5 Niels Bohr Quotes On Quantum Mechanics

Niels Bohr was a Danish physicist who made pioneering contributions to understanding atomic structure and quantum theory, for which Bohr was recognized with a Nobel Prize in 1922. Bohr was an active participant in the new quantum theory revolution that shook the foundations of classical physics.

Einstein, who was not ready to accept Heisenberg's uncertainty principle, as one of the cornerstones of modern physics, commented: God does not play dice with the universe. Bohr made peace with the uncertainty principle by developing the principle of complementarity.

According to complementarity, particles have certain pairs of interdependent properties that cannot all be observed or measured simultaneously. For example: position and momentum make such a pair.

Bohr regarded complementarity as an essential feature of quantum mechanics. It is said that Bohr replied to Einstein, who preferred the determinism of classical physics over the probabilistic new quantum physics: (1) "Stop telling God what to do."

In 1920, Bohr met Heisenberg for the first time. Bohr said, (2) What is it that we humans depend on? We depend on our words... Our task is to communicate experience and ideas to others. But when it comes to atoms, language can be used only as in poetry. The poet, too, is not nearly so concerned with describing facts as with creating images and establishing mental connections.

Some physicists depended on mathematical analysis to make sense of the quantum world. However, Bohr was not satisfied. (3) Even the mathematical framework helps nothing, I (Bohr) would first like to understand how Nature avoids the contradictions. (1927)

Bohr said further: Our experience in recent years has brought light to the insufficiency of our simple mechanical conceptions and, as a consequence, has shaken the foundation on which the customary interpretation of observation was based.

We can still use the objectifying language of classical physics to make statements about observable facts. But we can say nothing about the atoms themselves.

In the 1927 Solvay conference, Bohr and Einstein went head-to-head on the metaphysical and philosophical implications of quantum mechanics. Two legends, one defending the new-age probabilistic physics and another fighting for classical determinism. At the end, it was Bohr who emerged victorious and successfully established the probabilistic character of quantum measurement.

Niels Bohr wrote in 1934: (4) Isolated material particles are abstractions, their properties being definable and observable only through their interaction with other systems. Everything we call real is made of things that cannot be regarded as real.

In a 1952 conversation with Heisenberg and Pauli in Copenhagen, Bohr quipped: (5) "Those who are not shocked when they first come across quantum theory cannot possibly have understood it." This was most likely a reference to Einstein, who not only contributed to the new theory but also immediately taken aback by its bizarre results.