Editing Physics (section)

===Distinction between classical and modern physics===
{{merge|section=yes|Classical and modern physics|discuss=Wikipedia_talk:WikiProject_Physics#Classical_and_modern_physics|date=February 2025}}
{{further|History_of_physics#Division_into_classical_and_modern}}
[[File:Modernphysicsfields.svg|thumb|upright=1.5|left|Classical mechanics works for larger and slower objects; modern theories are needed otherwise.]]

In the first decades of the 20th century physics was revolutionized by the discoveries of quantum mechanics and relativity. The changes were so fundamental that these new concepts became the foundation of "modern physics", with other topics becoming "classical physics". The majority of applications of physics are essentially classical.<ref name="Thorne-2017">{{Cite book |last1=Thorne |first1=Kip S. |author-link1=Kip Thorne |title=Modern Classical Physics Optics, Fluids, Plasmas, Elasticity, Relativity, and Statistical Physics |last2=Blandford |first2=R.D. |publisher=Princeton University Press. |year=2017 |location=United States}}</ref>{{rp|xxxi|q=The resulting quantum mechanics and relativity occupied physicists for much of the succeeding century and today are viewed very differently from each other. Quantum mechanics is perceived as an abrupt departure from the tacit assumptions of the past, while relativity-though no less radical conceptually-is seen as a logical continuation of the physics of Galileo, Newton, and Maxwell.}} 
The laws of classical physics accurately describe systems whose important length scales are greater than the atomic scale and whose motions are much slower than the speed of light.<ref name="Thorne-2017"/>{{rp|xxxii}} Outside of this domain, observations do not match predictions provided by classical mechanics.<ref name=Krane-2019/>{{rp|6}}
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