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Young Sheldon Finally Explained One Of Big Bang Theory's Biggest Mysteries

The CBS sitcom "Young Sheldon" has proven its mettle as a successful spinoff from an incredibly successful parent program. "The Big Bang Theory" prequel series explores the life of a youthful Sheldon Cooper (Iain Armitage) as he grows to maturity in his small Texas hometown. In addition to Armitage playing the kid genius, Jim Parsons, who plays the older Sheldon on "The Big Bang Theory," provides narration from the perspective of the adult version of the character.

Over the years, "The Big Bang Theory" fans who watch "Young Sheldon" have witnessed a series of key moments in Sheldon's life play out that explain his adult preferences and behavioral habits. For instance, during Season 5, Episode 6, "Money Laundering and a Cascade of Hormones," we learn that an adult Sheldon prefers to use the term "coitus" as a tame descriptor for sexual congress. This development occurs after his fraternal twin sister, Missy Cooper (Raegan Revord), causes a ruckus at Sunday school when she asks their pastor questions about sex and love.

During the show's most recent episode, "An Introduction to Engineering and a Glob of Hair Gel" (via IMDb), another essential piece of Sheldon's backstory is officially explained.

A bad experience with a teacher forged Sheldon's hatred for engineering... and tenure

"Big Bang Theory" fans know that Sheldon has a negative opinion about one specific scientific discipline and those who practice it — engineering. On the CBS sitcom, he often used his dislike of the profession to mock his friend Howard Wolowitz (Simon Helberg), who has made a career in the discipline. It turns out that he developed this dislike during his youth due to the teaching style of one tough educator.

In "An Introduction to Engineering and a Glob of Hair Gel," Sheldon takes an engineering course at East Texas Tech with Professor Boucher (guest star Lance Reddick). Boucher's brusqueness eventually rubs Sheldon the wrong way after Sheldon repeatedly fails his professor's assignment to build a bridge, and the professor rips his every attempt at developing a new one to literal shreds. Sheldon appeals to the adults in his life for help, but the young boy's parents are persuaded that Boucher's tough love is good for him. Eventually, the pint-sized scientist figures out the problem with his creation — he hasn't factored in how real-life stressors such as wind will affect his bridge's stability. When he tries to share his revelation, he realizes that Boucher has locked him out of the class for being late.

He says that this is what caused him to develop a dislike for engineering. Howard — who co-narrates the episode — reacts in shock to that notion. The episode also explains Sheldon's dislike for professors who are tenured, which he made known on "The Big Bang Theory" in Season 6 during the episode "The Tenure Turbulence."