He was passionate about the aurora borealis

One of the most interesting facts about Anders Celsius you should know is that he was passionate about the aurora borealis. Celsius published the Nova Methodus distantiam solis a terra determinandi in 1730 (New Method for Determining the Distance from the Earth to the Sun). His research also included the investigation of auroral phenomena, which he carried out with the assistance of his assistant, Olof Petrus. Olof Petrus was an astronomer from Sweden. Following his studies in the Netherlands, he was appointed lecturer at the University of Uppsala in 1732 to replace the vacancy left by Anders Celsius, who was then on his grand tour of European observatories. He researched the aurora phenomena and other astronomical matters with Celsius beginning in 1737.

An aurora, often known as the polar lights, is a natural light display in the sky that is most commonly seen in high-latitude regions (around the Arctic and Antarctic). It exhibits dynamic patterns of bright lights that appear as curtains, rays, spirals, or dynamic flickers that cover the entire sky. Celsius was the first to propose a link between the aurora borealis and variations in the Earth's magnetic field. He studied the variations of a compass needle and discovered that larger deflections were associated with the more auroral activity. In 1733, he published a collection of 316 observations of the aurora borealis recorded by himself and others between 1716 and 1732 in Nuremberg.