Outside an atomic nucleus, a neutron decays into a proton, an electron and an anti-neutrino within 15 minutes.
From this, we can conclude
Time goes a little faster on Mercury than it does on Earth. This is why Mercury makes its rounds around the Sun a little quicker than predicted by Newton.
Newton introduced several concepts into physics in order to label the various parts of his equations. He did so without giving any specifics as to
Conventional physics has gravity as a constant force that depends on mass alone.
There is a constant G associated with the equation expressing the relationship
Contrary to popular belief, modern science is full of contradictions and unsolved puzzles, and it does not take more than mild curiosity to uncover these problems.