Niels Bohr Quotes

Quotes by physicist and Nobel laureate Niels Bohr

Quantum physicist Niels Bohr was one of the major figures in the early development of quantum physics, having laid the groundwork for the basic understanding of the atomic structure (i.e. the Bohr model of the atom). He received a Nobel Prize for this work in 1922, just a year after Albert Einstein received his.

It was through the process of a prolonged, spirited debate with Einstein about the finer points of quantum physics that Bohr, and others, refined some of their most important and memorable work in inspiring a century of thinking about quantum physics. One consequence of this was Einstein's development of the EPR paradox thought experiment ... an experiment that has since been carried out and has confirmed Bell's theorem, experimentally supporting the fundamentally non-local nature of quantum physics.

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If quantum mechanics hasn't profoundly shocked you ...

A photograph of Niels Bohr. Public Domain
I've found two two closely-related quotes on this subject which are attributed to Bohr:
  • If quantum mechanics hasn't profoundly shocked you, you haven't understood it yet.
  • If anybody says he can think about quantum physics without getting giddy, that only shows he has not understood the first thing about them.
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Einstein, stop telling God what to do!

This quote is in response to Albert Einstein's famous quote attacking quantum physics, wherein he said that "God does not play dice with the universe." Physicist Enrico Fermi is also reputed to have made a similar statement. Given how well known Einstein's criticisms of quantum theory were, it's possible that both physicists independently made the same sort of response. Or, alternately, the response was made once and has been mis-attributed somewhere in the retelling of the tale. At this point, it's doubtful we'll ever know for certain.

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Your theory is crazy ...

Again, I've got two variations of this particular one and continue to verify their authenticity. There's a good chance that one of them is a misquotation of the other:
  • We are all agreed that your theory is crazy. The question which divides us is whether it is crazy enough to have a chance of being correct. My own feeling is that it is not crazy enough.
  • Your theory is crazy, but it's not crazy enough to be true.
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It is wrong to think that the task of physics is ...

It is wrong to think that the task of physics is to find out how Nature is. Physics concerns what we say about Nature.
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A physicist is just an atom's way of looking at itself.

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How wonderful that we have met with a paradox....

How wonderful that we have met with a paradox. Now we have some hope of making progress.
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Everything we call real is made of things that cannot be regarded as real.

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Prediction is very difficult, especially if it's about the future.

This quote has been attributed to many people aside from Bohr, so its authenticity is in dispute. It was attributed to Bohr in Arthur K. Ellis' 1970 book Teaching and Learning Elementary Social Studies.

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There are some things so serious you have to laugh at them.

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An expert is ...

I found two similar quotes in this vein. I am investigating their authenticity. Presumably one is a mis-quote of the other:

  • An expert is a man who has made all the mistakes which can be made, in a narrow field.
  • An expert is someone who knows some of the worst mistakes which can be made, in a very narrow field.
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No, no, you're not thinking; you're just being logical.

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The best weapon of a dictatorship is ...

The best weapon of a dictatorship is secrecy, but the best weapon of a democracy should be the weapon of openness.

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Every sentence I utter ...

Every sentence I utter must be understood not as an affirmation, but as a question.
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The opposite of a fact is a falsehood ...

Once again, we have two closely related quotes:
  • The opposite of a fact is falsehood, but the opposite of one profound truth may very well be another profound truth.
  • There are trivial truths and the great truths. The opposite of a trivial truth is plainly false. The opposite of a great truth is also true.
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Every great and deep difficulty bears in itself its own solution....

Every great and deep difficulty bears in itself its own solution. It forces us to change our thinking in order to find it.
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Never express yourself more clearly than you are able to think.

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When it comes to atoms, language can be used only as in poetry....

We must be clear that, 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.

According to Werner Heisenberg, in his 1971 Physics and Beyond: Encounters and Conversations (p.41), Bohr said this upon their first meeting. This was quoted in the 1993 Steve Giles book Theorizing modernism: essays in critical theory (p. 28). Wikiquote, however, attributes this to something called Discussions about Language (1933), which I have been unable to locate.

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Truth and clarity are complementary.

This may well be a misquotation. In the 2000 book Quantum Theory and the Flight from Realism: Philosophical Responses to Quantum Mechanics, Christopher Norris quotes physicist John S. Bell (on page 234) who credits this quote to Bohr. On page 259, in the Endnotes, this quote is attributed to Bell's 1987 book Speakable and Unspeakable in Quantum Mechanics: collected papers on quantum philosophy, p. 190. This, in turn, is part of a 1986 essay called "Six possible worlds of quantum mechanics."

From what I can gather, therefore, this quote wasn't attributed to Niels Bohr prior to 1986 ... 24 years after Bohr's death. I consider this one a dubious source, but leave it here for your consideration.