The Women Who Changed Science and the Work That Did It

Grace Hopper used to hand out lengths of wire cut to 11.8 inches. That's how far light travels in a billionth of a second. She'd give one to an admiral, or a congressman, or a roomful of programmers who kept telling her the satellite delay couldn't be helped, and let the wire do the arguing. You can't feel a nanosecond. You can hold one.

That's the whole trick with science: find the object that makes the idea sit still long enough to look at.

What follows is a set of discoveries, not a set of biographies. The women who made them have been honored plenty with adjectives. They're better honored by somebody actually understanding what they found. Every one of these is explainable to a curious twelve-year-old in under two minutes, and most of them hold up a piece of the modern world.

Caroline Herschel found eight comets and got paid for it

In 1787, King George III put Caroline Herschel on a salary of 50 pounds a year to assist her brother William with his telescopes. That made her, as far as anybody can document, the first woman in England paid to do science.

She'd been a singer. She ended up sweeping the sky night after night with a small reflector, logging what she saw, and finding eight comets that nobody had seen before. She also built the catalog work underneath William's famous discoveries, correcting star positions that had been wrong for decades.

The Herschels are a family operation, which is the part usually left out. Brother and sister in a cold garden, one grinding mirrors, the other writing down numbers by candlelight while the dew came in. That's not a lesser kind of greatness. That's most of how greatness actually happens.

Henrietta Leavitt gave us the yardstick for the universe

The hardest problem in astronomy isn't seeing something. It's knowing how far away it is. A dim star nearby and a blazing star far off look identical from a porch in Ohio.

Leavitt worked at the Harvard College Observatory examining photographic plates, part of a team of women doing the arithmetic of the sky. Studying a particular kind of pulsing star, the Cepheid variables, she noticed something in 1908 and nailed it down by 1912: the brighter the star, the slower it pulsed. Time the blink, and you know its true brightness. Compare that to how bright it looks, and you know the distance.

That's the yardstick. Every measurement of the scale of the cosmos since runs through it, including Edwin Hubble's discovery that the Andromeda "nebula" was an entire other galaxy and that the universe is expanding. Hubble said as much. Leavitt died in 1921, before most of the consequences arrived.

Cecilia Payne figured out what stars are made of

In 1925, a graduate student submitted a doctoral thesis arguing that the sun is overwhelmingly hydrogen and helium. At the time everyone assumed stars had roughly the composition of the Earth, heavy on iron and silicon. Payne had applied new physics about how atoms absorb light at different temperatures, and the numbers said otherwise by a wide margin.

A senior astronomer advised her to add a line calling the result "almost certainly not real." She added it. She was right anyway, and he publicly agreed four years later.

The universe is about three-quarters hydrogen. Your sun is a ball of the lightest thing there is, squeezing itself into helium. A twenty-four-year-old worked that out from smudges on a spectrum.

Lise Meitner explained fission on a walk in the snow

Meitner spent thirty years in Berlin working on radioactivity with the chemist Otto Hahn. Being Jewish, she fled Germany in 1938 and landed in Sweden with almost nothing.

That December, Hahn wrote to her in confusion. He'd bombarded uranium with neutrons and found barium, an element barely half uranium's size. Chemistry said that was impossible.

Meitner spent Christmas in the town of Kungälv with her nephew Otto Frisch, and on a walk outdoors the two of them did the math on a scrap of paper. A uranium nucleus could split. The pieces would weigh slightly less than the original, and the missing mass would come out as energy, exactly as Einstein's equation predicted. Frisch called it fission, borrowing the word from cell biology.

Hahn received the Nobel in 1944. Meitner didn't. She refused to work on the atomic bomb. Element 109 is named meitnerium.

Chien-Shiung Wu broke a law of physics in six months

Physicists assumed the universe doesn't care about left and right. Mirror any experiment and it should behave the same. That's called parity, and in 1956 two theorists suggested it might fail in one specific corner of nature, the weak nuclear force. They needed somebody who could actually test it.

Wu cooled cobalt-60 to within a fraction of a degree of absolute zero, lined the nuclei up with a magnetic field, and watched which way the electrons flew out. They came out preferentially in one direction. The mirror universe behaves differently from ours.

The theorists won the Nobel the following year. Wu's experiment is the reason anybody believed them.

Barbara McClintock watched corn move its own genes

She grew maize at Cold Spring Harbor and stared at the color patterns on the kernels, year after year, mostly alone. By 1950 she was saying that pieces of chromosome pick up and move to new positions, switching genes on and off as they land. Genes were supposed to sit still like beads on a string.

The field ignored it for two decades. Then molecular biology caught up and found transposable elements everywhere, including in us. Roughly half the human genome is made of sequences that jump or once did.

She won the Nobel Prize in Physiology or Medicine in 1983, unshared. Nobody else was on the paper, because nobody else had been in the cornfield.

Grace Hopper made computers speak English

In the early 1950s the consensus was that computers do arithmetic and that telling one what to do means writing numbers. Hopper's view was that a machine ought to translate ordinary words into its own instructions. She built the first compiler to prove it, then built the languages on top.

Her work on FLOW-MATIC fed straight into COBOL, and COBOL is still running payroll and bank transfers at this hour. She retired from the Navy as a rear admiral at 79, which made her the oldest serving officer in the fleet.

Her line, the one worth taping above a desk: the most dangerous phrase in the language is "we've always done it this way."

Katherine Johnson checked the machine

Before John Glenn flew Friendship 7 in February 1962, NASA had an IBM 7090 compute his orbital path. Glenn didn't fully trust it. He asked them to have the girl run the numbers by hand, and if she got the same answer, he'd go.

Johnson did the trajectory math with a mechanical calculator and paper. The numbers matched. Glenn flew three orbits and came home.

She worked out the launch window for Alan Shepard's flight, the Earth-to-Moon trajectory for Apollo 11, and the backup procedures crews would use if the electronics quit. Three daughters at home the whole time.

What to do with all this

The history here gets flattened in both directions. Some of it really was a woman being shut out of a prize she earned. Some of it was a Nobel committee that can only name three people, or a scientist dying before the award she'd have won. Meitner's exclusion looks like prejudice. Leavitt's looks like bad timing and mortality. Read the specific case before you reach for the general grievance.

The better response isn't a slogan. It's the wire.

Cut a piece of string to 11.8 inches. Put it on the kitchen table tonight, tell your kids that's a nanosecond, and see if anybody asks a second question. If they do, you've got eight more of these in your pocket.