> Heliacal is a Greek word, how do you figure the term was an
> Egyptian invention ?
I don't believe this is attested until later times but I have read somewhere that the Egyptians celebrated the helical rising of Sirius and marked their years by this. Their calendar was off by some .24 days/ year but these things have been pretty thoroughly investigated.
They understood some pretty complicated concepts to invent the calendar. I believe they were excellent time keepers but can't prove it yet.