How old is Earth?

Although the universe is thought to be about 13.77 billion years old, planet Earth is much younger than that. Current estimates put the age of Earth at around 4.54 billion years, give or take about 50 million years, and like all other bodies in the solar system, Earth formed when a cloud of dust and gas collapsed due to gravity. This means our sun, planets, asteroids and moons are also around the same age.

To determine the age of Earth scientists today use a technique called radiometric dating. Ratios of different radioactive isotopes present in samples are measured to estimate its age. There are different kinds of radiometric dating that use different isotopes, including radiocarbon, lead-lead and uranium-lead dating. This technique was developed in the early 20th century and has since then has been constantly finetuned.

Through this technique, meteorites – bits of rock that have broken off from asteroids or comets in space and fallen to Earth – can be dated. Since almost everything in our solar system formed around the same time, meteorites that reach Earth are, in all probability, the same age as our planet.

In 1956, American geochemist Clair Cameron Patterson was the first to put forward an estimated age of Earth that is closest to today’s estimates. He used samples of the Canyon Diablo meteorite that landed about 50,000 years ago in what is now the US state of Arizona, and using lead-lead dating came up with an estimated age range of 4.53 billion to 4.58 billion years.

Since then, other meteorites have also been used to find the age of Earth. They are better preserved than even the oldest rocks on Earth, which get broken down and built back up over time through the movement of plate tectonics. Therefore, measuring how old meteorites are is more reliable than measuring even Earth’s oldest rocks when predicting the age of this planet.

Finding the age of different samples from different sources will get us closer to achieving a more accurate estimate for Earth’s age. Moon rocks brought back from the USA’s Apollo program and the Soviet Union’s Luna program during the 1970s have also been dated. The ages of different samples range from 3.16 to 4.44 billion years. China’s Chang’e 5 collected the most recent sample of moon rocks from a previously unexplored area of the moon in 2020, which might help us build an even clearer picture of how old Earth really is.