After sealing in a vault under the previous pleasing pallet of the god among the sycamore forests to the west of Paris, there is an apple size that puts pressure on the world.
Having formed against the background of a scientific and political assault following the French Revolution, a small cylinder of platinum-irritium alloy has mostly fought for almost 130 years as the world benchmark for exactly what, is a kilogram.
The international prototype of the kilogram, or "Le Grand K" as it is said to be a tender, is one of the most recognized discoveries of science, analogous against which all other pounds are compared to the total metric system and # 39; n fits with the period of freedom, equality and brotherhood.
It is definitely, in fact, that only four times since 1889 was weighed only and the room that is not home can only be opened in Pavilion de Breteuil when it is three live living holders – who for security reasons have to be of a different nationality – turn the lock at the same time.
And yet it will soon be out of office.
Hundreds of scientists from around the world will collect this week as a Opulence of Versailles Palace for the 26th General Conference on Value and Value.
Here, in fact, achieve much of the metric system organizational pledge of "For all ages, for all", they will replace the Grand K with a general formula that defines the kilogram using the nature of Natur laws.
"The kilogram is the last measurement unit based on a physical object," said Thomas Grenon, director of the French National Metropolitan and Testing Laboratory.
"The problem is that he had a life, it could vary. That's not good enough, given the level of detail we need today."
What's in a second?
With the adoption of the metric system, scientists at the end of the 18th century needed a structure that expressed distance, time, electrical processes and mass in similar, transferable measurement units.
They define a meter as it's naturally ten million running the quadrant of the Earth through Paris.
"We're now looking back and saying that the process was really good, we would not do it very different today," said Martin Milton, director of the BIPM, the international guardian of our measurement systems.
The meter was used in turn to define mass: however, this is the kilogram of the name that a tuber of a cubic dimimer (10cm x 10cm x 10cm) would be water.
But science has moved on since days and the revolution.
A meter has now been defined by how lightly it travels in vacuum during a fraction of a second.
The second itself was expressed in relation to Rotation of Earth. But since the 1960's, it has been officially the time it takes us cesium-133 to wrap 9,192,631,770 times – not a smaller revolution.
Instead of connecting to the mass of an individual physical object, the kilogram will be defined in the future in the consistent terms of Planck -the quantum energy ratio of a frequency of light can be carried to that same frequency, or 6.626 x 10-34 seconds joule.
Energy is mostly linked to mass, as Einstein has shown to the equation E = mc2.
The constant Planck can be used, together with two quantum phenomena that allow electrical power generation, to calculate mass based on the corresponding mechanical power needed to erase it.
"If you're pushing a mass, the power you need depends on that mass. And you can install that power on electrical power provided by our utmost consistency," said Milton at AFP.
The providers of this approach say that at least one million times will be more stable than physical artefacts and will have a range of practical applications in the future.
"For many applications, one kilogram is very big," said Milton.
Developments in pharmaceutical and chemical products mean that moderate ingredients in medicines are increasingly measured to the microgram, and they are becoming more precise.
"One kilogram is good for potatoes where you do not need a great degree of accuracy, but this is not the right weight for a number of applications in difficult science and industry. The new system is incredibly gradual."
States coming together & # 39;
Scientists will also use the Versailles summit to change the definition of ampere (electrical current), kelvin (temperature) and mole (atoms), expressed through general Nature laws.
Milton said that the decision was a way of ensuring that the world would always agree on what exactly it is a kilogram, a bag of sugar, a liter of water or a precise ratio.
"We are in a world where people are concerned that the campaign towards the prevalence of antagonism is potentially reversible. But here, in measuring science, we are told to all agree," he said.
As for Le Grand K, it may have been more than its utility as a perfect kilogram, but its contribution to science is far from a distance.
"He will stay here in the cottage in the conditions he had in 1889," said Milton.
"In fact it's a long-term experiment because we will weigh in the decades to come and see how it responds to the conditions. It's still an object of interest to science. "
Four base units of measurement in the metric system are about to be changed