The John J. McCarthy Observatory in New Milford will hold its next “Second Saturday Stars” program, “Einstein’s Theory of Relativity,” May 11 from 8 to 10 p.m. at the observatory behind New Milford High School.

Michael Tynski will discuss the history leading up to the theory being developed, the effects of time dilation and length contraction and black holes, as well as GPS satellites and corrections they use in order to be accurate.