He then tried many combinations until he discovered that ( approximately ) " " The square of the periodic times are to each other as the cubes of the mean distances " . " Although he gives the date of this epiphany ( March 8, 1618 ), he does not give any details about how he arrived at this conclusion.
12.
Johannes Kepler had proved by an elaborate series of measurements that each planet revolves in an foci of the orbit, that the radius vector of each planet drawn from the sun sweeps out equal areas in equal times, and that the squares of the periodic times of the planets are in the same proportion as the cubes of their mean distances from the sun.
13.
Power Nap allows flash storage-based Macintoshes ( late 2010 MacBook Air and later, or the MacBook Pro with Retina display ) to synchronize with iCloud ( Reminders, Calendars, Photo Stream, Notes, Mail, and Find My Mac ) while sleeping and also allows a Mac to download App Store and OS X updates as well as make periodic Time Machine backups when it is plugged in and sleeping.
