[alexander_busek]

It wasn’t just extra oxygen. The key that is hardly ever mentioned is that the atmospheric pressure must have been much higher as well. High enough, in fact, that the atmosphere’s pressure allowed extremely large creatures to live on land, due to buoyancy, like they still do below the oceans.

Sorry, but if you even DOUBLED the air density - i.e., the number of molecules of N2 and O2 per ccm - that would only increase it from about 1.4 gm/liter to 2.8 gm/liter. An animal weighing 100 kg and having a density of about 1 gm/ccm (like a human) would experience a reduction in perceived weight (due to the added buoyancy) of only 140 grams. That is negligible.

If you increased the air density by 10X, that STILL only reduces the apparent weight of a 100-kg human by 1.4 kg - or by 1.4%.

Regards,

[Boogieman]

“Sorry, but if you even DOUBLED the air density...”

Notice I said much higher? Even doubling the pressure is not enough to allow the size of terrestrial animals (and extremely large fliers) we see in the fossil record, so it must have been much higher than even that. I’d guess we are talking on the order of several hundred atmospheres, at least.

[null and void]

OTOH, the partial pressure of oxygen would double.

There would be roughly half again as much available oxygen due to the 21 to 30% increase, TIMES TWO due to the pressure increase.

These critters were 3X turbocharged!

[T-Bone Texan]

Thank you for doing the math on that one. Subject matter just alittle too dense to respond.