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[Closed] Geeky scientists only. And fatties

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I knew my scales were under reading. We're not as fat as we thought we were, the kg has been tricking us.

https://news.sky.com/story/scientists-redefine-kilogram-as-original-measure-loses-mass-11552690


 
Posted : 13/11/2018 7:29 am
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That will be negated by if the scales are on carpet or lino you will weigh less than you actually are, you will also weigh less the higher up you are.


 
Posted : 13/11/2018 8:42 am
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So it's lost 20ng - but what did they measure it against, to know that?


 
Posted : 13/11/2018 8:50 am
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20ng, That's about the weight of a human soul

They just weigh journalists before & after they sign a contract with the Daily Mail


 
Posted : 13/11/2018 8:55 am
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Surely we will get heavier. There's less kilogram than there used to be so we will be composed of more of them.


 
Posted : 13/11/2018 9:08 am
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That will be negated by if the scales are on carpet or lino you will weigh less than you actually are, you will also weigh less the higher up you are.

Might lead to inaccuracy, but not always. The scales measure the force acting through their axis, so if they're not level then the force is reduced when a mass is placed on them. But if they still sit level on a carpet/lino with the weight on them it won't matter whether they sink into it or not.

So it’s lost 20ng – but what did they measure it against, to know that?

I wondered that, presumably they know its composition and know at what rate any radioactive isotopes decay?


 
Posted : 13/11/2018 9:11 am
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There’s less kilogram than there used to be so we will be composed of more of them.

No, the kg is a constant, the piece of metal they use to represent that constant isn't constant and has lost weight.

So although my scales say 87kg, it's really 87 x a piece of metal that is considerably* less than 1kg.

* your definition may vary, i need all the help I can get

** if you want to be pedantic, 86.99999826kg  But it's in the right direction!


 
Posted : 13/11/2018 9:51 am
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theotherjonv - to be even more pedantic, only if your scales are recently calibrated to a certified reference standard 😉


 
Posted : 13/11/2018 11:04 am
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if you want to be pedantic, 86.99999826kg

No, it's 86.99999999826kg. 20ng is 20x10-9g, so it's 20x10-12kg.

Sorry, that means you're 0.00000173826kg heavier.


 
Posted : 13/11/2018 11:12 am
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well spotted. I knew my trousers felt tighter.


 
Posted : 13/11/2018 11:31 am
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No, the kg is a constant, the piece of metal they use to represent that constant isn’t constant and has lost weight.

Not yet it isn't. Kg is still referenced to the Parisian lump. Vote is on Friday and the actual switch over, to Plank's constant derived reference, will be at a later date.


 
Posted : 13/11/2018 11:56 am
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kg is mass not weight.


 
Posted : 13/11/2018 12:08 pm

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