Jean Picard

Jean -Felix Picard ( born July 21, 1620 La Flèche; † July 12, 1682 in Paris) was a priest and astronomer.

Picard certain 1669 first the length of a degree of a meridian arc - and thus the size of the earth - with a high accuracy (see also degree measurement). To this end, he surveyed with a telescope from different locations the distance of a star to the zenith. The results were published posthumously in 1684. These measurements used Isaac Newton to verify his theory of gravity.

Picard led the thread micrometer as an astronomical instrument. When he with a mercury barometer in 1675 examined the air pressure at different heights, he watched the barometer glow discharges ( cf. Geissler tube). However, Static electricity was not yet known.

Picard was also the founder of the first astronomical yearbook ( Connaissance des temps, 1679 ). It was founded in 1665 professor at the Collège de France.

The lunar crater Picard is named after him.