How we measure the world underwent a quantum leap on Monday as scientists adopted new hyper-accurate definitions for units of weight, electricity and temperature derived from the universal laws of Nature.&nbsp;

The change, on the occasion of World Metrology Day, sees one of science's most influential objects -- a metal cylinder used to define what a kilogram is -- retired in favour of an infinitely more precise measurement taken from a quantum ratio.&nbsp;

"Le Grand K", as the platinum-iridium object is known, stood as the world's benchmark of the kilogram for nearly 130 years before a decision was taken in November to bring several units of measurement into the 21st century.&nbsp;

"The kilogram is the last unit of measurement based on a physical object," Thomas Grenon, director of France's National Laboratory of Metrology and Testing, said after the decision last year.&nbsp;

"The problem is that it's had a life, it could fluctuate. That's not good enough, given the level of precision we need today."&nbsp;

Instead of relating to the mass of a singular physical object, the kilogram will now be defined in terms of the Planck constant -- the ratio of a frequency of light, on the one hand, to the quantum energy of that frequency, on the other.&nbsp;

Put another way, &nbsp;it is 6.626 x 10-34 joule seconds.&nbsp;

Energy is intrinsically linked to mass, as Einstein demonstrated with his equation E = mc squared.&nbsp;

The Planck constant, combined with two quantum phenomena that allow for the creation of electrical power, can be used to calculate mass based on the equivalent mechanical power needed to displace it.&nbsp;

Proponents of this approach say it will be at least one million times more stable than physical artefacts and will have a range of practical applications, from pharmaceutical measurements to scientific research.&nbsp;

Monday also saw new definitions adopted for the ampere -- the rate of electrical current flow; the kelvin -- the base unit of temperature; and the mole -- the unit measuring the amount of a given substance.&nbsp;

While changing how we define fundamental units might sound like a weighty affair, the BIPM, the Paris-based international custodian of measurement systems, said much care had been taken to ensure the shift will have "no perceptible impact on daily life."&nbsp;

"Few users outside national metrology laboratories will notice the changes," it said.

How we measure the world underwent a quantum leap on Monday as scientists adopted new hyper-accurate definitions for units of weight, electricity and temperature derived from the universal laws of Nature.

How we measure the world underwent a quantum leap on Monday as scientists adopted new hyper-accurate definitions for units of weight, electricity and temperature derived from the universal laws of Nature. The change, on the occasion of World Metrology Day, sees one of science's most influential objects -- a metal cylinder used to define what a kilogram is -- retired in favour of an infinitely more precise measurement taken from a quantum ratio. "Le Grand K", as the platinum-iridium object is known, stood as the world's benchmark of the kilogram for nearly 130 years before a decision was taken in November to bring several units of measurement into the 21st century. "The kilogram is the last unit of measurement based on a physical object," Thomas Grenon, director of France's National Laboratory of Metrology and Testing, said after the decision last year. "The problem is that it's had a life, it could fluctuate. That's not good enough, given the level of precision we need today." Instead of relating to the mass of a singular physical object, the kilogram will now be defined in terms of the Planck constant -- the ratio of a frequency of light, on the one hand, to the quantum energy of that frequency, on the other. Put another way, it is 6.626 x 10-34 joule seconds. Energy is intrinsically linked to mass, as Einstein demonstrated with his equation E = mc squared. The Planck constant, combined with two quantum phenomena that allow for the creation of electrical power, can be used to calculate mass based on the equivalent mechanical power needed to displace it. Proponents of this approach say it will be at least one million times more stable than physical artefacts and will have a range of practical applications, from pharmaceutical measurements to scientific research. Monday also saw new definitions adopted for the ampere -- the rate of electrical current flow; the kelvin -- the base unit of temperature; and the mole -- the unit measuring the amount of a given substance. While changing how we define fundamental units might sound like a weighty affair, the BIPM, the Paris-based international custodian of measurement systems, said much care had been taken to ensure the shift will have "no perceptible impact on daily life." "Few users outside national metrology laboratories will notice the changes," it said.

Mass movement: Scientists adopt new kilogram definition

It may not change how you buy bananas, but scientists have voted to redefine the value of a kilogram, in what they called a landmark decision that will boost the accuracy of scientific measurements.

Since 1889, a kilogram has been defined by a shiny lump of platinum-iridium kept in a special glass case and known as the International Prototype of the Kilogram. It is housed at the headquarters of the International Bureau of Weights and Measures (whose French acronym is BIPM), just outside Paris.

Members of the BIPM, which groups some 60 nations, agreed on Friday after a week-long meeting at the nearby Palace of Versailles to redefine a kilogram in terms of a tiny but unchanging value called the "Planck constant".

They also voted to update definitions for the ampere (electrical current), the kelvin (thermodynamic temperature) and the mole (amount of a substance).

All modern mass measurements are derived from the kilogram, whether micrograms of pharmaceutical medicine or gold dust, kilos of fruit or fish, or tonnes of steel.

The problem is the prototype doesn't always weigh the same. Even inside its three glass bell jars it picks up microparticles of dirt and is affected by the atmosphere. Sometimes it needs cleaning, which can affect its mass.

That can have profound implications. If the prototype were to lose mass, atoms would in theory weigh more since the base kilogram must by definition always weigh a kilogram.

Scientists have been trying for decades to define a constant value for the kilogram that is derived from immutable physics, in the same way they have done for other standard units (SI units) overseen by the BIPM.

For example, a metre isn't 100 centimetres, it's actually "the length of the path travelled by light in a vacuum during a time interval of 1/299,792,458 of a second".

The "Planck constant", which derives from quantum physics, can be used along with a Kibble balance, an exquisitely accurate weighing machine, to calculate the mass of an object using a precisely measured electromagnetic force.

"The SI redefinition is a landmark moment in scientific progress," said Martin Milton, director of the BIPM.

"Using the fundamental constants we observe in nature as a foundation for important concepts such as mass and time means that we have a stable foundation from which to advance our scientific understanding, develop new technologies and address some of society's greatest challenges."

Barry Inglis, who heads the committee for weights and measures, said the implications were immense.

"We will now no longer be bound by the limitations of objects in our measurement of the world, but have universally accessible units that can pave the way to even greater accuracy, and even accelerate scientific advancement," he said.

It is arguably the most significant redefinition of an SI unit since the second was recalculated in 1967, a decision that helped ease communication across the world via technologies like GPS and the internet.

The new definitions agreed by the BIPM will come into force on May 20, 2019. 
&nbsp;

It may not change how you buy bananas, but scientists have voted to redefine the value of a kilogram, in what they called a landmark decision that will boost the accuracy of scientific measurements.

It may not change how you buy bananas, but scientists have voted to redefine the value of a kilogram, in what they called a landmark decision that will boost the accuracy of scientific measurements. Since 1889, a kilogram has been defined by a shiny lump of platinum-iridium kept in a special glass case and known as the International Prototype of the Kilogram. It is housed at the headquarters of the International Bureau of Weights and Measures (whose French acronym is BIPM), just outside Paris. Members of the BIPM, which groups some 60 nations, agreed on Friday after a week-long meeting at the nearby Palace of Versailles to redefine a kilogram in terms of a tiny but unchanging value called the "Planck constant". They also voted to update definitions for the ampere (electrical current), the kelvin (thermodynamic temperature) and the mole (amount of a substance). All modern mass measurements are derived from the kilogram, whether micrograms of pharmaceutical medicine or gold dust, kilos of fruit or fish, or tonnes of steel. The problem is the prototype doesn't always weigh the same. Even inside its three glass bell jars it picks up microparticles of dirt and is affected by the atmosphere. Sometimes it needs cleaning, which can affect its mass. That can have profound implications. If the prototype were to lose mass, atoms would in theory weigh more since the base kilogram must by definition always weigh a kilogram. Scientists have been trying for decades to define a constant value for the kilogram that is derived from immutable physics, in the same way they have done for other standard units (SI units) overseen by the BIPM. For example, a metre isn't 100 centimetres, it's actually "the length of the path travelled by light in a vacuum during a time interval of 1/299,792,458 of a second". The "Planck constant", which derives from quantum physics, can be used along with a Kibble balance, an exquisitely accurate weighing machine, to calculate the mass of an object using a precisely measured electromagnetic force. "The SI redefinition is a landmark moment in scientific progress," said Martin Milton, director of the BIPM. "Using the fundamental constants we observe in nature as a foundation for important concepts such as mass and time means that we have a stable foundation from which to advance our scientific understanding, develop new technologies and address some of society's greatest challenges." Barry Inglis, who heads the committee for weights and measures, said the implications were immense. "We will now no longer be bound by the limitations of objects in our measurement of the world, but have universally accessible units that can pave the way to even greater accuracy, and even accelerate scientific advancement," he said. It is arguably the most significant redefinition of an SI unit since the second was recalculated in 1967, a decision that helped ease communication across the world via technologies like GPS and the internet. The new definitions agreed by the BIPM will come into force on May 20, 2019.

How much does a kilogram weigh? Depends on your 'Planck constant'

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