Science Focus (issue 26)

Directed by Park Dong-hoon, the movie opens with high school student Han Jiwoo (Kim Dong-hwi) and his struggles with mathematics. He crosses paths with security guard Lee Hak-sung (Choi Min-sik), a North Korean defector and reclusive mathematician whose story is gradually revealed throughout the movie, and ends up asking him for help in preparation for a tough exam. Hak-sung agrees to teach him – to appreciate math, rather than to cram. The movie then tracks their growing relationship (which the actors portray very well), the involvement of Ji-woo’s friend Park Bo-ram (Jo Yun-Seo), the impact of the exam and Hak-sung’s proof of the Riemann hypothesis (in reality still unsolved to this day). On the whole its setup has been compared to the 1997 film Good Will Hunting, which also features an anonymous but mathematically gifted university worker, but it has a strong story of its own and avoids rehashing the same plot. Without spoiling the movie, let’s see whether its plot makes sense in reality! Who Was the Old Man in Hak-sung's Flashback? At the end of Hak-sung’s first lesson he calls Jiwoo an “epsilon”. The memory that explains this is centered on Hak-sung’s childhood meeting with Paul Erdős, one of the most productive and eccentric mathematicians of the 20th century, who also independently proved the prime number theorem [1]. Erdős traveled around the world with only one suitcase of clothes, collaborating with so many different colleagues that mathematicians still use the “Erdős number” to track the network of people he worked with. He was also famous for his odd vocabulary, where he called women “bosses”, men “slaves”, lectures “sermons”, and nonmathematicians “trivial beings” [2]. (Hak-sung also calls Ji-woo a “trivial being” in the same scene.) Children were called “epsilons” because in calculus an epsilon represents a positive but very small number. Erdős met many “epsilons” throughout his life. According to his biographer, Paul Hoffman, Erdős “made it his mission to seek out child prodigies all over the world” and encourage them with further problems [3]. He met the 10-year-old Terence Tao at the 1985 International Mathematical Olympiad (IMO), very By Peace Foo 胡適之 Movie Review: In Our Prime (2022) 影評: 奇怪的數學家 (2022)