text: The term `` matter '' is used throughout physics in a bewildering variety of contexts : for example , one refers to `` condensed matter physics '' , `` elementary matter '' , `` partonic '' matter , `` dark '' matter , `` anti '' - matter , `` strange '' matter , and `` nuclear '' matter .
simplified: Matter attracts other matter with a force called gravity . Light is not matter , but its movement is changed by gravity as though it was matter .