[meteorite-list] Fw: term definitions and usage

[Richard Montgomery]

Hello List,

Another neophyte question  (I can use some clarification):  when / how are 
the time-measurements (relatively speaking) designations "Ga" and Ma" used, 
and their respective differences?

(I believe I know the difference through context, but why go through so many 
papers and texts with the question-mark over my head?)

Sincerely,
Richard Montgomery