This book is a popular science book written in the late 1600s. It is written as a series of conversations between a gallant philosopher and a countess, while walking in her garden and gazing at the stars. The philosopher explains the heliocentric (sun as the centre) model of the solar system and also muses on the possibility of extraterrestrial life. While it explains the heliocentric model, unlike other astronomy works of the time, it did not attract the attention of the Church. (Summary by TriciaG, modified from Wikipedia)