Clair Patterson: The man who calculated the Earth’s age

For a long time, sacred scriptures were the main sources of authority on the origins of the Earth and the universe. All religions have developed their own mythologies to explain the origins of everything, including the planet on which we live. In general, everything exists because at some point a god or goddess wanted it that way. As a generic explanation, it does its job, but a problem arises when we want more specificity. For example, when was the Earth formed? According to the account in Genesis, God created it in one week, so the universe, the Earth and life were all formed with very little time in between. Based on the Old Testament and the biblical patriarchs’ ages, archbishop and Trinity College Dublin professor James Ussher (1581-1656), ruled that the Earth was formed in the year 4004 BCE, on the evening of October 23 to be precise. Other authors, including astronomer Johannes Kepler (1571-1630), had previously attempted similar calculations but got different results.

However, many findings seemed to contradict the idea that the Earth was only about 6,000 years old. The appearance of extinct fauna remains, like dinosaurs, in strata without the remains of humans and present-day animals seems to indicate a large temporal separation. If man had coexisted with dinosaurs, we would find representations in rock art, or in tools made from dinosaur remains, but that has never happened, which seems to contradict the account that life and the universe were created several days apart. Thus, accurately estimating the age of the Earth remained a major scientific challenge.

Clair Patterson (1922-1995) was the son of a post office employee who was born in a small town in Iowa. His mother was very interested in education; when he was a child, she gave him a chemistry set that awakened his vocation. In 1944, he graduated from the University of Chicago with a degree in chemistry and worked on the Manhattan Project, which built the atomic bomb. After the war, he began his doctoral studies, which focused on measuring the presence of lead isotopes in meteorites. There are chemical elements that take various forms, depending on the number of neutrons in the nucleus. Some of these isotopes may be unstable and decay over time. Therefore, measuring the composition of different isotopes can give us an idea of a sample’s age. This is the logic behind the carbon-14 analysis used to date historical samples. Because the amount of carbon-14 in the original sample will have halved 14,000 years, it can be used to date the sample. Geological studies use more stable isotopes that have half-life spans of millions of years. This method is known as radiometric dating.

Using isotope analysis could probably give us an accurate measure of the age of the Earth. But it also poses a problem. Geological phenomena on Earth such as plate tectonics, hydrothermal events, erosion and human activity itself may have interfered with the planet’s original isotopic composition. Thus, the Earth has erased traces of its origins. But all was not lost. Most models of the origin of the solar system indicated that we were the result of the condensation of matter from a disk of dust and gas called a protosolar nebula. That means that all planets are the same age. Interestingly enough, it wasn’t just planets that were formed in that process, but also asteroids—such as those in the belt between Mars and Jupiter—and smaller matter that sometimes falls to Earth in the form of meteorites. According to this model, meteorites are like time capsules that date back to the birth of the solar system. If that theory were true, measuring different meteorites’ lead isotopes should yield similar radiodatations, which would indicate the age of the solar system. Thanks to Clair Patterson’s brilliant intuition, today we know that the Earth is approximately 4.5 billion years old. Judeo-Christian accounts of the world’s creation in a week are quite the understatement.

J. M. Mulet is a professor of biotechnology.

Sign up for our weekly newsletter to get more English-language news coverage from EL PAÍS USA Edition