In 1875, representatives from 17 countries signed the Metre Convention, laying the foundation for a unified global measurement system. This agreement has been and remains crucial for the advancement of science and industry, enabling greater connectivity and fair trade between nations. It established the basis for today's International System of Units (SI). Over time, most developed countries, including Slovenia, have joined the convention.
It all began with the establishment of two new units of measurement – the meter and the kilogram. Prior to this, different systems for measuring length and mass caused confusion, making trade and scientific research more difficult.
In the 19th century, scientists developed measuring instruments that took into account the latest discoveries about physical properties. The kilogram was defined as the mass of one liter of water at the melting point of ice, and the meter as one forty-millionth of the meridian through Paris. With the signing of the Metre Convention, based on these findings, the kilogram was defined by a platinum-iridium prototype (the kilogram prototype), and the meter was defined as the length of an international prototype also made of platinum and iridium, known as the "prameter." Today, modern measuring instruments for length, such as laser meters, can perform highly accurate measurements – down to picometer precision. Length standards are now tied to the speed of light in a vacuum, enabling even more precise measurements that are crucial in science and industry. The kilogram prototype was used until 2019, when the kilogram was redefined based on natural constants.
The poster exhibition on Gallus Embankment in Ljubljana marks the 150th anniversary of the signing of the Metre Convention. It vividly illustrates the transition from the past to the present – from the first international prototypes of units of measurement to today's high-tech standards, which allow for exceptionally precise measurements. Visitors will learn about the importance of metrology throughout history and how the Metre Convention was a pivotal moment in the development of civilisation.
The exhibition, celebrating the 150th anniversary of the signing of the Metre Convention, is designed as two interconnected and complementary walks.
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The first walk (from the centre towards Šentjakob Bridge) provides an overview of basic units of measurement – from the first definitions such as the prametre and kilogram prototype, to how basic units are defined today.
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The second walk (from Šentjakob Bridge towards the centre) offers an overview of the implementation of measurement units in practice. It shows how measurement traceability for basic and derived units is ensured in Slovenia today.
