The Medford Public Library concludes its summer Friday movie series with a screening of “Back to the Future”  in Bonsignore Hall.  In the 1985 film, starring Michael J. Fox, a 17-year-old high school student, Marty McFly, is accidentally sent 30 years into the past in a time-traveling DeLorean invented by his close friend, the maverick scientist Doc Brown. No registration is required.