: 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.

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

: Penny sells the car Leonard previously bought for her because her new pharmaceutical job provides a company car. When she tries to give Leonard the money back, it leads to a debate about financial independence and gender roles. They seek advice from Howard and Bernadette, only to find that the couple has their own deep-seated issues regarding Bernadette’s higher salary and Howard’s "stipend" for household chores. Key Details Director : Mark Cendrowski.

: 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

: Johnny Galecki (Leonard), Jim Parsons (Sheldon), Kaley Cuoco (Penny), Simon Helberg (Howard), Kunal Nayyar (Raj), Mayim Bialik (Amy), and Melissa Rauch (Bernadette).