A three-day celebration of what would have been John Glenn’s 100th birthday…begins in his birthplace and childhood hometown in Ohio, even as additional events were announced to mark the occasion. It all took place in Cambridge, where Glenn was born on July 18, 1921, and nearby New Concord, where he grew up and met his late wife. The event included a parade, the Friendship 7-Miler road race named for his famous aircraft, lectures, museum tours, space movies, biplane and rocket car rides, music and children’s science activities. It all wrapped up on Sunday.