On This Day

Johannes Kepler

Astronomer Johannes Kepler

Profession: Astronomer


Biography: A key figure in the 17th century scientific revolution, Johannes Kepler discovered how planets rotated the sun, with elliptical orbits. He formulated three laws, Kepler's Laws, and published them in works such as his "Astronomia Nova" (1609), "Harmonices Mundi" (1619), and "Epitome of Copernican Astronomy" (1617-21).

Kepler was working during a time when astronomy was still closely aligned with astrology with Kepler himself providing the bridge between this world and one where astronomy came to be more associated with physics. Carl Sagan called him "the first astrophysicist and the last scientific astrologer"

Kepler initially worked more theoretically until he moved in 1600 to assist astronomer Tycho Brahe in Prague. There he was able to use Brahe's observational records to document and develop his theories.

Kepler's work went on to provide one of the foundations of Isaac Newton's theory of universal gravitation.

Born: December 27, 1571
Birthplace: Weil der Stadt, Holy Roman Empire
Star Sign: Capricorn

Died: November 15, 1630 (aged 58)

Married Life

  • 1597-04-27 Astronomer Johannes Kepler marries widow Barbara Müller
  • 1613-10-30 Astronomer Johannes Kepler marries his second wife Susanna Reuttinger

Historical Events

  • 1571-05-16 German astronomer Johannes Kepler, by his own calculations, is conceived at 4:37 AM
  • 1595-07-19 Astronomer Johannes Kepler has an epiphany and develops his theory of the geometrical basis of the universe while teaching in Graz
  • 1600-02-04 Astronomers Tycho Brahe and Johannes Kepler meet for the first time near Prague
  • 1601-10-24 Johannes Kepler succeeds Tycho Brahe as imperial mathematician to Emperor Rudolph II
  • 1618-05-15 German astronomer Johannes Kepler discovers the third of his three planetary laws his "harmonics law"
  • 1620-08-07 Astronomer Johannes Kepler's mother arrested for witchcraft

Quotes by Johannes Kepler

  • "Nature uses as little as possible of anything."

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