Obungi bw’ennabuzimbe(amount of matter) eba mu kintu kye kiyitibwa “enzitoya”(mass) yakyo.Enzitoya y’ekintu ekimu yekwata ku nzitoya y’ekintu ekirala okuyita mu mpalirizo eyitibwa essikirizo(gravity). Essikirizo eba “ensikirizo ennene”(big attraction). Awo okiraba nti waliwo akakwate wakati w’ensikirizo(attraction) n’essikirizo (gravity).