Baby Trinity

Pregnant physicist observes first atomic bomb test, daughter born shortly thereafter.

By Brye Steeves | August 29, 2022

Trinity Opt
Elizabeth “Diz” Graves and her daughter, Marilyn, in 1959.

For Elizabeth "Diz" Graves, the summer months of 1945 were a symbolic intersection of her personal and professional lives. 

As a physicist at the then-secret lab in Los Alamos, Elizabeth participated in the trinity test the successful detonation of the worlds first nuclear weapon, which took place in the remote New Mexico desert on July 16, 1945.

Her role was to observe the explosion that advanced science into the atomic age. And, Elizabeth was seven months pregnant.

In a cabin approximately 35 miles east of the Trinity test site, the first-time-mother-to-be worked alongside her husband and fellow physicist, Alvin Graves. They listened to scientist Sam Allison on the radio: "three, two, one .... ," saw the unmistakable success of the gadget, and then monitored the fallout with survey meters. Not long after, Elizabeth gave birth to Marilyn, who was affectionately nicknamed "Trinity."

Marilyn was nicknamed Trinity because Elizabeth, a physicist, was seven months pregnant with her when she witnessed the Trinity test in 1945.

Starting a Career in Science

Elizabeth earned her Ph. D. In physics in 1940 from the University of Chicago, where she met and married Alvin. He was recruited to work for the Manhattan project, the U. S. Governments effort to create the atomic bombs and help end World War II, but Alvin would not accept the job unless Elizabeth was also offered a position, according to Their Day in the Sun: women of the Manhattan Project.

"She's a better physicist than I am," Alvin had said, according to his obituary in the New York Times.

The couple arrived in Los Alamos in early 1943.

A page of Elizabeth’s observations from the test are pictured.


"Might as well go to the Lab"

Elizabeth was known to be smart, funny, hard working, and maternal. "She was most outstanding in that she managed to combine successfully a career in physics and raising a family," a friend said in a 1972 article in the Los Alamos Monitor. The Graves would stay at the Lab for their entire careers, with Elizabeth eventually becoming a group leader in experimental physics and Alvin ultimately leading the field testing division for 17 years.

John Hopkins, who worked at the Lab as a nuclear physicist for 34 years and was the associate director responsible for the nuclear weapons program upon his retirement, remembers when Alvin preceded Elizabeth in death in 1965.

"Diz threw herself completely into research," Hopkins said. "When I commented about her long hours and dedication, she responded that when there was nothing at home she might as well go to the Lab."

Elizabeth died from cancer on January 6, 1972. She was 55.

After her death, her colleagues shared memories of Elizabeth, including from one of her pregnancies: she went into labor while conducting important experiments in her laboratory, according to the Atomic Heritage Foundation. Elizabeth was able to complete her work while also monitoring her contractions with a stopwatch. 🔎


The Trinity Test

At around 5:30 a.m. on July 16, 1945, the worlds first atomic device nicknamed The Gadget was detonated in the New Mexico desert, proving the feasibility of weaponizing energy from the atom. The successful explosion marked the beginning of the Atomic Age.


The power from The Gadget's detonation was equivalent to around 21,000 tons of TNT; its mushroom cloud grew to about 3,280 feet wide with a column of smoke to a height in excessof 40,000 feet.

The Gadget verified that an implosion-type plutonium bomb called Fat Man would be successful when released above Japan. Fat Man was the second of two atomic bombs to be used in combat. The plutonium implosion-type weapon was released above Nagasaki on August 9, 1945. Fat Man was 10,800 pounds, nearly 11 feet long, and 5 feet in diameter.


Little Boy was the first atomic bomb to be used in combat. The uranium gun-type weapon was released above Hiroshima on August 6, 1945. Little Boy was 9,700 pounds, 10 feet long, and just over 2 feet in diameter. It was not tested with a detonation; scientists knew it was a mathematical certainty that it would be successful in combat. 🔎