John Williams White, in his first Greek book, at the top of page 2, indicates that:
S4. Vowels are either short or long. There are separate Greek characters (ε, η, ο, ω) for the e and o sounds, but not for a, i, and u sounds. In this book the long vowels are designated by ᾱ, η, ῑ, ω, ῡ; the short vowels are α, ε, ι, ω, υ.
Ok, so η and ω are long . . . .
Then on page 5, section 21 he states that:
S21. The antepenult, if accented, takes the acute, as ἄν-θρω-πος, man; but it can have no accent if the last syllable is long or ends in ξ or ψ, as ἀν-θρώ-που, of a man.
Yet he does not indicate how you are to tell what is short and what is long! Based on this, -που is long, but how are you to know that? I have seen this same issue in other books too . . . no explaination. Does anyone know what the rules are regarding this?