Fields that changed the world: the story of the Avogadro project

You can answer the question “What is the most accurate thing in the world?” in different ways, and the choice of answer depends on the level of knowledge in science. For those who don’t know much about physics, the natural reaction might be something like, “How did you even measure roundness?”

Those who understand science a little better may remember how molten metal, falling from a height into water, creates perfect spheres. This method was used for the mass production of bullets and is one of the procedures most famous examples creation of round objects on Earth.

But for serious science geeks, there is only one correct answer: the silicon fields of the International Avogadro Project.

Silicon balls

Around the world, in countries such as Australia, the USA, Germany, Japan and others, there are seven areas that are very smart. These unique, almost perfect forms were created by an international community of scientists and government agencies with one goal – to change the world at a fundamental level.

Although the script for the next big step seems to be, the International Avogadro Project, which has brought together researchers from all over the world since the early 1990s, is completely real. They were the ones who commissioned the creation of these areas, which were carried out at the Australian Scientific and Industrial Research Organization (CSIRO) with incredible precision.

How much are these areas? National Institute of Standards and Technology ( NIST ), one of the project’s partners, noting that their surfaces are so flat that if they were expanded to the size of the Earth, the difference between the highest mountain and the deepest ocean only 3-5 meters.

Devices called optical interferometers were used to measure the diameter of the spheres with nanometer precision. Each scope costs approximately $3.2 million and was handcrafted by a leading lens maker.

However, the question arises: why is all this necessary?

This is not a kilogram

The Avogadro project aims to use idealized silicon spheres to accurately determine the value of Avogadro’s constant, a fundamental physical quantity. Hence the desire to use Avogadro’s constant to redefine the kilogram.

Initially, in the 18th century, units of measurement in the metric system were based on natural objects: the meter was defined as one ten millionth of the distance from the North Pole to the equator, the liter as the measure -fill 1/1000 cubic. a meter of water at the melting point of ice, and the kilogram as a mass of this volume of water in a vacuum.

To reinforce these definitions, the French Academy of Sciences created physical objects in 1799 to represent these units: a platinum rod exactly one meter long and a cylinder weighing exactly one kilogram – the “Big K” to the called ( The K ).

Over time, these units became popular around the world, and in 1875, 17 countries signed the Metric Convention, which established the General Conference on Weights and Measures. Measurements. A laboratory was established at Sèvres, near Paris, which became the home of the international standards for the meter and the kilogram, and copies were sent to all signatories to the metric system. distribution and coordination.

However, the system based on physical objects had its disadvantages. For example, in 1989, the mass of reference kilograms began to differ – the difference reached 50 micrograms. This showed that physical objects are not a reliable basis for accurate measurements.

How to create a kilogram

In 2005, the International Committee on Weights and Measures proposed to redefine the kilogram based on a universal constant. The most likely candidate was Planck’s constant. However, other methods were proposed, such as using Avogadro’s constant, which required the creation of an object from a precisely known substance.

In the end, the silicon spheres created by the project gave far more accurate data than the C. Even if these spheres were lost or damaged, this would not affect the definition of a kilogram, as it would not have to be defined by a physical object, but by a concept.

Although the kilogram was finally redefined based on Planck’s constant, other indicators of nature can also be used to verify the accuracy of this definition.

At the very least, the project produced extremely smooth and round balls, which is a great achievement in itself.