Survey of the Sciences
Writing Assignment # 1
Date Assigned: 6/25/13
Due Date: 7/2/13
The age old question, scientifically, of “how old is the earth?” goes back to late 18th- century. At the time most scientists either sided with Creationism or supposed as James Hutton theorized in Theory of the Earth (1795) “We find no vestige of a beginning, no prospect of an end”.
In 1862 physicist William Thomson, who would later be ennobled as Lord Kelvin, determined through the Laws of Thermodynamics that the earth had formed sometime between 20 and 400 million years ago. He, like most physicists of the day, believed that the earth was originally molten. Over time the surface cooled and solidified, but the core remained in a molten state. To determine the earth’s age Lord Kelvin theorized that a calculation of the time it would take the molten earth to cool to its present state is all that would be required. He figured that most all of the heat that had formed the earth had been generated by gravitational contraction. Using the second law of thermodynamics Lord Kelvin knew that the earth’s heat had steadily cooled, its heat radiating out into the cold vacuum of space. Then, using Jean-Baptiste-Joseph Fourier’s theory of heat conduction he predicted the age of the earth to be between 20 to 400 million years old.
Lord Kelvin’s theory startled and distressed geologists whose own research suggested earth’s age to be vastly older. Geologists believed that successive strata of rock and soil in a given area represented the order in which they had formed, and that if two layers from different sites contained the fossil materials that they could be considered to be of the equivalent geological age. Geologists then began to chronicle the strata, using these finds to make crude guesses