Werner Heisenberg

Natural science does not simply describe and explain nature; it is part of the interplay between nature and ourselves.

In the history of science, it has often happened that a new discovery had to be rejected for a long time because it contradicted the current prejudices.

The meaning of 'understanding' has changed in the course of the development of physics.

I was forced to find a new way of expressing the fundamental laws of nature, one which would not rely on the outdated concepts of classical physics.

The idea of a simple, objective reality existing independently of the observer has become untenable.

The decision to break with the tradition of classical physics was a very difficult one.

The world of atoms is a world of possibilities and not a world of things.

Modern physics has, in a certain sense, revived Plato's philosophy of forms in the atomic world.

If a man is to be a good physicist, he must have an intuitive grasp of the physical reality, which can be acquired only by much experience.

The human mind cannot be content with a description of phenomena; it wants to understand them.

The very act of observing changes the observed.

I was very much afraid of the consequences of the atom bomb, and I tried to delay its development.

The physical world is not real in the sense that it exists independently of our observing it.

The decision for a definite result is taken only when the measurement is made.

The world is not composed of 'things' but of 'events'.

Where there is no uncertainty, there is no quantum mechanics.

The history of physics is not only a sequence of experimental discoveries and observations, but also a history of concepts.

The more profound the knowledge, the more clear is the awareness of the limits of our knowledge.

The first gulp from the glass of natural sciences will turn you into an atheist, but at the bottom of the glass God is waiting for you.

An expert is someone who knows some of the worst mistakes that can be made in his subject and how to avoid them.