Four base units of measure in the metric system about to be changed

November 9, 2018 by Bob Yirka, Phys.org report
Credit: CC0 Public Domain

Officials with the General Conference on Weights and Measures (CGPM) have announced that at a meeting to be held next week, four of the base units used in the metric system will be redefined. The four units under review are the ampere, kilogram, mole and kelvin.

Currently, the is officially defined as the mass of a cylinder made of a platinum-iridium alloy housed in a bell jar in France—it has been removed from its protected spot every 40 years to serve as a calibration tool for other weights. But according to officials with CGPM, its days are numbered. This is because the 60 member nations that make up the body will be voting to change to a system in which the kilogram will be defined indirectly—by using the Planck constant.

The tool used to provide the new base unit is the Kibble balance—a very complex piece of equipment that first measures the amount of electric current necessary to create an that is equal to a force acting on a given mass. It is during the second stage that the Plank constant comes into play. The reason for the changeover is to reference a more stable basis of measurement and to allow for the development of more precise measuring devices. Several metrologists involved in bringing the changes to a vote have acknowledged that most people will neither understand the changes that have taken place, nor notice that a change has occurred.

The metric system is part of the International System of Units, and in places other than the United States, is commonly called SI. Efforts to make it more precise have been underway for years. The speed of light, for example, was updated in 1983, and is now defined as 299,792,458 meters per second.

For those interested in the proceedings, the CGPM will be streamed live on the internet. Officials have described the meeting as marking the end of SI measurements based on objects. Prior meetings have already resulted in updating the other three base units in the system: the second, meter and candela. If the measures pass, the changes will take effect in May of next year.

Explore further: CGPM set to update international system of weights and measures

More information: 26th meeting of the CGPM: 13-16 November 2018: www.bipm.org/en/cgpm-2018/

Related Stories

Scientists update four key fundamental constants

October 23, 2017

Paving the way for transforming the world's measurement system, an international task force has determined updated values for four fundamental constants of nature. The updated values comprise the last scientific piece of ...

How much does a kilogram weigh?

November 6, 2017

The kilogram doesn't weigh a kilogram any more. This sad news was announced during a seminar at CERN on Thursday, 26 October by Professor Klaus von Klitzing, who was awarded the 1985 Nobel Prize in Physics for the discovery ...

The kilogram gets a makeover

January 26, 2018

In Sèvres, a small commune on the outskirts of Paris, lies a gleaming lump of metal the size of a palm. Le Grand K, or Big K as they call the platinum and iridium alloy, sits underground in a high-security vault. It is held ...

Recommended for you

Bursting bubbles launch bacteria from water to air

November 15, 2018

Wherever there's water, there's bound to be bubbles floating at the surface. From standing puddles, lakes, and streams, to swimming pools, hot tubs, public fountains, and toilets, bubbles are ubiquitous, indoors and out.

Terahertz laser pulses amplify optical phonons in solids

November 15, 2018

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg/Germany presents evidence of the amplification of optical phonons ...

Designer emulsions

November 15, 2018

ETH material researchers are developing a method with which they can coat droplets with controlled interfacial composition and coverage on demand in an emulsion in order to stabilise them. In doing so they are fulfilling ...

Quantum science turns social

November 15, 2018

Researchers in a lab at Aarhus University have developed a versatile remote gaming interface that allowed external experts as well as hundreds of citizen scientists all over the world to optimize a quantum gas experiment ...

42 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

MJ3City
2 / 5 (4) Nov 09, 2018
I already feel sympathy to kids in school. While physics lessons in ground school in Poland are already limited (less than "religion" courses btw), now few of it will have to be devoted to explain what a 1 kg is.
Hyperfuzzy
1.3 / 5 (7) Nov 09, 2018
It's not so complicated; it's a countable pair of charges = 1 Kg apprx 5.98 E 26 pairs

rrwillsj
1.7 / 5 (11) Nov 09, 2018
but fzzy. only until pfence slips a document in front of trumpenella to sign as a presidential decree. With some fancy title such as "All Glory to Our Great Leader's Presidential Proclamation To Restore American Glory!"
In which the religious twits make it official that all children have to be taught that Pi equals 3.0. Cause the indeterminacy makes their pointed heads hurt.

The Bogus POTUS never reads past the headline anyway.
That would make his head hurt.

To dictate that every textbook containing information contradictory to theocracy,
such as the metric system,
shall be burned! Alonfg with the authors.
Hyperfuzzy
1 / 5 (2) Nov 09, 2018
Note: The Dynamics within the "mass" is undefined.
granville583762
2.2 / 5 (10) Nov 09, 2018
Except for one tinsey winsy minsey point
The speed of light is not exactly
299792458m/s
Exact to 299792458.01690158m/s
Or has the insignificant
Little detail
Escaped us all
The speed of light
Is not exactly 299792458m/s
And there is the other niggling worry
In the vacuous vacuum
The speed of light
Is almost
Certainly
Not constant
Down to the last
1/1000mm
Old_C_Code
4.4 / 5 (7) Nov 09, 2018
slips a document in front of trumpenella to sign as a presidential decree


Science is all political to those who've accomplished nothing in their young age, and expect all to revere their detailed genius commentary. No, not gonna happen.
StudentofSpiritualTeaching
1.8 / 5 (5) Nov 09, 2018
Your warning is very valid, rrwillsj. It would not be the first time that a stubborn belief-dogma slows mankind's scientific progress at the magnitude of centuries. Take the example of Christian insanities in the 4th century, while burning down the library of Alexandria and much more:

http://www.future...port_498
StudentofSpiritualTeaching
1.6 / 5 (7) Nov 10, 2018
And are we really sure that Pi is 3.14159… rather than 4/square root of Phi, that is 3.14460…
See: http://www.future...port_260
And could it be that the speed of light has gradually been slowing down since the big bang? See:
http://www.future...port_143
granville583762
3 / 5 (6) Nov 10, 2018
The speed of light is not exactly 299792458m/s

The kilogram is undefined
It could be the same in the
Equivalent number of C16 atoms
But
The mass of the proton is not fixed
The mass of the neutron is not fixed
It is a collection of entities
That changes their mass in radio-active decay
As the neutron in its halva's
Decays into a proton
With mass disappearing in particles
Now occupying the vacuum
And the velocity of light
Its true velocity i
Is not publicly given
Except
As
299792458m/s
Or
983571056.430446ft/s
As the conversion
Proves the point
The speed of light in feet/s
Is only accurate to
5.165352inch's/s
As an inch
Is 1/39.3700787402 of a metre
Further proves the speed light
Is not 299792458m/s
Because
If it was in feet/s
It would be
983571056.430446ft/s
Not as
983571056ft/s
As that would be inaccurate
To a considerable number of decimal places
granville583762
3.4 / 5 (5) Nov 10, 2018
The Kilogram, the Metre, the Second, the speed of Light

As highly accurately
Defined
Units of measure
The second as one day or 1/86400 days
Or defined as a frequency
9,192,631,770Hz
What is the earthly point
In defining the second
With a decimal accuracy
Of
0.00000000010878277571 fraction of a second
When we only
Define the speed of light
To an accuracy of
One metre
Shootist
4.4 / 5 (5) Nov 10, 2018
but fzzy. only until pfence slips a document in front of trumpenella to sign as a presidential decree.


dood, as you are well aware there are only two types of nations in the world. Those that use metric and those that sent men to the moon and returned them safely to Earth.

Carry on.
RNP
4.3 / 5 (11) Nov 10, 2018
@Shootist
You mean the same country whose 1999 Mars orbiter broke up in the atmosphere of Mars because one of its instruments gave readings in imperial units? :)
StudentofSpiritualTeaching
2.3 / 5 (3) Nov 10, 2018
@shootist
Yes, 2 types, one that has never ever shot atomic weapons for killing fellow human beings and the other that did and would not hesitate to shoot them again.
rrwillsj
1 / 5 (3) Nov 10, 2018
Well. you all made my point for me. The Universe is a randomly chaotic mess as the result of bungling Stupid Design. And in a few trillion years, it will all fall apart back into the constituent gravitron soup.

C'est la vie!
Da Schneib
3.8 / 5 (5) Nov 10, 2018
Pssst, don't bother @Shootie with those metric labels on all the food in the grocery store. It might have a stroke.
axemaster
4.8 / 5 (10) Nov 10, 2018
Shootist, you may not have known this, but everything in the scientific world is done in metric. That includes the US space program.

Speaking as an American who natively uses imperial units, I can tell you with confidence that metric is a vastly superior system.
granville583762
3.4 / 5 (5) Nov 10, 2018
Compounding errors

Using Planck constant in multiple multiples
Squares the errors in the velocity of light
If that is bad
It gets worse
No one knows the speed of light
Except to an inaccuracy
Of one metre
So as everyone does their calculations
The kilogram acquires errors
That
Without knowing to however many decimal places
Of the inaccuracy of the velocity of light
The kibble kilogram
Becomes an unknown factor
Does it end there
Oh no it gets worse
Because that other unknown factor
The speed of light
The second becomes 1/299792458 as the definition of one second
the metre becomes 1/299792458 as the definition of one metre
In a nutshell
The kilogram, the metre and the second
Are all inversely
Proportional to the velocity
Of the speed of light
That velocity that is only
Accurate to one metre
torbjorn_b_g_larsson
3.2 / 5 (9) Nov 10, 2018
Long expected, glad they could make the change. Now SI is defined from universal constants "as it should be".

I also enjoyed the hilarious sideshow where the usual trolls show they don't even know what a kilogram is, how it is measured or what causes it. That is the only good use for them, to provide the rest of the world with laughs, and here they really made good on their baloney.
tblakely1357
3 / 5 (2) Nov 10, 2018
When a Trump hater fully drop their mask you find someone who despises America: it's history, it's culture and most of it's citizens.
24volts
2.8 / 5 (4) Nov 10, 2018
While I totally applaud what they are trying to accomplish and it will work very well for mathematics it's going to be damn hard for people to standardize a physical scale with a number.
I think it's going to be a long time before anyone other than scientists will be using that
in their normal everyday type calculations in the physical side of the world.

StudentofSpiritualTeaching
2 / 5 (4) Nov 10, 2018
@tblakely

I am no Trump hater, try to hate nobody of our fellow beings. He certainly is the lesser evil for mankind when compared to Hillary, who would by now already have brought the next world war upon us.

I would reword your statement: when arrogance and a superiority complex is on display, there will be persons that reign in. As long as the reaction remains fair and factual there is nothing wrong with it.
Surveillance_Egg_Unit
3.7 / 5 (3) Nov 11, 2018
@SST
Perhaps tblakely was referring to rrwillsj's post above who IS a known Trump-hater and a reactionary against most things American, except for Socialist/Marxist ideologies, possibly even bordering on Communism - which would be an entrance to the chaotic universe that rrwilliejoe speaks so well of.
Da Schneib
3.4 / 5 (5) Nov 11, 2018
@24volts, EEs already use it. And new kilograms aren't going to be enough different to need to recalibrate the butcher's scales.
Da Schneib
4.2 / 5 (5) Nov 11, 2018
In case folks don't get it, these definitions allow a reference to be built in any lab. To any desired accuracy and precision. You don't have to reference against some piece of metal in Paris. See how that works?
Tessellatedtessellations
3.4 / 5 (5) Nov 11, 2018
@shootist
From wikipedia: .. As of 2018 the United States is one of only seven countries, including Myanmar, Liberia, Palau, the Marshall Islands, the Federated States of Micronesia, and Samoa. Pretty sure none of the others sent people to the moon or boast about things they personally can't do and would done nothing but bitch about the taxes to pay for.

Thomas Jefferson was going to make the USA one of the first countries to use SI. To our everlasting anal pain, pirates captured the ship carrying the kilogram standard from France and the guy carrying it died. So thanks to criminals, and now people with less intelligence or ambition than most of the rest of the world, we are stuck with an inferior measurement system.
granville583762
4 / 5 (4) Nov 11, 2018
One second = 299792458m, where one metre = 1/one second

The second is 299792458m, not how long it takes light to travel 299792458m
The metre is 1/299792458seconds as the second is now defined as 299792458m
The kilogram is one Newton
One Newton=ma
L= one metre, where a=L/T*
Where L= (1/299792458m)
And T= (299792458m)
So one Newton becomes
a=L/T* equals (1/299792458m)/ (299792458m)*
Where mass M is expressed as a unit of one
One Newton simply becomes L/T* equals (1/299792458m)/ (299792458m)*
The new definition
Of the kilogram
Is now undefined
As it is a unit of distance
As time is a unit of 1/distance
And the time it takes light
To travel 299792458m
Is one second
And one metre
Is 1/299792458seconds
That's at a fine mess every ones in once this is established
TrustTheONE
3 / 5 (3) Nov 11, 2018
When USA will stop this non sense and start using the SI ? My country is SI, but we still use many imperial units due to manufacture standards used by the US
rrwillsj
3 / 5 (2) Nov 11, 2018
Oh segue and tblak, I promise to hate both you trolls equally!

As for ideology? I consider self-proclaimed marxists and corporatecommunists to be right-wing fascists, Which means if altright fairytails such as segue and tblak were any closer to the edge of their flat earth? They'd fall off!

The only real difference between right fascists and left fascists? Is the whining from the right that the left is more competent at mass murder.

"... The animals gathered around to peer in the windows of the farmhouse.
Listening with amazement at the celebration within.
Looking at the boisterous drunks toast one another in mutual smug satisfaction.
As the animals watched dumb-founded?
They finally realized.
That as they looked back and forth from celebrant to celebrant.
They could no longer tell the difference between the men and the swine. ..."
24volts
3.5 / 5 (4) Nov 11, 2018

It would really be nice if people on here that comment would actually read what people say before they start popping off. I use to set scales for a while as a living for a couple of years and while I agree the minute difference isn't going to mean anything in 99.99 percent of commercial scales there is no way to set them without a physical standard to work with. Try to comprehend that simple fact. Like I said earlier, it works fine for math but once you get to the real world it's really difficult to count a bunch of atoms. Also, since many people don't seem to know it the US HAS been on the metric system for at least 40 years. We were taught it back in school and it's used all the time. The reason most people here still don't use it in everyday life is many of the values don't make any damn sense in the real world. Distance and speed make sense but none of that other stuff does unless you work in a lab. People need actual physical measurements for volume, weight,etc...
granville583762
4 / 5 (4) Nov 11, 2018
Defining the second as a frequency

9,192,631,770Hz
Simplifies the process of counting one second
Then 9,192,631,770Hz equals 299792458m, equal one second, equals the speed of light
Simplifying, 9,192,631,770Hz equals the speed of light
By simply counting oscillations
When reaching the requisite number
9,192,631,770
Equals one second
Equals 299792458m
Where
One metre equals (one second)/299792458
By defining one second as a definitive number of oscillations
And defining the speed of light as 299792458m/s
However long 9,192,631,770 vibrations take to occur is one second
As the vibrations are not constant in a varying Gravitational field
9,192,631,770 vibrations take longer to occur under increased gravity
This implies the mathematics is going askew
Taking longer to reach the requisite number of vibrations
Which means light is travelling a greater number of metres
A mathematical anomaly
That can only
Be corrected
If the strength
Of Gravity is Known
Anonym518498
1 / 5 (1) Nov 11, 2018
doesn't matter, physics is being debased and bastardized by political correctness, promoting mental midgets to positions of authority, it is pan-lysenkoism
Shootist
5 / 5 (2) Nov 11, 2018
@Shootist
You mean the same country whose 1999 Mars orbiter broke up in the atmosphere of Mars because one of its instruments gave readings in imperial units? :)


did that orbiter land on the moon and return its passengers safely to Earth?
Da Schneib
3.7 / 5 (3) Nov 11, 2018
@24volts, then buy a reference weight from a reputable standards lab just like I do to keep my oscilloscopes and DVMs in calibration. You're lucky; you only have to buy one. I have to buy new ones fairly often to have one that's not degraded by time.
PisoMojado
1 / 5 (1) Nov 11, 2018
Here are my recommendations for great simplification:

One kilometer to equal one mile.

One kilogram to equal 2.2 pounds of marajuana.

10 hours in one day, 10 days in one week, 10 weeks in one year.
shabd
4.2 / 5 (5) Nov 12, 2018
@StudentofSpiritualTeaching
And are we really sure that Pi is 3.14159… rather than 4/square root of Phi, that is 3.14460…
See: http://www.future...port_260


If you dabble in some simple geometry, you could calculate Pi yourself, understand what it is and skip such stupid comments.
StudentofSpiritualTeaching
1 / 5 (2) Nov 12, 2018
Don't know about you, Shabd, but I had mathematics courses at university, as part of a computer science master study. Be it as it is, I suggest that you try a practical proof for finding out that your "simple geometry" delivers a wrong value: http://measuringp...urement/

PS: full disclosure, I think that the mathematical proof attempts on that site are unfortunately flawed, using circular logic.
antialias_physorg
5 / 5 (4) Nov 12, 2018
I already feel sympathy to kids in school. While physics lessons in ground school in Poland are already limited (less than "religion" courses btw), now few of it will have to be devoted to explain what a 1 kg is.

Kids don't need to know how the exact standard of a unit is defined or maintained. If you start them off that 1kg is roughly the weight of 1 liter of water then that is good enough until they decide to study physics more in depth.

Here are my recommendations for great simplification:
...
10 hours in one day, 10 days in one week, 10 weeks in one year.

Why is this a simplification? 10 is not a 'natural' base. We only use it because homo sapiens happens to have 10 fingers. If we had 6 fingers on each hand we'd be using base 12 (which is a damn sight more convenient than base 10, BTW)

but everything in the scientific world is done in metric.

Yes. Every internationally published paper by a US scientist uses SI units.
taka
1 / 5 (2) Nov 12, 2018
What will be the force that is going to be balanced by electromagnetic force of a current? Weight in Earth gravity? That is certainly not a constant... Masses are moving around on Earth and Earth total mass is also changing in time. Mass should be constant, weight cannot be used to measure it. But weight can be used to compare two masses as it changes even out then.
shabd
5 / 5 (3) Nov 12, 2018
@StudentofSpiritualTeaching

Don't know about you, Shabd, but I had mathematics courses at university, as part of a computer science master study. Be it as it is, I suggest that you try a practical proof for finding out that your "simple geometry" delivers a wrong value: http://measuringp...urement/
PS: full disclosure, I think that the mathematical proof attempts on that site are unfortunately flawed, using circular logic.


I learned this in high school and did it myself. It satisfying to understand things.
Here is a nice 5 minute video on how to do it:

https://www.youtu...MZ-CT7YU

After you have (understand) the formula, the bigger number you use instead of "n" (number of sides) the better approximation of Pi you get.
24volts
3 / 5 (2) Nov 12, 2018
@24volts, then buy a reference weight from a reputable standards lab just like I do to keep my oscilloscopes and DVMs in calibration. You're lucky; you only have to buy one. I have to buy new ones fairly often to have one that's not degraded by time.


The company I worked for at the time had them. From .1 gram up to 50 lbs. Yea, they had both types. It was common for scales to still be in both systems back in the 70's.
Da Schneib
3 / 5 (2) Nov 12, 2018
Only they don't degrade over time.

Try to keep up. It's obvious you have never dealt with electronics references.
24volts
5 / 5 (1) Nov 12, 2018
Only they don't degrade over time.

Try to keep up. It's obvious you have never dealt with electronics references.


Actually, yes I have but not in a business setting. Only as an electronics hobbyist but I haven't messed with that stuff in about 15 years. I build custom electric/gas assisted-recumbent trikes for people as a hobby now.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.