Nicolaas Hartsoeker (26 March 1656 – 10 December 1725) was a Dutch mathematician and physicist who invented the screw-barrel simple microscope .
Biography
thumb|Principes de physique, 1696
He was the son of Anna van der Meij and Christiaan Hartsoeker (1626–1683), a Remonstrant minister in Moordrecht near Gouda. His father took the family to Alkmaar in 1661 and finally to Rotterdam in 1669. Nicolaas started to make a living as a lens maker in Rotterdam, and was instructed in optics by Antonie van Leeuwenhoek. In 1674, he and a fellow student, assisted by Van Leeuwenhoek, were the first to observe semen, a situation that would later lead to a priority dispute between Hartsoeker and Leeuwenhoek over the discovery of spermatozoids.
In 1677, Hartsoeker met Christiaan Huygens and initiated him in the making of lenses. In June 1678, Hartsoeker accompanied, in the role of an assistant, Huygens on a trip to Paris, where they made a great impression with their microscopes. However, Huygens failed to mention Hartsoeker even once in a subsequent publication in France, leading to a fall-out between the two.
Hartsoeker returned to Rotterdam, where his parents still lived and where he married Elisabeth Vettekeucken in October 1680. His business as an instrument maker and wine merchant failed and, after the death of his father in August 1683, he moved his family in 1684 to Paris, where he made instruments for the Paris observatory and the academy. Hartsoeker also came up with contrivances for aiming very large aerial telescopes originally popularized by Huygens. He remained there until 1698. The 1694 "Essay on dioptrics", in which this hypothesis appears, was a highly lauded book, in fact tackling several misconceptions of the time. For example, Hartsoeker disavows the contemporary position (e.g. of Robert Hooke) that with refractor telescopes one soon would be able to see man-sized creatures on the Moon, if any in fact existed.