Niels Bohr (1885–1962) was a Danish physicist who made foundational contributions to quantum theory and atomic structure. He proposed the Bohr model of the atom, which introduced the concept of quantized electron orbits around the nucleus. According to this model, electrons orbit the nucleus in specific energy levels, or shells, and can transition between these levels by emitting or absorbing photons of specific energy. Bohr’s model successfully explained the spectral lines of hydrogen and laid the groundwork for understanding atomic structure. He also played a key role in the development of quantum mechanics, particularly through his correspondence principle, which states that classical physics arises as a limit of quantum mechanics for large systems. Bohr’s insights profoundly influenced modern physics and earned him the Nobel Prize in Physics in 1922. His work continues to shape our understanding of the atomic world and remains fundamental in the study of quantum mechanics.

Niels Bohr Quotes

1. “If you aren’t confused by quantum mechanics, you haven’t really understood it.”
— Niels Bohr

2. “An expert is a man who has made all the mistakes which can be made, in a narrow field.”
— Niels Bohr

3. “Prediction is very difficult, especially if it’s about the future.”
— Niels Bohr

4. “A physicist is just an atom’s way of looking at itself.”
— Niels Bohr

5. “Everything we call real is made of things that cannot be regarded as real.”
— Niels Bohr

6. “If quantum mechanics hasn’t profoundly shocked you, you haven’t understood it yet.”
— Niels Bohr

7. “I go into the Upanishads to ask questions.”
— Niels Bohr

8. “No paradox, no progress.”
— Niels 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.”
— Niels Bohr

10. “In the great drama of existence we are audience and actors at the same time.”
— Niels Bohr

11. “No, no, you’re not thinking; you’re just being logical.”
— Niels Bohr

12. “How wonderful that we have met with a paradox. Now we have some hope of making progress.”
— Niels Bohr

13. “When we measure something we are forcing an undetermined, undefined world to assume an experimental value. We are not measuring the world, we are creating it.”
— Niels Bohr

14. “Never express yourself more clearly than you are able to think.”
— Niels Bohr

15. “One must always do what one really cannot.”
— Niels Bohr

16. “Opposites are not contradictory but complementary.”
— Niels Bohr

17. “If we couldn’t laugh at ourselves, that would be the end of everything.”
— Niels Bohr

18. “If anybody says he can think about quantum physics without getting giddy, that only shows he has not understood the first thing about them.”
— Niels Bohr

19. “When it comes to atoms, language can be used only as in poetry.”
— Niels Bohr

20. “Nothing exists until it is measured.”
— Niels Bohr

21. “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.”
— Niels Bohr

22. “We all know your idea is crazy. The question is whether it is crazy enough.”
— Niels Bohr

23. “Einstein, stop telling God what to do!”
— Niels Bohr

24. “Physics is the belief that a simple and consistent description of nature is possible.”
— Niels Bohr

25. “Every valuable human being must be a radical and a rebel, for what he must aim at is to make things better than they are.”
— Niels Bohr

26. “When searching for harmony in life one must never forget that in the drama of existence we are ourselves both actors and spectators.”
— Niels Bohr

27. “The opposite of every great idea is another great idea.”
— Niels Bohr

28. “There are some things so serious you have to laugh at them.”
— Niels Bohr

29. “The best weapon of a dictatorship is secrecy, but the best weapon of a democracy should be the weapon of openness.”
— Niels Bohr

30. “Accuracy and clarity of statement are mutually exclusive.”
— Niels Bohr

31. “The opposite of a fact is falsehood, but the opposite of one profound truth may very well be another profound truth.”
— Niels Bohr

32. “What is that we human beings ultimately depend on? We depend on our words. We are suspended in language. Our task is to communicate experience and ideas to others.”
— Niels Bohr

33. “It is the hallmark of any deep truth that its negation is also a deep truth.”
— Niels Bohr

34. “Your theory is crazy, but it’s not crazy enough to be true.”
— Niels Bohr

35. “Every sentence I utter must be understood not as an affirmation, but as a question.”
— Niels Bohr

36. “The meaning of life consists in the fact that it makes no sense to say that life has no meaning.”
— Niels Bohr

37. “Address to Albert Einstein: You are not thinking. You are merely being logical.”
— Niels Bohr

38. “Truth and clarity are complementary.”
— Niels Bohr

39. “We are trapped by language to such a degree that every attempt to formulate insight is a play on words.”
— Niels Bohr

40. “A deep truth is a truth so deep that not only is it true but it’s exact opposite is also true.”
— Niels Bohr

41. “Isolated material particles are abstractions, their properties being definable and observable only through their interaction with other systems .”
— Niels Bohr

42. “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.”
— Niels Bohr

43. “The present state of atomic theory is characterized by the fact that we not only believe the existence of atoms to be proved beyond a doubt, but also we even believe that we have an intimate knowledge of the constituents of the individual atoms.”
— Niels Bohr

44. “A person who wasn’t outraged on first hearing about quantum theory didn’t understand what had been said.”
— Niels Bohr

45. “Those who are not shocked when they first come across quantum theory cannot possibly have understood it.”
— Niels Bohr

46. “There are two sorts of truth: trivialities, where opposites are clearly absurd, and profound truths, recognised by the fact that the opposite is also a profound truth.”
— Niels Bohr

47. “Some subjects are so serious that one can only joke about them.”
— Niels Bohr

48. “Sometimes the child in one behaves a certain way and the rest of oneself follows behind, slowly shaking its head.”
— Niels Bohr

49. “If you think you understand it, that only shows that you don’t know the first thing about it.”
— Niels Bohr

50. “It is wrong to think that the task of physics is to find out how Nature is. Physics concerns what we say about Nature.”
— Niels Bohr

51. “If you have a correct statement, then the opposite of a correct statement is of course an incorrect statement, a wrong statement. But when you have a deep truth, then the opposite of a deep truth may again be a deep truth.”
— Niels Bohr

52. “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.”
— Niels Bohr

53. “Our task is not to penetrate the essence of things, the meaning of which we do not know anyway, but rather to develop concepts which allow us to talk in a productive way about phenomena in nature.”
— Niels Bohr

54. “In our description of nature the purpose is not to disclose the real essence of the phenomena but only to track down, so far as it is possible, relations between the manifold aspects of our experience.”
— Niels Bohr

55. “If an idea does not appear bizarre, there is no hope for it.”
— Niels Bohr

56. “We are suspended in language.”
— Niels Bohr

57. “It is a great pity that human beings cannot find all of their satisfaction in scientific contemplativeness.”
— Niels Bohr

58. “Everything we call real is made of things that cannot be regarded as real. If quantum mechanics hasn’t profoundly shocked you, you haven’t understood it yet.”
— Niels Bohr

59. “In quantum mechanics… an observation here and now changes in general the ‘state’ of the observed system… I consider the unpredictable change of the state by a single observation… to be an abandonment of the idea of the isolation of the observer from the course of physical events outside himself.”
— Niels Bohr

60. “Un experto es una persona que ha cometido todos los errores que se pueden cometer en un determinado campo.”
— Niels Bohr

61. “The measurement we get when we measure something is not a property of the thing measured.”
— Niels Bohr

62. “Anyone who is not shocked by the quantum theory has not understood it.”
— Niels Bohr

63. “You must come to Copenhagen to work with us. We like people who can actually perform thought experiments!”
— Niels Bohr

64. “The Stone Age didn’t end because the World ran out of stones.”
— Niels Bohr

65. “It is, indeed, perhaps the greatest prospect of humanistic studies to contribute through an increasing knowledge of the history of cultural development to that gradual removal of prejudices which is the common aim of all science.”
— Niels Bohr

66. “You are not thinking, you are just being logical.”
— Niels Bohr

67. “There is no hope for any speculation that does not look absurd at first glance.”
— Niels Bohr

68. “Perhaps I have found out a little about the structure of atoms.”
— Niels Bohr

69. “An expert is a person who has found out by his own painful experience all the mistakes that one can make in a very narrow field.”
— Niels Bohr

70. “An independant reality in the ordinary physical sense can neither be ascribed to the phenomenon nor to the agencies of observation.”
— Niels Bohr

71. “Oh what idiots we have all been, this is just as it must be.”
— Niels Bohr

72. “Vivere est Cogitare.”
— Niels Bohr

73. “It is not enough to be wrong, one must also be polite.”
— Niels Bohr

74. “Rutherford is a man you can rely on; he comes regularly and enquires how things are going and talks about the smallest details – Rutherford is such an outstanding man and really interested in the work of all the people around him.”
— Niels Bohr

75. “Stop telling God what to do with his dice.”
— Niels Bohr

76. “Truth is something that we can attempt to doubt, and then perhaps, after much exertion, discover that part of the doubt is not justified.”
— Niels Bohr

77. “All rising curves that show unwelcome trends in human affairs will approach infinity if extended far enough, but it is we who dictate the curve and not vice versa.”
— Niels Bohr

78. “I myself find the division of the world into an objective and a subjective side much too arbitrary. The fact that religions through the ages have spoken in images, parables, and paradoxes means simply that there are no other ways of grasping the reality to which they refer. But that does not mean that it is not a genuine reality. And splitting this reality into an objective and a. subjective side won’t get us very far.”
— Niels Bohr

79. “The great extension of 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.”
— Niels Bohr

80. “The very fact that knowledge is itself the basis for civilization points directly to openness as the way to overcome the present crisis.”
— Niels Bohr

81. “I feel personally responsible for the universe’s inevitable heat death.”
— Niels Bohr

82. “Physics is to be regarded not so much as the study of something a priori given, but rather as the development of methods of ordering and surveying human experience. In this respect our task must be to account for such experience in a manner independent of individual subjective judgement and therefore objective in the sense that it can be unambiguously communicated in ordinary human language.”
— Niels Bohr

83. “For a parallel to the lesson of atomic theory regarding the limited applicability of such customary idealizations, we must in fact turn to quite other branches of science, such as psychology, or even to that kind of epistemological problems with which already thinkers like Buddha and Lao Tzu have been confronted, when trying to harmonize our position as spectators and actors in the great drama of existence.”
— Niels Bohr

84. “There is no quantum world. There is only an abstract quantum physical description. It is wrong to think that the task of physics is to find out how nature is. Physics concerns what we can say about Nature.”
— Niels Bohr