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Physics

study of matter and its motion, along with related concepts such as energy and force

Physics is the science of the natural world, which deals with the fundamental particles the universe is made of, the interactions between them, and the interactions of objects composed of them (nuclei, atoms, molecules, etc).

The supreme task of the physicist is the discovery of the most general elementary laws from which the world-picture can be deduced logically. But there is no logical way to the discovery of these elemental laws. There is only the way of intuition [...]. ~ Albert Einstein

Quotes

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A hundred times every day I remind myself that my inner and outer life are based on the labors of other men, living and dead, and that I must exert myself in order to give in the same measure as I have received and am still receiving... ~ Albert Einstein
 
The "paradox" is only a conflict between reality and your feeling of what reality "ought to be." ~ Richard Feynman
  • At present, physicists are enamoured of symmetry and search only for continuous pictures of fundamental physics. Maybe, one day, they will be motivated to look at possible structures of a fundamentally discrete world.
    • John D. Barrow, Theories of Everything: The Quest for Ultimate Explanation (1991) p. 37.
  • Theoretical physicists live in a classical world, looking out into a quantum-mechanical world. The latter we describe only subjectively, in terms of procedures and results in our classical domain.
    • John Stewart Bell "Introduction to the hidden-variable question" (1971), included in Speakable and Unspeakable in Quantum Mechanics (1987), p. 29
  • 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 therefor objective in the sense that it can be unambiguously communicated in ordinary human language.
    • Niels Bohr, "The Unity of Human Knowledge" (October 1960)
  • Physicists use the wave theory on Mondays, Wednesdays and Fridays and the particle theory on Tuesdays, Thursdays and Saturdays
    • William Henry Bragg; quoted in Dictionary of Scientific Quotations by Alan L. Mackay, Institute of Physics Publishing, Bristol, 1994, p. 37 [1]
    • Variant: On Mondays, Wednesdays and Fridays we teach the wave theory and on Tuesday, Thursdays and Saturdays the corpuscular theory.
    • Quoted in Physically Speaking: A Dictionary of Quotations on Physics and Astronomy by C.C. Gaither, 1997, ISBN 0750304707. [2]
    • unsourced variant: God runs electromagnetics by wave theory on Monday, Wednesday, and Friday, and the Devil runs them by quantum theory on Tuesday, Thursday, and Saturday.
  • Its utility is to allow us to forsee and to fortell physical phenomena. ...it suggests definite experiments which might never have been thought of, and permits us to anticipate new relationships and new laws and to discover new facts. ...by establishing a rational connection between seemingly unconnected phenomena, it enables us to detect the harmony and unity of nature which lie concealed under an outward appearance of chaos.
  • The human imagination, including the creative scientific imagination, can ultimately function only by evoking potential or imagined sense impressions... I confess I never met an experimental physicist who does not think of the hydrogen atom by evoking a visual image of what he would see if the particular atomic model with which he is working existed literally on a scale accessible to the sense impressions - even while realizing that in fact the so-called internal structure of the hydrogen atom is in principle inaccessible to direct sensory perception. This situation has far-reaching consequences for the method of experimental investigation.
    • Martin Deutsch, "Evidence and Inference in Nuclear Research," Daedalus (Fall 1958) 87, p. 167.
  • Mathematical physics represents the purest image that the view of nature may generate in the human mind; this image presents all the character of the product of art; it begets some unity, it is true and has the quality of sublimity; this image is to physical nature what music is to the thousand noises of which the air is full...
  • And so in its actual procedure physics studies not these inscrutable qualities, but pointer-readings which we can observe, The readings, it is true, reflect the fluctuations of the world-qualities; but our exact knowledge is of the readings, not of the qualities. The former have as much resemblance to the latter as a telephone number has to a subscriber.
  • The supreme task of the physicist is the discovery of the most general elementary laws from which the world-picture can be deduced logically. But there is no logical way to the discovery of these elemental laws. There is only the way of intuition, which is helped by a feeling for the order lying behind the appearance, and this Einfühlung [literally, empathy or 'feeling one's way in'] is developed by experience.
  • How strange is the lot of us mortals! Each of us is here for a brief sojourn; for what purpose he knows not, though he sometimes thinks he senses it. But without deeper reflection one knows from daily life that one exists for other people — first of all for those upon whose smiles and well-being our own happiness is wholly dependent, and then for the many, unknown to us, to whose destinies we are bound by the ties of sympathy. A hundred times every day I remind myself that my inner and outer life are based on the labors of other men, living and dead, and that I must exert myself in order to give in the same measure as I have received and am still receiving...
  • No current physics experiment or theory explains the nature—or even the existence—of emotions, money, fine art, football games, or people. What can physics say about such things?
    Physics is the model of what a successful science should be. It provides the basis for the other physical sciences and biology because everything in our world, including ourselves, is made of the same fundamental particles, whose interactions are governed by the same fundamental forces.
    It’s no surprise then, as Princeton University’s Philip Anderson has noted, that physics represents the ultimate reductionist subject: Physicists reduce matter first to molecules, then to atoms, then to nuclei and electrons, and so on, the goal being always to reduce complexity to simplicity (see Physics Today, July 1991, page 9). The extraordinary success of that approach is based on the concept of an isolated system. Experiments carried out on systems isolated from external interference are designed to identify the essential causal elements underlying physical reality.
    The problem is that no real physical or biological system is truly isolated, physically or historically.
  • The concepts which now prove to be fundamental to our understanding of nature—a space which is finite; a space which is empty, so that one point [of our 'material' world] differs from another solely in the properties of space itself; four-dimensional, seven- and more dimensional spaces; a space which for ever expands; a sequence of events which follows the laws of probability instead of the law of causation—or alternatively, a sequence of events which can only be fully and consistently described by going outside of space and time—all these concepts seem to my mind to be structures of pure thought, incapable of realisation in any sense which would properly be described as material.
  • Today there is a wide measure of agreement, which on the physical side of science approaches almost to unanimity, that the stream of knowledge is heading towards a non-mechanical reality; the universe begins to look more like a great thought than like a great machine. Mind no longer appears as an accidental intruder into the realm of matter; we are beginning to suspect that we ought rather to hail it as a creator and governor of the realm of matter...
  • And the substance out of which this bubble is blown, the soap-film, is empty space welded onto empty time.
  • Physics and philosophy are at most a few thousand years old, but probably have lives of thousands of millions of years stretching away in front of them. They are only just beginning to get under way.
  • It is impossible, and it has always been impossible, to grasp the meaning of what we nowadays call physics independently of its mathematical form.
    • Jacob Klein, Greek Mathematical Thought and the Origin of Algebra (1968)
  • For every symmetry there comes a constraint. ...If physics is to look the same when the origin of time is shifted... [o]nly those processes that conserve energy are allowed. ...If physical law is to be immune to the arbitrary displacement of our spatial axes, then nature requires the conservation of linear momentum. ...If the laws are to be unaffected by the arbitrary rotation of a coordinate system, then angular momentum must be conserved. ...If the laws are to be the same for all inertial observers, then the space-time interval must be invariant. ...[A]nother constraint ...so beautiful as to make one jaw drop in wonder ...symmetry creates force. ...[T]he symmetry of identical particles forces matter ...to be enrolled as either fermion or boson ...Bosons, typified by the photon, carry the fundamental forces that cause fermions to attract and repel. Fermions, led by electrons and quarks, become constituents of ordinary matter. ...Gravity. Electromagnetism. The strong force. The weak force. Each fundamental interaction is called into being by the requirements of a particular local symmetry.
    • Michael Munowitz, Knowing: The Nature of Physical Law (2005)
  • All science is either physics or stamp collecting.
    • Ernest Rutherford, as quoted in Rutherford at Manchester (1962) by J. B. Birks
    • Unsourced variants:
    • That which is not measurable is not science. That which is not physics is stamp collecting.
    • Physics is the only real science. The rest are just stamp collecting.
    • That which is not measurable is not science. — (which is also attributed to Lord Kelvin)
  • The physicist ... engages in complex and difficult calculations, involving the manipulating of ideal, mathematical quantities that, at first glance, are wholly lacking in the music of the living world and the beauty of the resplendent cosmos. It would seem as if there exists no relationship between these quantities and reality. Yet these ideal numbers that cannot be grasped by one's senses, these numbers that only are meaningful from within the system itself, only meaningful as part of abstract mathematical functions, symbolize the image of existence. ... As a result of scientific man's creativity there arises an ordered, illumined, determined world, imprinted with the stamp of creative intellect, of pure reason and clear cognition. From the midst of the order and lawfulness we hear a new song, the song of the creature to the Creator, the song of the cosmos to its Maker.
  • Science deals with but a partial aspect of reality, and... there is no faintest reason for supposing that everything science ignores is less real than what it accepts. ...Why is it that science forms a closed system? Why is is that the elements of reality it ignores never come in to disturb it? The reason is that all the terms of physics are defined in terms of one another. The abstractions with which physics begins are all it ever has to do with...
  • As soon as we venture on the paths of the physicist, we learn to weigh and measure, to deal with time and space and mass and their related concepts, and to find more and more our knowledge expressed and our needs satisfied through the concept of number, as in the dreams of Plato and Pythagoras.
  • The medieval theologians would not be surprised at a prerequisite of a degree in physics for a degree in theology. In their time, the highest degree in philosophy—which included the most advanced knowledge of physics of the day—was a prerequisite before a student was permitted to begin study for a degree in theology ...Kenny has shown the Aquinas' Five Ways—his five proofs of God's existence—are absolutely dependent on Aristotelian physics... Aquinas... was one of the leading scholars of Aristotelian physics... and... was primarily responsible for... [its] general acceptance throughout Europe. We could call Aquinas a great physicist as well as a great theologian, for, although Aristotelian physics was wrong, it was an essential precursor of modern physics.
    • Frank J. Tippler, The Physics of Immortality: Modern Cosmology, God and the Resurrection of the Dead (1994) p. 329. Ref: Anthony Kenny, The Five Ways: St. Thomas Aquinas' Proof of God's Existence (1969) p. 329.
  • Do parallel universes exist? We don't know, uhm parallel universes are losing favor to the multiverse we have some cogent theoretical expectations that our universe might be just one of many spawned from this, sort of, this hyper-dimensional medium which we'll call the multiverse there's no data to support it but we have good theoretical premise to think that it's there and we have philosophical precedent we used to think Earth was special and unique. It wasn't, we got 8 .. 9 .. 8 planet we thought the Sun was special it's one of a hundred billion suns, the galaxy's special, no there's a hundred billion galaxies we have one universe or do we? The track record said why should there only be one? be open to the possibility that you don't live in the majority looking? universe that's out there Would a separate universe .. when you say "different universe" slightly different laws of physics which (that's what I'm asking) oh this is the fun part because if you find, if you manage to get a portal to another universe don't be the first one to volunteer to go through because your atoms are working in this universe if a slightly different law of physics.. you could implode, explode come out with three heads who knows?
  • It has seemed to me for some years that among physicists there is almost a cult, although certainly not an organized one, which I please to call a cult of obscurity. The creed of the cult is that a member disgraces the profession if he ever writes, lectures or teaches intelligibly to anyone but his immediate colleagues in the profession.
  • I had spent six years slugging my way through many dozens of physics textbooks that were carefully written with the best of pedagogical plans, but there was something missing. Physics is the most interesting subject in the world because it is about how the world works, and yet the textbooks had been thoroughly wrung of any connection with the real world. The fun was missing.
    • Jearl Walker, David Halliday, and Robert Resnick, Fundamentals of Physics (10th ed., 2014), Preface

See also

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