The kilogram has been reinvented! Scientists formally change the measurement based on a piece of metal to a calculation based on the speed of light
- Since 1889, Le Grand K has been stored in France under safe lock and key
- It is the determining mass against which all other kilos are measured
- Definition of kilograms formally changed from today after the vote in November 2018
- From now on it will be measured by the ratio of energy to frequency of the photon
The official definition of a kilogram has changed today – just six months after scientists voted for a whole new interpretation.
Previously, Le Grand K – a piece of metal – was the defining object with which all other odometer measurements were made and completely dependent on.
Scientists have sought a way to replace it sustainably in the unfortunate event that it was destroyed.
Stored under secure lock and key in France since it was made in 1889, the carefully calibrated aluminum cylinder is now retired.
It has served as the global standard for weighing things for 130 years, with dozens of copies stored around the world to standardize the weights of individual countries.
Now scientists are measuring the kilogram via the crumbling balance.
Based on Planck's constant constant, this instrument follows small changes in electrical current to calculate the gravity acting on a mass – the two components of the weight.
Le Grand K (right) is an alloy cylinder that has been used to standardize kilos for more than a century and that has been kept safe and locked in Paris since it was made in 1889. The weight is stored under two clock pots (center) to stop it from catching dust and dirt
WHAT IS LE GRAND K?
Le Grande K is the determining mass against which all other kilos are measured.
It is a carefully calibrated aluminum cylinder that has been kept under lock and key in France since it was made in 1889.
Dozens of copies have been created and stored around the world to standardize the weights of individual countries.
Le Grande K is stored in the Louis XIV Pavillon de Breteuil, a building that also houses the International Bureau for Weights and Measures.
The weight is so precious that it is only removed once every forty years to make copies for other countries.
& # 39; One of the main reasons for doing this work is to provide international security, & # 39; Ian Robinson, head of engineering measurement at the NPL, told the Luxembourg magazine Delano.
& # 39; If the Pavillon de Breteuil burned down tomorrow and the kilogram had melted in its vaults, we would no longer have a reference for the world's metric weight system.
& # 39; There would be chaos. After all, the current definition of the kilogram is the weight of that cylinder in Paris. & # 39;
The Kibble balance calculates the weight with small changes in an electric current.
It measures the electrical current required to produce an electromagnetic force that is equal to gravity acting on a mass.
Scientists have been working for decades on the development of a new global weight standard. The device, known as a lump balance, measures small changes in electrical current to calculate the gravity acting on a mass – the two components of the weight
HOW WOULD A KIBBLE BALANCE CONSTANT THE PLANCK?
A Kibble balance would redefine the kilogram by giving scientists the most accurate measurement of the Planck constant so far.
It consists of a wire coil in a magnetic field that is suspended from the balance.
A kilogram mass is also placed on this arm that exerts a downward force by gravity.
An electric current is passed through the coil and generates a force, the strength of which depends on the magnitude of the current, the strength of the field and the length of the coil.
The value of current is varied until the downward force of the kilomass is compensated by the force of the coil in the magnetic field.
The mass is then removed and the coil is moved in the field, which induces a voltage in the coil.
By following the current and voltage, the Planck constant can be measured in terms of mass, length and time.
This precise flow measurement is used to produce the most accurate calculation of the Planck constant, which is then used to define a kilogram.
The Planck constant – one of nature's fundamental constants – can be combined with certain properties of light and Einstein's # 39; s e = mc2 to give the new kilo.
If you use these machines as an international standard, you do not need to keep Le Grand K and its copies under strict security.
& # 39; We are going to develop a method to accurately weigh the kilogram to the end of time & # 39 ;, Robinson said.
& # 39; We will have freed ourselves from a single point of failure. & # 39;
Later this month, delegates at the international General Conference on Weights and Measures held in France are expected to vote to retire Le Grande K.
Le Grande K is kept under lock and key in the Louis XIV Pavillon de Breteuil (photo)
The Louis XIV Pavillon de Breteuil in Paris houses the International Bureau for Weights and Measures
The Kibble balance is expected to replace it, allowing the kilo to be added to a wide range of modernized standard measurements.
The meter, once standardized with an alloy rod stored in Paris, is defined as the distance traveled by a light particle in 1 / 299,792,458 second since 1983.
For more than a century, the second decades were measured as 1 / 86,400 of an average day.
Because the rotation of the earth is variable, the unit is now updated as the time it takes a cesium atom to vibrate exactly 9,192,631,770 times.
HOW CAN THE PLANCK CONSTANT REDEFINE THE KILO?
The Planck constant is a fundamental constant in nature that sets a limit to the accuracy with which we can measure physical systems.
It depends on the SI units of length, mass and time: the meter, kilogram and second, respectively.
The second and meter are already defined by universal constants.
The meter, once standardized with an alloy rod stored in Paris, is now defined as the distance traveled by a light particle in 1 / 299,792,458 of a second.
The second is defined as the time it takes for a cesium atom to vibrate exactly 9,192,631,770 times.
Because we already have precise measurements for the second and meter, these can be used in combination with a fixed value of the Planck constant to redefine the kilogram.
This would eliminate the need for Le Grand K, also known as the international prototype Kilogram.
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