Galileo Galilei to the biography by Vincenzo Viviani) that these began by watching the swings of the bronze chandelier in the cathedral of Pisa, using his pulse as a timer. Later experiments are described in his "Two New Sciences". Galileo claimed that a simple pendulum is isochronous, i.e. that its swings always take the same amount of time, independently of the amplitude. In fact, this is only approximately true, as was discovered by Christiaan Huygens. Galileo also found that the square of the period varies directly with the length of the pendulum. Galileo's son, Vincenzo, sketched a clock based on his father's
Galileo Galilei references such as Psalm , , and 1 Chronicles which include text stating that "the world is firmly established, it cannot be moved." In the same manner, says, "the Lord set the earth on its foundations; it can never be moved." Further, Ecclesiastes states that "And the sun rises and sets and returns to its place." Galileo defended heliocentrism based on his astronomical observations of 1609 ("Sidereus Nuncius" 1610). In December 1613, the Grand Duchess Christina of Florence confronted one of Galileo's friends and followers, Benedetto Castelli, with biblical objections to the motion of the earth. According to Maurice Finocchiaro,