in the past 100 odd years we have developed many machines and techniques to mesure the weights of atomic , subatomic particles.....but wont the mass, weight of ALL things be continously changing??? it is for sure that all these atoms , molecules ect are continously going through collisons....and this will leed to a constant change of energy of the system and the mass of the body.....all the weights of atoms , electrons,ect are done in special conditons (vaccume,ect..) and after all this we use these constant weights in normal condition experiments...wont it make a difference...how ever samll the variation of mass,weight may be ,when viewd in a large picture will effect the expereiment......after all this why do we use these so called "accurate weights".....???