用英语介绍重力的物理知识两分钟的演讲
用英语介绍重力的物理知识
两分钟的演讲
用英语介绍重力的物理知识两分钟的演讲
用英语介绍重力的物理知识
两分钟的演讲
Gravitation,orgravity,isanaturalphenomenonbywhichphysicalbodiesattractwithaforceproportionaltotheirmass.Gravitationismostfamiliarastheagentthatgivesweighttoobjectswithmassandcausesthemtofalltothegroundwhendropped.Gravitationcausesdispersedmattertocoalesce,andcoalescedmattertoremainintact,thusaccountingfortheexistenceoftheEarth,theSun,andmostofthemacroscopicobjectsintheuniverse.
GravitationisresponsibleforkeepingtheEarthandtheotherplanetsintheirorbitsaroundtheSun;forkeepingtheMooninitsorbitaroundtheEarth;fortheformationoftides;fornaturalconvection,bywhichfluidflowoccursundertheinfluenceofadensitygradientandgravity;forheatingtheinteriorsofformingstarsandplanetstoveryhightemperatures;andforvariousotherphenomenaobservedonEarth.
Gravitationisoneofthefourfundamentalinteractionsofnature,alongwithelectromagnetism,andthenuclearstrongforceandweakforce.ModernphysicsdescribesgravitationusingthegeneraltheoryofrelativitybyEinstein,inwhichitisaconsequenceofthecurvatureofspacetimegoverningthemotionofinertialobjects.ThesimplerNewton'slawofuniversalgravitationprovidesanaccurateapproximationformostphysicalsituations.