[split] Distances between files and ranks

[Nathan Ross]

8 rows of men of 10 files in each century with each row being 9 feet apart in "close order"... the last line would be around 90 feet from the front line

Why are they 9 feet apart? Polybius (and you, in fact!) says there were three feet between ranks, just as there are between files in 'open order'.

I would imagine the pila are thrown at relatively close range - as each rank throws pila they close up with the rank in front, so as the enemy advance they are struck by rapid volleys of missiles delivered from about the same distance.

Light infantry might fight 6foot apart - but not heavy.

Nobody is talking about men standing 6 feet apart. The 6-foot-per-soldier thing is from Polybius (see above), and he is describing legionary tactics, not light infantry. If you find this unlikely, or you own experience of the ancient battlefield suggests otherwise, best take the matter up with him!