1618 in science

The year 1618 in science and technology involved some significant events.

• March 8 – May 15 – Johannes Kepler formulates the third law of planetary motion.
• July 21 – Pluto (not known at this time) reaches an aphelion. It next comes 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. James I described it as "Venus with a firebrand in her arse".

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

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

• April 2 – Francesco Maria Grimaldi, Italian physicist, discoverer of the diffraction of light (died 1663)
• Jeremiah Horrocks, English astronomer (died 1641)

• June 6 – Sir James Lancaster, English navigator (born 1554)
• October 29 – Walter Ralegh, English explorer (born c. 1554)
• Luca Valerio, Italian mathematician (born 1553)