We can only track impacts on the earth if we witness them or find evidence. The majority of objects that get through the earth's atmosphere without burning up w

We can only track impacts on the earth if we witness them or find evidence. The majority of objects that get through the earth's atmosphere without burning up will impact in the ocean, which covers 70% of the surface, and leave no trace. And we can't observe or know about impacts that occurred prior to human beings keeping track of them. We just have estimates. We have no way to know how many objects struck the moon since it formed, if the solar system contained fewer or more such objects that might strike the moon during all of that time, with no one observing or measuring. It's possible that 90% of the impact craters on the moon happened in the first million years after it was formed, then the supply of objects in intersecting orbits got exhausted, and the rate of impacts declined. How could we guess at that? And supposing we did guess, how would that help us derive the age of the moon -- your original question? Besides an estimate of the rate of impacts since the moon was formed, we would still need to know how long the moon existed to sustain those impacts. Other problems occur to me, mainly that later impacts would wipe out traces of earlier impacts, so we can't even count the impact craters. The size of an impact crater depends both on the mass of the object that struck the moon and its velocity, so just knowing the rate of impact without knowing the masses and velocities doesn't tell us enough. And we're still left not know over what period of time the moon accumulated those impact craters -- its age -- which would have to be part of any calculation involving a rate. Do you understand that rate means the number of incidents happening over a given duration of time?