I know what you mean. But an object of 1Kg today would still be 1Kg in 1000 years since everything gained mass (that includes what you are using to calculate the mass)... but like I said in my first response I am in no way the best person to give an answer to this question (still I lost karma :P). It is just a subject I find interesting!
> But an object of 1Kg today would still be 1Kg in 1000 years since everything gained mass
Yes, but a 1m rule will get longer if everything gained mass, won't it? (I mean, the meter will get shorter, and the atoms should get bigger, even after compensating for the change on meter. Is there something I'm missing?)