Many authors choose to present the history of a complex subject by breaking it up into major threads and following the history of each thread separately.
These were long on armchair speculation and short on substantive supporting evidence.Ussher accepted the Biblical account at face value, relying on the Biblical genealogies and on extant historical records.He implicitly assumed that the world was created much as it is now.There were various attempts to estimate the Earth's age, working back from sedimentation rates and other geophysical phenomena.The attempts produced estimates from about 100 million years up to several billion years. The first is that the geological history was still being reconstructed.The great debate was won by the uniformitarians, so much so that the degree of gradualism was overstated and the importance of catastrophes was unduly minimized.The modern period has been marked by an enormous expansion of the detailed knowledge of the geological history of the Earth and the processes that have acted during that history.Descartes, however, attempted to discern a physical history of the Earth.His account was plausible by the immature standards of the Science of his times; however it quite definitely did not match the Biblical account of a completed creation in six days.Notable observations included: ran from about 1780-1850.By the end of the 18'th century it was clear that the Earth had a long and varied history. The major debate was between the catastrophists, e.g., Cuvier, who held that the history of Earth was dominated by major catastrophic revolutions and the uniformitarians, e.g.In the 1700's belief in a 6000 year old Earth crumbled.Attempts to calculate the age of the Earth from physical considerations yielded estimates that ranged from 75,000 years (Buffon, 1774) to several billion years (de Maillet, Buffon).It was not ruled out, per se, but it was not necessary. In the new science, however, rational explanation was desirable. In 1640 Ussher produced his famous calculation that the Earth was created in 4004 BC.