CBS has announced Episode 2.17, "The Terminator Decoupling", which will air March 9th. Summer Glau ("Terminator: Sarah Connor Chronicles") guest stars. With a special cameo appearance by renowned astrophysicist Dr. George Smoot, whose work helped cement the big bang theory.

"The Terminator Decoupling" - A train trip to San Francisco takes a major detour when Leonard (Johnny Galecki), Sheldon (Jim Parsons), Wolowitz (Simon Helberg) and Raj (Kunal Nayyar) discover that beautiful sci-fi actress Summer Glau ("Terminator: The Sarah Connor Chronicles") is onboard, on THE BIG BANG THEORY, Monday, March 9 (8:00-8:30 PM, ET/PT) on the CBS Television Network. The episode also features a cameo by Nobel Laureate Dr. George Smoot.

Summer Glau is well known to television audiences for her roles in "Terminator: The Sarah Connor Chronicles" and "Firefly." A sci-fi favorite, Glau is a two-time Saturn Award winner and a Teen Choice Award nominee.

Dr. George Smoot, recipient of the Nobel Prize in Physics, as well as the Einstein Medal, is one of the world's most renowned astrophysicists. His research helped cement the big bang theory of the universe.

You can get more information in our Episode Guide.