For Robbie

For Robbie,20 = no longer a teenager. In Old Testament law, 20 years old was counted as old enough to be a warrior and be fully responsible for adult things and counted in censuses as adults. Levites began service at 20 years old. Jacob served Laban for twenty years; Joseph was sold for twenty pieces of silver; Samson judges Israel for 20 years; and the temple was 20 cubits wide; in fact, the Holy of Holies was 20 x 20 x 20. Spiritually, it seems to denote either a doubling of the order of 10 (like the temple examples) or an expectant waiting (like Jacob's work, the 20 years Solomon took to build the temple and his palace, the 20 years Jeremiah prophesied Babylonian captivity, etc.).Mathematically, 20 is a tetrahedral number, meaning that a triangular pyramid of oranges (or any balls) 4 levels tall has 20 objects in it. [Picture a triangle of 10 like a bowling pin configuration on the bottom, the next layer has a triangle of 6, the next has 3, with 1 on the top.]In physics, 20 protons and neutrons in an atomic nucleus is considered a "magic" number, with a complete atomic shell and a very stable nucleus.20 = 2 + 4 + 6 + 8 (who do we appreciate?)The ancient Mayans had a numbering system with base-20. (Ours is base-10, of course.)Humans have 20 amino acids in their bodies.Clear sight is called 20/20; 20/20 is also a long-running news show.A classic game is Twenty Questions.Twentieth Century Fox is outdated now, of course. And there's the band, Matchbox Twenty.A period of 20 years has its own word: a score.
So, score! You're a score old.Happy birthday, #1 nephew.
(Thanks Uncle Matt!)