The kilogram is about to be redefined

rjh01

Gentleman of leisure
rjh01
Joined
May 6, 2005
Messages
29,982
Location
Flying around in the sky
Reality is about to change. The kilogram which until now, has been defined as the mass of a certain artefact (or big K) held in a vault in Paris. They will define the kilogram by defining as planks constant as exactly 6.62607015 X 10^-34 Js. This then determines how big a kilogram is.

This will mean that the values for the kelvin, mole and ampere will all now be fixed.

Avogadro's constant will be 6.02214076 X 10^23
The charge on an electron will be 1.602176634X10^-19C
Boltzmann constant = 1.380649X10^-23J/K

See this YouTube for details



Or https://www.cnet.com/news/scientists-are-about-to-redefine-how-much-a-kilogram-weighs/

This thread is a duplicate of this one http://www.internationalskeptics.com/forums/showthread.php?t=90329. Started in 2007. So the discussion has been going on for some time. Come to think of it my science teacher mentioned it in the 1970s.
 
And this will have a practical effect just how, even if my most accurate scale only weighs to 1/ 70,000 of a pound? (1/10 grain)

How will it effect shipping cost per metric tonne ?

How much will the defined weight of even the Earth change?
 
I'm so glad this has come to pass and now all uncertainty can be swept aside. Just yesterday, I was wondering if my kilogram was a little off.
 
rjh01 said:
Reality is about to change. The kilogram which until now, has been defined as the mass of a certain artefact (or big K) held in a vault in Paris. They will define the kilogram by defining as planks constant as exactly 6.62607015 X 10^-34 Js. This then determines how big a kilogram is.

This will mean that the values for the kelvin, mole and ampere will all now be fixed.

Avogadro's constant will be 6.02214076 X 10^23
The charge on an electron will be 1.602176634X10^-19C
Boltzmann constant = 1.380649X10^-23J/K

See this YouTube for details



Or https://www.cnet.com/news/scientists-are-about-to-redefine-how-much-a-kilogram-weighs/

Old number 6.022140857 × 1023
New number 6.02214076 X 10^23

This thread is a duplicate of this one http://www.internationalskeptics.com/forums/showthread.php?t=90329. Started in 2007. So the discussion has been going on for some time. Come to think of it my science teacher mentioned it in the 1970s.
Click to expand...

Old number 6.02214085 × 10^23
New number 6.02214076 X 10^23

It looks to me like they are making a mole smaller. We are are being cheated out or OUR molecules! It must be Trump, in bed with industry, to cheat the little people of the world!

(The intarwebs need a new rule, like Godwinning, except with "Trump" instead of "Nazi". There, I did them both. )
 
rjh01 said:
Reality is about to change. The kilogram which until now, has been defined as the mass of a certain artefact (or big K) held in a vault in Paris. They will define the kilogram by defining as planks constant as exactly 6.62607015 X 10^-34 Js. This then determines how big a kilogram is.

..,.
Click to expand...

So now that I know that, can I make my own artefact(sic) standard? It's going to take a mighty fine microscope to count all them Joules individually...

I don't think they are going to be selling the IPK for scrap just yet.
 
casebro said:
So now that I know that, can I make my own artefact(sic) standard? It's going to take a mighty fine microscope to count all them Joules individually...

I don't think they are going to be selling the IPK for scrap just yet.
Click to expand...

If I have a scale that is accurate to 11 digits, a file that I can use to grind off a few molecules (how many?), and a Joule-o-meter that measures to 12 digits, my answer would be in the 10^23 range. I'm off to the US Government Surplus site, they have EVERYTHING.
 
casebro said:
Old number 6.02214085 × 10^23
New number 6.02214076 X 10^23

It looks to me like they are making a mole smaller. We are are being cheated out or OUR molecules! It must be Trump, in bed with industry, to cheat the little people of the world!

(The intarwebs need a new rule, like Godwinning, except with "Trump" instead of "Nazi". There, I did them both. )
Click to expand...

******* Euros! They're making a mountain out of a mole hill!! :boxedin:
 
The Great Zaganza said:
more importantly, how will it affect my bathroom scales?
Click to expand...

Good news. It will not. But if you want to do a science experiment that the result relies on how big a kilogram is, for the first time you can give consistent results. Until now doing the same experiment can give slightly different results in different countries because they define the kilogram slightly differently. This will have implications, though exactly what I am not sure.
 
I always thought that designing the kilogram as equal to the weight of a liter of water was a particularly brilliant way to ensure a standard value.
 
Brainster said:
I always thought that designing the kilogram as equal to the weight of a liter of water was a particularly brilliant way to ensure a standard value.
Click to expand...

It is a good standard. Though trying to get a litre of pure water using certain concentrations of isotopes of hydrogen and oxygen will be very hard. Remember if the measurement is out by one part in 10^7 it is wrong. That is why I suggest it went out in the 19th century.
 
I thought the deterioration of the standard sample would amount to a few molecules and be virtually undetectable. One report I say said that is has lost enough to equal the weight of an eyelash. That seems particularly significant to me.
 
Brainster said:
I always thought that designing the kilogram as equal to the weight of a liter of water was a particularly brilliant way to ensure a standard value.
Click to expand...

It isn't, because of difficulties in making such a liter actually constant. The easy part is making sure they're at the same temperature and pressure (the triple point of water defines those). But they also have to have the same isotope ratio, they have to have the same impurities (or lack thereof), they have to have the same amount of dissolved gasses.

Plus, getting the volume exact actually isn't trivial either. You might think, just make a cube 10cm on each side. But it's very hard to make a cube where all the sides are exactly 90 degrees apart. Any slight skew, and the volume changes, even if the sides are the perfect length. So even measuring volume precisely is very, very hard to do. Length is much easier to measure than volume.
 
Ziggurat said:
Plus, getting the volume exact actually isn't trivial either. You might think, just make a cube 10cm on each side. But it's very hard to make a cube where all the sides are exactly 90 degrees apart. Any slight skew, and the volume changes, even if the sides are the perfect length. So even measuring volume precisely is very, very hard to do. Length is much easier to measure than volume.
Click to expand...

Can't you use trig? For example a triangle with sides with lengths 3u, 4u and 5u necessarily has a 90 degree angle. If the lengths are accurate then so is the angle.
 
Last edited:
You must log in or register to reply here.

Back
Top Bottom