How Women Served as Human Computers During the Manhattan Project and the Development of the Bomb that Ended World War II
Ron Brock, author of The Thicket’s Prodigy

It was August 7, 1945; President Harry S. Truman’s announcement was brief:

“16 hours ago, an American airplane dropped one bomb on Hiroshima, an important Japanese army base. That bomb had more power than 20,000 tons of TNT… Which is the largest bomb ever used in the history of warfare. It is an atomic bomb. The force from which the sun draws its power has been loosed against those who brought war to the Far East…”

In a statement issued later that day Secretary of War, Henry L Stimson, described the new weapon as perhaps “the greatest achievement of the combined efforts of science, industry, labor, and the military in all history.”

What was not included was how it all came together. The key ingredients? Some of the world’s most brilliant scientists, and the women who supported the calculations leading to the conclusions required to enable bomb formatting, a function particularly critical to the Plutonium bomb, “Fat Man.”  I write about this as well as the points below—and much more—in my book, The Thicket’s Prodigy.

Lise Meitner, Austrian-Swedish physicist was one of those responsible for the discovery of the element protactinium and nuclear fission.

Before the Calculations:
A Woman Discovers the Possibility of the Atomic Bomb 

In 1938 an Austrian physicist, Lise Meitner, and her nephew Otto Frisch, had mathematically proven the possibility that a nuclear chain reaction, if left unchecked, could create an explosion of colossal force. They named the process “fission.”

That’s right. Possibility of an atomic bomb was the discovery of a brilliant scientist who just happened to be a woman. And one who wanted no part of recognition for having discovered one of the 20th century’s most significant scientific breakthroughs. At that point, that fission could be more than theoretical was uncertain as a bomb was concerned, but was soon to become reality.

Mathematics and the Manhattan Project

Implementing Ms. Meitner’s postulate, the Manhattan Project was assembled, dedicated to building a “super-bomb.” Italian physicist, Enrico Fermi, had recently proven that Uranium 235 would fission under controlled conditions. But the physics regarding a bomb remained theoretical. They had the concept; implementation was another story. Until they could conduct actual tests, verifying the concepts’ validity could only be done mathematically. And such a project was materially immense.

They needed help.

Los Alamos’ Women Computers

Anyone assuming the Manhattan Project to have had cutting-edge computation support would be correct, at least when taken in context with the times. The high-speed systems we know today were still futuristic.

To think of women as computers sounds Orwellian. It wasn’t quite like hooking them up in parallel to a machine that then performs calculations, but in some manner, it was a little bit like that. The word “computer” applied to a single individual working with a Frieden or Marchant desktop adding machine dedicated to completing the overwhelming number of calculations required for atomic fission’s theoretical equations. For hours daily, most often seven days per week, these human computers labored under the same enormous time pressures experienced by the individuals feeding them the raw data to be processed. Imagine the intensity.

Jean Dow Bachar was a human “computer” at Los Alamos during the Manhattan project

Who were these women? And how did they end up in Los Alamos? Well, many, if not most, were the wives of some of the world’s most brilliant scientists. Included among this group of what Robert Oppenheimer referred to as his “luminaries,” were: Hans Bethe, Edward Teller, Enrico Fermi, Leo Szilard, and many more were to come.

It was not unusual that they had met their future wives in graduate schools while the women themselves were pursuing their own advanced scientific degrees. Now this, also brilliant, group was in Los Alamos, and in need of something to do.

These women, no less dedicated than the scientists who were relying on their support, were so effective they wore out the machines they were working with, resulting in regular breakdowns. It seems you could expect that as a machine wore out it would be replaced by a new one. But not so. It was wartime, and everything was scarce. As a result, critical computational needs were disrupted with inconvenient frequency.

Solving the problem, two young physicists, Nicholas Metropolis, and Richard Feynman assumed the task of repairing the non-functioning machines, becoming as indispensable as the women they were supporting.

It was nearing the War’s end when it was discovered that newly developed IBM punch card machines could perform needed computation tasks at a rate faster than even the highly accomplished ladies could muster. It was the beginning of another new scientific revolution, a mechanical means of increasing the speed of calculating complex problems.

But it was the women of Los Alamos and their desktop adding machines that made possible the calculations required of building a bomb.  It’s time to give them the recognition they deserve.



Ron Brock’s career included a role as a Senior Product Manager at Frito Lay where he was responsible for the highly successful launch of Nacho Cheese flavored Doritos brand tortilla chips.  His memoir The Thicket’s Prodigy: The Extraordinary Life of an Improbable Genius, details his life story, including time spent in Los Alamos, New Mexico where his father worked as part of a team redesigning the Manhattan Project’s atomic bomb. Ron, also the author of Gamebreaker: Guide to World Class Selling, resides in Scottsdale, Arizona.  Learn more at