Friedrich Wilhelm Heinrich Alexander von Humboldt (; 14 September 1769 – 6 May 1859) was a Prussian geographer, naturalist, explorer, and influential proponent of romantic philosophy. He was the younger brother of the Prussian minister, philosopher, and linguist Wilhelm von Humboldt (1767–1835). Humboldt's quantitative work on botanical geography laid the foundation for the field of biogeography. Humboldt's advocacy of long-term systematic geophysical measurement laid the foundation for modern geomagnetic and meteorological monitoring.