She no longer had to wonder.
Two atomic bombs obliterated Hiroshima and Nagasaki and ended World War II.
Her father and his fellow scientists had introduced the human race to a weapon capable of wiping out hundreds of thousands of lives in moments. It was a weapon that would hold the world in thrall forever.
Nella Fermi finally realized what those weeks-long secret trips meant, why her father, Nobel Prize-winning physicist Enrico Fermi, had a code name, Henry Farmer, and a bodyguard, and why they had lived all those wary years in Chicago and Los Alamos, N.M.
It meant the end of secret lives for the families of the Manhattan Project, men, women and children. It meant sizing up the future in which the prospect of fiery death would always be just over the horizon.
The atomic bomb shook the entire Earth when its meaning sank in. Some of the scientists who created it felt the guilt of its impact on humanity and immediately sought to ban the atom as a weapon.
But for Nella Fermi, the oldest child of Enrico and Laura Fermi, there were never any recriminations, never any lingering questions, never a sense of guilt. She shared with her father the conviction that the bomb was an inevitable outcome of learning about the atom.
A half-century later, she remembers a letter from Fermi's sister "in which she said it had been reported in the Italian media that Enrico had been involved in the bomb, and she trusted that this was not so."
"My reaction was amazement because at the time they were heroes, no question about it.
"Most people felt this was something that needed to be done."
It was the only hint of criticism she can remember.
Even before the first bomb was dropped, scientists suggested that a demonstration of its power might suffice to end the war, without loss of life. After the bombs were dropped, the scientists who made it were of mixed feelings. Proud at achieving their goals, comforted by the end of the war, most felt a tremendous responsibility to control its subsequent use.
In fact, many of the atomic scientists started peace movements on their own. A group of scientists at the University of Chicago began a journal called "The Bulletin of the Atomic Scientists."
It still has a doomsday clock on the cover signifying the Cold War crises and the nearness of nuclear warfare. When it first appeared, the clock's hands showed eight minutes to midnight. When the Soviets fired their H-Bomb, it was reduced to three minutes to midnight. With the end of the Cold War, the hands were set back.
"A lot of scientists were in fact worried that this was not the weapon to end all weapons, but the weapon to end all mankind," said Nella, now 62.
When she was in her early teens, she guessed about what her father was doing. She had read something in a physics textbook that suggested that machines to come would run on nuclear energy. She thought of engines for battleships or submarines.
"I knew my father was an atomic scientist," she said. "I knew he was doing secret war work. I knew that all these other guys around were physicists. It didn't take any great leap of the imagination. But my mother being older and wiser . . . I think it's reasonable speculation (that she knew about the bomb)." But, she insists, her father never told his wife or children, such was his loyalty to his new country. Nor did the subject come up.
It was a strange world for a young girl and teen-ager. Her famous father would disappear for weeks at a time to work in secret laboratories where people had code names.
The code names often would sit themselves down at the Fermi dining table. One was the Danish physicist Niels Bohr, code-named Nicholas Baker. Everyone called him Uncle Nick.
Also at the table, especially on Sunday nights, were Fermi's students, some of whom went on in peaceful times to earn Nobel Prizes of their own.
But for Nella, snatched from the anti-Semitism and saber-rattling of Mussolini's Italy, it was an adult world, often frightening and lonely. In Rome in 1938 there was talk of war in the air.
"My father came home with a bunch of gas masks one day. And that was scary. He didn't have one for (baby brother) Judd because he couldn't find one small enough."
She and her 3-year-old brother would see their childhoods rearranged. Their father was from a Roman Catholic peasant family; their mother was upper-middle class and Jewish.
There were three reasons the Fermi family left Italy. The first was the promulgating of anti-Semitic laws by Mussolini, the second the fear of war. The third was Fermi's Nobel Prize which facilitated their escape to America via Stockholm and England.
Their U.S. itinerary began in New York, then happy days for her in a suburb in New Jersey absorbing American language and culture.
But her father lived in a security web. As an enemy immigrant, this Nobel laureate had to take an aptitude test in which two of the questions were to add 15 and 27, and to divide 29 by 2.
One day, she says, her father decided to teach her algebra. He bit off more than he could chew. A child's mind that already had learned two languages was not ready for a third.
The highlight of those years was the transfer to the government-built scientific city of Los Alamos.
The campus was a converted private boys' school with riding horses and stables. The school's faculty housing came to be called "Bathtub Row" because they were the only houses with bathtubs. All other quarters had showers.
More important in Los Alamos was her new high school, a no-nonsense academy for the children of the scientists and staff, a breath of fresh air after the affluent high school at the University of Chicago.
At Los Alamos, Nella found two other girls her age, companions at last.
"It was fun and games, like playing spies. It was like, 'Oh boy, we've got a secret and nobody knows what it is.'
"The grown-ups would probably deny it, but even they felt it. It was, for them, like being in college again.
"It was a campus, a very exclusive campus, a campus you couldn't be on unless you were certified brilliant. And really just everybody reveled in that feeling.
"The secrecy became a game, a scientist's game too. People would invent codes to send to their clever friends outside, to get through the censors." There was little social life. The closest thing to dating was attending the square dances at the community hall.
"Actually," Nella said, "It was a very stratified society. Top of the ladder were the scientists, then came the engineers and the tech people. And then were those who did maintenance; a lot of them were Spanish-Americans.
"I mean even the neighborhoods were segregated."
When the bombs were dropped, it meant the end of a long journey for the Italian physicist and his small family.