member_of john archibald wheeler
Newton ' ___MASK43___ law of universal gravitation states that a particle attracts every other particle in the universe using a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them . This is a general physical law derived from empirical observations by what Isaac Newton called inductive reasoning . It is a part of classical mechanics and was formulated in Newton ' ___MASK43___ work " Philosophiæ Naturalis Principia Mathematica " (" the " Principia ""), first published on 5 July 1687 . ( When Newton ' ___MASK43___ book was presented in 1686 to the ___MASK75___ , Robert Hooke made a claim that Newton had obtained the inverse square law from him ; see the History section below .) Niels Henrik David Bohr ( 7 October 1885  18 November 1962 ) was a Danish physicist who made foundational contributions to understanding atomic structure and ___MASK58___ theory , for which he received the Nobel Prize in Physics in 1922 . Bohr was also a philosopher and a promoter of scientific research . The one - electron universe postulate , proposed by John Wheeler in a telephone call to Richard Feynman in the spring of 1940 , hypothesises that all electrons and positrons are actually manifestations of a single entity moving backwards and forwards in time . According to Feynman : The electron is a subatomic particle , symbol or , with a negative elementary electric charge . Electrons belong to the first generation of the lepton particle ___MASK77___ , and are generally thought to be elementary particles because they have no known components or substructure . The electron has a mass that is approximately 1 / 1836 that of the proton . Quantum mechanical properties of the electron include an intrinsic angular momentum ( spin ) of a half - integer value , expressed in units of the reduced Planck constant , "  ". As it is a fermion , no two electrons can occupy the same quantum state , in accordance with the Pauli exclusion principle . Like all matter , electrons have properties of both particles and waves : they can collide with other particles and can be diffracted like light . The wave properties of electrons are easier to observe with experiments than those of other particles like neutrons and protons because electrons have a lower mass and hence a larger De Broglie wavelength for a given energy . Gravity , or gravitation , is a natural phenomenon by which all things with mass are brought toward ( or " gravitate " toward ) one another , including planets , stars and galaxies . Since energy and mass are equivalent , all forms of energy , including light , also cause gravitation and are under the influence of it . On Earth , gravity gives weight to physical objects and causes the ocean tides . The gravitational attraction of the original gaseous matter present in the Universe caused it to begin coalescing , forming stars  and the stars to ___MASK99___ together into galaxies  so gravity is responsible for many of the large scale structures in the Universe . Gravity has an infinite range , although its effects become increasingly weaker on farther objects . John Archibald Wheeler ( July 9 , 1911 -- April 13 , 2008 ) was an American theoretical physicist . He was largely responsible for reviving interest in general relativity in the United States after World War II . Wheeler also worked with Niels Bohr in explaining the basic principles behind nuclear fission . Together with Gregory Breit , Wheeler developed the concept of Breit -- Wheeler process . He is also known for popularizing the term `` black hole '' , for coining the terms `` neutron moderator '' , `` ___MASK58___ foam '' , `` wormhole '' , and `` it from bit '' , and for hypothesizing the `` one - electron universe '' . Wheeler earned his doctorate at Johns Hopkins University under the supervision of Karl Herzfeld , and studied under Breit and Bohr on a National Research Council fellowship . In 1939 he teamed up with Bohr to write a series of papers using the liquid drop model to explain the mechanism of fission . During World War II , he worked with the Manhattan Project ' ___MASK43___ Metallurgical Laboratory in Chicago , where he helped design nuclear reactors , and then at the Hanford Site in Richland , Washington , where he helped DuPont build them . He returned to Princeton after the war ended , but returned to government service to help design and build the hydrogen bomb in the early 1950s . For most of his career , Wheeler was a professor at Princeton University , which he joined in 1938 , remaining until his retirement in 1976 . At Princeton he supervised 46 PhDs , more than any other professor in the Princeton physics department . The Holocaust ( from the Greek ': " hólos ", " whole " and " kaustós ", " burnt "), also referred to as the Shoah "' ( Hebrew : , " HaShoah ", " the catastrophe "), was a genocide in which Adolf Hitler ' ___MASK43___ Nazi Germany and its collaborators killed about six million Jews . The victims included 1 . 5 million children and represented about two - thirds of the nine million Jews who had resided in Europe . Some definitions of the Holocaust include the additional five million non - Jewish victims of Nazi mass murders , bringing the total to about 11 million . Killings took place throughout Nazi Germany , German - occupied territories , and territories held by allies of Nazi Germany . World War II ( often abbreviated to WWII or WW2 ), also known as the Second World War , was a global war that lasted from 1939 to 1945 , although related conflicts began earlier . It involved the vast majority of the world ' ___MASK43___ nations  including all of the great powers  eventually forming two opposing military alliances : the Allies and the Axis . It was the most widespread war in history , and directly involved more than 100 million people from over 30 countries . In a state of " total war ", the major participants threw their entire economic , industrial , and scientific capabilities behind the war effort , erasing the distinction between civilian and military resources . Marked by mass deaths of civilians , including the Holocaust ( in which approximately 11 million people were killed ) and the strategic bombing of industrial and population centres ( in which approximately one million were killed , and which included the atomic bombings of Hiroshima and Nagasaki ), it resulted in an estimated 50 million to 85 million fatalities . These made World War II the deadliest conflict in human history . In nuclear physics and nuclear chemistry , nuclear fission is either a nuclear reaction or a radioactive decay process in which the nucleus of an atom splits into smaller parts ( lighter nuclei ). The fission process often produces free neutrons and gamma photons , and releases a very large amount of energy even by the energetic standards of radioactive decay . In nuclear physics and nuclear chemistry , a nuclear reaction is semantically considered to be the process in which two nuclei , or else a nucleus of an atom and a subatomic particle ( such as a proton , neutron , or high energy electron ) from outside the atom , collide to produce one or more nuclides that are different from the nuclide ( ___MASK43___ ) that began the process . Thus , a nuclear reaction must cause a transformation of at least one nuclide to another . If a nucleus interacts with another nucleus or particle and they then separate without changing the nature of any nuclide , the process is simply referred to as a type of nuclear scattering , rather than a nuclear reaction . In classical mechanics , linear momentum , translational momentum , or simply momentum ( pl . momenta ; SI unit kg · m / ___MASK43___ ) is the product of the mass and velocity of an object , quantified in kilogram - meters per second . It is dimensionally equivalent to impulse , the product of force and time , quantified in newton - seconds . Newton ' ___MASK43___ second law of motion states that the change in linear momentum of a body is equal to the net impulse acting on it . For example , a heavy truck moving rapidly has a large momentum , and it takes a large or prolonged force to get the truck up to this speed , and would take a similarly large or prolonged force to bring it to a stop . If the truck were lighter , or moving more slowly , then it would have less momentum and therefore require less impulse to start or stop . In theoretical physics , ___MASK58___ field theory ( QFT ) is the theoretical framework for constructing ___MASK58___ mechanical models of subatomic particles in particle physics and quasiparticles in condensed matter physics . QFT treats particles as excited states of the underlying physical field , so these are called field quanta . The Pauli exclusion principle is the ___MASK58___ mechanical principle that states that two or more identical fermions ( particles with half - integer spin ) cannot occupy the same ___MASK58___ state within a ___MASK58___ system simultaneously . In the case of electrons in atoms , it can be stated as follows : it is impossible for two electrons of a poly - electron atom to have the same values of the four ___MASK58___ numbers : " n ", the principal ___MASK58___ number , ', the angular momentum ___MASK58___ number , " m ", the magnetic ___MASK58___ number , and " m ", the spin ___MASK58___ number . For example , if two electrons reside in the same orbital , and if their " n ", ', and " m " values are the same , then their " m " must be different , and thus the electrons must have opposite half - integer spins of 1 / 2 and - 1 / 2 . This principle was formulated by Austrian physicist Wolfgang Pauli in 1925 for electrons , and later extended to all fermions with his spin - statistics theorem of 1940 . Strategic bombing is a military strategy used in a total war with the goal of defeating the enemy by destroying its morale or its economic ability to produce and transport materiel to the theatres of military operations , or both . It is a systematically organized and executed attack from the air which can utilize strategic bombers , long - or medium - range missiles , or nuclear - armed fighter - bomber aircraft to attack targets deemed vital to the enemy ' ___MASK43___ war - making capability . Paul Ehrenfest ( January 18 , 1880  September 25 , 1933 ) was an Austrian and Dutch theoretical physicist , who made major contributions to the field of statistical mechanics and its relations with ___MASK58___ mechanics , including the theory of phase transition and the Ehrenfest theorem . The Planck constant ( denoted , also called Planck ' ___MASK43___ constant ) is a physical constant that is the quantum of action , central in quantum mechanics . Hawking radiation is blackbody radiation that is predicted to be released by black holes , due to ___MASK58___ effects near the event horizon . It is named after the physicist Stephen Hawking , who provided a theoretical argument for its existence in 1974 , and sometimes also after Jacob Bekenstein , who predicted that black holes should have a finite , non - ___MASK96___ temperature and entropy . ___MASK58___ mechanics ( QM ; also known as ___MASK58___ physics or ___MASK58___ theory ), including ___MASK58___ field theory , is a branch of physics which is the fundamental theory of nature at small scales and low energies of atoms and subatomic particles . Classical physics , the physics existing before ___MASK58___ mechanics , derives from ___MASK58___ mechanics as an approximation valid only at large ( macroscopic ) scales . ___MASK58___ mechanics differs from classical physics in that energy , momentum and other quantities are often restricted to discrete values ( quantization ), objects have characteristics of both particles and waves ( wave - particle duality ), and there are limits to the precision with which quantities can be known ( Uncertainty principle ). In physics , special relativity ( SR , also known as the special theory of relativity or STR ) is the generally accepted and experimentally well - confirmed physical theory regarding the relationship between space and time . In Albert Einstein ' ___MASK43___ original pedagogical treatment , it is based on two postulates : In physics , a ___MASK58___ ( plural : quanta ) is the minimum amount of any physical entity involved in an interaction . The fundamental notion that a physical property may be " quantized ," referred to as " the hypothesis of quantization ". This means that the magnitude of the physical property can take on only certain discrete values . General relativity ( GR , also known as the general theory of relativity or GTR ) is the geometric theory of gravitation published by Albert Einstein in 1915 and the current description of gravitation in modern physics . General relativity generalizes special relativity and Newton ' ___MASK43___ law of universal gravitation , providing a unified description of gravity as a geometric property of space and time , or spacetime . In particular , the "" is directly related to the energy and momentum of whatever matter and radiation are present . The relation is specified by the Einstein field equations , a system of partial differential equations . In politics and military planning , a war effort refers to a coordinated mobilization of society ' ___MASK43___ resources  both industrial and human  towards the support of a military force . Depending on the militarization of the culture , the relative size of the armed forces and the society supporting them , the style of government , and the popular support for the military objectives , such war effort can range from a small industry to complete command of society . Modern physics is the post - Newtonian conception of physics . It implies that classical descriptions of phenomena are lacking , and that an accurate , " modern ", description of nature requires theories to incorporate elements of ___MASK58___ mechanics or Einsteinian relativity , or both . In general , the term is used to refer to any branch of physics either developed in the early 20th century and onwards , or branches greatly influenced by early 20th century physics . In particle physics , ___MASK58___ field theory in curved spacetime is an extension of standard , Minkowski space ___MASK58___ field theory to curved spacetime . A general prediction of this theory is that particles can be created by time - dependent gravitational fields ( multigraviton pair production ), or by time - independent gravitational fields that contain horizons . A black hole is a region of spacetime exhibiting such strong gravitational effects that nothing  not even particles and electromagnetic radiation such as light  can escape from inside it . The theory of general relativity predicts that a sufficiently compact mass can deform spacetime to form a black hole . The boundary of the region from which no escape is possible is called the event horizon . Although the event horizon has an enormous effect on the fate and circumstances of an object crossing it , no locally detectable features appear to be observed . In many ways a black hole acts like an ideal black body , as it reflects no light . Moreover , ___MASK58___ field theory in curved spacetime predicts that event horizons emit Hawking radiation , with the same spectrum as a black body of a temperature inversely proportional to its mass . This temperature is on the order of billionths of a kelvin for black holes of stellar mass , making it essentially impossible to observe . In chemistry and physics , nucleons are the proton and the neutron , which are the constituents of the atomic nucleus , and are themselves composed of ___MASK3___ and up quarks . The number of nucleons defines an isotope ' ___MASK43___ mass number ( nucleon number ). The atom is made up of a nucleus surrounded by electrons . In physics , mass is a property of a physical body . It is the measure of an object ' ___MASK43___ resistance to acceleration ( a change in its state of motion ) when a net force is applied . It also determines the strength of its mutual gravitational attraction to other bodies . The basic SI unit of mass is the kilogram ( kg ). The Einstein field equations ( EFE ; also known as " Einstein ' ___MASK43___ equations ") are the set of 10 equations in Albert Einstein ' ___MASK43___ general theory of relativity that describes the fundamental interaction of gravitation as a result of spacetime being curved by mass and energy . First published by Einstein in 1915 as a tensor equation , the EFE equate local spacetime curvature ( expressed by the Einstein tensor ) with the local energy and momentum within that spacetime ( expressed by the stress  energy tensor ). The Nobel Prize in Physics is a yearly award given by the ___MASK6___ for those who conferred the most outstanding contributions for mankind in the field of physics . It is one of the five Nobel Prizes established by the will of Alfred Nobel in 1895 and awarded since 1901 ; the others being the ___MASK29___ , Nobel Prize in Literature , Nobel Peace Prize , and Nobel Prize in Physiology or Medicine . Gregory Breit ( Grigory Alfredovich Breit - Shneider ; July 14 , 1899 , Mykolaiv  September 11 , 1981 , Houston , Texas ) was an American physicist and professor at NYU ( 1929  1934 ), U . of Wisconsin  Madison ( 1934  1947 ), Yale ( 1947  1968 ), and Buffalo ( 1968  1973 ). In 1921 , he was Paul Ehrenfest ' ___MASK43___ assistant in Leiden . Richard Phillips Feynman ( May 11 , 1918  February 15 , 1988 ) was an American theoretical physicist known for his work in the path integral formulation of ___MASK58___ mechanics , the theory of ___MASK58___ electrodynamics , and the physics of the superfluidity of supercooled liquid helium , as well as in particle physics for which he proposed the parton model . For his contributions to the development of ___MASK58___ electrodynamics , Feynman , jointly with Julian Schwinger and Sin ' ichir Tomonaga , received the Nobel Prize in Physics in 1965 . Hiroshima is perhaps best known as the first city in history to be targeted by a nuclear weapon when the ___MASK89___ Air Forces ( USAAF ) dropped an atomic bomb on the city ( and later on Nagasaki ) at 8 : 15 a . m . on August 6 , 1945 , near the end of World War II . The neutron is a subatomic particle , symbol or , with no net electric charge and a mass slightly larger than that of a proton . Protons and neutrons , each with mass approximately one atomic mass unit , constitute the nucleus of an atom , and they are collectively referred to as nucleons . Their properties and interactions are described by nuclear physics . ___MASK58___ foam ( also referred to as space - time foam ) is a concept in ___MASK58___ mechanics devised by John Wheeler in 1955 . The " foam " is supposed to be conceptualized as the foundation of the fabric of the universe . A photon is an elementary particle , the ___MASK58___ of the electromagnetic field including electromagnetic radiation such as light , and the force carrier for the electromagnetic force ( even when static via virtual photons ). The photon has ___MASK96___ rest mass and is always moving at the speed of light . Like all elementary particles , photons are currently best explained by ___MASK58___ mechanics and exhibit wave  particle duality , exhibiting properties of both waves and particles . For example , a single photon may be refracted by a lens and exhibit wave interference with itself , and it can behave as a particle with definite and finite measurable position and momentum . The photon ' ___MASK43___ wave and quanta qualities are two observable aspects of a single phenomenon , and cannot be described by any mechanical model ; a representation of this dual property of light , which assumes certain points on the wavefront to be the seat of the energy , is not possible . The quanta in a light wave cannot be spatially localized . Some defined physical parameters of a photon are listed . Albert Einstein ( 14 March 1879  18 April 1955 ) was a German - born theoretical physicist . He developed the general theory of relativity , one of the two pillars of modern physics ( alongside ___MASK58___ mechanics ). Einstein ' ___MASK43___ work is also known for its influence on the philosophy of science . Einstein is best known in popular culture for his mass  energy equivalence formula ( which has been dubbed " the world ' ___MASK43___ most famous equation "). He received the 1921 Nobel Prize in Physics for his " services to theoretical physics ", in particular his discovery of the law of the photoelectric effect , a pivotal step in the evolution of ___MASK58___ theory . Electric charge is the physical property of matter that causes it to experience a force when placed in an electromagnetic field . There are two types of electric charges : positive and negative . Like charges repel and unlike attract . An object is negatively charged if it has an excess of electrons , and is otherwise positively charged or uncharged . The SI derived unit of electric charge is the coulomb ( C ). In electrical engineering , it is also common to use the ampere - hour ( Ah ), and , in chemistry , it is common to use the elementary charge (" e ") as a unit . The symbol " Q " often denotes charge . Early knowledge of how charged substances interact is now called classical electrodynamics , and is still accurate for problems that don ' t require consideration of ___MASK58___ effects .