Johannes Kepler was a German mathematician, astronomer, and astrologer. A key figure in the 17th century scientific revolution, he is best known for his laws of planetary motion, based on his works Astronomia nova, Harmonices Mundi, and Epi...

The calendar used throughout the world today is the Gregorian calendar. It is sometimes called a "Christian" calendar. The Gregorian calendar is the one commonly used today. It was proposed by Aloysius Lilius, a physician from Naples, and a...

Andreas Cellarius was a Dutch-German cartographer, best known for his Harmonia Macrocosmica of 1660, a major star atlas, published by Johannes Janssonius in Amsterdam. He was born in Neuhausen (now a part of Worms), and was educated in H...

Giovanni Domenico Cassini was an Italian mathematician, astronomer, astrologer and engineer. Cassini was born in Perinaldo, near Imperia, at that time in the County of Nice, part of the Duchy of Savoy. Cassini is known for his work in the f...

Christiaan Huygens was a prominent Dutch mathematician and scientist. He is known particularly as an astronomer, physicist, probabilist and horologist. Huygens was a leading scientist of his time. His work included early telescopic studi...

Edmond Halley, Astronomer, remembered because his name is attached to a comet. Leaving Queen's College, Oxford, without a degree in 1676, he went to St Helena to map the southern stars. After a famous meeting with Wren and Hooke, he visited...

Mikhail Lomonosov was a Russian polymath, scientist and writer, who made important contributions to literature, education, and science. Among his discoveries was the atmosphere of Venus. His spheres of science were natural science, chemistr...

Guillaume Le Gentil was a French astronomer. He discovered what are now known as the Messier objects M32, M36 and M38, as well as the nebulosity in M8, and he was the first to catalogue the dark nebula sometimes known as Le Gentil 3 (in the...

Alexander von Humboldt was a German naturalist and explorer, and the younger brother of the Prussian minister, philosopher, and linguist, Wilhelm von Humboldt (1767-1835). Humboldt's quantitative work on botanical geography was foundational...

Albert Einstein was a German-born theoretical physicist. Einstein developed the theory of relativity, one of the two pillars of modern physics (alongside quantum mechanics). Einstein's work is also known for its influence on the philosophy...

Edwin Powell Hubble was an American astronomer who played a crucial role in establishing the field of extragalactic astronomy and is generally regarded as one of the most important observational cosmologists of the 20th century. Hubble is k...

Fritz Zwicky was a Swiss astronomer. He worked most of his life at the California Institute of Technology in the United States of America, where he made many important contributions in theoretical and observational astronomy. In 1933, Zwick...

Jan Hendrik Oort was a Dutch astronomer who made significant contributions to the understanding of the Milky Way and who was a pioneer in the field of radio astronomy. His New York Times obituary called him “one of the century's foremost ex...

Clyde William Tombaugh was an American astronomer. Although he is best known for discovering the dwarf planet Pluto in 1930, the first object to be discovered in what would later be identified as the Kuiper belt, Tombaugh also discovered ma...

Wernher von Braun was a German, later American, aerospace engineer, and space architect. He was the leading figure in the development of rocket technology in Germany and the father of rocket technology and space science in the United States...