The force of Earth's gravity is measured to come from within its own atoms and not from some infinite gravitational medium far beyond its surface.
Gravity is presented here as a principle of measurement and not a "theory". Conclusions of measurement are used to explain the dynamics of gravity and no metaphysical assumptions are made prior to measurement other than assuming the accuracy of measuring instruments. Two simple measurements can be made to easily illustrate the gravity principle in terms metaphysical gravitational theories. The first measurement quantifies the true natural dynamics of gravitational force and motion that is common to all gravitational theories. The second test measures the true direction and velocity of gravitational motion and the results can be used to either verify or falsify all four of the basic classes of gravity theories. The first test uses accelerometers to measure the upward force at Earth's surface and atomic clocks to measure the gravitational motion produced by both gravitational force and the inertial acceleration of rockets. The second gravity cannon experiment answers the age old paradox of what really happens when a gold ball is dropped into a bottomless pit. This second test is an opposite but complementary measurement of the first, in that it measures downward gravitational deceleration that balances measured upward gravitational acceleration. Whereas, the first test uses atomic clocks and accelerometers to measure gravitational motion and force at all points above Earth's center, the gravity cannon uses a video camera clock to measure gravitational motion and force at Earth's center.