How many virtual gravitons do the sun and earth exchange in one year?
What are their wavelengths?
Dear Jim, Let us suppose that gravitons exist, even though a quantum field theory of gravity per se does not. Still gravitons are bosons. There is no conservation of "boson" number.
There is no way to count them, even so when virtual. This is also true for the repulsion of two electrons, which happens with virtual photons. They are not countable.