is the sixth episode of the eighth season of The Big Bang Theory , originally aired on October 20, 2014. The episode features two primary storylines: Sheldon and Raj testing their endurance for an upcoming dark matter research project, and Leonard and Penny dealing with a financial disagreement. Plot Summary
: Sheldon and Raj consider joining a research team in a salt mine to detect dark matter. To see if they can handle the claustrophobic and harsh conditions, they decide to spend time in the university's underground steam tunnels as a simulation. During their stay, Raj shares personal stories, but the "expedition" ends abruptly after just 11 minutes when a family of rats scares Sheldon into fleeing and abandoning Raj. [S8E6] The Expedition Approximation
: Johnny Galecki (Leonard), Jim Parsons (Sheldon), Kaley Cuoco (Penny), Simon Helberg (Howard), Kunal Nayyar (Raj), Mayim Bialik (Amy), and Melissa Rauch (Bernadette). is the sixth episode of the eighth season
: Raj's monologue about the Voyager space probe and the reveal of Howard’s incomplete set of Star Trek collectible plates. The Expedition Approximation | The Big Bang Theory Wiki To see if they can handle the claustrophobic