Bettina Hoerlin

and Gino Segrè

are authors of the recently published "The Pope of Physics: Enrico Fermi and the Birth of the Atomic Age" (Henry Holt)

In 1939, when an Italian immigrant arrived for his appointment with a Navy admiral in Washington, he overheard the desk officer announcing, "There's a wop outside."

The immigrant had been designated by key physicists to warn American military leaders about the impending peril of the Nazis developing nuclear weapons. The scientists thought that Enrico Fermi, having just won the 1938 Nobel Prize for physics, would give extra weight to the military's fears.

Fermi had reached American shores a mere two months earlier, picking up his Nobel in Sweden as he traveled his escape route from fascism and anti-Semitism in Italy.

Today the derogatory term wop, roughly meaning Italian thug, is rarely used. But America has regrettably found other ways of stigmatizing immigrants, equally demeaning and conveying a clear message of their not being wanted or valued. Luckily Fermi ignored the insult and went on to become one of this country's most loyal citizens and among its most celebrated physicists.

Under Fermi's leadership, the world's first nuclear self-sustaining chain reaction was achieved Dec. 2, 1942, at the University of Chicago. This seminal event marked the birth of the atomic age and was the necessary precursor to nuclear weapons, as it was to nuclear medicine.

Shrouded in secrecy, the discovery became a basis for the Manhattan Project, the major industrial enterprise employing 100,000 people, all sharing the common mission of beating Nazi Germany in building an atomic bomb. Fermi was recruited to its Los Alamos Laboratory site as an associate director and a special division became named after him.

On this remote mesa in New Mexico, Fermi joined forces with several other fellow refugees who had fled tyranny and persecution to live in a country of freedom and tolerance. They, too, were drawn to Los Alamos by the desire to participate in the war effort and by the urgency of the task.

Sometimes called "refugee scientists," they were renowned in the world of physics. Many were Jewish or, like Fermi, were married to someone Jewish. The cafeteria at the Los Alamos Scientific Laboratory was abuzz with foreign languages, although the scientists were all urged to speak English with one another. They did so gladly, although occasionally, when excited about a result, Italians, Germans, Hungarians, and others might break into their native tongues, only to immediately correct themselves.

The discoveries of yet another refugee to America had been instrumental to the tasks at Los Alamos. Fermi had prophetically noted in 1922 that Einstein's famous equation of E=mc2 implied the possible delivery of a vast quantity of nuclear energy. "It does not seem possible, at least in the near future," he observed, "to discover a way to release such a frightening amount of energy, just as well for its first effect would be to smash into smithereens the physicist who had the misfortune of finding the way to produce it."

Little did Fermi realize that he would be one of those physicists who found "a way to produce it." He was involved in every phase of the Manhattan Project, whether as a researcher, an administrator, or an adviser, and he played a pivotal role in its success. All of this is particularly remarkable because government bureaucracies had alternatively regarded Fermi as a security risk, an enemy alien, and most hurtfully, a committed fascist. When the Army had performed a background check of him in August 1940, its report concluded, "Employment of this person on secret work is not recommended." That recommendation was thankfully overruled.

In 1941, when the United States officially entered WWII, the government imposed a set of restrictions on Italian, German, and Japanese immigrants, labeling them enemy aliens. For Fermi, this meant it was cumbersome to commute between Columbia University, where he taught, to the University of Chicago, where he headed a research team intent on proving that fission could be controlled.

Every time Fermi traveled, he needed special permission that was granted only grudgingly by authorities. It was made more complicated by the secret nature of his mission that prohibited him from explaining the reason for frequent trips to questioning bureaucrats. But by the time Fermi moved to Los Alamos in the summer of 1944, his status had changed from enemy alien to one of holding this nation's highest security clearance. And he had become a U.S. citizen.

Upon Fermi's untimely death at age 53 in 1954, the iconic broadcaster Edward R. Murrow commented: "It was the good fortune of this country that Dr. Fermi found asylum in 1938. Under the present immigration laws, he might not be admissible. . . . His exclusion would be shared by other immigrant founding fathers of the atomic age."

With trademark astuteness, Murrow was alluding to the rampant McCarthyism of the time that was sullying America's reputation as a decent and inclusive country. Murrow brought to the fore an issue that still resounds in America.

Obviously not all refugees are Fermis, but there just might be one like him among them. It is worth noting that five of the six U.S. recipients of 2016 Nobel Prizes are immigrants. Even in the case of the one outlier - Bob Dylan - it was his grandparents, not he, who came to America in search of a better life.

With the growing threat of sweeping changes to immigration policies, America's place as a welcoming land of opportunity is more important to preserve than ever.