In 2013, The New York Times published an obituary for Yvonne Brill: “She made a mean beef stroganoff... and took eight years off from work to raise three children.” In the second paragraph, we learn Brill was a rocket scientist who invented a propulsion system to keep communications satellites in orbit. Rachel Swaby’s collected profiles include Nobel Prize winners, innovators, and significant scientists, all of whom are worthy of attention. Swaby is a freelance writer and editor.

ADA LOVELACE

1815–1852

MATHEMATICS • BRITISH

Ada Lovelace (née Augusta Byron) was given a famous name before she made her own. Her father was Lord Byron, the bad boy of English Romantic poetry, whose epic mood swings could be topped only by his string of scandalous affairs—affairs with women, men, and his half sister. Little Lovelace’s mother had had enough. One month after the girl was born, she took the baby and quit the marriage. Lord Byron left England and never returned.

However brief their time in each other’s company, Lord Byron was ever present in Lovelace’s upbringing—as a model of what not to be. Worried that Ada might lean toward the lyrical, her mother pushed a practical curriculum of grammar, arith­metic, and spelling on the child. When Lovelace became sick with the measles, she was bedridden, only permitted to rise to a sitting position thirty minutes a day. Any impulsive behavior was systematically ironed out.

It may have been a strict upbringing, but Lovelace’s mother did provide her daughter with a solid education—one that would pay off when Lovelace was introduced to the mathemati­cian Charles Babbage. The meeting occurred in the middle of her “season” in London, that time when noblewomen of a cer­tain age were paraded around to attract potential suitors. Bab­bage was forty-one when he made Lovelace’s acquaintance in 1833. They hit it off. And then he extended the same offer to her that he had to so many: come by to see my Difference Engine.

Babbage’s Difference Engine was a two-ton, hand-cranked calculator with four thousand separate parts designed to expe­dite time-consuming mathematical tasks. Lovelace was imme­diately drawn to the machine and its creator. She would find a way to work with Babbage. She would.

Her first attempt was in the context of education. Lovelace wanted tutoring in math, and in 1839, she asked Babbage to take her on as his student. The two corresponded, but Babbage didn’t bite. He was too busy with his own projects. He was, after all, dreaming up machines capable of streamlining indus­try, automating manual processes, and freeing up workers tied to mindless tasks.

Lovelace’s mother may have tried to purge her of her fa­ther’s influence, but as she reached adulthood, her Byron side started to emerge. Lovelace experienced stretches of depression and then fits of elation. She would fly between frenzied hours of harp practice to the concentrated study of biquadratic equa­tions. Over time, she shook off the behavioral constraints im­posed by her mother, and gave herself over to whatever pleased her. All the while, she produced a steady stream of letters. A playfulness emerged. To Babbage, she signed her letters, “Your Fairy.”

Meanwhile, Babbage began spreading the word of his Ana­lytical Engine, another project of his—a programmable beast of a machine, rigged with thousands of stacked and rotating cogwheels. It was just theoretical, but the plans for it were to far exceed the capabilities of any existing calculators, including Babbage’s own Difference Engine. In a series of lectures deliv­ered to an audience of prominent philosophers and scientists in Turin, Italy, Babbage unveiled his visionary idea. He convinced an Italian engineer in attendance to document the talks. In 1842, the resulting article came out in a Swiss journal, pub­lished in French.

A decade since their first meeting, Lovelace remained a be­liever in Babbage’s ideas. With this Swiss publication, she saw her opening to offer support. Babbage’s Analytical Engine de­served a massive audience, and Lovelace knew she could get it in front of more eyeballs by translating the article into English.

Lovelace’s next step was her most significant. She took the base text from the article—some eight thousand words—and annotated it, gracefully comparing the Analytical Engine to its antecedents and explaining its place in the future. If other ma­chines could calculate, reflecting the intelligence of their own­ers, the Analytical Engine would amplify its owner’s knowledge, able to store data and programs that could process it. Lovelace pointed out that getting the most out of the Analytical Engine meant designing instructions tailored to the owner’s interests. Programming the thing would go a long way. She also saw the possibility for it to process more than numbers, suggesting “the engine might compose elaborate and scientific pieces of music of any degree of complexity or extent.”

Reining in easily excitable imaginations, Lovelace also ex­plained the Engine’s limitations (“It can follow analysis; but it has no power of anticipating any analytical relations or truths”) and illustrated its strengths (“the Analytical Engine weaves al­gebraical patterns just as the Jacquard-loom weaves flowers and leaves”).

The most extraordinary of her annotations was Lovelace’s so-called Note G. In it, she explained how a punch-card-based algorithm could return a scrolling sequence of special rational numbers, called Bernoulli numbers. Lovelace’s explanation of how to tell the machine to return Bernoulli numbers is con­sidered the world’s first computer program. What began as a simple translation, as one Babbage scholar points out, became “the most important paper in the history of digital computing before modern times.”

Babbage corresponded with Lovelace throughout the an­notation process. Lovelace sent Babbage her commentary for feedback, and where she needed help and clarification, he of­fered it. Scholars differ on the degree of influence they believe Babbage had on Lovelace’s notes. Some believe that his mind was behind her words. Others, like journalist Suw Charman-Anderson, call her “[not] the first woman [computer program­mer]. The first person.”

Lovelace guarded her work, and sometimes fiercely. To one of Babbage’s edits, she replied firmly, “I am much annoyed at your having altered my Note . . . I cannot endure another per­son to meddle with my sentences.” She also possessed a strong confidence in the range of her own abilities. In one letter, she confided, “That brain of mine is something more than merely mortal. . . . Before ten years are out, the Devil’s in it if I haven’t sucked out some of the lifeblood from the mysteries of the uni­verse, in a way that no purely mortal lips or brains could do.”

For what it’s worth, Babbage himself was effusive about her contributions. “All this was impossible for you to know by intu­ition and the more I read your notes the more surprised I am at them and regret not having earlier explored so rich a vein of the noblest metal.”

The Department of Defense named a computer language after her. Ada Lovelace Day celebrates the extraordinary achievements of women in science, technology, engineering, and math. The “Ada Lovelace Edit-a-thon” is an annual event aimed at beefing up online entries for women in science whose accomplishments are unsung or misattributed. When her name is mentioned today, it’s more than a tip of the hat; it’s a call to arms.

BARBARA MCCLINTOCK

1902–1992

GENETICS • AMERICAN

At the University of Missouri, Barbara McClintock, an acclaimed geneticist working on how one generation of corn passes its genetic traits on to the next, was known as a trou­blemaker. The marks against her—wearing pants in the field instead of knickers, allowing students to stay in the lab past their curfew, managing with a firm, no-nonsense style—were practical choices, ones McClintock believed would improve her work and that of others. But to her superiors, her behavior was obstinate. McClintock was excluded from faculty meetings, her requests for research support were denied, and her chances for advancement were made clear: If she ever decided to marry, she’d be fired. If her research partner left the university, she’d be fired. The dean was just waiting for an excuse.

There are times for perseverance and there are times to get out quick. In 1941, after five years at the University of Missouri, McClintock found the door, slamming it behind her.

Never one to be burdened with possessions (or weighed down by the limited vision of others), McClintock hopped in her Model A Ford and, like a dandelion seed surfing the breeze, set out not knowing where she and her masterful canon of genetics work would land. When she turned her back on the University of Missouri, it was possible she was also losing the career that she’d worked so hard to cultivate.

But freedom felt like home to McClintock. When she was a baby, her mother used to set her on a pillow and leave her to amuse herself. Simply mulling over the world and all of its amazing patterns and peculiarities was a happy pastime of Mc­Clintock’s earliest years. “I didn’t belong to that family, but I’m glad I was in it,” she said. “I was an odd member.”

Her outsider status was not so different in the scientific community. Though she absolutely belonged there and was fully absorbed in her work, McClintock never completely integrated. One part of the issue was societal. Getting a faculty position at a university was exponentially harder for women in the 1920s than it was during World War II, when positions opened up for women when men were called to war. Though up to 40 per­cent of graduate students in the 1920s in the United States were women, that didn’t translate into jobs—especially in science. Fewer than 5 percent of female scientists in America were able to land jobs at coed institutions. And even then, the home eco­nomics and physical education departments were the biggest hirers. Women rarely rose to posts as prestigious as professor. In the Venn diagram of female biologists hired as professors at major research institutions, the middle was a lonely place. Mc­Clintock never got there.

McClintock’s work also kept her out of the mainstream. She was either ahead of her time, with experimental methods so dense and complicated that they were difficult for her peers to understand, or she chose subjects that operated outside trends in biology.

During her first year of graduate school at Cornell Univer­sity, for example, McClintock took it upon herself to identify discrete parts of corn’s chromosomes. Her short-term advisor, a cryptologist, had been after the same tricky-to-find prize for a long time. McClintock saddled up to the microscope and—bam—“I had it done within two or three days—the whole thing done, clear, sharp, nice.” She revealed the answer so quickly that it bruised her advisor’s ego. McClintock was so thoroughly hopped up on the quest that she hadn’t even considered the pos­sibility that she would upstage her superior. In other instances, her groundbreaking experiments required an interpreter. When she laid out her case for the location of genes on corn’s distin­guishable ten chromosomes, her method remained a mystery to her colleagues until a scientist from another school visited and unpacked the study design for public consumption. “Hell,” said the interpreter. “It was so damn obvious. She was something special.”

McClintock adored biology at Cornell. She was no typical high achiever. Following the acknowledgment of her corn chro­mosome discovery as a master’s student, she attracted a pack of professors and PhDs who trailed her around campus, “lapping up the stimulation she provided,” said one, like puppies tum­bling after castoff treats. Together the group, with McClintock as its intellectual leader, ushered in an especially bright period of genetics. McClintock proudly recounted how the “very pow­erful work with chromosomes . . . began to put cytogenetics, working with chromosomes, on the map. . . . The older people couldn’t join; they just didn’t understand. The young people were the ones who really got the subject going.”

Post-PhD, McClintock spent a few more years at Cornell, publishing papers, teaching botany, and advising students. In 1929, she and a graduate student bred together one strain of corn with waxy, purple kernels with another strain that had ker­nels that were neither waxy nor eggplant-colored. McClintock’s experiments showed that some kernels inherited one trait but not the other, for example, brightly colored kernels without the waxy texture. When McClintock looked at the chromosomes through a microscope, she found that their appearance was no­ticeably different, and in the cases where kernels had one trait but not the other, parts of a chromosome had traded places.

The discovery was hailed as one of the greatest experiments of modern biology. At just twenty-nine years old, McClintock proved herself a powerful force in genetics research—but with­out a permanent faculty position. The head of the department was in favor of bringing her on to become a professor but the Cornell faculty forbade it. So McClintock left, picking up fel­lowships here and there, searching for a new place to put down roots.

The country’s greatest research institutions should have fought over McClintock, but instead she ended up searching for a space to plant her corn. She found one at Cold Spring Harbor in Long Island, New York. The facility was initially founded in 1890 as a place for high school and college teachers to learn about marine biology. When McClintock arrived, it was a genet­ics institute. The atmosphere was ideal; McClintock wouldn’t have to teach, and there were no restrictions on her research, which would be entirely self-directed. She could wear jeans and stay as late and as often as she wanted. The place suited her so well that when she socialized, she would invite friends to the lab instead of to her “home,” an unheated, converted garage down the street used for nothing more than sleep.

McClintock was extraordinarily organized. Clothes in her closet all faced the same direction, and each of her scientific specimens was assiduously labeled. Sometimes she’d get so en­grossed in her work that peering into a microscope would feel to her like spelunking through the deep secrets of a cell. “You’re not conscious of anything else,” she remembered. “You’re so absorbed that even small things get big.”

At Cold Spring Harbor, McClintock spent six years on her greatest scientific accomplishment. When she finally unveiled her findings to a group of researchers, her hour-long talk was met with silence. One listener recalled that the talk landed “like a lead balloon.” McClintock had just laid out a meticu­lously researched case that genetics was much, much more fluid than what scientists had previously realized, with genes able to switch on and off and change locations. The prevailing belief was that genes were like bolted- down pieces of furniture. In the 1950s, scientists from all different fields of study were getting into the genetics game; chemists and physicists applied their disciplines to understanding inherited traits. With so many new ways to look at our genetic makeup, corn had fallen out of favor. “I was startled when I found they didn’t understand it, didn’t take it seriously,” she said of the talk. “But it didn’t bother me. I knew I was right.”

That she was. The acceptance of her ideas didn’t come until nearly two decades later, when molecular biologists finally saw in bacteria what McClintock had seen in corn. At the news, McClintock was overjoyed. “All the surprises . . . revealed recently give so much fun,” she wrote to a friend. “I am thoroughly enjoying the stimulus they provide.” Public acknowledgment brought a string of awards— the MacArthur Foundation Fellowship, the Albert Lasker Basic Medical Research Award— but no Nobel. Then finally, in 1983, thirty- two years after her big- but- ignored discovery, she heard her name announced on the radio. She had finally won science’s most prestigious prize. Her “discovery of mobile genetic elements” was touted by the Nobel Committee as “one of the two great discoveries of our times in genetics.”

In the ensuing years, she was asked time and time again the same question, some delicately worded take on Were you bitter it took so long? Her answer: “No, no, no. You’re having a good time. You don’t need public recognition, and I mean this quite seriously, you don’t need it.” With characteristic confidence, she added, “When you know you’re right you don’t care. It’s such a pleasure to carry out an experiment when you think of something. . . . I’ve had such a good time, I can’t imagine having a better one. . . . I’ve had a very, very satisfying and interesting life.”

From HEADSTRONG: 52 WOMEN WHO CHANGED SCIENCE AND THE WORLD. Used with the permission of the publisher, Broadway Books, an imprint of Penguin Random House LLC. Copyright © 2015 by Rachel Swarby.