What did an ordinary tape measure have to do with a revolution in the treatment of tenured women faculty at the Massachusetts Institute of Technology?

Everything, it turns out.

That is the story New York Times reporter Kate Zernike tells in her new book, The Exceptions: Nancy Hopkins, MIT, and the Fight for Women in Science.

Zernike, whose late parents Frits and Barbara lived in Essex, will talk at the Essex Library on Saturday, April 15 at 4 p.m. in conversation with Sam Tanenhaus, the retired editor of the New York Times Sunday Book Review.

There is another a local connection in The Exceptions. Sarah Goldberg, the daughter of Essex Library Executive Director Ann Thompson, worked with Zernike when Goldberg was an editor at Scribner’s, the publisher of the book.

Now for the tape measure.

In the mid-1990s, when tenured MIT biology professor and cancer researcher Nancy Hopkins’ cramped laboratory could no longer accommodate her experiments, her equipment, and her graduate students, she asked for a modest amount of added space. The head of the biology department countered, telling Hopkins her office was the same size as other tenured faculty members and his own office was only a bit more spacious.

Hopkins’ eyes told her that was inaccurate, but she was a scientist, so she wanted data. In the evening, when her building was unoccupied, she took a tape and measured each office and each lab. The head of the department’s office was four times as large, and every other faculty member in the department, all male, had more space than she had.

Zernike’s book, however, is not about office real estate. It is about the discrimination, often unconscious, that finally persuaded 16 female professors, noted scientists all, to form a committee in 1995 to confront MIT’s administration with the ongoing inequality in their situation: less money, less lab space, less equipment, slights in everything from teaching to committee assignments.

The female scientists had explained the slights away by not fitting them into a pattern of bias but rather seeing each as an exception. Hence the double significance of the book’s title, The Exceptions; a story about exceptional women who looked at the common inequities they encountered in their professional lives as exceptions, not paradigms of ongoing inequality.

The unconscious bias, Zernike added, often became evident not as the woman started out but mid-career, as they attempted to build the kind of professional lives far more available to their male colleagues.

“The first big paper on unconscious bias was written in 1995, and in 1999 unconscious bias was still not much known,” Zernike said. Still, it was in 1999, after working with the committee of 16 women, that MIT issued an extraordinary report, admitting that what their report called “underlying marginalization” had negatively impacted the careers of tenured women faculty.

Zernike, who was part of a Pulitzer Prize-winning team at the New York Times in 2002 for reporting on al-Quaeda, first wrote about the MIT admission of bias as a reporter for the Boston Globe in 1999. To her surprise as well as that of the 16 female faculty members, the article drew national attention to the issue.

Over 20 years later, Zernike felt there was still more to tell and revisited the story with a perspective informed by 21st century events like the Me Too movement as well as by the availability of Nancy Hopkins’ papers. Zernike had access to the papers, as well as access to Hopkins, now retired, herself. In addition, she was also able to interview the other surviving members of the group of 16 women.

The challenge was not only to tell the stories of the participants but to describe the science they were involved in. “I wanted to get the science right,” Zernike said. “I wanted to make it understandable but not dumbed-down.”

She also wanted her audience to know more about women in science. “If people know a woman scientist, it is usually nothing beyond Marie Curie,” she said. “I wanted young women to be excited by a career in science.”

Her literary agent told her that she had succeeded in that and more, describing the book’s theme as resonating across generations. “She said she wanted to give it to her 20-year-old granddaughter and her 80-year-old mother,” Zernike said.

Today, the place of women at MIT has changed since the time when scientists profiled in The Exceptions worked there. Now the president is a woman, as are the provost and the chancellor. And Nancy Hopkins’ measuring tape is in the MIT museum.

Kate Zernike in conversation with Sam Tanenhaus. Essex Library, 33 West Avenue, on Saturday, April 15, 4 p.m. The event is free but registration required Sign up at 860-767-1560 or e-mail staff.essexlib@gmail.com.