That one man? Apple software engineer Andrew Carol. He used 1,500 Lego Technic pieces (which are more advanced than you're usual pegs-'n'-bricks) to construct the 110 gears and four gearboxes that run the machine. Each box is its own little piece of computing hardware, crunching one equation per box, and when you input some calender data into it, it should be able to tell you when the next solar eclipse will be.
See the Antikythera mechanism in action in the video below, complete with overly epic music.
Engadget, via TUAW