How We're Redefining the kg
Veritasium3 HN recommenders · 2017–2024
2.8M views · explainer · evergreen · Uploaded 2017-07-12
Veritasium explains why the kilogram is being redefined in terms of Planck's constant rather than a physical metal artifact. It visits NIST to show the Kibble balance and why measuring mass precisely is hard.
Praised as an excellent, accessible account of why the kilogram's definition changed, in redefinition threads.
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3 comments from Hacker News
> Does anyone have an example of where a change like this would be important? Well, it's important today, because the reference samples used across the world have drifted apart, and not in a consistent fashion. Which raises the question of whether the exemplar kg has drifted as well. So, we don't really know if the kg we're using today is the same kg we were using 10 years ago. Given how important mass is to many scientific calculations, a drifting standard could directly impact all the other work we do. I found the Veritasium video to be a bit more interesting for the "why" aspect of this change: [VIDEO]
There's also an excellent video from Veritasium, a science and education YouTube channel, about what's being done to define the kilogram [VIDEO]
Veritasium (Derick, who I've met personally) does a fantastic job on these fundamental science subjects. Le Grande K was the definition of the kilogram. Derick explains the question at hand, how Plancks constant is now used. Derick's quality is supreme & he is always very careful and confident about claims. [VIDEO]