Quote:
Originally Posted by DGthe3
the claim was made that the earth has doubled in size? Did it double in radius? Area? Volume? Land area makes the most sense considering the topic that was discussed. Doubling in area means that the volume would be 2.83x larger. So density would then have to have gone down by an equal factor for mass to remain the same. So, given that the current density for the earth is ~5.5g/cc, it would have had to have a density of 15.6 g/cc before expansion. This is halfway between the density of lead and gold.
One other problem with this though, if the earth had to double in area while maintaining the same mass, the force of gravity at the surface would have been twice as strong before it grew. Unfortunately, this would have made dinosaurs impossible to stand.
If the earth had significantly less mass eons ago, the moon would never have maintained a stable orbit. Since we have a moon and dinosaurs fossils, I think that proves that this guy is talking out of his ass.
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I agree, and the gravity at the surface is something I didn't really piece together at the time. Using the equation I mentioned, gravity would be a bitch at the surface. This would infer smaller animals than we see today, rather than larger ones. (Though, I guess you could argue the atmospheric pressure would also be increased, meaning more molecules of oxygen per unit volume. More oxygen = larger animals).
I really think the only
credible argument is that the Earth did not gain much mass, but rather lowered its density. I was working on some equations with densities of magma vs temp and pressure, but I don't feel like going through it all right now. Basically, you'd have to have a pretty amazing material to double its volume in a cooling process. I don't think anything like that exists.