1618 in science

Astronomy

• March 8 – May 15 – Johannes Kepler formulates the third law of planetary motion.
• July 21 – Pluto reaches an aphelion. It also came to aphelion in 1866.
• Johann Baptist Cysat, Swiss Jesuit geometer and astronomer and one of Christoph Scheiner's pupils, becomes the first to study a comet through the telescope and gives the first description of the nucleus and coma of a comet.
• September 6–25 – The Great Comet of 1618 is visible to the naked eye.

  Biology

• Fortunio Liceti's De spontaneo Viventium Ortu supports the theory of spontaneous generation of organisms.

  Medicine

• The College of Physicians of London publishes the Pharmacopœia Londinensis.

  Births

• April 2 – Francesco Maria Grimaldi, Italian physicist, discoverer of the diffraction of light
• Jeremiah Horrocks, English astronomer

  Deaths

• June 6 – Sir James Lancaster, English navigator
• October 29 – Walter Ralegh, English explorer
• Luca Valerio, Italian mathematician