physics

Basicdefinition

Physicsisanaturalsciencethatfocusesonthestudyofmatter,Energy,space,time,especiallytheirrespectivepropertiesandtheirinterrelationships.Physicsistheknowledgeaboutthelawsofnature;morebroadlyspeaking,physicsexploresandanalyzesthephenomenathatoccurinnaturetounderstanditsrules.

Physics(physics)researchobjects:physicalphenomena,matterstructure,matterinteraction,mattermotionlaw.

Thescaleofphysicsresearch-thelevelandmagnitudeofthematerialworld

Spatialscale:

Atoms,nuclei,elementaryparticles,DNAlength,thesmallestcell,Galaxyclusters,MilkyWay,distancesofstars,solarsystem,superclusters,Hubbleradius,etc.Theimageofhumansnakeswallowingtailvividlyshowsthelevelofphysicalspacesize.

Microscopicparticles:protonsm

Mesoscopic

Macroscopic

Cosmos(cosmological)quasarsm

Timescale:

Elementaryparticlelifetime10^-25s

Thelifetimeoftheuniverseis10¹⁸s

Dividedaccordingtothespatialscale:quantummechanics,classicalphysics,andcosmicphysics.

Dividedbyspeed:relativisticphysics,non-relativisticphysics.

Dividedaccordingtothesizeoftheobject:micro,meso,macro,cosmos.

Dividedbymovementspeed:lowspeed,mediumspeed,highspeed.

Dividedbyresearchmethods:experimentalphysics,theoreticalphysics,andcomputationalphysics.

Introductiontoclassification

●Newtonianmechanicsandanalyticalmechanicsstudythebasiclawsofthemechanicalmotionofobjectsandthelawsabouttherelativityoftimeandspace.

●Electromagnetism(electromagnetism)andelectrodynamics(electrodynamics)studyelectromagneticphenomena,thelawofelectromagneticmotionofmatterandthelawofelectromagneticradiation.

●Thermodynamicsandstatisticalmechanicsstudythestatisticallawsofthethermalmotionofmatteranditsmacroscopicperformance.

●Specialrelativity(specialrelativity)studiestheeffectsofhigh-speedmotionofobjectsandrelateddynamiclaws.

●Generalrelativity(generalrelativity)studiesthedynamicbehaviorofobjectsinthevicinityofmassiveobjectsunderstronggravitationalfields.

●Quantummechanicsstudiesthemotionphenomenaandbasicmotionlawsofmicroscopicmatter.

Inaddition,thereare:

ParticlePhysics,NuclearPhysics,AtomicandMolecularPhysics,SolidStatePhysics,CondensedMatterPhysics,LaserPhysics,PlasmaPhysics,Geophysics,Biophysics,Astrophysics,etc.

ResearchFields

Thefieldofphysicsresearchcanbedividedintothefollowingfourmajorareas:

1.Condensedmatterphysics-thestudyofthemacroscopicpropertiesofmatter.Thephasecontainsaverylargenumberofcomponents,andtheinteractionbetweenthecomponentsisextremelystrong.Themostfamiliarcondensedphasesaresolidsandliquids,whichareformedbybondsbetweenatomsandelectromagneticforces.MorecondensedphasesincludesupercurrentandBose-Einsteincondensedmatter(foundincertainatomicsystemsatverylowtemperatures);superconductingphasesappearinginconductiveelectronsincertainmaterials;atomiclatticesFerromagneticandantiferromagneticphases.Condensedmatterphysicshasalwaysbeenthelargestresearchfield.Historically,ithasgrownphysicallyfromsolids.ThisnamewasfirstproposedbyPhilipAndersonin1967.

2.Atomic,molecularandopticalphysics-studytheinteractionofmatter-matterandlight-matterwithintherangeofatomicsizeorseveralatomicstructures.Thesethreeareasarecloselyrelated.Becausetheyusesimilarmethodsandrelatedenergyscales.Theyallincludeclassicalandquantumprocessingmethods;dealingwithproblemsfromamicroscopicperspective.Atomicphysicsdealswithatomicshells,focusingonquantumcontrolofatomsandions;coolingandtrapping;low-temperaturecollisiondynamics;accuratemeasurementoffundamentalconstants;collectiveeffectsofelectronsinstructuraldynamics.Atomicphysicsisaffectedbythenucleus.However,nuclearinternalphenomenasuchasnuclearfissionandnuclearsynthesisbelongtohigh-energyphysics.Molecularphysicsfocusesonpolyatomicstructuresandtheirinternalandexternalinteractionswithmatterandlight.Opticalphysicshereonlystudiesthebasicpropertiesoflightandtheinteractionbetweenlightandmatterinthemicroscopicfield.

3.High-energy/particlephysics-particlephysicsstudiesthebasiccomponentsofmatterandenergyandtheirinteraction;itcanalsobecalledhigh-energyphysics.Becausemanyelementaryparticlesdonotoriginallyexistinnature,theyonlyappearwhentheycollidewithotherparticlesathighenergyinaparticleaccelerator.Accordingtothestandardmodelofinteractionofelementaryparticles,thereare12elementaryparticlemodels(quarksandlightparticles)ofknownmatter.Theyinteractthroughstrong,weakandelectromagneticfundamentalforces.TheStandardModelalsopredictstheexistenceofaHiggs-Boseparticle.Nowlookingforit.

4.Astrophysics-Astrophysicsandmodernastronomyapplyphysicaltheoriesandmethodstostudythestructureandevolutionofstars,theoriginofthesolarsystem,andrelatedissuesoftheuniverse.Becauseofthewidescopeofastrophysics,itusesmanyprinciplesofphysics,includingmechanics,electromagnetism,statisticalmechanics,thermodynamics,andquantummechanics.In1931,Carldiscoveredradiosignalsfromcelestialbodiesandbeganradioastronomy.Thefrontiersofastronomyhavebeenexpandedbyspaceexploration.Theinterferenceoftheearth’satmospherenecessitatestheuseofinfrared,ultra-ultraviolet,gammarays,andX-raystoobservespace.Physicalcosmologystudiestheformationandevolutionoftheuniverseonalargescale.Einstein'stheoryofrelativityplayedacentralroleinthemoderntheoryoftheuniverse.Intheearly20thcentury,Hubblediscoveredthattheuniversewasexpandingfromthepicture,whichpromotedthediscussionbetweenthetheoryofstablestateoftheuniverseandthebigbang.Thediscoveryofthecosmicmicrowavebackgroundin1964provedthattheBigBangtheorymaybecorrect.TheBigBangmodelisbasedontwotheoreticalframeworks:Einstein'sgeneraltheoryofrelativityandtheprinciplesofcosmology.CosmologyhasestablishedtheACDMuniverseevolutionmodel,whichincludestheexpansionoftheuniverse,darkenergyanddarkmatter.FromthenewdataoftheFermiGamma-raytelescopeandtheimprovementoftheexistinguniversemodel,manypossibilitiesanddiscoveriescanbeexpected.Especiallyinthenextfewyears,theremaybemanydiscoveriesarounddarkmatter.

HistoryofPhysics

●GalileoGalilei(1564~1642),thefounderofmodernhumanphysics,laidthefoundationforthedevelopmentofmodernhumanphysicalscience.

●Quantummechanicswasestablishedfrom1900to1926.

●Fermi-Diracstatisticswereestablishedin1926.

●TheBlochwavetheorywasestablishedin1927.

●In1928Sommerfeldproposedtheconjectureofenergyband.

●In1929,Pyersproposedtheconceptofforbiddenbandandcavity,andBetteproposedtheconceptofFerminoodlesinthesameyear.

●In1947,Barding,BrattonandShockleyofBellLabsinventedthetransistor,markingthebeginningoftheinformationage.

●In1957PipademeasuredthefirstFermisurfacesuperlatticematerialnanomaterialphoton.

●JackKilbyinventedtheintegratedcircuitin1958.

●Large-scaleintegratedcircuitsappearedinthe1970s.

Therelationshipbetweenphysicsandphysicaltechnology:

●Theinventionanduseofheatenginesprovidethefirstmode:technology-physics-technology

●Theprocessofelectrificationprovidesasecondmodel:Physics-Technology-Physics

Today,thetwomodelsoftherelationshipbetweenphysicsandscienceandtechnologycoexist,intersectandpromoteeachother."Withoutthebasicscienceofyesterday,therewouldbenotechnologicalrevolutiontoday."Forexample:theuseofnuclearenergy,thegenerationoflasers,tomography(CT),superconductingelectrontechnology,particlescatteringexperiments,thediscoveryofX-rays,stimulatedemissiontheory,cryogenicsuperconductingmicroscopictheory,andthebirthofelectroniccomputers.Almostallthecreationofmajornew(high-tech)fieldshavebeenbrewedinphysicsforalongtimebeforehand.

Researchmethods

Physicsmethodsandscientificattitudes:proposingpropositions→theoreticalexplanations→theoreticalpredictions→experimentalverification→revisingtheories.

Modernphysicsisahighlyprecisesciencethatcombinestheoryandexperiment.Itsproductionprocessisasfollows:

1. PhysicspropositionsaregenerallybasedonnewobservationfactsorExtractedfromexperimentalfacts,ordeducedfromexistingprinciples;

2. Firsttrytouseknowntheoriestoexplainpropositions,logicalreasoningandmathematicalcalculations.Iftheexistingtheorycannotbeexplainedperfectly,itisnecessarytomodifytheoriginalmodelorproposeanewtheoreticalmodel;

3. Thenewtheoreticalmodelmustmakepredictions,andthepredictionscanbeconfirmedbyexperiments;

4. Intheend,allphysicaltheoriesmustbebasedonobservationsorexperimentalfacts.Whenatheorydoesnotmatchtheexperimentalfacts,itfacesmodificationoroverthrow.

●Howtolearnphysics?

ThefamousphysicistFeynmansaid:"Scienceisamethod.Itteachespeople:howsomethingsareunderstood,whatisknown,towhatextent,howtodealwithquestionsandUncertainty,whatlawstheevidenceobeys;howtothinkaboutthings,makejudgments,andhowtodistinguishbetweentrueandfalseandsuperficialphenomena?”ThefamousphysicistEinsteinsaid:“DevelopingthegeneralabilityofindependentthinkingandindependentjudgmentshouldalwaysbeplacedFirst,professionalknowledgeshouldnotbeputfirst.Ifapersonmastersthebasictheoryofhissubjectandlearnstothinkandworkindependently,hewilldefinitelyfindhisownway,andmoreimportantlythanthat,toobtaindetailedknowledgeForthosewhotrainthecontent,hewilldefinitelybetteradapttoprogressandchanges."

●Learningpointofview:learnphysicslogicallyandcoordinatelyasawhole,andunderstandeachbranchofphysicsInterrelationshipsbetween.

●Theessenceofphysics:Physicsdoesnotstudytheultimatemechanismofnaturalphenomena(orcannotstudyatall).WecanonlyfeeltherulesofnatureincertainphenomenaandtrytoexplainthembytheserulesAnythingthathappensinnature.Ourlimitedintelligenceisalwaystryingtounderstandnatureandtrytochangeit.Thisisthecommongoalofphysicsandevenallnaturalsciences.

Relevantsciencesbasedonphysicsinclude:chemistry,materialsscience,astronomy,physicalgeography,etc.

Thenatureofthesubject

Thebasicnature

Physicsisaregularsummaryofpeople’sknowledgeofthemovementandtransformationofmatterinnature.ThismovementandThereshouldbetwotransitions.Thefirstistheextensionofearlypeoplethroughthesensesandvision;thesecondisthatmodernpeopleinventedandcreatedscientificinstrumentsforobservationandmeasurement,andtheresultsofexperimentswerebasedontheindirectunderstandingoftheinternalcompositionofmatter.Physicscanberoughlydividedintotwoparts:microscopicandmacroscopicfromdifferentresearchperspectivesandviewpoints:Macroscopicphysicsdoesnotanalyzeindividualeffectsinagroupofparticles,butdirectlyconsiderstheoveralleffect,whichhasappearedintheearlieststage;thebirthofmicrophysics,Originatedfromthefactthatmacroscopicphysicscannotwellexplainnewexperimentalphenomenasuchasblackbodyradiation,photoelectriceffect,andatomicspectroscopy.Itisarevisionofmacroscopicphysics,andgraduallyimprovedwiththedevelopmentofexperimentaltechnologyandtheoreticalphysics.

Secondly,physicsisanotherkindofintelligence.

AstheNobelLaureateinPhysicsandGermanscientistBornsaid:"Itisbecausemypublishedworkcontainsadiscoveryofanaturalphenomenon.ItisbettertosaythatitcontainsaOnthebasisofscientificthinkingandmethodsofnaturalphenomena."Thereasonwhyphysicsisrecognizedasanimportantscienceisnotonlybecauseitdeeplyrevealsthelawsoftheobjectiveworld,butalsobecauseitisintheprocessofdevelopmentandgrowth.Asetofuniqueandeffectivethinkingmethodsystemhasbeenformed.Becauseofthis,physicshasbecomeawell-deservedcrystallizationofhumanintelligenceandatreasureofcivilization.

Alotoffactsshowthatphysicalideasandmethodsarenotonlyvaluabletophysicsitself,butalsomakeimportantcontributionstothedevelopmentoftheentirenaturalsciencesandevensocialsciences.Someonehascountedthatsincethemiddleofthe20thcentury,morethanhalfofthewinnersoftheNobelPrizeinChemistry,BiologyandMedicine,andevenEconomicsPrizeshaveabackgroundinphysics-whichmeanstheylearnedfromphysics.Absorbedintelligence,andsucceededinnon-physicalfields.Conversely,therehaveneverbeeninstancesofscientistswithnon-physicalbackgroundswinningtheNobelPrizeinPhysics.Thisisthepowerofphysicalintelligence.Nowondersomeforeignexpertspointedoutverysharply:anationwithoutphysicalaccomplishmentisastupidnation!

Inshort,physicsisasummaryofthelawsofnature,andatheoreticalunderstandingofempiricalscience.

Sixproperties

1.Truth:Theoriesandexperimentsofphysicsrevealthemysteriesofnatureandreflecttheobjectivelawsofmaterialmovement.

2.Harmonyandunity:themovementofcelestialbodiesinthemysteriousspace,underthedescriptionofKepler'sthreelaws,showshowharmoniousandorderly.Severalgreatunificationsinphysicsalsoshowasenseofbeauty.Newtonusedthethreelawsofuniversalgravitationtounifyallmacroscopicobjectsintheskyandontheearth.TheestablishmentofMaxwell'selectromagnetictheoryunifieselectricityandmagnetism.Einstein'smass-energyequationestablishesaunityofmassandenergy.Thewave-particledualitytheoryoflightunifiestheparticleandwaveproperties.Einstein'stheoryofrelativityunifiestimeandspace.

3.Simplicity:Themathematicallanguageofthelawsofphysicsreflectsthesimplicityofphysics.Forexample:Newton'ssecondlaw,Einstein'smass-energyequation,Faraday'slawofelectromagneticinduction.

4.Symmetry:Symmetrygenerallyreferstothesymmetryoftheshapeofanobject,anddeepsymmetryismanifestedinthedevelopmentandchangeofthingsorthesymmetryofobjectivelaws.Forexample:thespatiallatticestructureofvariouscrystalsinphysicshasahighdegreeofsymmetry.Verticalthrowingmotion,simpleharmonicmotion,wavemirrorsymmetry,magnetoelectricsymmetry,forceandreactionforcesymmetry,positiveparticlesandantiparticles,positivematterandantimatter,positiveandnegativeelectricity,etc.

5.Predictability:Thecorrectphysicaltheorycannotonlyexplainthephysicalphenomenadiscoveredatthattime,butalsopredictthephysicalphenomenathatcouldnotbedetectedatthattime.Forexample:Maxwell'selectromagnetictheorypredictstheexistenceofelectromagneticwaves,Rutherfordpredictstheexistenceofneutrons,Fresnel'sdiffractiontheorypredictsthatthereisaPoissonspotinthecenterofthediscdiffraction,andDiracpredictstheexistenceofelectrons.

6.Sophistication:Physicsexperimenthassophistication.Theingeniousdesignmethodmakesthephysicalphenomenonmoreobvious.

NobelPrize

PreviousNobelPrizewinnersinPhysics:

Time

People

Reasonforwinning