"I'm a person who believes in doing the right thing," says Katherine Johnson who was named one of PEOPLE's 25 Women Changing the World in this week's issue

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Katherine Johnson thinks all of her accomplishments over the 98 years she’s been alive are “ordinary.”

But to the rest of the world, they’re anything but.

Johnson, a physicist, space scientist and mathematician graduated from high school at 14 years old, attended college the very next year and was the first African-American woman to desegregate the graduate school at West Virginia University.

She fell in love with math and in college took every math course possible.

“I was very happy,” says Johnson, who was named one of PEOPLE’s 25 Women Changing the World last November and whose amazing life story has inspired the critically acclaimed film Hidden Figures, which won the Screen Actors Guild Award on Sunday for Outstanding Performance by a Cast in a Motion Picture

In 1953, after years of being a teacher, she began working for NASA where she was nicknamed the “human computer.”

Johnson was able to calculate the trajectory for numerous space missions, including for the space flight of Alan Shepard, the first American in space and the trajectory for the 1969 Apollo 11 flight to the Moon.

“I’d do them over if I had to,” she says when she looks back at her career. “I’d do anything for anyone.”

Katherine Johnson People video screen grab

Despite her age, Johnson isn’t slowing down anytime soon.

“I like to learn,” she says. “That’s an art and a science. I’m always interested in learning something new.”

As a young girl she’d stop by the library on her home way in the evening and would pick up a book.

“I finally persuaded them to let me look at two books,” she recalls. “I could have read more than that in one night if they had let me.”

Johnson’s life served as the basis for a nonfiction book titled Hidden Figures: The American Dream and the Untold Story of the Black Women Mathematicians Who Helped Win the Space Race, which inspired the SAG Award-winning motion picture, starring star Taraji P. Henson as Johnson, along with Janelle Monáe as Mary Jackson and Octavia Spencer as Dorothy Vaughn — Jackson’s groundbreaking colleagues.

Johnson, who was given the Presidential Medal of Freedom by President Barack Obama in 2015, thinks she was able to succeed because she always loved what she did. It’s one piece of advice she has for young girls today.

“Find out what her dream is,” she says, “and work at it because if you like what you’re doing, you will do well.”

Johnson also taught her daughters a few life lessons.

“Don’t accept failure,” says Joylette Goble, who says she has always been in awe of her mother. “If there is a job to be done, you can do it and do it until you finish.”

She adds: “Be aware of people and help them when you can.”

Johnson’s other daughter, Katherine Goble Moore, says her mother has always been her role model.

“I will always be grateful for her,” she says.

A version of this story was originally published on Nov, 4, 2016.