"The Wildebeest Implementation" - Episode 4.22

While Sheldon works on refining the mechanics of his new 3-person chess variant, Leonard and Priya have a double date with Howard and Bernadette. Encouraged by Amy Farrah Fowler, Bernadette agrees to spy on the couple and report back on the status of their romance to Penny. When Penny learns that Leonard is planning a trip to India to meet Priya's family, she grows concerned.

Meanwhile, a depressed Raj goes to hang out with Sheldon and decides that he needs to become more sociable. He takes some social anxiety pills which contains "some sort of beta-blocker attached to a molecule extracted from the urine of cows." Unfortunately, the experimental medication works a bit too well, leading him to an unfortunate encounter in a coffee shop.

Albert Einstein, sex, and time machines - When Sheldon implies that Leonard's regular sex life is getting in the way of his logical thinking, Leonard counters that Einstein had an active sex life. Sheldon points out that this could have been a contributing factor to why Einstein was unable to successfully develop a unified field theory, which is the scientific goal to which he devoted nearly half of his life. While I don't know (nor do I wish to get into) the details of Einstein's sex life, and the degree to which it may have hindered his scientific work, Sheldon is completely correct that Einstein failed at his efforts to unify gravity with the other forces of nature. Sheldon's claim "we'd all have time machines" is based on the idea that any theory of time travel will require a more refined, quantum version of general relativity.

Sheldon Cooper: I must say, Leonard, ever since you've been having regular intercouse, your mind has lost its keen edge. You should reflect on that.
Leonard Hofstadter: Excuse me, but Einstein had a very busy sex life.
Sheldon Cooper: Yes, and he never unified gravity with the other forces. If he hadn't been such a hound dog, we'd all have time machines.

Raj Koothrappali: [Considering taking anti-anxiety medicine] As a scientist, thinking is my bread and butter. I'm afraid if I take these I might lose that unique, special something that has made me so successful in my field.
Sheldon Cooper: Rajesh, I've had the privilege of working alongside you for many years. My advice to you is that you gobble these up like Tic-Tacs.