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Comment by hackerpacker | Hacker News Reader

>The definition of units are done in the most convenient and precise way possible.

testing my scale with a mirror that contains a kg of photons doesn't sound very convenient.

You were also never going to test your scale with a weight that is stored in a vault in Paris. So far you would test with a replica of a replica of that weight, in the best case (getting a copy directly from the local standards body). With the new definition in principle anybody can create an object that weighs exactly one kg and sell it to you.

Ahem, with a mass of 1kg. They might sell you a particular weight but it won't be the same when you get it home to your [local gravitational] field!

will this increase the probability of adoption of the SI system? I have often had the impression that some nations avoided transitioning to SI out of principle, not wanting to depend on the maintenance and cooperation of another nation?

If you speak about USA - they are already using the metric system, they just add their weird conversion on top of it to make things more confusing.

It's actually really hard to imagine an actual physical apparatus for producing a "reference" Kg mass using the new definition of Kg.

I get the feeling this just changes the definition of "Kg", but not how reference Kg's are actually produced?

https://en.wikipedia.org/wiki/Kibble_balance

The standard changed because people came out with a apparatus for using it. If there wasn't one, it wouldn't have changed.

But it's fit for measuring micrograms up to grams. One won't measure actual kg on it, at least not currently.

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