During the Gjøa and Discovery expeditions (1901–1906), weak geomagnetic signatures were observed simultaneously with visual polar cap auroras.  Main types are transpolar arcs, poleward-moving substorm arcs, and Sun-aligned arcs.  The first two are infrequent, while the last one occurs often. They appear like the regular magnetic solar Sq variation.  It is suggested that they are embedded in polar rain and dependent on the density and energy of photoelectrons.

Karl Terzaghi reached out to Laurits Bjerrum in 1954, impressed by his paper on Norwegian quick clays' stability. At 36, Bjerrum, already a PhD and NGI director, emphasised practical research integration, influenced by centres like Imperial College London. He advocated for soil mechanics in civil engineering education and founded its chair in 1960. Bjerrum left a lasting legacy, earning international acclaim for his NGI work and collaborations with geotechnicians like Terzaghi and Casagrande.

The explanation of thunder and lightning in encyclopedias from ancient times to Wikipedia is described and discussed.

In December 2021, the agonic line crossed the Royal Observatory of Madrid on its westward drift. The previous crossing by the agonic line, drifting eastward, is not accurately dated because declination measurements of that time are scarce. After collecting the data obtained in the Iberian Peninsula over the last 500 years and reducing them to ROM coordinates, a geomagnetic declination curve was generated. As a result, the previous cross ing been the agonic line was dated around the year 1652.

The DC-powered service of the Berlin suburban railways disturbed the observations in Potsdam and Seddin. A suitable location for the establishment of a new observatory was found near the small town of Niemegk. The "Adolf-Schmidt-Observatorium für Erdmagnetismus Niemegk" was officially opened on 23 July 1930, Adolf Schmidt’s 70^th.  The observations started on 1 January 1932. The Niemegk measurement series spans 92 years, only interrupted at the end of World War II.

This article collects and analyzes reports of auroras published in the Extremadura newspaper from 1923 to 2017. We identified 31 news items describing these events, including major auroras in 1926, 1938, 1957, and 1991. This research highlights the value of newspapers in reconstructing past solar activity.