Libra: A 1 kg Mass of Precision

Introduction

The kilogram (kg), the base unit of mass in the International System of Units (SI), has been defined by a physical artifact since 1889. This artifact, known as the International Prototype Kilogram (IPK), is a cylinder of platinum-iridium alloy that is stored at the International Bureau of Weights and Measures (BIPM) in Paris, France. However, the IPK has been losing mass at a rate of about 50 micrograms per year, which has led to concerns about its long-term stability.

In response to these concerns, the BIPM has been working on developing a new definition of the kilogram that is based on a fundamental constant of nature. In 2018, the BIPM proposed a new definition of the kilogram based on the Planck constant, which is a fundamental constant that relates the energy of a photon to its frequency. This new definition was adopted by the General Conference on Weights and Measures (CGPM) in 2019, and it will take effect on May 20, 2024.

The New Definition of the Kilogram

The new definition of the kilogram is based on the following equation:

1 kg = (6.62607015 × 10^-34) J s

where:

• J is the joule, the SI unit of energy
• s is the second, the SI unit of time

This equation defines the kilogram as the mass of a body that has a kinetic energy of 1 joule when it is moving at a speed of 1 meter per second.

The Advantages of the New Definition

The new definition of the kilogram has several advantages over the old definition:

• It is based on a fundamental constant of nature, which means that it is not subject to change over time.
• It is more accurate than the old definition, which was based on a physical artifact that could lose mass over time.
• It is more reproducible, which means that it can be easily replicated in different laboratories around the world.

The Applications of the New Definition

The new definition of the kilogram will have a wide range of applications, including:

• Metrology: The new definition will provide a more accurate and reliable way to measure mass. This will be important for a variety of applications, including scientific research, manufacturing, and trade.
• Science: The new definition will enable scientists to make more precise measurements of the mass of atoms and molecules. This will be important for a variety of fields, including chemistry, physics, and biology.
• Industry: The new definition will provide a more accurate and reliable way to measure the mass of products. This will be important for a variety of industries, including food, pharmaceuticals, and manufacturing.

Conclusion

The new definition of the kilogram is a major breakthrough in metrology. It is based on a fundamental constant of nature, it is more accurate than the old definition, and it is more reproducible. The new definition will have a wide range of applications, including metrology, science, and industry.

Tables

Table 1: Comparison of the Old and New Definitions of the Kilogram

Table 2: Applications of the New Definition of the Kilogram

Table 3: Timeline for the Implementation of the New Definition of the Kilogram

Table 4: Tips and Tricks for Using the New Definition of the Kilogram

• Use a balance that is calibrated to the new definition.
• Make sure that the balance is level and stable.
• Place the object to be weighed in the center of the balance pan.
• Read the mass display carefully.

Thoughts for the Audience

The new definition of the kilogram is a significant change, but it is also an important step forward. The new definition will provide a more accurate and reliable way to measure mass, which will benefit a wide range of applications.

If you have any questions about the new definition of the kilogram, please feel free to contact your local weights and measures authority.