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{{Short description|Truths and principles of the study of matter, space, time and energy}}

In [[Philosophy:Philosophy|philosophy]], '''philosophy of physics''' deals with conceptual and interpretational issues in modern [[Physics:Physics|physics]], many of which overlap with research done by certain kinds of [[Physics:Theoretical physics|theoretical physicists]]. Philosophy of physics can be broadly divided into three areas:
* [[Physics:Interpretations of quantum mechanics|interpretations of quantum mechanics]]: mainly concerning issues with how to formulate an adequate response to the [[Physics:Measurement problem|measurement problem]] and understand what the theory says about reality.
* the nature of [[Space|space]] and [[Time|time]]: Are space and time substances, or purely relational? Is simultaneity conventional or only relative? Is temporal asymmetry purely reducible to thermodynamic asymmetry?
* inter-theoretic relations: the relationship between various physical theories, such as [[Physics:Thermodynamics|thermodynamics]] and [[Physics:Statistical mechanics|statistical mechanics]]. This overlaps with the issue of scientific reduction.

==Philosophy of space and time==
{{Main|Physics:Philosophy of space and time}}

The existence and nature of space and time (or space-time) are central topics in the philosophy of physics.<ref name="MaudlinSTa">{{cite book|last1=Maudlin|first1=Tim|title=Philosophy of Physics: Space and Time|date=2012|publisher=Princeton University Press|isbn=978-0691143095|page=xi|url=https://books.google.com/books?id=siyNQV8F0y8C&q=central+topic|access-date=3 October 2017|language=en|quote=...the existence and nature of space and time (or space-time) is a central topic.}}</ref>

===Time===
{{Main| Physics:Time in physics}}
[[File:Wooden hourglass.jpg|thumb|right|Time, in many philosophies, is seen as change.]]
[[Time]] is often thought to be a fundamental quantity (that is, a quantity which cannot be defined in terms of other quantities), because time seems like a fundamentally basic concept, such that one cannot define it in terms of anything simpler. However, certain theories such as [[Physics:Loop quantum gravity|loop quantum gravity]] claim that spacetime is emergent. As [[Biography:Carlo Rovelli|Carlo Rovelli]], one of the founders of [[Physics:Loop quantum gravity|loop quantum gravity]] has said: "No more fields on spacetime: just fields on fields".<ref>Rovelli, C. (2004). Quantum Gravity. Cambridge Monographs on Mathematical Physics. p. 71.</ref> Time is defined via measurement—by its standard time interval. Currently, the standard time interval (called "conventional [[Second|second]]", or simply "second") is defined as 9,192,631,770 oscillations of a hyperfine transition in the 133 [[Chemistry:Caesium|caesium]] [[Physics:Atom|atom]]. ([[Physics:ISO 31-1|ISO 31-1]]). What time is and how it works [[Logical consequence|follows from]] the above definition. Time then can be combined mathematically with the fundamental quantities of [[Space|space]] and [[Physics:Mass|mass]] to define concepts such as [[Physics:Velocity|velocity]], [[Physics:Momentum|momentum]], [[Physics:Energy|energy]], and [[Physics:Field|fields]].

Both [[Biography:Isaac Newton|Newton]] and Galileo,<ref>[[Biography:Roger Penrose|Roger Penrose]], 2004. ''[[The Road to Reality]]: A Complete Guide to the Laws of the Universe''. London: Jonathan Cape. {{ISBN|0-224-04447-8}} (hardcover), 0-09-944068-7 (paperback).
</ref>
as well as most people up until the 20th century, thought that time was the same for everyone everywhere.
The modern conception of time is based on [[Biography:Albert Einstein|Einstein]]'s [[Physics:Theory of relativity|theory of relativity]] and [[Biography:Hermann Minkowski|Minkowski]]'s [[Physics:Spacetime|spacetime]], in which rates of time run differently in different inertial frames of reference, and [[Space|space]] and time are merged into [[Physics:Spacetime|spacetime]]. Einstein's [[Physics:General relativity|general relativity]] as well as the [[Astronomy:Redshift|redshift]] of the light from receding distant galaxies indicate that the entire [[Astronomy:Universe|Universe]] and possibly space-time itself began about [[Astronomy:Age of the universe|13.8 billion years ago]] in the [[Astronomy:Big Bang|Big Bang]]. Einstein's theory of special relativity mostly (though not universally) made theories of time where there is something metaphysically special about the present seem much less plausible, as the reference-frame-dependence of time seems to not allow the idea of a privileged present moment.

===Time travel===
{{Main| Physics:Time travel}}
Some theories, most notably general relativity, suggest that suitable geometries of [[Physics:Spacetime|spacetime]], or certain types of motion in [[Space|space]], may allow time travel into the past and future. Concepts that aid such understanding include the [[Closed timelike curve|closed timelike curve]].

[[Biography:Albert Einstein|Albert Einstein]]'s special theory of relativity (and, by extension, the general theory) predicts [[Physics:Time dilation|time dilation]] that could be interpreted as time travel. The theory states that, relative to a stationary observer, time appears to pass more slowly for faster-moving bodies: for example, a moving clock will appear to run slow; as a clock approaches the speed of light its hands will appear to nearly stop moving. The effects of this sort of time dilation are discussed further in the popular "[[Physics:Twin paradox|twin paradox]]".  Although these results are experimentally observable, an intrinsic aspect of Einstein' theory is an equation applicable to the operation of GPS satellites and other high-tech systems used in daily life.

A second, similar type of time travel is permitted by [[Physics:General relativity|general relativity]]. In this type a distant observer sees time passing more slowly for a clock at the bottom of a deep [[Physics:Gravity well|gravity well]], and a clock lowered into a deep gravity well and pulled back up will indicate that less time has passed compared to a stationary clock that stayed with the distant observer.

Many in the scientific community believe that backward time travel is highly unlikely, because it violates [[Causality|causality]]<ref name="Bolonkin">{{cite book |title=Universe, Human mmortality and Future Human Evaluation |first1=Alexander |last1=Bolonkin |publisher=Elsevier |year=2011 |isbn=978-0-12-415810-8 |page=32 |url=https://books.google.com/books?id=IFZWTf93KwgC}} [https://books.google.com/books?id=IFZWTf93KwgC&pg=PA32 Extract of page 32]</ref> i.e. the logic of cause and effect. For example, what happens if you attempt to go back in time and kill yourself at an earlier stage in your life (or your grandfather, which leads to the [[Physics:Grandfather paradox|grandfather paradox]])? [[Biography:Stephen Hawking|Stephen Hawking]] once suggested that the absence of tourists from the future constitutes a strong argument against the existence of time travel&mdash; a variant of the [[Astronomy:Fermi paradox|Fermi paradox]], with time travelers instead of alien visitors.<ref name="Bolonkin" />

===Space===
{{Main|Space}}

Space is one of the few fundamental quantities in [[Physics:Physics|physics]], meaning that it cannot be defined via other quantities because there is nothing more fundamental known at present. Thus, similar to the definition of other fundamental quantities (like [[Time|time]] and [[Physics:Mass|mass]]), space is defined via [[Measurement|measurement]]. Currently, the standard space interval, called a standard metre or simply metre, is defined as the [[Physics:Speed of light|distance traveled by light in a vacuum]] during a time interval of 1/299792458 of a second (exact).

In [[Physics:Classical physics|classical physics]], space is a three-dimensional [[Euclidean space]] where any position can be described using three [[Coordinate system|coordinate]]s and parameterised by time.  Special and general relativity use four-dimensional [[Physics:Spacetime|spacetime]] rather than three-dimensional space; and currently there are many speculative theories which use more than four spatial dimensions.

==Philosophy of quantum mechanics==
{{Main|Physics:Quantum foundations}}
Quantum mechanics is a large focus of contemporary philosophy of physics, specifically concerning the correct interpretation of quantum mechanics. Very broadly, much of the philosophical work that is done in quantum theory is trying to make sense of superposition states:<ref>{{cite web|url=https://www.youtube.com/watch?v=J8k_2oD66mI&t=128| archive-url=https://ghostarchive.org/varchive/youtube/20211211/J8k_2oD66mI| archive-date=2021-12-11 | url-status=live|title=Eleanor Knox (KCL) – The Curious Case of the Vanishing Spacetime|last=BristolPhilosophy|date=19 February 2013|access-date=7 April 2018|via=YouTube}}{{cbignore}}</ref> the property that particles seem to not just be in one determinate position at one time, but are somewhere 'here', and also 'there' at the same time. Such a radical view turns many common sense metaphysical ideas on their head. Much of contemporary philosophy of quantum mechanics aims to make sense of what the very empirically successful formalism of quantum mechanics tells us about the physical world.

===Uncertainty principle===
{{Main|Physics:Uncertainty principle}}
The [[Physics:Uncertainty principle|uncertainty principle]] is a mathematical relation asserting an upper limit to the accuracy of the simultaneous measurement of any pair of [[Physics:Conjugate variables|conjugate variables]], e.g. position and momentum. In the formalism of [[Physics:Operator#Operators in quantum mechanics|operator notation]], this limit is the evaluation of the [[Physics:Canonical commutation relation|commutator]] of the variables' corresponding operators.

The uncertainty principle arose as an answer to the question: How does one measure the location of an electron around a nucleus if an electron is a wave?  When quantum mechanics was developed, it was seen to be a relation between the classical and quantum descriptions of a system using wave mechanics.

==="Locality" and hidden variables===
{{main|Physics:EPR paradox|Bell's theorem}}
[[Bell's theorem]] is a term encompassing a number of closely related results in physics, all of which determine that [[Physics:Quantum mechanics|quantum mechanics]] is incompatible with [[Local hidden-variable theory|local hidden-variable theories]] given some basic assumptions about the nature of measurement. "Local" here refers to the [[Physics:Principle of locality|principle of locality]], the idea that a particle can only be influenced by its immediate surroundings, and that interactions mediated by [[Physics:Field|physical fields]] cannot propagate faster than the [[Physics:Speed of light|speed of light]]. "[[Hidden-variable theory|Hidden variables]]" are putative properties of quantum particles that are not included in the theory but nevertheless affect the outcome of experiments. In the words of physicist [[Biography:John Stewart Bell|John Stewart Bell]], for whom this family of results is named, "If [a hidden-variable theory] is local it will not agree with quantum mechanics, and if it agrees with quantum mechanics it will not be local."<ref>{{cite book  | first = John S. | last = Bell |  title = Speakable and Unspeakable in Quantum Mechanics | publisher = Cambridge University Press | date = 1987  | page = 65 | isbn = 9780521368698 | oclc = 15053677}}</ref>

The term is broadly applied to a number of different derivations, the first of which was introduced by Bell in a 1964 paper titled "On the [[Physics:EPR paradox|Einstein Podolsky Rosen Paradox]]". Bell's paper was a response to a 1935 [[Thought experiment|thought experiment]] that [[Biography:Albert Einstein|Albert Einstein]], [[Biography:Boris Podolsky|Boris Podolsky]] and [[Biography:Nathan Rosen|Nathan Rosen]] proposed, arguing that quantum physics is an "incomplete" theory.<ref name="EPR">{{cite journal | title = Can Quantum-Mechanical Description of Physical Reality be Considered Complete? | date = 1935-05-15 | first1 = A. | last1 = Einstein |first2=B. |last2 = Podolsky |first3=N. |last3 = Rosen |  author-link2 = Boris Podolsky | author-link3 = Nathan Rosen | journal = [[Physics:Physical Review|Physical Review]] | volume = 47 | issue = 10 | pages = 777–780 | bibcode = 1935PhRv...47..777E |doi = 10.1103/PhysRev.47.777 | doi-access = free }}</ref><ref name=Bell1964>{{cite journal | last1 = Bell | first1 = J. S. | author-link = John Stewart Bell | year = 1964 | title = On the Einstein Podolsky Rosen Paradox | url = https://cds.cern.ch/record/111654/files/vol1p195-200_001.pdf | journal = [[Physics:Physics Physique Физика|Physics Physique Физика]] | volume = 1 | issue = 3| pages = 195–200 | doi = 10.1103/PhysicsPhysiqueFizika.1.195 }}</ref> By 1935, it was already recognized that the predictions of quantum physics are [[Probability|probabilistic]]. Einstein, Podolsky and Rosen presented a scenario that involves preparing a pair of [[Physics:Particle|particle]]s such that the [[Physics:Quantum state|quantum state]] of the pair is [[Quantum entanglement|entangled]], and then separating the particles to an arbitrarily large distance. The experimenter has a choice of possible [[Physics:Measurement in quantum mechanics|measurements]] that can be performed on one of the particles. When they choose a measurement and obtain a result, the quantum state of the other particle apparently [[Physics:Wave function collapse|collapses]] instantaneously into a new state depending upon that result, no matter how far away the other particle is.  This suggests that either the measurement of the first particle somehow also interacted with the second particle at faster than the speed of light, ''or'' that the entangled particles had some unmeasured property which pre-determined their final quantum states before they were separated.  Therefore, assuming locality, quantum mechanics must be incomplete, as it cannot give a complete description of the particle's true physical characteristics. In other words, quantum particles, like [[Physics:Electron|electron]]s and [[Physics:Photon|photon]]s, must carry some property or attributes not included in quantum theory, and the uncertainties in quantum theory's predictions would then be due to ignorance or unknowability of these properties, later termed "hidden variables".

Bell carried the analysis of quantum entanglement much further. He deduced that if measurements are performed independently on the two separated particles of an entangled pair, then the assumption that the outcomes depend upon hidden variables within each half implies a mathematical constraint on how the outcomes on the two measurements are correlated. This constraint would later be named the ''Bell inequality''. Bell then showed that quantum physics predicts correlations that violate this inequality. Consequently, the only way that hidden variables could explain the predictions of quantum physics is if they are "nonlocal", which is to say that somehow the two particles are able to interact instantaneously no matter how widely they ever become separated.<ref name="C.B. Parker 1994 542">{{cite book | first = Sybil B. | last = Parker | title = McGraw-Hill Encyclopaedia of Physics | edition = 2nd | page = [https://archive.org/details/mcgrawhillencycl1993park/page/542 542] | date = 1994 | publisher = McGraw-Hill | isbn = 978-0-07-051400-3 | url = https://archive.org/details/mcgrawhillencycl1993park| url-access = registration }}</ref><ref name = "ND Mermin 1993-07">{{cite journal | last = Mermin |first = N. David |title = Hidden Variables and the Two Theorems of John Bell | journal = [[Physics:Reviews of Modern Physics|Reviews of Modern Physics]] | volume = 65 |pages = 803–15 | number = 3| date = July 1993  | url = http://cqi.inf.usi.ch/qic/Mermin1993.pdf |arxiv=1802.10119|doi = 10.1103/RevModPhys.65.803 |bibcode = 1993RvMP...65..803M |s2cid = 119546199 }}</ref>

Multiple variations on Bell's theorem were put forward in the following years, introducing other closely related conditions generally known as Bell (or "Bell-type") inequalities. The first rudimentary experiment designed to test Bell's theorem was performed in 1972 by [[Biography:John Clauser|John Clauser]] and [[Biography:Stuart Freedman|Stuart Freedman]].<ref>{{cite press release |url=https://www.nobelprize.org/prizes/physics/2022/press-release/ |title=The Nobel Prize in Physics 2022 |date=October 4, 2022 |work=Nobel Prize |publisher=The Royal Swedish Academy of Sciences |access-date=6 October 2022}}</ref> More advanced experiments, known collectively as ''[[Physics:Bell test|Bell test]]s'', have been performed many times since. To date, Bell tests have consistently found that physical systems obey quantum mechanics and violate Bell inequalities; which is to say that the results of these experiments are incompatible with any local hidden variable theory.<ref name="NAT-20180509">{{cite journal |author=The BIG Bell Test Collaboration |title=Challenging local realism with human choices |date=9 May 2018 |journal=Nature |volume=557 |issue=7704 |pages=212–216 |doi=10.1038/s41586-018-0085-3 |pmid=29743691 |bibcode=2018Natur.557..212B |arxiv=1805.04431 |s2cid=13665914 }}</ref><ref>{{Cite web|url=https://www.quantamagazine.org/physicists-are-closing-the-bell-test-loophole-20170207/|title=Experiment Reaffirms Quantum Weirdness|last=Wolchover|first=Natalie|date=2017-02-07|work=Quanta Magazine|language=en-US|access-date=2020-02-08}}</ref>

The exact nature of the assumptions required to prove a Bell-type constraint on correlations has been debated by physicists and by philosophers. While the significance of Bell's theorem is not in doubt, its full implications for the [[Physics:Interpretation of quantum mechanics|interpretation of quantum mechanics]] remain unresolved.

===Interpretations of quantum mechanics===
{{Main|Physics:Interpretation of quantum mechanics}}
In March 1927, working in [[Biography:Niels Bohr|Niels Bohr]]'s institute, [[Biography:Werner Heisenberg|Werner Heisenberg]] formulated the principle of uncertainty thereby laying the foundation of what became known as the [[Physics:Copenhagen interpretation|Copenhagen interpretation]] of quantum mechanics. Heisenberg had been studying the papers of [[Biography:Paul Dirac|Paul Dirac]] and [[Biography:Pascual Jordan|Pascual Jordan]].  He discovered a problem with measurement of basic variables in the equations. His analysis showed that uncertainties, or imprecisions, always turned up if one tried to measure the position and the momentum of a particle at the same time. Heisenberg concluded that these uncertainties or imprecisions in the measurements were not the fault of the experimenter, but fundamental in nature and are inherent mathematical properties of operators in quantum mechanics arising from definitions of these operators.<ref>Niels Bohr, ''Atomic Physics and Human Knowledge, p. 38</ref>

The term "Copenhagen interpretation" is somewhat loosely defined, as many physicists and philosophers of physics have advanced similar but not identical views of quantum mechanics. It is principally associated with Heisenberg and Bohr, despite their philosophical differences.<ref name="Faye-Stanford">{{Cite book|last=Faye|first=Jan|title=[[Stanford Encyclopedia of Philosophy]]|publisher=Metaphysics Research Lab, Stanford University|year=2019|editor-last=Zalta|editor-first=Edward N.|chapter=Copenhagen Interpretation of Quantum Mechanics|chapter-url=https://plato.stanford.edu/entries/qm-copenhagen/}}</ref><ref name="camilleri2015">{{cite journal|first1=K. |last1=Camilleri |first2=M. |last2=Schlosshauer |title=Niels Bohr as Philosopher of Experiment: Does Decoherence Theory Challenge Bohr's Doctrine of Classical Concepts? |arxiv=1502.06547 |journal=Studies in History and Philosophy of Modern Physics |volume=49 |pages=73–83 |year=2015 |doi=10.1016/j.shpsb.2015.01.005|bibcode=2015SHPMP..49...73C |s2cid=27697360 }}</ref> Features common to Copenhagen-type interpretations include the idea that quantum mechanics is intrinsically indeterministic, with probabilities calculated using the [[Physics:Born rule|Born rule]], and the principle of [[Physics:Complementarity|complementarity]], which states that objects have certain pairs of complementary properties that cannot all be observed or measured simultaneously.<ref>{{cite book|last=Omnès |first=Roland |author-link=Roland Omnès |chapter=The Copenhagen Interpretation |title=Understanding Quantum Mechanics |publisher=Princeton University Press |year=1999 |pages=41–54 |doi=10.2307/j.ctv173f2pm.9 |s2cid=203390914 |quote=Bohr, Heisenberg, and Pauli recognized its main difficulties and proposed a first essential answer. They often met in Copenhagen ... 'Copenhagen interpretation has not always meant the same thing to different authors. I will reserve it for the doctrine held with minor differences by Bohr, Heisenberg, and Pauli.}}</ref> Moreover, the act of "observing" or "measuring" an object is irreversible, and no truth can be attributed to an object, [[Physics:Counterfactual definiteness|except according to the results of its measurement]]. Copenhagen-type interpretations hold that quantum descriptions are objective, in that they are independent of any arbitrary factors in the physicist's mind.<ref name="omnes">{{cite book|first=R. |last=Omnès |author-link=Roland Omnès |title=The Interpretation of Quantum Mechanics |publisher=Princeton University Press |year=1994 |isbn=978-0-691-03669-4 |oclc=439453957 }}</ref>{{Rp|85–90}}

The Everett, or many-worlds interpretation of quantum mechanics claims that the wave-function of a quantum system is telling us claims about the reality of that physical system. It denies wavefunction collapse, and claims that [[Superposition principle|superposition]] states should be interpreted literally as describing the reality of many-worlds where objects are located, and not simply indicating the indeterminacy of those variables. This is sometimes argued as a corollary of [[Philosophy:Scientific realism|scientific realism]],<ref>David Wallace, 'The Emergent Multiverse', pp. 1–10</ref> which states that scientific theories aim to give us literally true descriptions of the world.

One issue for the Everett interpretation is the role that probability plays on this account. The Everettian account is completely deterministic, whereas probability seems to play an ineliminable role in quantum mechanics.<ref>David Wallace, 'The Emergent Multiverse', pp. 113–117</ref> Contemporary Everettians have argued that one can get an account of probability that follows the [[Physics:Born rule|Born rule]] through certain decision-theoretic proofs,<ref>David Wallace, 'The Emergent Multiverse', pg. 157–189</ref> but there is as yet no consensus about whether any of these proofs are successful.<ref name=kent2009>{{Cite book|arxiv=0905.0624|last1=Kent|first1=Adrian|chapter=One world versus many: The inadequacy of Everettian accounts of evolution, probability, and scientific confirmation|title=Many Worlds? Everett, Quantum Theory and Reality |editor=S. Saunders |editor2=J. Barrett |editor3=A. Kent |editor4=D. Wallace |publisher=Oxford University Press|year=2010|bibcode=2009arXiv0905.0624K}}</ref><ref>{{cite journal | last1 = Kent | first1 = Adrian | year = 1990 | title = Against Many-Worlds Interpretations | arxiv = gr-qc/9703089 | journal = International Journal of Modern Physics A | volume = 5 | issue = 9| pages = 1745–1762 |bibcode = 1990IJMPA...5.1745K |doi = 10.1142/S0217751X90000805 | s2cid = 14523184 }}</ref><ref>{{Cite book| last1=Price |first1=Huw | chapter=Decisions, Decisions, Decisions: Can Savage Salvage Everettian Probability?|title=Many Worlds? Everett, Quantum Theory and Reality |editor=S. Saunders |editor2=J. Barrett |editor3=A. Kent |editor4=D. Wallace |publisher=Oxford University Press|year=2010|arxiv = 0802.1390}}</ref>

Physicist [[Biography:Roland Omnès|Roland Omnès]] noted that it is impossible to experimentally differentiate between Everett's view, which says that as the wave-function decoheres into distinct worlds, each of which exists equally, and the more traditional view that says that a decoherent wave-function leaves only one unique real result. Hence, the dispute between the two views represents a great "chasm". "Every characteristic of reality has reappeared in its reconstruction by our theoretical model; every feature except one: the uniqueness of facts."<ref>{{cite book|last1=Omnès|first1=Roland|title=Quantum philosophy : understanding and interpreting contemporary science|date=2002|publisher=Princeton University Press|location=Princeton|isbn=978-1400822867|page=213|edition=1st paperback |others=Arturo Spangalli (transl.)|language=fr|chapter=11}}</ref>

==Philosophy of thermal and statistical physics==
The philosophy of thermal and statistical physics is that part of the philosophy of physics whose subject matter is an amalgam of classical [[Physics:Thermodynamics|thermodynamics]], [[Physics:Statistical mechanics|statistical mechanics]], and related theories. Its central questions include: What is [[Physics:Entropy|entropy]], and what does the second law of thermodynamics say about it? What is the correct resolution of the [[Physics:Maxwell's demon|Maxwell's demon]] paradox? Does either thermodynamics or statistical mechanics contain an element of [[Time|time]]-irreversibility? If so, what does statistical mechanics tell us about the [[Physics:Arrow of time|arrow of time]]? What is the nature of the probabilities that appear in statistical mechanics?<ref>{{cite SEP|url-id=statphys-statmech |title=Philosophy of Statistical Mechanics |author-first1=Roman |author-last1=Frigg |author-first2=Charlotte |author-last2=Werndl |date=2023-01-10}}</ref>

==History==
===Aristotelian physics===
{{Disputed section|date=September 2022}}
[[Physics:Aristotelian physics|Aristotelian physics]] viewed the universe as a [[Astronomy:Sublunary sphere|sphere]] with a center. Matter, composed of the [[Philosophy:Classical element#Greece|classical elements]], earth, water, air, and fire, sought to go down towards the center of the universe, the center of the Earth, or up, away from it. Things in the [[Philosophy:Aether (classical element)|aether]] such as the Moon, the Sun, planets, or stars circled the center of the universe.<ref name = MaudlinPPST3 >[[Biography:Tim Maudlin|Tim Maudlin]] (2012-07-22). ''Philosophy of Physics: Space and Time: Space and Time'' (Princeton Foundations of Contemporary Philosophy) (p. 3). Princeton University Press. Kindle Edition. "Because it is a sphere, Aristotle's universe contains a geometrically privileged center, and Aristotle makes reference to that center in characterizing the natural motions of different sorts of matter. 'Upward', 'downward', and 'uniform circular motion' all are defined in terms of the center of the universe."</ref> Movement is defined as change in place,<ref name = MaudlinPPST3 /> i.e. space.<ref name = MaudlinPPST4 >[[Biography:Tim Maudlin|Tim Maudlin]] (2012-07-22). ''Philosophy of Physics: Space and Time: Space and Time'' (Princeton Foundations of Contemporary Philosophy) (p. 4). Princeton University Press. Kindle Edition.  "Aristotle adopts the concept of space, and the correlative concept of motion, that we all intuitively employ."</ref>

===Newtonian physics===
The implicit axioms of Aristotelian physics with respect to movement of matter in space were superseded in [[Physics:Classical mechanics|Newtonian physics]] by [[Biography:Isaac Newton|Newton's]] [[Physics:Newton's laws of motion#Newton's first law|First Law of Motion]].<ref name = MaudlinPPST3-4 >[[Biography:Tim Maudlin|Tim Maudlin]] (2012-07-22). ''Philosophy of Physics: Space and Time: Space and Time'' (Princeton Foundations of Contemporary Philosophy) (pp. 4–5). Princeton University Press. Kindle Edition. "Newtonian physics is implicit in his First Law of Motion: Law I : Every body perseveres in its state either of rest or of uniform motion in a straight line, except insofar as it is compelled to change its state by impressed forces. 1 This single law smashes the Aristotelian universe to smithereens."</ref>{{cquote|Every body perseveres in its state either of rest or of uniform motion in a straight line, except insofar as it is compelled to change its state by impressed forces.}}
"Every body" includes the Moon, and an apple; and includes all types of matter, air as well as water, stones, or even a flame. Nothing has a natural or inherent motion.<ref name = MaudlinPPST5>[[Biography:Tim Maudlin|Tim Maudlin]] (2012-07-22). ''Philosophy of Physics: Space and Time: Space and Time'' (Princeton Foundations of Contemporary Philosophy) (pp. 5). Princeton University Press. Kindle Edition.</ref> Absolute space being [[Three-dimensional space|three-dimensional]] [[Euclidean space]], infinite and without a center.<ref name = MaudlinPPST5 /> Being "at rest" means being at the same place in absolute space over time.<ref name = MaudlinPPST9-10  >[[Biography:Tim Maudlin|Tim Maudlin]] (2012-07-22). ''Philosophy of Physics: Space and Time: Space and Time'' (Princeton Foundations of Contemporary Philosophy) (pp. 9–10). Princeton University Press. Kindle Edition. "Newton believed in the existence of a spatial arena with the geometrical structure of E{{smallsup|3}}. He believed that this infinite three-dimensional space exists at every moment of time. And he also believed something much more subtle and controversial, namely, that identically the same points of space persist through time."</ref> The [[Topology|topology]] and [[Affine space|affine structure]] of space must permit movement in a [[Line (geometry)|straight line]] at a uniform velocity; thus both space and time must have definite, stable dimensions.<ref name = Maudlin12 >[[Biography:Tim Maudlin|Tim Maudlin]] (2012-07-22). ''Philosophy of Physics: Space and Time: Space and Time'' (Princeton Foundations of Contemporary Philosophy) (p. 12). Princeton University Press. Kindle Edition. "...space must have a topology, an affine structure, and a metric; time must be one-dimensional with a topology and a metric; and, most importantly, the individual parts of space must persist through time.</ref>

===Leibniz===
[[Biography:Gottfried Wilhelm Leibniz|Gottfried Wilhelm Leibniz]], 1646–1716, was a contemporary of Newton. He contributed a fair amount to the statics and dynamics emerging around him, often disagreeing with Descartes and [[Biography:Isaac Newton|Newton]]. He devised a new theory of [[Physics:Motion|motion]] ([[Physics:Dynamics (mechanics)|dynamics]]) based on [[Physics:Kinetic energy|kinetic energy]] and [[Physics:Potential energy|potential energy]], which posited space as relative, whereas Newton was thoroughly convinced that space was absolute. An important example of Leibniz's mature physical thinking is his ''Specimen Dynamicum'' of 1695.<ref>Ariew and Garber 117, Loemker §46, W II.5. On Leibniz and physics, see the chapter by Garber in Jolley (1995) and Wilson (1989).</ref>

Until the discovery of subatomic particles and the [[Physics:Quantum mechanics|quantum mechanics]] governing them, many of Leibniz's speculative ideas about aspects of nature not reducible to statics and dynamics made little sense.

He anticipated [[Biography:Albert Einstein|Albert Einstein]] by arguing, against Newton, that [[Space|space]], [[Time|time]] and motion are relative, not absolute:<ref name=Ferraro>{{cite book |title =Einstein's Space-Time: An Introduction to Special and General Relativity|page= 1| url=https://books.google.com/books?id=wa3CskhHaIgC&q=time+%22absolute+space%22&pg=PA1|author=Rafael Ferraro |isbn=978-0-387-69946-2 |publisher=Springer |year=2007}}</ref> "As for my own opinion, I have said more than once, that I hold space to be something merely relative, as time is, that I hold it to be an order of coexistences, as time is an order of successions."<ref>See H. G. Alexander, ed., ''The Leibniz-Clarke Correspondence'', Manchester: Manchester University Press, pp. 25–26.</ref>

==See also==
{{Div col|colwidth=23em}}
* [[Astronomy:Anthropic principle|Anthropic principle]]
* [[Physics:Arrow of time|Arrow of time]]
* [[Physics:Causality|Causality]]
* [[Philosophy:Causal closure|Causal closure]]
* [[Unsolved:Constructor theory|Constructor theory]]
* [[Determinism]]
* [[Physics:Digital physics|Digital physics]]
* Mind-body dualism
* [[Physics:Field|Field]]
* [[Functional decomposition]]
* [[Physics:Fundamental interaction|Fundamental interaction]]
* [[Holism]]
* [[Philosophy:Instrumentalism|Instrumentalism]]
* [[Physics:Laws of thermodynamics|Laws of thermodynamics]]
* [[Physics:Macroscopic|Macroscopic]]
* Mesoscopic scale
* [[Philosophy:Modal realism|Modal realism]]
* [[Philosophy:Monism|Monism]]
* [[Philosophy:Pluralism|Pluralism]]
* Physical ontology
* [[Philosophy:Naturalism|Naturalism]]:
** [[Metaphysical naturalism|Metaphysical]]
** [[Philosophy:Methodological naturalism|Methodological]]
* Operationalism
* [[Philosophy:Phenomenology|Phenomenology]]
** Phenomenology (particle physics)
* [[Philosophy:Philosophy of science|Philosophy of]]:
** [[Physics:Philosophical interpretation of classical physics|Classical physics]]
** [[Physics:Philosophy of space and time|Space and time]]
** [[Physics:Philosophy of thermal and statistical physics|Thermodynamics and statistical mechanics]]
**[[Philosophy:Philosophy of motion|Motion]]
* Physical
** Bodies
** [[Physical law|Law]]
** [[Physics:Physical system|System]]
* [[Physicalism]]
* [[Physics:Physics|Physics]]
** [[Philosophy:Physics (Aristotle)|Aristotle]]
* [[Philosophy:Physics envy|Physics envy]]
* [[Physics:Quantum mechanics|Quantum theory]]:
** Bohr-Einstein debates
** [[Physics:Einstein's thought experiments|Einstein's thought experiments]]
** [[Physics:EPR paradox|EPR paradox]]
** [[Physics:Interpretation of quantum mechanics|Interpretations of]]
** Metaphysics
** [[Physics:Quantum mysticism|Mysticism]]
* [[Philosophy:Reductionism|Reductionism]]
* [[Physics:Theory of relativity|Relativity]]:
** [[Physics:Introduction to general relativity|General]]
** [[Physics:Special relativity|Special]]
* [[Space]]
** [[Philosophy:Absolute theory|Absolute theory]]
** [[Philosophy:Container space|Container space]]
** [[Physics:Free space|Free space]]
** [[Physics:Relational space|Relational space]]
** [[Relational theory]]
** [[Physics:Spacetime|Spacetime]]
* [[Philosophy:Supervenience|Supervenience]]
* Symmetry in physics
* [[Physics:Theophysics|Theophysics]]
* [[Physics:Time in physics|Time in physics]]
{{Div col end}}

==References==
{{Reflist}}

== Further reading ==
* David Albert, 1994. ''Quantum Mechanics and Experience''. Harvard Univ. Press.
* [[Biography:John D. Barrow|John D. Barrow]] and [[Biography:Frank J. Tipler|Frank J. Tipler]], 1986. ''[[Astronomy:Anthropic principle|The Cosmological Anthropic Principle]]''. Oxford Univ. Press.
* Beisbart, C. and S. Hartmann, eds., 2011. "Probabilities in Physics". Oxford Univ. Press.
* John S. Bell, 2004 (1987), ''Speakable and Unspeakable in Quantum Mechanics''. Cambridge Univ. Press.
* [[Biography:David Bohm|David Bohm]], 1980. ''[[Philosophy:Wholeness and the Implicate Order|Wholeness and the Implicate Order]]''. Routledge.
* [[Biography:Nick Bostrom|Nick Bostrom]], 2002. ''[https://web.archive.org/web/20060826121429/http://www.anthropic-principle.com/book/ Anthropic Bias: Observation Selection Effects in Science and Philosophy]''. Routledge.
* Thomas Brody, 1993, Ed. by [[Biography:Luis de la Peña|Luis de la Peña]] and [[Biography:Peter E. Hodgson|Peter E. Hodgson]] ''The Philosophy Behind Physics'' Springer {{ISBN|3-540-55914-0}}
* [[Biography:Harvey Brown (philosopher)|Harvey Brown]], 2005. ''Physical Relativity. Space-time structure from a dynamical perspective''. Oxford Univ. Press.
* Butterfield, J., and [[Biography:John Earman|John Earman]], eds., 2007. ''Philosophy of Physics, Parts A and B''. Elsevier.
* [[Biography:Craig Callender|Craig Callender]] and Nick Huggett, 2001. ''Physics Meets Philosophy at the Planck Scale''. Cambridge Univ. Press.
* [[Biography:David Deutsch|David Deutsch]], 1997. ''[[Astronomy:The Fabric of Reality|The Fabric of Reality]]''. London: The Penguin Press.
* [[Biography:Bernard d'Espagnat|Bernard d'Espagnat]], 1989. ''Reality and the Physicist''. Cambridge Univ. Press. Trans. of ''Une incertaine réalité; le monde quantique, la connaissance et la durée''.
* --------, 1995. ''Veiled Reality''. Addison-Wesley.
* --------, 2006. ''On Physics and Philosophy''. Princeton Univ. Press.
* [[Biography:Roland Omnès|Roland Omnès]], 1994. ''The Interpretation of Quantum Mechanics''. Princeton Univ. Press.
* --------, 1999. ''[[Physics:Quantum Philosophy|Quantum Philosophy]]''. Princeton Univ. Press.
* Huw Price, 1996. ''Time's Arrow and Archimedes's Point''. Oxford Univ. Press.
* Lawrence Sklar, 1992. ''Philosophy of Physics''. Westview Press. {{ISBN|0-8133-0625-6}}, {{ISBN|978-0-8133-0625-4}}
* Victor Stenger, 2000. ''Timeless Reality''. Prometheus Books.
* [[Biography:Carl Friedrich von Weizsäcker|Carl Friedrich von Weizsäcker]], 1980. ''The Unity of Nature''. Farrar Straus & Giroux.
* [[Biography:Werner Heisenberg|Werner Heisenberg]], 1971. ''Physics and Beyond: Encounters and Conversations''. Harper & Row (''World Perspectives'' series), 1971.
* William Berkson, 1974. ''Fields of Force''. Routledge and Kegan Paul, London. {{ISBN|0-7100-7626-6}}
* [http://www.britannica.com/topic/philosophy-of-physics Encyclopædia Britannica, Philosophy of Physics, David Z. Albert]

==External links==
* [http://plato.stanford.edu/ Stanford Encyclopedia of Philosophy]:
** "[http://plato.stanford.edu/entries/spacetime-theories/ Absolute and Relational Theories of Space and Motion]"—Nick Huggett and Carl Hoefer
** "[http://plato.stanford.edu/entries/spacetime-bebecome/ Being and Becoming in Modern Physics]"—Steven Savitt
** "[http://plato.stanford.edu/entries/statphys-Boltzmann/ Boltzmann's Work in Statistical Physics]"—Jos Uffink
** "[http://plato.stanford.edu/entries/spacetime-convensimul/ Conventionality of Simultaneity]"—Allen Janis
** "[http://plato.stanford.edu/entries/genrel-early/ Early Philosophical Interpretations of General Relativity]"—Thomas A. Ryckman
** "[http://plato.stanford.edu/entries/qm-everett/ Everett's Relative-State Formulation of Quantum Mechanics]"—Jeffrey A. Barrett 
** "[http://plato.stanford.edu/entries/physics-experiment/ Experiments in Physics]"—Allan Franklin
** "[http://plato.stanford.edu/entries/physics-holism/ Holism and Nonseparability in Physics]"—Richard Healey
** "[http://plato.stanford.edu/entries/physics-interrelate/ Intertheory Relations in Physics]"—Robert Batterman
** "[http://plato.stanford.edu/entries/naturalism/ Naturalism]"—David Papineau
** "[http://plato.stanford.edu/entries/statphys-statmech/ Philosophy of Statistical Mechanics]"—Lawrence Sklar
** "[http://plato.stanford.edu/entries/physicalism/ Physicalism]"—Daniel Sojkal
** "[http://plato.stanford.edu/entries/qm/ Quantum Mechanics]"—Jenann Ismael
** "[http://plato.stanford.edu/entries/physics-Rpcc/ Reichenbach's Common Cause Principle]"—Frank Artzenius
** "[http://plato.stanford.edu/entries/structural-realism/ Structural Realism]"—James Ladyman
** "[http://plato.stanford.edu/entries/physics-structuralism/ Structuralism in Physics]"—Heinz-Juergen Schmidt
** "[https://plato.stanford.edu/entries/spacetime-supertasks/ Supertasks]"—JB Manchak and Bryan Roberts
** "[http://plato.stanford.edu/entries/symmetry-breaking/ Symmetry and Symmetry Breaking]"—Katherine Brading and Elena Castellani
** "[http://plato.stanford.edu/entries/time-thermo/ Thermodynamic Asymmetry in Time]"—Craig Callender
** "[http://plato.stanford.edu/entries/time/ Time]"—by [[Biography:Ned Markosian|Ned Markosian]]
** "[https://plato.stanford.edu/entries/time-machine/ Time Machines]" —John Earman, Chris Wüthrich, and JB Manchak
** "[http://plato.stanford.edu/entries/qt-uncertainty/ Uncertainty principle]"—Jan Hilgevoord and Jos Uffink
** "[http://plato.stanford.edu/entries/scientific-unity/ The Unity of Science]"—Jordi Cat

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