Niels Bohr Quotes

It is a curious historical fact that modern quantum mechanics began with two quite different mathematical formulations: the differential equation of Schroedinger and the matrix algebra of Heisenberg. The two apparently dissimilar approaches were proved to be mathematically equivalent.

It is often stated that of all the theories proposed in this century, the silliest is quantum theory. In fact, some say that the only thing that quantum theory has going for it is that it is unquestionably correct.

Einstein's theory of relativity does a fantastic job for explaining big things. Quantum mechanics is fantastic for the other end of the spectrum - for small things.

The uncertainty principle refers to the degree of indeterminateness in the possible present knowledge of the simultaneous values of various quantities with which the quantum theory deals; it does not restrict, for example, the exactness of a position measurement alone or a velocity measurement alone.

If we look at the way the universe behaves, quantum mechanics gives us fundamental, unavoidable indeterminacy, so that alternative histories of the universe can be assigned probability.

The birth of science as we know it arguably began with Isaac Newton's formulation of the laws of gravitation and motion. It is no exaggeration to say that physics was reborn in the early 20th-century with the twin revolutions of quantum mechanics and the theory of relativity.

Because the theory of quantum mechanics could explain all of chemistry and the various properties of substances, it was a tremendous success. But still there was the problem of the interaction of light and matter.

Today, all physicists know from studying Einstein and Bohr that sometimes an idea which looks completely paradoxical at first, if analyzed to completion in all detail and in experimental situations, may, in fact, not be paradoxical.

The development of quantum mechanics early in the twentieth century obliged physicists to change radically the concepts they used to describe the world.

Quantum mechanics broke the mold of the previous framework, classical mechanics, by establishing that the predictions of science are necessarily probabilistic.

Quantum physics is one of the hardest things to understand intuitively, because essentially the whole point is that our classical picture is wrong.

Since Einstein developed his theory of relativity, and Rutherford and Bohr revolutionised physics, our picture of the world has radically changed.

Quantum mechanics brought an unexpected fuzziness into physics because of quantum uncertainty, the Heisenberg uncertainty principle.

Old Newtonian physics claimed that things have an objective reality separate from our perception of them. Quantum physics, and particularly Heisenberg's Uncertainty Principle, reveal that, as our perception of an object changes, the object itself literally changes.

Nothing can create something all the time due to the laws of quantum mechanics, and it's - it's fascinatingly interesting.

No one intuitively understands quantum mechanics because all of our experience involves a world of classical phenomena where, for example, a baseball thrown from pitcher to catcher seems to take just one path, the one described by Newton's laws of motion. Yet at a microscopic level, the universe behaves quite differently.

There are a lot of mysteries about quantum mechanics, but they mostly arise in very detailed measurements in controlled settings.

Quantum theory also tells us that the world is not simply objective; somehow it's something more subtle than that. In some sense it is veiled from us, but it has a structure that we can understand.

Nevertheless, all of us who work in quantum physics believe in the reality of a quantum world, and the reality of quantum entities like protons and electrons.

The verbal interpretation, on the other hand, i.e. the metaphysics of quantum physics, is on far less solid ground. In fact, in more than forty years physicists have not been able to provide a clear metaphysical model.

If quantum mechanics hasn't profoundly shocked you, you haven't understood it yet.

Since the founding of quantum mechanics in the 1920s, theoretical physics had nurtured an extremely radical tradition.

Things on a very small scale behave like nothing that you have any direct experience about. They do not behave like waves, they do not behave like particles, they do not behave like clouds, or billiard balls, or weights on springs, or like anything that you have ever seen.

I am not aware of any sensible theory of how classical gravity could interact with quantum matter, and I can't imagine how such a theory might work.

In its efforts to learn as much as possible about nature, modern physics has found that certain things can never be "known" with certainty. Much of our knowledge must always remain uncertain. The most we can know is in terms of probabilities.