Terraforming the Pre-Earth? (Algol's video)

[Algr]

TL;DR

Is this video accurate? How realistic is terraforming in general?

I find this video absolutely amazing, and have watched it over a dozen times now. It helps if you can use the spacebar to pause it and read the text, and arrow keys to back up 5 seconds. - This is NOT phone friendly! Big monitor and 1440p recommended.

So two different questions for Physics forums:
1) How accurate is this video? Do we really know the rough shapes of ancient continents like this? Is this a good teaching tool?

2) Looking at the numbers indicating atmospheric composition, it is striking to me how small a fraction of Earth's history contains air humans can breathe! There seems to be a bit during the permian era where CO2 gets low enough, but then it rises again until the late cretaceous. Am I correct that the atmosphere needs to be under 0.1% CO2 for humans to breathe?

This makes me wonder: If we found a planet that was exactly like Earth two minutes into the video, (27°c, 8hr 40m day) Would it be terraformable? (Within, say a few thousand years?). What would we have to do? At what point in the video could we drop in some modern (genetically engineered?) Earth plants and expect them to survive and make a breathable atmosphere? This makes the whole subject of terraforming seem a bit unlikely.

 

[jim mcnamara]

I do not know that terraforming is the word that applies to the video. As a general statement the energy cost to make those changes is unbelievably high. Terraforming won't happen until we have spare quadrillions of joules of free energy. Plus we would have get plate tectonics going - which is sloooow.
The skating islands and continents are moving only inches per century. They are involved deeply with life on Earth.

Here is an evergreen piece on nutrient cycles & plate tectonics:
https://theconversation.com/plate-tectonics-may-have-driven-the-evolution-of-life-on-earth-44571

1. From what I know continents seem reasonable, very early "islands" - who knows definitely?
2. for teaching it goes VERY fast, really requires large screens - Desktops.

The content is okay.

For breathing look at the $O_2$ numbers - they need to be probably in the teens (estimate)
Yes, $CO_2$ affects breathing. Less than 1000ppm probably is passable. NASA has done rebreather tests, go over there and see.

Start here:
https://www.hq.nasa.gov/alsj/LM15_Portable_Life_Support_System_ppP1-5.pdf

Nice video.

 

[jim mcnamara]

On terraforming - for everything to work right for us and our ecosystems requires the mineral nutrient profile in the crust of another planet to pretty closely match Earth.

We likely got our surface minerals mostly from a later meteor bombardment(s). Our core had formed by then - and the formation - google Iron Catastrophe. (a hypothesis) - of a crust with minerals that got lost into the core - like iron - required a fresh input of the missing goodies.

Anyway, regardless of how Earth formed, suppose:
Our target Planet X and the crust of Earth had very different levels of say, Iodine. We could not live there without redesigning the biology of all of supporting species and us humans to cope with it. Or how about Arsenic?

It is fun to think about. Not very practical today.

 

[Algr]

The video isn't about terraforming at all, it just made me think about how the popular imagination may be drastically underestimating how difficult such an endeavor may be. People seem to think we could just crash a few comets into Mars and then drop some seeds and a breathable atmosphere will pop up.

Education: Nothing is more effective than getting the student to want to learn. Sure the text runs fast, but I just needed to read it somehow. So much education today is about pouring data into kids heads as if it were ingredients in a hamburger. Why did they make me memorize a list of African tribes? I like learning stuff off the internet today - I hated school as a kid.

 

[jim mcnamara]

Distance learning definitely does not work for everyone - we have several threads you should take a peek at:
https://www.physicsforums.com/threads/what-have-educators-learned-about-distance-learning.988260/

Kids are not all motivated to want to learn. Reading skills are a big player:
https://files.eric.ed.gov/fulltext/EJ1161358.pdf

This is why US Junior College enrollment no longer has predominantly so-called traditional students. i.e., the 18-19 freshman. And also why we have technical schools.

Let's not derail this thread with our lamentations of education problems.

You asked about using the video for teaching - I gave my opinion, you gave yours. My opinion still is: it was great for somebody like me, but as soon as you say 'teaching' the whole world changes. Can you imagine a 14 y/o with the attention span of a gnat trying to deal with the video? Great music - no explosions

And people with weak reading skills are turned off by "speed text". IMO.

 

[Algr]

I guess it is about finding the right audience for it. Thanks for the links, I already posted in one of those other threads, so yes, this is dovetailing into there.

 

[jim mcnamara]

@Ophiolite , @Genava - ignoring the terra-forming discussion, what is your opinion of the video above? I think it would be suitable for US college freshmen. Possibly AP level US high school students. In 10 years the content will be out of date, I would assume.

 

[Genava]

@Ophiolite , @Genava - ignoring the terra-forming discussion, what is your opinion of the video above? I think it would be suitable for US college freshmen. Possibly AP level US high school students. In 10 years the content will be out of date, I would assume.

A big mistake is that the Earth cooled faster after the Moon formation, in a few million years the temperature dropped for liquid water to be the common state at the surface. According to this review, it took 10 million years to reach a few hundreds °C (but with the massive atmospheric pressure, it enabled liquid water):
https://cshperspectives.cshlp.org/content/2/6/a002527.full.pdf

And probably in less than 100 million years the surface temperature reached values below 100°C, it depends on when the subduction of carbonate started (strongly decreasing the temperature and the atmospheric pressure).

I think there are two missing features in the chart on the right: the atmospheric pressure and the solar irradiance. It would have greatly helped the understanding of the processes involved at each step in the beginning.

Finally, a lacking feature is that the Alpine orogeny is not depicted on the map at the end (I am Swiss so I take this personally ).

Otherwise, it seems good enough for high school students.

 

[Algr]

the atmospheric pressure and the solar irradiance.

Yes:
First appearance of liquid water: 360°C
Earliest date of first life: 210°C

I asked the creator about these numbers and he told me about air pressure making them possible. The video is pretty info packed as it is, but that would help. His other video about the solar system has solar irradiance info. I like that one too:



Edit: I asked the creator of the video. I didn't ask God about precambrian atmospheric pressure.

 

[Genava]

First appearance of liquid water: 360°C

I think I understand what he did. He took the age of the oldest zircon, because they are already showing the presence of an ocean (thanks to isotopic ratio), as a threshold to reach this temperature. But that's not really the proof that the ocean formed at this moment, this is only our oldest evidence of it.

Earliest date of first life: 210°C

Which is quite high, even for hyperthermophile. The theoretical limit for life is around 150°C, even by accounting the increasing pressure enabling liquid water, because higher temperature increases hydratation (from a chemical point of view).