The year 1642 in science and technology involved some significant events.

• Rundetårn astronomical observatory for the University of Copenhagen is completed, as is also the Panzano Observatory.

• 19-year-old Blaise Pascal begins to develop the Pascaline, the first practical mechanical calculator, initially to help with the recording of taxes.^[1]

• November 24 – Abel Tasman, Dutch explorer, is the first European known to sight Tasmania, which he names Anthoonij van Diemenslandt.^[2]
• December 13 – Tasman is the first European known to sight New Zealand.

• Opening throughout of the Briare Canal in France, the first summit level canal in Europe built using pound locks.
• The printmaking process of mezzotint is developed by Ludwig von Siegen.

• March (possible date) – Seki Takakazu, Japanese mathematician (died 1708)
• December 25 (OS) – Isaac Newton, English polymath (died 1727)

• January 8 – Galileo Galilei, Italian astronomer (born 1564)