The rotation doesn't cause gravity. Rotation spins outward, it radiates, therefore we would get flung out into space. If the sky was the center of the earth then rotation would cause gravity.
For that to be true we would be living in a hollow earth or torus.
Correct. But it has an influence on gravity. Objects at the poles weigh "scientifically accurately", they weigh less at the equater just as you mentioned, so the earths rotation is involved. Its impossible to isolate one from the other, it is essentially a system of interconnected forces. Gravity is a mass relation equation in relation to relative sizes and densities and I dont like mathematics, never was very good at it, so thats the extent of what i know.
The gravitational pull isn't even uniform, there are places that have more or less than "standard" gravity. Some are counter intuitive, the lightest place on earth is below sea level near Antarctica.
I wonder how they isolated it to just gravity measurements in that situation. That would be a lot of variables to sort out. It obviously had to be done in a submarine or some sort of diving bell, otherwise pressures from the sea above would be tremendous. I wonder if the atmosphere they were breathing at those depths would factor into the results. It would have to be a nitrox or helium mix of some sort. That would be an interesting study to read.
https://nasaviz.gsfc.nasa.gov/11234
It could just be CGI bullshit, you never know.
My guess would be computer modeling rather than empirical data gathering.
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