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Who said: “As far as the laws of mathematics refer to reality, they are not certain; and as far as they are certain, they do not refer to reality.”
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Home > Dictionary of Science Quotations > Scientist Names Index H > Werner Heisenberg Quotes

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Werner Heisenberg
(5 Dec 1901 - 1 Feb 1976)

German physicist and philosopher remembered for his Uncertainty Principle (1927) and other developments in quantum mechanics. He was awarded the 1932 Nobel Prize for Physics.

Science Quotes by Werner Heisenberg (37 quotes)

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Ein Fachmann ist ein Mann, der einige der gröbsten Fehler kennt, die man in dem betreffenden Fach machen kann, und der sie deshalb zu vermeiden versteht.
An expert is someone who knows some of the worst mistakes that can be made in his subject, and how to avoid them.
— Werner Heisenberg
From the original German, “Ein Fachmann ist ein Mann, der einige der gröbsten Fehler kennt, die man in dem betreffenden Fach machen kann, und der sie deshalb zu vermeiden versteht”, in Der Teil und das Ganze: Gespräche im Umkreis der Atomphysik (The Part and the Whole: Conversations in the Atomic Physics) (1969, 2001), 247. Excerpt in magazine article, 'Kein Chaos, aus dem nicht wieder Ordnung würde,' Die Zeit (22 August 1969), 34. English version in Werner Heisenberg and Arnold J. Pomerans (trans.), Physics and Beyond: Encounters and Conversations (1971), 210.
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A natural science is one whose propositions on limited domains of nature can have only a correspondingly limited validity; and that science is not a philosophy developing a world-view of nature as a whole or about the essence of things.
— Werner Heisenberg
In The Physicist’s Conception of Nature (1958), 152. Translated by Arnold J. Pomerans from Das Naturbild der Heutigen Physik (1955).
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According to Democritus, atoms had lost the qualities like colour, taste, etc., they only occupied space, but geometrical assertions about atoms were admissible and required no further analysis. In modern physics, atoms lose this last property, they possess geometrical qualities in no higher degree than colour, taste, etc. The atom of modern physics can only be symbolized by a partial differential equation in an abstract multidimensional space. Only the experiment of an observer forces the atom to indicate a position, a colour and a quantity of heat. All the qualities of the atom of modern physics are derived, it has no immediate and direct physical properties at all, i.e. every type of visual conception we might wish to design is, eo ipso, faulty. An understanding of 'the first order' is, I would almost say by definition, impossible for the world of atoms.
— Werner Heisenberg
Philosophic Problems of Nuclear Science, trans. F. C. Hayes (1952), 38.
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Atoms are not things.
— Werner Heisenberg
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Can quantum mechanics represent the fact that an electron finds itself approximately in a given place and that it moves approximately with a given velocity, and can we make these approximations so close that they do not cause experimental difficulties?
— Werner Heisenberg
Physics and Beyond: Encounters and Conversations, trans. Arnold J. Pomerans (1971), 78.
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Even for the physicist the description in plain language will be a criterion of the degree of understanding that has been reached.
— Werner Heisenberg
In Physics and Philosophy: The Revolution in Modern Science (1958, 1962), 168.
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Even in science the object of research is no longer nature itself, but man’s investigation of nature.
— Werner Heisenberg
In The Physicist's Conception of Nature (1958), 24.
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I believe that certain erroneous developments in particle theory ... are caused by a misconception by some physicists that it is possible to avoid philosophical arguments altogether. Starting with poor philosophy, they pose the wrong questions. It is only a slight exaggeration to say that good physics has at times been spoiled by poor philosophy.
— Werner Heisenberg
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I remember discussions with Bohr which went through many hours till very late at night and ended almost in despair; and when at the end of the discussion I went alone for a walk in the neighboring park I repeated to myself again and again the question: Can nature possibly be as absurd as it seemed to us in these atomic experiments?
— Werner Heisenberg
In Physics and Philosophy: The Revolution in Modern Science (1958, 1962), 42.
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I think that the discovery of antimatter was perhaps the biggest jump of all the big jumps in physics in our century.
— Werner Heisenberg
From 'Development of Concepts in the History of Quantum Theory', in Jagdish Mehra (ed.) The Physicist's Concept of Nature (1973), Vol. 1972, 271.
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In general, scientific progress calls for no more than the absorption and elaboration of new ideas—and this is a call most scientists are happy to heed.
— Werner Heisenberg
In Werner Heisenberg and Arnold J. Pomerans (trans.), Physics and Beyond: Encounters and Conversations (1971), 70.
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In the strict formulation of the law of causality—if we know the present, we can calculate the future—it is not the conclusion that is wrong but the premise.
On an implication of the uncertainty principle.
— Werner Heisenberg
Quoted in David C. Cassidy, Beyond Uncertainty: Heisenberg, Quantum Physics, and the Bomb (2009), 162.
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It is not surprising that our language should be incapable of describing the processes occurring within the atoms, for, as has been remarked, it was invented to describe the experiences of daily life, and these consists only of processes involving exceedingly large numbers of atoms. Furthermore, it is very difficult to modify our language so that it will be able to describe these atomic processes, for words can only describe things of which we can form mental pictures, and this ability, too, is a result of daily experience. Fortunately, mathematics is not subject to this limitation, and it has been possible to invent a mathematical scheme—the quantum theory—which seems entirely adequate for the treatment of atomic processes; for visualization, however, we must content ourselves with two incomplete analogies—the wave picture and the corpuscular picture.
— Werner Heisenberg
The Physical Principles of the Quantum Theory, trans. Carl Eckart and Frank C. Hoyt (1949), 11.
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It seems sensible to discard all hope of observing hitherto unobservable quantities, such as the position and period of the electron... Instead it seems more reasonable to try to establish a theoretical quantum mechanics, analogous to classical mechanics, but in which only relations between observable quantities occur.
— Werner Heisenberg
In Helge Kragh, Quantum Generations: A History of Physics in the Twentieth Century (1999), 161.
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It was about three o’clock at night when the final result of the calculation [which gave birth to quantum mechanics] lay before me ... At first I was deeply shaken ... I was so excited that I could not think of sleep. So I left the house ... and awaited the sunrise on top of a rock.
[That was “the night of Heligoland”.]
— Werner Heisenberg
Quoted in Abraham Pais, Niels Bohr’s Times: in Physics, Philosophy, and Polity (1991), 275. Cited in Mauro Dardo, Nobel Laureates and Twentieth-Century Physics (2004), 179.
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Modern physics has changed nothing in the great classical disciplines of, for instance, mechanics, optics, and heat. Only the conception of hitherto unexplored regions, formed prematurely from a knowledge of only certain parts of the world, has undergone a decisive transformation. This conception, however, is always decisive for the future course of research.
— Werner Heisenberg
In Philosophical Problems of Nuclear Science: Eight Lectures (1952), 18.
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Modern theories did not arise from revolutionary ideas which have been, so to speak, introduced into the exact sciences from without. On the contrary they have forced their way into research which was attempting consistently to carry out the programme of classical physics—they arise out of its very nature. It is for this reason that the beginnings of modern physics cannot be compared with the great upheavals of previous periods like the achievements of Copernicus. Copernicus’s idea was much more an import from outside into the concepts of the science of his time, and therefore caused far more telling changes in science than the ideas of modern physics are creating to-day.
— Werner Heisenberg
In Philosophical Problems of Nuclear Science: Eight Lectures (1952), 13.
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Natural science does not simply describe and explain nature; it is part of the interplay between nature and ourselves; it describes nature as exposed to our method of questioning.
— Werner Heisenberg
In Physics and Philosophy: The Revolution in Modern Science (1959, 1962), 81.
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Nature is made in such a way as to be able to be understood. Or perhaps I should put it—more correctly—the other way around, and say that we are made in such a way as to be able to understand Nature.
— Werner Heisenberg
Attributed. (If you know a primary source, please contact webmaster.)
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Our scientific work in physics consists in asking questions about nature in the language that we possess and trying to get an answer from experiment by the means at our disposal. In this way quantum theory reminds us, as Bohr has put it, of the old wisdom that when searching for harmony in life one must never forget that in the drama of existence we are ourselves both players and spectators. It is understandable that in our scientific relation to nature our own activity becomes very important when we have to deal with parts of nature into which we can penetrate only by using the most elaborate tools.
— Werner Heisenberg
The Copenhagen Interpretation of Quantum Theory (1958). In Steve Adams, Frontiers (2000), 13.
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Revere those things beyond science which really matter and about which it is so difficult to speak.
— Werner Heisenberg
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Science no longer is in the position of observer of nature, but rather recognizes itself as part of the interplay between man and nature. The scientific method ... changes and transforms its object: the procedure can no longer keep its distance from the object.
— Werner Heisenberg
The Representation of Nature in Contemporary Physics', Symbolism in Religion and Literature (1960), 231. Cited in John J. Stuhr, Philosophy and the Reconstruction of Culture (1993), 139.
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Since the measuring device has been constructed by the observer … we have to remember that what we observe is not nature itself but nature exposed to our method of questioning. Our scientific work in physics consists in asking questions about nature in the language that we possess and trying to get an answer from experiment by the means that are at our disposal.
— Werner Heisenberg
Physics and Philosophy: The Revolution in Modern Science (1958), 78.
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The basic idea is to shove all fundamental difficulties onto the neutron and to do quantum mechanics in the nucleus.
— Werner Heisenberg
Letter to Niels Bohr, 20 Jun 1932. Quoted in David C. Cassidy, Uncertainty: The Life and Science of Werner Heisenberg (1992), 292.
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The conception of objective reality … has thus evaporated … into the transparent clarity of mathematics that represents no longer the behavior of particles but rather our knowledge of this behavior.
— Werner Heisenberg
In 'The Representation of Nature in Contemporary Physics', Daedalus (1958), 87, 95-108. As cited in Karl Popper, Quantum Theory and the Schism in Physics (1992), 85.
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The concepts of ‘soul’ or ‘life’ do not occur in atomic physics, and they could not, even indirectly, be derived as complicated consequences of some natural law. Their existence certainly does not indicate the presence of any fundamental substance other than energy, but it shows only the action of other kinds of forms which we cannot match with the mathematical forms of modern atomic physics ... If we want to describe living or mental processes, we shall have to broaden these structures. It may be that we shall have to introduce yet other concepts.
— Werner Heisenberg
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The dangers threatening modern science cannot be averted by more experimenting, for our complicated experiments have no longer anything to do with nature in her own right, but with nature charged and transformed by our own cognitive activity.
— Werner Heisenberg
As quoted by Erich Heller in The Disinherited Mind: Essays in Modern German Literature and Thought (1952), 26.
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The hope that new experiments will lead us back to objective events in time and space is about as well founded as the hope of discovering the end of the world in the unexplored regions of the Antarctic.
— Werner Heisenberg
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The incomplete knowledge of a system must be an essential part of every formulation in quantum theory. Quantum theoretical laws must be of a statistical kind. To give an example: we know that the radium atom emits alpha-radiation. Quantum theory can give us an indication of the probability that the alpha-particle will leave the nucleus in unit time, but it cannot predict at what precise point in time the emission will occur, for this is uncertain in principle.
— Werner Heisenberg
The Physicist's Conception of Nature (1958), 41.
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The mathematically formulated laws of quantum theory show clearly that our ordinary intuitive concepts cannot be unambiguously applied to the smallest particles. All the words or concepts we use to describe ordinary physical objects, such as position, velocity, color, size, and so on, become indefinite and problematic if we try to use them of elementary particles.
— Werner Heisenberg
In Across the Frontiers (1974), 114.
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The more I think about the physical portion of Schrödinger’s theory, the more repulsive I find it…. What Schrödinger writes about the visualizability of his theory “is probably not quite right”; in other words it’s crap.
— Werner Heisenberg
Letter to Wolfgang Pauli (8 Jun 1926). 17. In a subsequent letter to Pauli, he referred to Dirac’s theory as “learned crap.”
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The smallest particles of matter were said [by Plato] to be right-angled triangles which, after combining in pairs, ... joined together into the regular bodies of solid geometry; cubes, tetrahedrons, octahedrons and icosahedrons. These four bodies were said to be the building blocks of the four elements, earth, fire, air and water ... [The] whole thing seemed to be wild speculation. ... Even so, I was enthralled by the idea that the smallest particles of matter must reduce to some mathematical form ... The most important result of it all, perhaps, was the conviction that, in order to interpret the material world we need to know something about its smallest parts.
[Recalling how as a teenager at school, he found Plato's Timaeus to be a memorable poetic and beautiful view of atoms.]
— Werner Heisenberg
In Werner Heisenberg and A.J. Pomerans (trans.) The Physicist's Conception of Nature (1958), 58-59. Quoted in Jagdish Mehra and Helmut Rechenberg, The Historical Development of Quantum Theory (2001), Vol. 2, 12. Cited in Mauro Dardo, Nobel Laureates and Twentieth-Century Physics (2004), 178.
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Thus one becomes entangled in contradictions if one speaks of the probable position of the electron without considering the experiment used to determine it ... It must also be emphasized that the statistical character of the relation depends on the fact that the influence of the measuring device is treated in a different manner than the interaction of the various parts of the system on one another. This last interaction also causes changes in the direction of the vector representing the system in the Hilbert space, but these are completely determined. If one were to treat the measuring device as a part of the system—which would necessitate an extension of the Hilbert space—then the changes considered above as indeterminate would appear determinate. But no use could be made of this determinateness unless our observation of the measuring device were free of indeterminateness. For these observations, however, the same considerations are valid as those given above, and we should be forced, for example, to include our own eyes as part of the system, and so on. The chain of cause and effect could be quantitatively verified only if the whole universe were considered as a single system—but then physics has vanished, and only a mathematical scheme remains. The partition of the world into observing and observed system prevents a sharp formulation of the law of cause and effect. (The observing system need not always be a human being; it may also be an inanimate apparatus, such as a photographic plate.)
— Werner Heisenberg
The Physical Principles of the Quantum Theory, trans. Carl Eckart and Frank C. Hoyt (1949), 58.
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When Einstein has criticized quantum theory he has done so from the basis of dogmatic realism.
— Werner Heisenberg
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You may object that by speaking of simplicity and beauty I am introducing aesthetic criteria of truth, and I frankly admit that I am strongly attracted by the simplicity and beauty of mathematical schemes which nature presents us. You must have felt this too: the almost frightening simplicity and wholeness of the relationship, which nature suddenly spreads out before us.
— Werner Heisenberg
Letter to Albert Einstein. In Ian Stewart, Why Beauty is Truth (), 278.
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[We should] abandon all attempts to construct perceptual models of atomic processes.
— Werner Heisenberg
In Physics and Beyond (1971), 76.
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…separation of the observer from the phenomenon to be observed is no longer possible.
— Werner Heisenberg
Quoted in Robert J. Scully, The Demon and the Quantum (2007), 3.
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Quotes by others about Werner Heisenberg (5)

Many scientists have tried to make determinism and complementarity the basis of conclusions that seem to me weak and dangerous; for instance, they have used Heisenberg’s uncertainty principle to bolster up human free will, though his principle, which applies exclusively to the behavior of electrons and is the direct result of microphysical measurement techniques, has nothing to do with human freedom of choice. It is far safer and wiser that the physicist remain on the solid ground of theoretical physics itself and eschew the shifting sands of philosophic extrapolations.
In New Perspectives in Physics (1962), viii.
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In both social and natural sciences, the body of positive knowledge grows by the failure of a tentative hypothesis to predict phenomena the hypothesis professes to explain; by the patching up of that hypothesis until someone suggests a new hypothesis that more elegantly or simply embodies the troublesome phenomena, and so on ad infinitum. In both, experiment is sometimes possible, sometimes not (witness meteorology). In both, no experiment is ever completely controlled, and experience often offers evidence that is the equivalent of controlled experiment. In both, there is no way to have a self-contained closed system or to avoid interaction between the observer and the observed. The Gödel theorem in mathematics, the Heisenberg uncertainty principle in physics, the self-fulfilling or self-defeating prophecy in the social sciences all exemplify these limitations.
Inflation and Unemployment (1976), 348.
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The quantum entered physics with a jolt. It didn’t fit anywhere; it made no sense; it contradicted everything we thought we knew about nature. Yet the data seemed to demand it. ... The story of Werner Heisenberg and his science is the story of the desperate failures and ultimate triumphs of the small band of brilliant physicists who—during an incredibly intense period of struggle with the data, the theories, and each other during the 1920s—brought about a revolutionary new understanding of the atomic world known as quantum mechanics.
Beyond Uncertainty: Heisenberg, Quantum Physics, and the Bomb (2009), 90. Selected and contributed to this website by the author.
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[Heisenberg's seminal 1925 paper initiating quantum mechanics marked] one of the great jumps—perhaps the greatest—in the development of twentieth century physics.
In Abraham Pais, Niels Bohr's Times: in Physics, Philosophy, and Polity (1991), 276. Cited in Mauro Dardo, Nobel Laureates and Twentieth-Century Physics (2004), 179.
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It’s the Heisenberg principle. Me asking the question changes the answer.
On caution collecting opinions from advisors to refine decision-making. As quoted in Michael Lewis, 'Obama’s Way', Vanity Fair (Oct 2012).
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See also:
  • 5 Dec - short biography, births, deaths and events on date of Heisenberg's birth.
  • Booklist for Werner Heisenberg.

Carl Sagan Thumbnail In science it often happens that scientists say, 'You know that's a really good argument; my position is mistaken,' and then they would actually change their minds and you never hear that old view from them again. They really do it. It doesn't happen as often as it should, because scientists are human and change is sometimes painful. But it happens every day. I cannot recall the last time something like that happened in politics or religion. (1987) -- Carl Sagan
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