How Old is the Earth?

Planet Earth.

The Earth is the third planet from the Sun, rotating about its axis about 365.25 times in one orbit around the sun. it is the only known object in the universe that can support life. The gravity of the earth interacts with objects in the solar system including the sun and the moon. The Earth might have been formed over 4 billion years ago, based on the evidence obtained from radiometric age-dating of the meteorite. Thus, the age of the Earth is approximately one-third of the age of the universe. The accretion of the Earth may have begun soon after calcium-aluminum-rich inclusion was formed. Since the formation of Earth, several geological changes have occurred, accompanied by the emergence of life and the process of evolution. But what exactly is the age of the Earth?

Early Calculations

Early calculations by William Thomson placed the age of the Earth to at most 400 million years old. He argued that the Earth was formed as a molten object, and estimated the period it would take for the object to cool to the present temperature. Thomson’s calculation did not consider the amount of heat released through radioactive decay and the convection inside the Earth. Further, Thomson’s estimation of the age of the sun was more constraining since he based his estimate on the sun’s thermal output. Several geologists found it difficult to accept such a short age of the earth as was estimated by Thomson. Other scientists such as Hermann Von Helmholtz and Simon Newcomb suggested that the Earth might have been formed 22 and 18 million years respectively.

Modern Geological Concept

Studies of Strata suggest that the Earth may have undergone series of changes during its existence. The rock and earth layers contain fossilized remains of the unknown creature, with some scientist interpreting a progression of the organism from one layer to another. Nicolas Steno, a 17th-century naturalist, was the first person to draw a connection between fossil remains and strata by formulating the stratigraphic concept. John Philips, a student, and nephew of William Smith calculated the age of the Earth in the 1790s to about 96 million years old by analyzing two layers of rocks from different locations. Mikhail Lomonosov, an 18th-century naturalist suggested that the Earth may have been formed before the rest of the universe. In 1779, Comte du Buffon estimated that the Earth was about 75,000 years old after creating a model of the Earth and measuring its rate of cooling. In the 19th century, several naturalists inaccurately constructed the history of the Earth since they did not know the amount of time it took to lay down the stratigraphic layer.

Radiometric Dating

The discovery of radioactivity introduced an important factor in the calculation of the age of the Earth, overthrowing the old calculations and providing a basis for new calculation. Radioactivity was pioneered by Bertram B Boltwood and Rutherford who were inspired to study the relationships between elements in various decay series. The development of radiometric dating is credited to Arthur Holmes. He was part of the committee that was appointed in 1931 by the National Research Council to investigate the age of the Earth. After series of investigations and estimations, the ancient Archaean lead ores of Galena were used to estimate the age of the Earth since they were the earliest formed lead-only minerals on Earth. They returned an age of 4.54 billion years with a margin of 1% for error. Thus, the Earth is about 4.54 +/-0.05 billion years old.


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