NIELS BOHR was deeply intuitive, a pioneering physicist who moved insightfully from the theoretical to the real of atomic structure.

Bohr was deeply human, a Danish man by a Jewish mother who would escape the Nazis as he made his way to Sweden, Britain and then the United States.

Bohr was deeply humanistic, a Manhattan Project participant who passionately voiced great concern about how nations would work together — or not — in a new era exploded into being by the atomic bomb.

Bohr was deeply respected, a man and mind who received the Nobel Prize in 1922 for his work on deepening our understanding of the atom and quantum mechanics.

And today, Bohr is deeply celebrated. Google marks what would have been the scientist’s 127th birthday — he was born in Copenhagen in 1885 — with a Doodle inspired by his work on the atom.

As the Nobel Prize site explains, in part: “By introducing conceptions borrowed from the Quantum Theory as established by Planck, ... [Bohr] succeeded in working out and presenting a picture of atomic structure that, with later improvements (mainly as a result of Heisenberg’s ideas in 1925), still fitly serves as an elucidation of the physical and chemical properties of the elements.”

A scientist as thoughtful as Bohr is perhaps best remembered in his own words — as well as the words of key colleagues. So here, to help celebrate the occasion, are our 12 favorite quotes by and about Niels Henrik David Bohr (*according to numerous sources, with the wording sometimes varying slightly by source):

1. “Prediction is very difficult, especially if it’s about the future.”

— Niels Bohr

2. “Never express yourself more clearly than you are able to think.”

— Bohr

3. “No, no, you’re not thinking — you’re just being logical.”

— Bohr

4. “One of the favorite maxims of my father was the distinction between the two sorts of truths — profound truths recognized by the fact that the opposite is also a profound truth, in contrast to trivialities where opposites are obviously absurd.”

— Son Hans Henrik Bohr, from “My father” in “Niels Bohr: His Life and Work As Seen By His Friends and Colleagues (1967)

(Another son, theoretical physicist Aage Bohr, shared in the Nobel Prize for Physics in 1975.)

5. “How wonderful that we have met with a paradox. Now we have some hope of making progress.”

— Bohr

6. “The first thing Bohr said to me was that it would only then be profitable to work with him if I understood that he was a dilettante. ... Evidently Bohr was serious. He explained how he had to approach every new question from a starting point of total ignorance. It is perhaps better to say that Bohr’s strength lay in his formidable intuition and insight rather than erudition.”

Abraham Pais

7. “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.”

— Bohr

8. “An expert is someone who knows some of the worst mistakes, which can be made, in a very narrow field.”

— Bohr

9. “Every great and deep difficulty bears in itself its own solution. It forces us to change our thinking in order to find it.”

— Bohr

10. “Not often in life has a human being caused me such joy by his mere presence as you did.”

Albert Einstein, in a letter to Bohr

11. “Einstein, stop telling God what to do.”

— Bohr “in response to [Einstein’s] famous quote attacking quantum physics, wherein he said that ‘God does not play dice with the universe,’ ” according to

12. “Every sentence I utter must be understood not as an affirmation, but as a question.”

— Bohr