[Le_SDT]

I am not sure to understand your question, it has been said in the article that if everything's mass was increasing proportionally we could not test it since we have to compare two things to see an increase. But I am no physicist I don't know if there would be another way actually to test mass increase without comparing two objects.

[hga]

What about a test over time?

I'd guess the time scale required is a bit long....

[Le_SDT]

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!

[marcosdumay]

> 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?)