Before Bezos ever sold a single book online, he was a physics major at Princeton University in the 1980s. And despite being one of the top 25 students in his honors program, Bezos believed he wasn’t smart enough to compete.

So he changed his major to electrical engineering and computer science, according to Wired, and it changed the course of his life. 

“I looked around the room and it was clear to me that there were three people in the class who were much, much better at [physics] than I was, and it was much, much easier for them,” Bezos told Wired in 1999.

“It was really sort of a startling insight, that there were these people whose brains were wired differently,” he said.

Bezos had this epiphany after unsuccessfully struggling to solve a math problem for hours.

“I can’t solve this partial differential equation,” he told the Economic Club of Washington in September 2018. “It’s really really hard. I’m studying with my roommate, Joe, who is also really good at math. The two of us worked on this one homework problem for three hours and got nowhere.”

He and his roommate finally asked a friend, Yasantha Rajakarunanayake, for help.

“We show him this problem, and he looks at it, stares at it for a while, and says ‘Cosine, that’s the answer.’ And i’m like ‘That’s the answer?’ And he’s like ‘Yes, let me show you,’” Bezos said.

“He brings us into his room, he sits us down, he writes out three pages of detailed algebra, everything crosses out, and the answer is cosine. I said, ‘Did you just do that in your head?’ And he said, ‘No, that would be impossible. Three years ago, I solved a very similar problem. I was able to map this problem onto that problem, and then it was immediately obvious that the answer was cosine.’”

According to Bezos, that was the moment he realized he should pursue a different career.

“That was an important moment for me, because that was the very moment when I realized I was never going to be a great theoretical physicist,” he said at the Economic Club. “I started doing some soul searching. In most occupations, if you’re in the 90th percentile, you’re going to contribute. In theoretical physics, you gotta be one of the top 50 people in the world, or you’re really not helping out much.”

Bezos changed his major and “committed to starting and running his own business,” according to Wired.

Bezos graduated from Princeton in 1986 with a degree in electrical engineering and computer science.

In 1994 while working at a hedge fund, Bezos found a staggering statistic the web was growing at 2,300% per year, which inspired him to launch Amazon as an online bookseller in 1995. Today the so-called “everything store,” has a market capitalization of over $1 trillion.

“I saw the writing on the wall, and I changed my major very quickly to electrical engineering and computer science,” Bezos said at the Economic Club.