Earth is estimated to be 4.54 billion years old, plus or minus about 50 million years. Scientists have scoured the Earth searching for the oldest rocks to radiometrically date. In northwestern Canada, they discovered rocks about 4.03 billion years old. Then, in Australia, they discovered minerals about 4.3 billion years old. Researchers know that rocks are continuously recycling, due to the rock cycle, so they continued to search for data elsewhere. Since it is thought the bodies in the solar system may have formed at similar times, scientists analyzed moon rocks collected during the moon landing and even meteorites that have crash-landed on Earth. Both of these materials dated back to around 4.4 and 4.5 billion years.
Finding super old rocks is conceptually straightforward, but practically difficult. The processes of plate tectonics mean that the Earth is constantly recycling its rock, breaking it down into magma in the interior before pumping it back up to the surface once more. Scientists have made several attempts to date the planet over the past 400 years. They’ve attempted to predict the age based on changing sea levels, the time it took for Earth or the sun to cool to present temperatures and the salinity of the ocean. As the dating technology progressed, these methods proved unreliable; for instance, the rise and fall of the ocean was shown to be an ever-changing process rather than a gradually declining one.
Although the universe is thought to be about 13.77 billion years old, 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 as Earth.