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View Full Version : Nat-Geo's Earth: Making of a Planet



Githyanki
2011-Apr-04, 10:20 PM
For one, they state there was no air on early Earth, just CO2 etc. (that's air); the go one to suggest that the Earth had no water until the Late Heavy-Bombardment 700MY after it's creation; since the Late Heavy-Bombardment was composed of a lot of cometary materials, it would seem that Earth would have lots of elements that indicate most of the water came from comets, but Earth's oceans don't...

publiusr
2011-Apr-06, 09:51 PM
Then too, no list of instructions came with the box.

John Jaksich
2011-Apr-09, 04:10 PM
For one, they state there was no air on early Earth, just CO2 etc. (that's air); the go one to suggest that the Earth had no water until the Late Heavy-Bombardment 700MY after it's creation; since the Late Heavy-Bombardment was composed of a lot of cometary materials, it would seem that Earth would have lots of elements that indicate most of the water came from comets, but Earth's oceans don't...

I do not want to drub your post too much--but Nat Geo does not typically aim for an audience that is taxing on the details as most "real" scientists like to be---if anything I can remember reading Nat Geo when 12 or 13 years old--and attempting to write a good "school report" for my courses---

It is unfortunate that there is a "dumbing down" associated with such inaccuracies--although very accurate in your judgement

AbsherL
2011-Aug-29, 11:29 AM
I do not want to drub your post too much--but Nat Geo does not typically aim for an audience that is taxing on the details as most "real" scientists like to be---if anything I can remember reading Nat Geo when 12 or 13 years old--and attempting to write a good "school report" for my courses---

It is unfortunate that there is a "dumbing down" associated with such inaccuracies--although very accurate in your judgement

I am fully agree with you!

SkepticJ
2011-Aug-30, 04:02 AM
For one, they state there was no air on early Earth, just CO2 etc. (that's air)

Rather depends on your definition. It's an atmosphere, certainly, but air is generally understood to contain a sizable fraction of oxygen. Why? Because we breath oxygen.

Don't take my word for it, that's how dictionaries and encyclopedias define it.


. . . the go one to suggest that the Earth had no water until the Late Heavy-Bombardment 700MY after it's creation; since the Late Heavy-Bombardment was composed of a lot of cometary materials, it would seem that Earth would have lots of elements that indicate most of the water came from comets, but Earth's oceans don't...

That was 4 x 10^9 years ago! Do you honestly think what's suspended and dissolved in the oceans is what's been there the whole time? Oceanic water is subducted along with the rock at subduction zones--that's where the water that makes certain magma so explosive (via steam pressure) comes from. How else would water get down into the mantle? If this didn't happen, we should find much more uranium, gold, and other heavy elements in the water than we do. The oceans would be getting saltier all the time from erosion.

Now from my understanding it's currently thought that the bulk of Earth's water doesn't have its origin in cometary material, but for different reasons.