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Comment by bostonpete | Hacker News Reader

I get that this is a significant milestone but this seems extremely overstated:

"the new changes will have wide-reaching impact in science, technology, trade, health and the environment, among many other sectors."

Am I missing something?

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Mostly yes, it does seem over-stated. I guess if you squint "wide-reaching" does not necessarily mean "important" just, you know, "wide-reaching". Like the "wide-reaching" effect of dropping a pebble into an otherwise undisturbed swimming pool maybe? The ripples go pretty far, they don't really matter, but they do go far.

With the old definitions, the values of the known constants were just approximations, but now that the unit is defined based on the constants, we can consider the constant as being the exact value, no matter how imprecise it was when it was measured using old definitions of the units.

So it's the equivalent of removing a magic number from your code and putting it into a const variable.

I don't know about trade, but kilo standards were deviating by tens of micrograms from eachother, some things are sold at prices which warrant accounting for those micrograms, so a completely stable international definition seems helpful.

Certain types of scientific instrument will need to be recalibrated to meet the new definitions.

Is there any scale in the world that can measure a kilogram to within the accuracy of a microgram?

And if you buy a kilogram of something and they accidentally short you by a few micrograms, haven't you only overpaid by a few parts per billion? Even on a billion dollar order you've only overpaid by a few dollars...

For your first question some Kibble balances have accuracy parts per billion in measurement of the kilogram.

For your second question, agreed - no trade deals care about the accuracy of the new kilogram vs old.

I agree that nobody cares for this level of precision in comercial trade, but as a thought experiment ...

According to the first result in Google https://brightside.me/wonder-curiosities/the-16-most-expensi...

> 1. Antimatter — $62.5 trillion per gram

> 2. Californium — $25-27 million per gram

So the difference is a few dollars per milligram of antimatter, and less than a cent per kilogram of Californium.

From https://en.wikipedia.org/wiki/United_States_Bullion_Deposito...

> As of November 2017, Fort Knox holdings are 4,582 metric tons (147.3 million oz. troy), with a market value of over $100 billion.

So the difference is a few hundred dollars.

Your math is off..... 62T / 1g = $62B /mg = $62M/ug.

$100 million dollar rounding error.....

If you're buying 1 milligram of a substance, how much are you affected by an one microgram error in the definition of a kilogram?

Hint: not by one microgram.

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