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I wonder: the article states that the SI unit for Kg up to this point was defined using a single object. Doesn't this definition also involve the fact that it's placed on earth, thus requiring two objects for its definition?



Nope. Mass != weight. The weight of 1kg on Earth is about 10N (and varies by location). The weight of the same 1kg object on the moon would be much less, but the mass remains the same.


Mass is constant across all gravitational fields (and anywhere there isn't) for any given object.

People interchangeably use lbs <-> kg but the actual equivalence is lbs <-> newton (N). The difference doesn't matter in the average person's life since we're all down here where gravity is homogeneous enough for most applications and people.


Nothing prevents you from measuring it on Mars.




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