I had to laugh at myself there regarding the time of the dinosaurs and thank you for pointing this out.
Also thanks for finding the Earth's centrifugal force to Earth's Gravity ratio, this puts scope of the Earth's rotation in perspective.
Here is a link showing how small the centrifugal force...
There are a number of factors involved in weight experienced by a particular mass on the surface of the earth.
There is of course the Mass of the Earth itself, the variable distribution of heavier elements in the Earth itself, the motion of the ocean mass due to tides etc, the motion of the...
Drakkith's explanation is very good>>If you were in the center of the Earth you would have near equal amounts of mass on every side of you, so you wouldn't feel a pull in anyone direction like you do on the surface.>>
To be precise, every particle of your body would be feeling an equal pull in...