A Kansas State cosmologist will discuss the expanding universe during an informal talk at Mueller Planetarium in Lincoln.

The talk by Bharat Ratra is titled “Dark Matter, Dark Energy and the Accelerating Universe.”

It is scheduled to begin at 4 p.m. Saturday at the planetarium, which is in the University of Nebraska State Museum of Natural History’s Morrill Hall.

Mueller Planetarium shows a dome program, “Dark,” on Saturdays and Sundays at 2 and 3 p.m. The program complements Ratra’s talk, because it provides an introductory look at the complex principles of dark matter.