Robert Oppenheimer's relationship with Catalan musician Pau Casals

"Cher Maitre," the American theoretical physicist known as the "father of the atomic bomb," Robert Oppenheimer, wrote to Catalan musician Pau Casals on January 14, 1960.

In a letter read by Catalan News, the physicist was explaining his plans to visit Puerto Rico. Although Casals' health had not "been good," Oppenheimer requested that "if it permits a visit, it would be an honor and a great pleasure for us [his wife and him] to call on you," as the text kept at Catalonia's National Archive and the Pau Casals Foundation (Fundació Pau Casals/Arxiu Nacional de Catalunya. Fons Pau Casals) reads.

The two men met on October 24, 1958 when Casals performed for the first time at the headquarters of the United Nations in New York City, US. He had not played in years due to his stance against Spain's dictatorship under Francisco Franco. In the room, Oppenheimer enjoyed the show. They were later introduced to each other.

Casals had just spoken against nuclear weapons, and Oppenheimer, after his time in the Los Alamos laboratory, had a similar point of view.

Years later, in 1960, the University of Puerto Rico had invited the physicist for a conference in an amphitheater defined as "one of those widely-accepted scandals; complain about it and you get shrugs and puzzled glances from the hardened denizens of the Rio Piedras campus," an article seen by Catalan News published by the regional newspaper of The Island Times reads.

"It is a scandal, nevertheless. If it can't be cleaned up regularly, surely the budget could cover times when distinguished guests have been invited," as Oppenheimer's lecture was delivered "against the hitter acoustical opposition of the air conditioner and in a setting of almost unparalleled griminess," the text written in 1960 reads.

The lecture took place on February 17, 1960 at night.

And at that time, Oppenheimer was supposed to meet up with Pau Casals, as another letter published by the Spanish newspaper La Vanguardia reads, a text kept at the US Library of Congress, under Oppenheimer's archives.

"I am very happy to know that you are coming to Puerto Rico, and it will be a pleasure and honor to receive you any day at any time which is convenient to you," Pau Casals wrote in response to Oppenheimer "with admiration and cordial regards," from Santurce, Puerto Rico on January 26, 1960.

But while the wish to meet up was shared by both figures, it was impossible to find a moment, as Oppenheimer was ill and had a busy schedule.

"It was with sorrow and a sense of loss that I had to abandon the high honor and great pleasure of calling on you last week. The doctor would not let me do anything that went beyond the minimum obligations of my visit to the University, and I was indeed too ill to make a good guest. At the University, the authorities were kind enough to speak with a certain insistence of my returning within the year. I hope that that will give us an occasion to make up the loss, and come to see you," the physicist wrote.

Casals too was not feeling well, as La Vanguardia reports, meaning that the visit was impossible, although both hoped to see each other in the future.