The New York City lunch hour is nothing if not elastic. Some days we only have time for a power bar while other days we indulge a lengthy, liquor-soaked power lunch. Either way, the ever-changing lunch options in New York are a reflection of the evolving attitudes and cultures of the city. Using documents such as menus and photographs from all over its archives, The New York Public Library’s new “Lunch Hour NYC” exhibit explores New York lunches, from 3-cent school lunches to the luxurious afternoon meals of NYC’s first power brokers, as they’ve changed over the last century. (Fun fact: Did you know that school lunches originated in New York?) The exhibit will open this Friday and run through February 2013. Vintage food carts and an actual recreation of a Horn & Hardart (a long shuttered automat food service company) machine will also appear in the exhibit. Stephen A. Schwarzman Building, Gottesman Exhibition Hall, Fifth Ave. at 42nd St.