Historical day for SI

[lajoswinkler]

We've got all relevant units defined through kilogramme which is no longer defined as equal to the one in Sevres vault.

I wonder why it took this long.

https://www.bipm.org/en/measurement-units/rev-si/

[Shpaget]

So, the (no longer) prototype is no longer priceless, only expensive for sentimental reasons.

Speaking of which, (and probably a question for "Shower thoughts" thread) how much does it weigh?

[TheSaint]

12 minutes ago, Shpaget said:

Speaking of which, (and probably a question for "Shower thoughts" thread) how much does it weigh?

[StrandedonEarth]

28 minutes ago, Shpaget said:

So, the (no longer) prototype is no longer priceless, only expensive for sentimental reasons.

Speaking of which, (and probably a question for "Shower thoughts" thread) how much does it weigh?

Weigh? 9.8 Newtons 

[Green Baron]

 

Just for completeness:

 

[Shpaget]

1 minute ago, StrandedonEarth said:

Weigh? 9.8 Newtons 

Funny thing is, I tried googling for a proper and a decent sounding term to ask about the mass, but just couldn't find anything. I figured if somebody gives me an accurate enough answer in N, I can do the math.

So to rephrase, what is the mass of the old prototype?

(You see! It doesn"t sound nice at all. It's cluncky.)

[Green Baron]

15 minutes ago, Shpaget said:

So to rephrase, what is the mass of the old prototype?

It was per definition 1kg until recently. It is little bit less now because of all the rubbing and cleaning and photographing ...

I can imagine that an x-act number in reference to the freezing point of water will be available in a few cesium atom vibrations.

Edited November 16, 2018 by Green Baron

[Superfluous J]

23 minutes ago, Shpaget said:

So to rephrase, what is the mass of the old prototype?

(You see! It doesn"t sound nice at all. It's cluncky.)

That doesn't sound clunky at all to me.

[Bill Phil]

33 minutes ago, Shpaget said:

Funny thing is, I tried googling for a proper and a decent sounding term to ask about the mass, but just couldn't find anything. I figured if somebody gives me an accurate enough answer in N, I can do the math.

So to rephrase, what is the mass of the old prototype?

(You see! It doesn"t sound nice at all. It's cluncky.)

What’s the weight in kgf?

[lajoswinkler]

1 hour ago, Shpaget said:

So, the (no longer) prototype is no longer priceless, only expensive for sentimental reasons.

Speaking of which, (and probably a question for "Shower thoughts" thread) how much does it weigh?

Its mass will be exactly 1 kg up to the moment of official decision on next year's Metrology day. After that it diverge from the value.

[YNM]

 

4 hours ago, Shpaget said:

So, the (no longer) prototype is no longer priceless, only expensive for sentimental reasons.

It's still priceless for historic reasons. Even those that helped throw it away. (also, they still use mass balances for normal 'daily' stuff.)

4 hours ago, Shpaget said:

how much does it weigh now ?

1 kg, plus or minus a few mg (which will have to be weighed).

It's just like 1 litre of water at 4 deg C and normal pressure is actually 999.975 g, but in the ancient times that was regarded as 1 kg (and it was really good already).

Edited November 17, 2018 by YNM

[Shpaget]

7 hours ago, lajoswinkler said:

Its mass will be exactly 1 kg up to the moment of official decision on next year's Metrology day. After that it diverge from the value.

Oh, I thought the switch was done.

I'll be back in a year.

[lajoswinkler]

5 hours ago, Shpaget said:

Oh, I thought the switch was done.

I'll be back in a year.

If someone damages the standard kilogramme by then, we're screwed. 

[kerbiloid]

Spoiler

Why not just take a standard Coca-Cola bottle as the standard? 

+ one more filled up to the low mark

There is a lot of such bottles, they can't destroy them all.

 

[magnemoe]

19 minutes ago, kerbiloid said:

  Hide contents

Why not just take a standard Coca-Cola bottle as the standard? 

+ one more filled up to the low mark

There is a lot of such bottles, they can't destroy them all.

 

Standard coke bottles is 1/3 of an liter (unless they cheat who is unlikely because its an standard)
You also have the air on the top and its dependent on temperature, one reason for the air on top. 

[kerbiloid]

1 minute ago, magnemoe said:

Standard coke bottles is 1/3 of an liter

That's even better. 3 bottles = 1 standard kg.

[magnemoe]

Just now, kerbiloid said:

That's even better. 3 bottles = 1 standard kg.

Water expands with temperature. So do any material, because it displace air this generates inaccuracy. 
This is not for measuring up flour for cooking but. Not even for testing that an package contains 250g but for science experiments, some is used for legal testing other for research. 
We don't use bottlecaps for currency either  

[Shpaget]

1 hour ago, magnemoe said:

Water expands with temperature. So do any material, because it displace air this generates inaccuracy.

That's a flaw with measurement method, not the prototype itself.

[magnemoe]

8 minutes ago, Shpaget said:

That's a flaw with measurement method, not the prototype itself.

No its an practical issue, you do not get perfect measurement conditions. even if you require an climate controlled room it will still be errors. using an heavy metal who don't expand much with temperature would be better. 
 

[Gargamel]

7 hours ago, kerbiloid said:

That's even better. 3 bottles = 1 standard kg.

But does that include the mass of the bottle and cap?  And coke isn't exactly the same density as water, so if a 1 liter bottle is exactly 1 liter of Coke, it won't be the same mass as 1 liter of water.    Which is about 2 pounds.    Ha!

Edited November 18, 2018 by Gargamel

[Ozymandias_the_Goat]

Moving on...

I would have suspected that the kilogramme would be redefined as a some number of atoms of a specific isotope. Does anybody know why this was not done? I am under the impression that the consensus of the scientific community was to relate SI measurements with universal constants, which admittedly does make a lot of sense, but still. Wasn’t that a proposed definition once?

Moving on...

I would have suspected that the kilogramme would be redefined as a some number of atoms of a specific isotope. Does anybody know why this was not done? I am under the impression that the consensus of the scientific community was to relate SI measurements with universal constants, which admittedly does make a lot of sense, but still. Wasn’t that a proposed definition once?

[kerbiloid]

Quote

One newton is the force needed to accelerate one kilogram of mass at the rate of one metre per second squared in the direction of the applied force.

Will they now have to redefine a newton as well?

***

As the mass itself is a secondary value relative to energy and impulse, they should redefine kilogram in some way like "1 kg is the mass required for a job equal to 1 J to be produced along 1 m distance in the 1 m/s² gravity field" or "1 kg is the mass needed for a non-relativistic body to have 1/2 J of kinetic energy at 1 kgm/s impulse"

On 11/20/2018 at 10:30 PM, Ozymandias_the_Goat said:

I would have suspected that the kilogramme would be redefined as a some number of atoms of a specific isotope.

1 kg = 45945947.489854 plancks.

Edited November 25, 2018 by kerbiloid