Impact Cratering on the Moon
Apparently, there is evidence that the rate at which the moon -- and by inference, the earth -- was hit by "cratering impacts" with much higher frequency roughly 4 billion years ago. It has been estimated cratering was occurring at a pace roughly 100 times higher than it has been occurring recently.
This would support the idea that gravity has, on the average, been diminishing over the life of the Galaxy. (See also, Increase in Dust from Volcanoes or Asteroid Impacts)