1655 in science

Astronomy

• March 25 – Titan, Saturn's largest moon, is discovered by Christiaan Huygens.

  Biology

• Botanical garden established at Uppsala University.
• Thomas Muffet's Healths Improvement, or, Rules comprising and discovering the nature, method, and manner of preparing all sorts of food used in this nation is published posthumously in England, containing, inter alia, descriptions of a wide range of wildfowl to be found in the country.

  Mathematics

• John Wallis introduces the symbol ∞ to represent infinity.

  Births

• January 6 – Jacob Bernoulli, Swiss mathematician
• September 10 – Caspar Bartholin the Younger, Danish anatomist

  Deaths

• February 1 – Giovanni Baptista Ferrari, Italian Jesuit botanist and linguist
• October 16 – Rabbi Joseph Solomon Delmedigo, Cretan-born peripatetic physician and scientist
• October 24 – Pierre Gassendi, French physicist who played a crucial role in the revival of atomism
• Francesco Pona, Veronese physician and poet