How Old Is The Earth, and How Did It Start?

A deeper look into the Earth’s beginnings and how scientists radiometrically date rocks

Compared to the age of the Earth, a year is only about a second in regard to the human lifespan. The age of Earth is over 62 million times the average person’s lifespan and 181 million generations would have spanned if you had ancestors since the Earth’s beginning. In other words, a family member from the beginning of Earth would be your great, great, great… (181 million more greats), great grandparent (1). Scientists have worked hard to determine the age and origin of the Earth.

To calculate the age of the Earth, scientists researched four-billion-year old rocks. Scientists discovered the age of these rocks through radiometric dating (1). Radiometric dating is when scientists collect stones and examine the elements they are composed of to find their age. Radioactive elements inside rocks begin to decompose from one element into another over long periods of time. For example, the element rubidium slowly decays into strontium. Because the decay rate of an element, known as the element’s half-life, is always the same, scientists can compare the amount of rubidium to the amount of strontium in the rock and determine the rock’s age. For example, Rubidium would take 48.8 billion years to become 50 percent strontium. The oldest rocks have been found in Canada and Australia, dating back to as far as 4.3 billion years ago (2). 

Scientists believe the entire solar system began around the same time, which means the Earth is around the same age as the moon and the meteorites floating around in space (1). Rocks from the moon have been brought back to Earth, analyzed, and found to be around 4.5 billion years old. The meteorites that landed on Earth have also been radiometrically dated and were found to be formed around the same time as the rocks from the moon. This allowed scientists to form an idea of when the Earth was created: around 4.5 billion years ago (2). 

Scientists don’t know exactly how the Earth and the Solar System began, but they hypothesize that a star exploded and pulled a massive amount of dust together while making it spin. This spinning dust created various gases which eventually formed the sun. The rest of this dust spun around the sun and formed into clusters which grew into planets and dwarf planets (3). 

When the Earth was created, it didn’t look exactly like it does now. The Earth was very rocky and covered in magma (3). Over time, the Earth cooled and solidified. Asteroids filled with water crashed into the Earth, giving it water. During the next few billion years, a massive piece of land called Pangea formed. Magma from volcanoes started to crack and separate this piece of land. Eventually, Pangea split into the current seven continents there are now (4).

It was a long process for Earth to become what it is today. 4.5 billion years is incredibly long ago, and it’s remarkable that the explosion of a single star created the world society inhabits today (3). 

An example of a rock decaying into a new element over time

Pangea with today’s countries labeled


  1. National Geographic Society. (n.d.). Age of earth collection. Retrieved October 9, 2022, from   
  2. U.S. Department of the Interior. (n.d.). Radiometric age dating. National Parks Service. Retrieved October 9, 2022, from  
  3. National Geographic Society. (2022, June 2). Formation of earth.  Retrieved October 9, 2022, from  
  4. U.S. Geological Survey. (n.d.). What was Pangea? Retrieved October 9, 2022, from  
  5. The Smithsonian Institution’s Human Origins Program. (2021, January 22). Homo sapiens. Retrieved October 9, 2022, from   


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