How Do Creationists Calculate Earth’s Age, and Why Can’t They Agree?

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Oct. 12 2012 2:33 PM

Is the Earth 6,000 Years Old, 9,000 Years Old, or 13,000 Years Old?

How biblical literalists get their numbers.

A print by Albrecht Durer titled Adam and Eve (The Fall of Man).
A print of Albrecht Durer's "Adam and Eve (The Fall of Man)"

Photo by Rafa Rivas/AFP/Getty Images.

Rep. Paul Broun, R-Ga., called evolution “lies from the pit of hell” in a speech last month and argued that the Earth is 9,000 years old. Scientists have determined the Earth’s age is 4.5 billion years, based on evidence from meteorites and molecular decay rates. How do biblical literalists come up with their estimates?

Using Greek history. The Bible provides plenty of internal chronological information. Adam lived 930 years, and his son Seth 912 years. The Israelites lived in Egypt for 430 years “to the very day.” Saul reigned as king of Israel for 42 years. Summing up the dates is tedious, but it’s doable. The real challenge is that the Bible is a “floating chronology:” It doesn’t date the beginning or ending of its story. Irishman James Ussher, the 17th-century archbishop of Armagh, famously solved this puzzle by comparing events in the Bible with histories from other civilizations. Most critically, Ussher found a reference to the death of Babylonian king Nebuchadnezzar in the Second Book of Kings. Ussher then used Ptolemy’s history of Babylonian kings, combined with Greek historical events of known dates, to pinpoint the death of Nebuchadnezzar in 562 B.C. Adding together the generations of Old Testament begetting and the reigns of kings, Usher surmised that 3,442 years passed between the creation and Nebuchadnezzar’s death. Ussher thereby arrived at his now famous estimate for the Earth’s creation: 4,004 B.C. He eventually went one step further, marking the Earth’s birthday as 6 p.m. on Saturday, Oct. 22, 4004 B.C.

Many biblical chronologists have come up with roughly similar estimates. Second-century St. Theophilus of Antioch guessed 5529 B.C. In his 1583 work De emendatione temporum, Frenchman Joseph Juste Scaliger put the creation in 3949 B.C. There are, however, occasional outliers. American doomsday evangelist Harold Camping believes that time began in 11013 B.C.

Most of these variations result from differences in Old Testament interpretation. For example, one of Ussher’s greatest dilemmas was choosing which text to follow. The Greek Septuagint version suggested that 2,242 years elapsed between the dawn of time and the biblical flood. Ussher rejected that estimate because, if it were accurate, Armageddon should already have occurred. (Seventeenth-century theologians thought the earth would end after 6,000 years.) The Samaritan Pentateuch suggested 1,307 years between the creation and the flood, but Ussher eventually went with the traditional Hebrew text’s 1,656-year-estimate. Harold Camping’s methodology in arriving at a vastly different date is perplexing. He added together the lifespans of Old Testament fathers and sons, assuming that their lives didn’t overlap.

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It’s not clear how Rep. Broun settled on 9,000 years, but Ussher’s creation date of 4004 B.C. is by far the most cited. It was, and possibly remains, the most meticulous Bible-based calculation ever attempted. Ussher’s estimate for the death of Nebuchadnezzar is still the authoritative date. Perhaps more importantly, Ussher’s research yielded an auspicious number. Theologians and astronomers of his day estimated that Christ was born in the year 4 B.C., based on the mention of a lunar eclipse in the work of first-century historian Josephus. Ussher’s creation calculations thus suggested that precisely 4,000 years passed between the creation and the birth of the Christian messiah. The 1960 film Inherit the Wind also cemented Ussher’s place in the American imagination. In the movie, Matthew Harrison Brady insists on the witness stand that Ussher’s estimate is “literal fact.” When the crowd turns on him, Brady is reduced to hysterics, turning to his wife and memorably declaring, “They’re laughing at me, mother. I can’t stand it when they laugh at me!”

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Brian Palmer writes about science, medicine, and the environment for Slate and Earthwire. Email him at explainerbrian@gmail.com. Follow him on Twitter.