The number of years Earth has existed, resulting in a subject of controversy. Creationists and many fundamental religious sects believe that Earth’s age is only several thousand years, while orthodox science puts the age at about 5 billion years. Establishing the age of Earth has always been marked by tension between the scientific and religious communities. Whether or not a divine force lies behind the historical event of Earth’s creation fuels the debate and helps determine whether study of Earths age falls within the realm of science or pseudoscience.
The central figure who believed in a youthful Earth was Archbishop Ussher. In the 17th century, he carefully worked out from the Old Testament (with computations where the text was uncertain) that the Earth was formed in 4004 B.C.E., establishing a precise date and time for the event. Sir Charles LYELL, the geologist, changed this date. He could not see how the fossil record of life could possibly fit into such a timespan. In the 1890s, Lord Kelvin (1824-1907), the eminent physicist, applied the best science of his day to the problem. He reasoned that the Earth, initially a body of molten material, would cool according to the laws of thermodynamics, and calculated that it would take between 20 and 400 million years to reach its present temperature not a precise estimate, but more acceptable to uniformitarians like Lyell and much longer than several thousand years. In reasoning thus, Kelvin assumed that no internal heat was being added to the cooling mass. Soon afterwards, it was discovered that radioactive material had been decaying throughout the Earth’s existence, generating heat and thereby invalidating Kelvins calculations, making his estimate too low.