Rambam’s Kiddush Hachodesh

Compare the Sun and Moon through true conjunctions, solar cycles, traditional measures and daily sky progression.

The first topic in Rambam’s Kiddush Hachodesh explores the length of the lunar and solar year, with conjunctions, sky positions, and day and night shown together.

Compare successive lunar conjunctions with measured solar periods and the traditional molad, Rav Adda and Shmuel reckonings.

Jewish Cosmology is an interactive research and educational web application connecting Hebrew dates, traditional Jewish calendar calculations and halachic concepts of time with the observable motions of the Sun, Moon and planets, astronomical seasons and eclipses.

JavaScript is required for the interactive explorers and calculations. The descriptions and navigation remain available without JavaScript.