[ThePythonicCow]

how the gravitational force of a planet of basically constant mass changes over time

Perhaps the earth was rotating faster, which it would have if it was smaller -- same mass, but smaller diameter. Then the centrifugal force would have partially counteracted gravity.

Somewhere, I saw once an interesting article that further explained the moon's creation as matter flying off an earth spinning too fast to hold together, but I can't find a link to that right now.

I did find however a very interesting YouTube link http://www.youtube.com/v/VjgidAICoQI, in a blog entry at http://hitxp.wordpress.com/2007/05/11/continental-drift-is-wrong/.

If you watch this video, you will see a clear presentation of how the earth's continental plates all fit together, covering the -entire- surface. Then over the last 65 million years the earth expands, spreading apart the plates apart, growing young oceans in the new expanse.

[ThePythonicCow]

Aha - here's an article explaining the other piece of this, how the moon flew off the rapidly spinning earth 65 million years ago. Prior to then, the earth had become quite oblate, bulging at the equator, with a single plate covering its entire surface, but with the equatorial belt as dry land, and the water (oceans) toward the poles.

See further http://www.brojon.org/frontpage/WHAT_REALLY_KILLED_THE_DINOSAURS.html.

The weight of the giant dinosaurs just before that cataclismic event would have approached zero.

[samtheman]

Smaller diameter would mean stronger gravity, not weaker.

As for the length of the earth day, I think that has been increasing, due to tidal friction, but at a much slower rate than would significantly effect the net gravitational force 65 million years ago.

As for the moon, I think it’s pretty well established that it was created 4 billion years ago when another planet collided with and merged with our own, blowing off the lunar chunk in the process.

I haven’t looked at your links yet, and I will. But the posted article here seems to me not real science but some kind of Däniken type silliness.

[Raymann]

Well the Earth was spinning faster, but at best the day would have only been an hour shorter at the K/T event. The tidal effects of the moon slow the Earth down some but even that is slowing as the Moon gets further away.

As for the oxygen, it could have been up to 28% before the K/T event but you’d probably only find concentrations that high before the Triassic...long before the dinosaurs mentioned here evolved yet.

This article is BS...period. If there were no giraffes, people like this would be saying that they would be biologically impossible. We simply don’t know enough about the biology of dinosaurs to understand how the large sauropods functioned and automatically jumping to the conclusion that the gravity was somehow less back then is just stupid beyond belief.

[DouglasKC]

If you watch this video, you will see a clear presentation of how the earth's continental plates all fit together, covering the -entire- surface. Then over the last 65 million years the earth expand

Thank you for providing that link to that video. It was fascinating.

In your opinion, what would happen, what would be the physical effects if the earth began to contract?