
New measurement will help redefine international unit of mass - dnetesn
https://phys.org/news/2017-06-redefine-international-mass.html
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jbmorgado
This is really interesting - in a geeky way.

Until now all fundamental units were defined in terms that depended on the
constants of nature.

For instance:

\- the metre as the length of the path travelled by light in a vacuum in 1/299
792 458 seconds.

\- the second as: the duration of 9 192 631 770 periods of the radiation
corresponding to the transition between the two hyperfine levels of the ground
state of the caesium 133 atom

And so on EXCEPT for the kg.

The kg was the only odd one out. There was this object stored somewhere and
when people wanted to measure very well the kg they had to go there and try to
measure the mass of that object as accurately as possible... which is a rather
odd thing to do when aiming for accuracy.

Now we finally have the means to express the kg with a physical experience in
universal terms.

~~~
sandworm101
It is called "le grand k" and is kept in France. Even with these new
measurements, they are still just a representation of the original grand k.

~~~
analog31
Indeed, but the hope is that you could (in principle) lose or damage the grand
k, and be able to get on with life. Just like with the second and the meter,
the kg will be defined using an agreed upon number that provides the best
possible agreement with the old artifact. Then the artifact will have been
replaced by a number whose value is largely of historical interest.

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gregfjohnson
Interesting background in
[http://www.npr.org/templates/story/story.php?storyId=1120033...](http://www.npr.org/templates/story/story.php?storyId=112003322)
The standard kilogram has been losing mass over time (when compared to a
collection of copies). Apparently, we have been getting progressively less
banana... (about 50 parts per billion between these comparison exercises)

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exabrial
I thought I was getting a new unit to buy bananas in other than lbs... turns
out they just measured Planck's constant very accurately in an impressive
manner.

Slightly disappointed.

~~~
jbmorgado
Sad truth is that you buy bananas in lbf and in most of the world we use Kgf.

This world is lost I tell you, can't even pay for something according to it's
mass.

~~~
analog31
Amusingly, all of the "English" units used in the US are defined in terms of
metric units. For instance there's no standard inch. Rather, the inch is
exactly 2.54 cm.

