accuricy of mass,weights...is ?? ZERO

[harsh]

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".....???

[fuhrerkeebs]

We measure the mass of atoms, electrons, etc--not the weight. Mass is independent of enviroment...and things like electrons are in a group of particles called leptons...and as far as we can tell, leptons are fundamental. This means that all electrons have the same rest mass. And atoms are made up of stable particles, so you can be pretty sure that there isn't going to be a big--if there is at all--deviation in mass between two of the same kind of atoms.