It might seem bizarre that they're redefining a unit of mass using electric current, but the image they provide is really helpful. Fascinating to think that we're still living in an era where our...
It might seem bizarre that they're redefining a unit of mass using electric current, but the image they provide is really helpful.
Fascinating to think that we're still living in an era where our way to measure the universe is being adjusted.
People reading this article might also be interested in this previous post: What defines a kilogram? Before standardization, units of measurement were often manipulated by tyrants to cheat...
And for even more additional information: Derek from Veritasium did a video many years ago covering how the kilogram was historically defined, as well as literally got a chance to "get his hands...
And for even more additional information: Derek from Veritasium did a video many years ago covering how the kilogram was historically defined, as well as literally got a chance to "get his hands on" the Avogadro project's €1M "world's roundest object" made from a single crystal of Silicon 28 atoms, which was one of the proposed alternatives to this newly adopted Kibble (Watt) balance system for re-standardizing the kilogram.
Oh sweet, that video perfectly covers the subject of this topic. I wonder how I missed that one... I thought I had seen every Veritasium video, but apparently not. Thanks for the link.
Oh sweet, that video perfectly covers the subject of this topic. I wonder how I missed that one... I thought I had seen every Veritasium video, but apparently not. Thanks for the link.
It's crazy to me that for any length of time, kilogram was defined as "something that weighs the same as this block of metal" I mean, I understand there wasn't really a better way and it was very...
It's crazy to me that for any length of time, kilogram was defined as "something that weighs the same as this block of metal" I mean, I understand there wasn't really a better way and it was very well kept and protected, but it just seems like such an unstable system. I guess that's why we're getting the new definition.
But that block of metal was originally defined as being the weight of one litre of water at 0° at one atmosphere of pressure. It wasn't totally arbitrary (even though it kind of was).
kilogram was defined as "something that weighs the same as this block of metal"
But that block of metal was originally defined as being the weight of one litre of water at 0° at one atmosphere of pressure. It wasn't totally arbitrary (even though it kind of was).
My favourite line from a previous article about this was that, by definition, if a technician broke a piece off Le Grand K everything in the world would immediately become proportionately heavier....
My favourite line from a previous article about this was that, by definition, if a technician broke a piece off Le Grand K everything in the world would immediately become proportionately heavier.
I've been following this story with a general scientific interest for the better part of a decade, but that really brought home to me the meaning of the word 'definitive'!
Well the most important part of that is having many identical blocks made so they could be distributed, then it kind of makes sense. It's just a block so you have something to compare.
Well the most important part of that is having many identical blocks made so they could be distributed, then it kind of makes sense. It's just a block so you have something to compare.
The history of the french revolution and standardized everything is very interesting. This was just one of many standards to come out. They got a lot wrong, but the stuff that stuck really moved...
The history of the french revolution and standardized everything is very interesting. This was just one of many standards to come out. They got a lot wrong, but the stuff that stuck really moved the world forward. I believe there were thousands of weights and measures used in France alone before standardized measures.
Forced the rest of the world to follow suit and made the industrial revolution a possibility with the tools that could be precisely produced.
Still not sure about the calendar they tried to introduce though.
The most wrong thing of everyday level is that kilogram is, unlike other units, suddenly kilo. Kilo is a thousand of something, not the basic unit. That's confusing. We got used to kilogram, but...
The most wrong thing of everyday level is that kilogram is, unlike other units, suddenly kilo. Kilo is a thousand of something, not the basic unit. That's confusing. We got used to kilogram, but this is still sometimes weird.
But the measurement they've devised depends on gravity. The article even says that a kilogram is a measure of weight instead of mass. Does anyone have the formal definition?
But the measurement they've devised depends on gravity. The article even says that a kilogram is a measure of weight instead of mass. Does anyone have the formal definition?
From the Wikipedia article on the redefinitions: "The kilogram, symbol kg, is the SI unit of mass. It is defined by taking the fixed numerical value of the Planck constant h to be 6.62607015×10−34...
"The kilogram, symbol kg, is the SI unit of mass. It is defined by taking the fixed numerical value of the Planck constant h to be 6.62607015×10−34 when expressed in the unit J⋅s, which is equal to kg⋅m2⋅s−1, where the metre and the second are defined in terms of c and ΔνCs"
This redefines the kilogram to a constant relationship of metres and seconds, which are tied to fundamental constants of the speed of light in a vacuum, and vibration frequency of the caesium 133 atom.
EDIT: What's also interesting is that this redefinition of the kilogram is part of a sweeping set of redefinitions of all SI base units. Very cool stuff.
Just FYI, you can use <sup>#</sup> to get superscipt, and <sub>#</sub> to get subscript, for more legible scientific/mathematical notation here on Tildes. E.g....
Just FYI, you can use <sup>#</sup> to get superscipt, and <sub>#</sub> to get subscript, for more legible scientific/mathematical notation here on Tildes. E.g.
The kilogram, symbol kg, is the SI unit of mass. It is defined by taking the fixed numerical value of the Planck constant h to be 6.62607015×10−34 when expressed in the unit J⋅s, which is equal to kg⋅m2⋅s−1, where the metre and the second are defined in terms of c and ΔνCs
One thing that i've never understood is the kilogram is a base unit. Why can't gram be the base unit like everything else? Kilometer and Kiloliter are both derived, but kilogram isn't?
One thing that i've never understood is the kilogram is a base unit. Why can't gram be the base unit like everything else? Kilometer and Kiloliter are both derived, but kilogram isn't?
I think Veritasium has a video on that, Here's an answer from physics SE: https://physics.stackexchange.com/questions/64562/why-metric-system-uses-kilogram-as-a-basic-si-unit
I think Veritasium has a video on that, Here's an answer from physics SE:
The reason why "kilogram" is the name of a base unit of the SI is an artefact of history.
Louis XVI charged a group of savants to develop a new system of measurement. Their work laid the foundation for the "decimal metric system", which has evolved into the modern SI. The original idea of the king's commission (which included such notables as Lavoisier) was to create a unit of mass that would be known as the "grave". By definition it would be the mass of a litre of water at the ice point (i.e. essentially 1 kg). The definition was to be embodied in an artefact mass standard.
After the Revolution, the new Republican government took over the idea of the metric system but made some significant changes. For example, since many mass measurements of the time concerned masses much smaller than the kilogram, they decided that the unit of mass should be the "gramme". However, since a one-gramme standard would have been difficult to use as well as to establish, they also decided that the new definition should be embodied in a one-kilogramme artefact. This artefact became known as the "kilogram of the archives". By 1875 the unit of mass had been redefined as the "kilogram", embodied by a new artefact whose mass was essentially the same as the kilogram of the archives.
The decision of the Republican government may have been politically motivated; after all, these were the same people who condemned Lavoisier to the guillotine. In any case, we are now stuck with the infelicity of a base unit whose name has a "prefix".
The MKS (meter-kilogram-second) and CGS (centimeter-gram-second) are the two main metric unit systems and both involve prefixes on one unit or another. If you're talking about objects on the order...
The MKS (meter-kilogram-second) and CGS (centimeter-gram-second) are the two main metric unit systems and both involve prefixes on one unit or another.
If you're talking about objects on the order of meters (e.g. people), then kilograms make more sense than grams, but if you're talking about objects on the order of centimeters, then grams make more sense (e.g. 1 cm3 of water is 1 gram). There aren't too many times where meters and grams are both the right order of magnitude simultaneously.
It might seem bizarre that they're redefining a unit of mass using electric current, but the image they provide is really helpful.
Fascinating to think that we're still living in an era where our way to measure the universe is being adjusted.
I loved that they included that too. I actually heard this on the radio first and couldn't quite understand it until I saw the image.
People reading this article might also be interested in this previous post: What defines a kilogram? Before standardization, units of measurement were often manipulated by tyrants to cheat peasants and steal land.
And for even more additional information:
Derek from Veritasium did a video many years ago covering how the kilogram was historically defined, as well as literally got a chance to "get his hands on" the Avogadro project's €1M "world's roundest object" made from a single crystal of Silicon 28 atoms, which was one of the proposed alternatives to this newly adopted Kibble (Watt) balance system for re-standardizing the kilogram.
And Brady from Objectivity did a video a few years ago where he actually got to handle some of the Royal Society's old standard weights and measures objects from the 19th Century, including a solid Platinum Troy pound.
Veritasium also has another video describing how the Kibble balance is used to measure the Planck constant.
Oh sweet, that video perfectly covers the subject of this topic. I wonder how I missed that one... I thought I had seen every Veritasium video, but apparently not. Thanks for the link.
It's crazy to me that for any length of time, kilogram was defined as "something that weighs the same as this block of metal" I mean, I understand there wasn't really a better way and it was very well kept and protected, but it just seems like such an unstable system. I guess that's why we're getting the new definition.
But that block of metal was originally defined as being the weight of one litre of water at 0° at one atmosphere of pressure. It wasn't totally arbitrary (even though it kind of was).
From 1889 to 1960 the fundamental unit of length, the metre, was defined as the length of a particular block of metal sitting in France.
My favourite line from a previous article about this was that, by definition, if a technician broke a piece off Le Grand K everything in the world would immediately become proportionately heavier.
I've been following this story with a general scientific interest for the better part of a decade, but that really brought home to me the meaning of the word 'definitive'!
Well the most important part of that is having many identical blocks made so they could be distributed, then it kind of makes sense. It's just a block so you have something to compare.
I know I would be! (Love that series, thanks!)
The history of the french revolution and standardized everything is very interesting. This was just one of many standards to come out. They got a lot wrong, but the stuff that stuck really moved the world forward. I believe there were thousands of weights and measures used in France alone before standardized measures.
Forced the rest of the world to follow suit and made the industrial revolution a possibility with the tools that could be precisely produced.
Still not sure about the calendar they tried to introduce though.
The most wrong thing of everyday level is that kilogram is, unlike other units, suddenly kilo. Kilo is a thousand of something, not the basic unit. That's confusing. We got used to kilogram, but this is still sometimes weird.
Its weird but it causes no harm really, or at least not enough to be worth changing.
But the measurement they've devised depends on gravity. The article even says that a kilogram is a measure of weight instead of mass. Does anyone have the formal definition?
From the Wikipedia article on the redefinitions:
"The kilogram, symbol kg, is the SI unit of mass. It is defined by taking the fixed numerical value of the Planck constant h to be 6.62607015×10−34 when expressed in the unit J⋅s, which is equal to kg⋅m2⋅s−1, where the metre and the second are defined in terms of c and ΔνCs"
This redefines the kilogram to a constant relationship of metres and seconds, which are tied to fundamental constants of the speed of light in a vacuum, and vibration frequency of the caesium 133 atom.
EDIT: What's also interesting is that this redefinition of the kilogram is part of a sweeping set of redefinitions of all SI base units. Very cool stuff.
Just FYI, you can use
<sup>#</sup>to get superscipt, and<sub>#</sub>to get subscript, for more legible scientific/mathematical notation here on Tildes. E.g.https://docs.tildes.net/text-formatting#superscript-and-subscript
Thanks! I was just lazy with a copy-paste and didn't fix the formatting like I should have ;)
Finally! The question of how to relate the fundamental unit of mass to universal constants was a debate back when I was in high school.
One thing that i've never understood is the kilogram is a base unit. Why can't gram be the base unit like everything else? Kilometer and Kiloliter are both derived, but kilogram isn't?
I think Veritasium has a video on that, Here's an answer from physics SE:
https://physics.stackexchange.com/questions/64562/why-metric-system-uses-kilogram-as-a-basic-si-unit
The MKS (meter-kilogram-second) and CGS (centimeter-gram-second) are the two main metric unit systems and both involve prefixes on one unit or another.
If you're talking about objects on the order of meters (e.g. people), then kilograms make more sense than grams, but if you're talking about objects on the order of centimeters, then grams make more sense (e.g. 1 cm3 of water is 1 gram). There aren't too many times where meters and grams are both the right order of magnitude simultaneously.