Exhibit of the Month is a series initiated by the Jagiellonian University Museum with the beginning of the new academic year. Each month we will explain the Museum collection to you, choosing a single exhibit or a group of exhibits which usually are not shown to the open public. This month's feature is a coin with the portrait of Marcin Biem of Olkusz.

Marcin Biem is recognised as the first meteorologist in the history of Poland. While we have earlier weather notes left by various authors, it was this professor from the University of Krakow who first did it in a planned, systematic, and long-lasting manner in history. Marcin Biem's records of changing atmospheric conditions in Kraków and Olkusz remain an outstanding source of information.

The notes made by Biem from Olkusz were initially sporadic but became more systematic in the first half of the 16th century. Written in the margins of astronomical calendars, they reveal his astrometeorological interests. They were attempts to explain weather changes and climatic phenomena based on the positions and movements of celestial bodies, but also to verify this information through his own observations. Marcin Biem not only determined the degree of cloud cover but also, guided by subjective perceptions — we should remember that measurement instruments were not available at that time — he established the air temperature, wind speed and direction!

Marcin Biem recorded extreme phenomena, for example: "in 1538, a drought led to meadow and forest fires, but the grapevines flourished very well." He also noted daily weather changes, for example: January 15, 1529 — "snowfall and strong frost," or under the date April 1, 1529 — "dry with partial cloudiness." Thanks to this, his notes are an incredibly valuable source of information for reconstructing the climate of Europe in the 16th century.

The Copernicus Year currently celebrated in Poland is a perfect opportunity to remember the great sky researchers who worked at the University of Kraków five centuries ago. One of them, undoubtedly, was Marcin Biem of Olkusz. An image of his face can be found on the "Exhibit of the Month" medal presented in 1973 on the occasion of the 500th anniversary of Nicolaus Copernicus' birth.

Łukasz Pieróg