How Scientists Know Earth's Age
Scientists determine Earth's age using radiometric dating, a method that measures the decay of radioactive elements in rocks. When rocks form, they contain radioactive atoms that decay at a predictable rate over time. By measuring how much a radioactive element has decayed, scientists can calculate how long ago the rock formed. The most commonly used method is potassium-argon dating and uranium-lead dating.
Evidence from Meteorites
Some of the strongest evidence for Earth's age comes from meteorites that fell to Earth. These meteorites are pieces of the early solar system and formed around the same time as Earth. When scientists tested meteorites using radiometric dating, they found them to be about 4.54 billion years old. This suggests that Earth itself is approximately the same age as these ancient space rocks.
Earth's Oldest Rocks
The oldest rocks ever found on Earth are about 4.03 billion years old. These ancient rocks are found in Canada, Australia, and Greenland. They are much younger than Earth itself because the planet's surface has been constantly changing through erosion, plate tectonics, and volcanic activity. Rocks on the surface get recycled back into Earth's interior, so older rocks are destroyed over time.
Formation of Earth
Earth formed from a giant disk of dust and gas around the young sun about 4.6 billion years ago. Small particles stuck together to form larger objects, and eventually these objects collided to create Earth. The planet was extremely hot when it first formed and was bombarded by asteroids and meteorites. Over millions of years, Earth cooled down and developed the layers we see today. 
Answer