Veritasium
6 HN recommenders · recommended in 6 months, 2013–2018
11:44 · 38M views · Mar 25, 2013
Veritasium explains the effort to redefine the kilogram, which was still defined by a physical artifact, and how a near-perfect silicon sphere from the Avogadro project helps. It also covers the history of the unit's odd naming.
Recommended in kilogram-redefinition threads as a clear, short explainer of the Avogadro and Planck approaches.
9 comments from Hacker News
Fantastic video by Vertiasium on this: this video (side note: that video is about a sphere, but the current standard kilogram and its copies are actually shaped like little bells)
For anyone interested in the Planck and Avogadro projects to redefine the kilo, this video is an imperative watch: this video
"Weirdly, it’s not even known if the IPK is getting lighter, or if the national prototypes are getting heavier — but either way, something is causing these kilos to change weight, by around 50 micrograms every 100 years." Well they COULD always do that thing with the water where they heat it to 4 degrees celcius and measure its volume and weight. Then they'd know which it is. That said, there's a nice video on this: this video
One cubic centimetre of water at 4 degrees Celsius used to define one gram (or more precisely one litre -> one kilogram, which comes out to be the exact same thing) [1], [2]. Although 1 cm^3 of water is still pretty damn close to 1g. [1] [LINK] [2] this video (around 1:50, and actually the whole video is excellent)
I stumbled upon a very interesting short documentary about the metric system and the world's roundest object. Well worth 10 minutes of your break today. this video