Easter falls on the first Sunday after the first full moon following the March equinox. But by the 1500s, the Julian calendar was out of sync with the solar year, making it hard to calculate the right date.

Enter the Gregorian calendar, introduced in 1582 (when Galileo was just a teenager). The Catholic Church, keen to fix the Easter date, turned to astronomers, funding observatories and research. This curiosity helped spark Galileo’s rise… and fall. 

Discover more in Galileo: Scientist, Astronomer, Visionary – a world-first interactive exhibition touring Australia from 2027.