Conversations on the Plurality of Worlds in France and elsewhere, and was regularly published. In 1691, Fontenelle was elected to the Académie française. Conversations on the Plurality of Worlds Conversations on the Plurality of Worlds () is a popular science book by French author Bernard le Bovier de Fontenelle, published in 1686. It offered an explanation of the heliocentric model of the Universe, suggested by Nicolaus Copernicus in his 1543 work "De revolutionibus orbium coelestium". The book is Fontenelle's most famous work and is considered to be one of the first major works of the Age of Enlightenment. Unlike many scientific works of its time, "Conversations
Age of the Earth it would take for the near-surface to cool to its present temperature. His calculations did not account for heat produced via radioactive decay (a process then unknown to science) or, more significantly, convection inside the Earth, which allows more heat to escape from the interior to warm rocks near the surface. Even more constraining were Kelvin's estimates of the age of the Sun, which were based on estimates of its thermal output and a theory that the Sun obtains its energy from gravitational collapse; Kelvin estimated that the Sun is about 20 million years old. Geologists such as Charles Lyell