Como Conference

The International Congress of Physicists (Italian: Congresso internazionale dei fisici), better known as the Como Conference or the Volta Conference, was an international academic conference held from 11 to 27 September 1927, near Lake Como, Italy as part of a series of celebrations of the hundredth anniversary of the death of Alessandro Volta. This conference inspired the Volta Congresses held in Rome and organized since 1931.

It concerned the topic of Volta's work and quantum mechanics. It gathered 61 physicists and mathematicians from all over the world. During the conference, Niels Bohr first introduced the principle of complementarity. The first quantum theory of metals was also discussed through the works of Arnold Sommerfeld and Enrico Fermi.

The conference was part of the Volta centennial anniversary celebrations (Italian: Celebrazioni voltiane [it]) ordered by the government of Benito Mussolini.

The physics conference was organized by the Italian Physical Society. The program was organized by Quirino Majorana, president of the society. He was joined by Hendrik Lorentz, Aimé Cotton, Robert Andrews Millikan, Max von Laue and Giancarlo Vallauri as vicepresidents of the congress.

The first four days were dedicated to works related to Volta, and the rest of the time was reserved for the topic of matter and radiation. The venue was the Carducci Institute at Como. Due to the presence of Guglielmo Marconi, many of the discussions were broadcast via radio.

During the conference, Mussolini hosted a reception with the participants in Rome, in his residence at Villa Torlonia.

On the 16th September, Niels Bohr presented a seminal lecture titled "The Quantum Postulate and the Recent Development of Atomic Theory" that introduced the principle of complementarity. Bohr argued that phenomena at the quantum level exhibit a dual nature—wave–particle duality—but these aspects are excluded of being observed simultaneously.

Oskar Klein and Bohr's brother Harald, helped him prepare the speech. The idea was motivated by a discussion in February–March with Werner Heisenberg, who had recently introduced the uncertainty principle. For Bohr, these two principles were key for the new quantum mechanics. The complementarity principle became the essence of what would become the Copenhagen interpretation, the standard interpretation of quantum mechanics.