that:
1)Oxygen levels have been much higher and lower over the past few hundreds of millions of years. 20% is kind of arbitrary.
2)What mechanism do you propose for oxygen to just stop accumulating more?

[MathAndCode]

1)Oxygen levels have been much higher and lower over the past few hundreds of millions of years. 20% is kind of arbitrary.

Where would you propose? One third?

2)What mechanism do you propose for oxygen to just stop accumulating more?

Enough organisms evolve to use it to get energy to cancel out the photosynthesizers.

[Schiaparelliorbust]

Where would you propose? One third?

Not sure. On the Wikipedia chart it actually rises until its peak in the Carboniferous, but its rise does slow down around the Cambrian explosion at a bit under 20%.

Enough organisms evolve to use it to get energy to cancel out the photosynthesizers.

Do you think we need multicellular organisms to achieve balance?

[MathAndCode]

Do you think we need multicellular organisms to achieve balance?

Yes, but I think that multicellular organisms are likely to arise anyway.

[FUNNYMAN2]

We now need the complex psychology in this, don't we? Depending on the envirronement, the being creates different behaviors through its experiencing. So what would yall suggest?

[MathAndCode]

We now need the complex psychology in this, don't we? Depending on the envirronement, the being creates different behaviors through its experiencing. So what would yall suggest?

Let's wait until we have organisms with nervous systems before considering that. Right now, we don't even have multicellular organisms.

[FUNNYMAN2]

oh yeah true sorry for interrupting, I thought I was on previous page

[Schiaparelliorbust]

Yes, but I think that multicellular organisms are likely to arise anyway.

We could have an even more ancient supercontinent that breaks apart flooding the oceans with minerals along with there being a lot of oxygen to speed up multicellular organism diversification. Are we at this stage now?

[MathAndCode]

We could have an even more ancient supercontinent that breaks apart flooding the oceans with minerals along with there being a lot of oxygen to speed up multicellular organism diversification. Are we at this stage now?

The minerals would likely absorb some of the oxygen since many of them likely would not have been completely oxidized beforehand. However, according to Biblaridion's series, the cause of the diversification in the Cambrian Explosion was the emergence of predation, so something similar could happen here.

[Schiaparelliorbust]

The minerals would likely absorb some of the oxygen since many of them likely would not have been completely oxidized beforehand. However, according to Biblaridion's series, the cause of the diversification in the Cambrian Explosion was the emergence of predation, so something similar could happen here.

Well yeah I was thinking about predation. It will probably arise once multicellular organisms start moving, albeit slowly at first. Can oxidized minerals still be useful?

[MathAndCode]

Well yeah I was thinking about predation. It will probably arise once multicellular organisms start moving, albeit slowly at first. Can oxidized minerals still be useful?

Yes. For example, the organisms should still be to use transition metals inside to form coordination complexes.