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S A T U R D A Y

Shakespeare goofed when he had Julius Caesar refer to himself as “constant as the Northern star”: There was no polestar in Caesar’s day. Because Earth wobbles like a top spinning off-center, the axis points first to one star, then to its neighbor, then to empty space. In “Where is My Wandering Polestar Tonight?,” planetarium director James Sharp discusses this phenomenon and its implications for pathfinders of the past and future. At 9:30 a.m. at the National Air & Space Museum’s Einstein Planetarium, 6th & Independence Ave. SW. FREE. (202) 357-2700. (Greg Kitsock)