  The intense activity of cratering on the Moon and in the inner regions of the
solar system was accomplished during the first 10^9 years [1]. Occasionally,
some impact events occur even nowadays. In Section 1, we treat, from a
historical point of view, the Earth-based observation of lunar impacts. In
Section 2, we consider the visibility conditions of such events evaluating the
luminosity of the background upon which an impact shines. In Section~3, the
luminosity of an impact is discussed. The occurrence of lunar impact events
outside of meteor shower periods is calculated using the hourly rate of the
sporadic meteors and their population index. The evidence of a larger rate of
impacts of meteoroids in the past under these hypotheses is presentend in the
last section.
