Even Newton suggested it absurd that mass by virtue of being massive can exert a force through a vacuum. There is a medium. Modern physics is leaning towards everything being a field.
No offense, but I sincerely doubt you have a very thorough knowledge of QFT. I don't really know much about QFT either. A poor understanding of a very complicated theory is a recipe for bad conclusions. For example...
How can space (vacuum) be nothing? There has to be a medium by which the electromagnetic and nuclear forces are transferred. If space was nothing, including the space between an electron and the nucleus of an atom, everything would collapse.
So the effect might be the same -- things falling at 9.8m/s2 until a terminal velocity due to atmospheric resistence. But I don't believe the Earth being big is the reason why.
As far as I know, your arguments against the existence of a true vacuum are correct, depending on how you define a "medium". However, I fail to see the connection between that and the implausibility of mass being the cause of gravity. In fact, gravity is very well defined as a classical field associated with a mass.
Disclaimer: As far as I know, gravity isn't well understood under QFT. Anyone who figures this out is pretty much guaranteed a Nobel prize. That doesn't mean that there is any evidence that gravity isn't associated with mass.
But why no anomaly? Is the Earth so perfectly homogeneous? Has it been proven to be so? Why would the center of mass be perfectly perpendicular to the core? Is it that much more dense and somehow more massive then all of the rest of the mass on Earth? Does the sloshing molten metal have a pull to it?
Of course there are
anomalies. You can personally detect the
anomalies with a
cheap lab scale. Of course the earth isn't perfectly homogeneous. The earth is
approximately spherically symmetric, but definitely NOT homogeneous.
How did it become spherically symmetric? Because gravity naturally lends itself to creating spherically symmetric objects. Everything tends to gravitate towards the densest part. Heavy elements tend to sink down towards the middle. Lighter stuff tends to float towards the top. This results in roughly spherically symmetric layers. Also, the stuff in the middle is under a lot of pressure from the stuff around it, making it more dense.
It doesn't make sense if a particle is attracted to every other particle inversely proportional to the distance that everything would perfectly want to be drawn to the center of the sphere.
How good are you at calculus? It makes perfect sense. See
the shell theorem.
Are you familiar with the Tamarack Mines Experiments?
Thanks for this. I had vaguely heard of it, but never read any details. I can think of two explanations of the results off the top of my head:
1. Static charge built up on the bobs caused them to repulse each other.
2. Gravitational attraction to the edges of the mine shaft.
I have no idea if these explanations would survive the actual calculations, but they seem plausible. I would hope that the author of the paper took into account these possible explanations, but I don't see them mentioned in the paper.
Also, I still don't see how this is evidence that gravity isn't a function of mass. Interesting experiment nonetheless.