This is a huge resolution range. On an 11″ MacBook Air, a
72-pixel line — which would measure 1 inch long against an
onscreen ruler — is just 0.53 physical inches long. On a 21.5″
iMac, that same line is 0.70 inches long. User interface items,
like buttons, menu items, and scroll bars are 30% bigger on the
iMac than on the Air.