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Fri Nov 16, 2018, 11:21 AM

It's official -- a kilogram isn't what it used to be

Source: Associated Press, via CBC

It's official -- a kilogram isn't what it used to be

Key measurement units kelvin, ampere and mole also get new definitions in Friday vote in France

The Associated Press Posted: Nov 16, 2018 8:17 AM ET Last Updated: an hour ago

The international system of measurements has been overhauled with new definitions for the kilogram and other key units.

At a meeting in Versailles, France, countries have voted to approve the wide-ranging changes that underpin vital human activities like global trade and scientific innovation.

The most closely watched change was the revision to the kilo, the measurement of mass.

Until now, it has been defined as the mass of a platinum-iridium lump, the so-called Grand K, that is kept in a secured vault on the outskirts of Paris. It has been the world's one true kilo, against which all others were measured, since 1889.

Read more: https://www.cbc.ca/news/technology/kilogram-ampere-mole-definition-1.4908449



All that's left is for Betsy DeVos to require that the Biblical version be taught too.

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The Washington Post had a better story, but it was dated yesterday.

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Dave Weigel Retweeted

https://twitter.com/daveweigel

Are you ready to be inspired .... by measurement?

Tomorrow, people from around the globe will come together to *agree* on something, even though it is hard, even though it is costly, because it reflects a fundamental fact about the universe




A massive change: Nations redefine the kilogram

https://www.washingtonpost.com/science/a-massive-change-nations-will-vote-to-redefine-the-kilogram/2018/11/15/b5704b0a-e6c7-11e8-b8dc-66cca409c180_story.html

By Sarah Kaplan November 15 at 7:27 PM

Humanity just made a weighty decision. On Friday, representatives of more than 60 nations, gathered in Versailles, France, approved a new definition for the kilogram.

Since the 19th century, scientists have based their definition of the fundamental unit of mass on a physical object -- a shining platinum iridium cylinder stored in a locked vault in the bowels of the International Bureau of Weights and Measures (BIPM) in Sevres, France. A kilogram was equal to the heft of this aging hunk of metal, and this cylinder, by definition, weighed exactly a kilogram. If the cylinder changed, even a little bit, then the entire global system of measurement had to change, too.

With Friday's vote, scientists redefined the kilogram for the 21st century by tying it to a fundamental feature of the universe -- a small, strange figure from quantum physics known as Planck's constant, which describes the smallest possible unit of energy.

Thanks to Albert Einstein's revelation that energy and mass are related, determining exactly how much energy is in that unit can let scientists define mass in terms of Planck's constant -- a value that should hold up across space and time -- rather than relying on an inconstant metal cylinder. (Mass determines something's weight, and for most purposes mass and weight are interchangeable.) ... The redefinition is the result of a decades-long, worldwide quest to measure Planck's constant precisely enough that the number would stand up to scientific scrutiny.
....

Sarah Kaplan is a science reporter covering news from around the nation and across the universe. She previously worked overnights on The Washington Post's Morning Mix team. Follow https://twitter.com/sarahkaplan48

18 replies, 1914 views

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Arrow 18 replies Author Time Post
Reply It's official -- a kilogram isn't what it used to be (Original post)
mahatmakanejeeves Nov 2018 OP
brooklynite Nov 2018 #1
lagomorph777 Nov 2018 #15
Zambero Nov 2018 #2
dalton99a Nov 2018 #3
mahatmakanejeeves Nov 2018 #5
packman Nov 2018 #4
SeattleVet Nov 2018 #14
JohnnyRingo Nov 2018 #6
muriel_volestrangler Nov 2018 #9
JohnnyRingo Nov 2018 #11
missingthebigdog Nov 2018 #7
Historic NY Nov 2018 #8
JustABozoOnThisBus Nov 2018 #10
MineralMan Nov 2018 #12
Iggo Nov 2018 #13
lagomorph777 Nov 2018 #16
Iggo Nov 2018 #17
Cold War Spook Nov 2018 #18

Response to mahatmakanejeeves (Original post)

Fri Nov 16, 2018, 11:27 AM

1. Does this mean I have to go on a diet?

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Response to brooklynite (Reply #1)

Fri Nov 16, 2018, 05:19 PM

15. Well, try to avoid eating an Avogadro's Number of avocados.

That would mess up your diet for sure.

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Response to mahatmakanejeeves (Original post)

Fri Nov 16, 2018, 11:28 AM

2. Are Cheech & Chong aware of this?

A kilo then is not a kilo now???

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Response to mahatmakanejeeves (Original post)

Fri Nov 16, 2018, 11:30 AM

3. The WP article is very well written

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Response to dalton99a (Reply #3)

Fri Nov 16, 2018, 11:33 AM

5. Sarah Kaplan has been writing about science for the WaPo for years.

I would much rather have used that, but the timestamp was over 12 hours old.

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Response to mahatmakanejeeves (Original post)

Fri Nov 16, 2018, 11:32 AM

4. Snobs - I'll keep my inch, my foot and my yard

my teaspoon, tablespoon, pint, quart, ounce and pound. Good enuff for my mother's cookie recipes, good enuff for me. So there!

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Response to packman (Reply #4)

Fri Nov 16, 2018, 04:54 PM

14. I've been slowly but steadily converting all of my recipes to sensible units.

I keep my kitchen scale on the grams setting, and have sets of measuring cups and spoons marked in milliliters. Any time I use an old recipe I either hand-write the real units on it, or make a change in the computer file before I re-save it.

I figure that the time spent doing that is almost made up for by not having to constantly convert, for instance, tablespoons to cups when multiplying a recipe.

We don't measure speed in furlongs per fortnight (by the way, that's US furlongs, which makes the speed of light 1.803e+12 furlongs/fortnight), so why base other measurements on, for example, the length of 3 barleycorns, or a king's body part?

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Response to mahatmakanejeeves (Original post)

Fri Nov 16, 2018, 11:41 AM

6. Switching to a scientific formula

The kilo heretofore was defined by a lump of plutonium in a glass case. That was essential in the middle ages, but now we can define it more precisely with modern science.

Unfortunately, the article doesn't go into detail.

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Response to JohnnyRingo (Reply #6)

Fri Nov 16, 2018, 02:14 PM

9. Thankfully, it wasn't "plutonium"

Because the radioactive disintegration would be constantly changing its mass. Plus, you know, the dangerous radioactivity.

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Response to muriel_volestrangler (Reply #9)

Fri Nov 16, 2018, 03:30 PM

11. I got the first letter right

I think that displays pretty good reading skills for my advanced vintage. Can your president do that? hahaha

"Until now, it has been defined as the mass of a platinum-iridium lump, the so-called Grand K..."

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Response to mahatmakanejeeves (Original post)

Fri Nov 16, 2018, 11:42 AM

7. TLDR. Do I weigh more or less under this change?

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Response to missingthebigdog (Reply #7)

Fri Nov 16, 2018, 11:50 AM

8. That important...wish I knew yesterday at the Dr's.

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Response to missingthebigdog (Reply #7)

Fri Nov 16, 2018, 03:06 PM

10. Less.

Always less.

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Response to mahatmakanejeeves (Original post)

Fri Nov 16, 2018, 03:55 PM

12. It's all a conspiracy by the manufacturers of scales.

Now, everyone will have to throw out their old scales and buy new ones, see...

Still, If they're throwing out that cylinder of platinum and iridium, I'll take it. Yes, indeed.

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Response to mahatmakanejeeves (Original post)

Fri Nov 16, 2018, 03:58 PM

13. I've been using 1 kilo equals 2.2 pounds since I learned there were kilos.

Is that wrong? (yes)

Was it always wrong? (i just looked it up and it's closer to 2.205 pounds)

What's the new conversion?

One kilo equals how many pounds?

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Response to Iggo (Reply #13)

Fri Nov 16, 2018, 05:21 PM

16. Same, unless you go out to 20 decimal places.

Can your scale do that?

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Response to lagomorph777 (Reply #16)

Fri Nov 16, 2018, 05:53 PM

17. Ah, okay, cool. And no, I've never needed a scale that precise.

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Response to mahatmakanejeeves (Original post)

Fri Nov 16, 2018, 07:43 PM

18. Does this change how many joints you can roll from a kilo?

 

More I hope.

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