How Do Scientists Know the Age of the Earth?

Scientists use special clocks inside rocks to tell how old the Earth is. Imagine you have a big jar of candy, and every year you eat one piece. If there are 4.6 billion pieces left, that means the jar has been around for about 4.6 billion years. Scientists do something similar with rocks and minerals in the Earth. They count how many times atoms changed from one type to another over billions of years. That’s like counting the candy pieces!

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Examples

  1. A rock that has been around for billions of years is like a slow clock inside the Earth.
  2. Scientists count how many times atoms changed in rocks to know their age, just like we count candies in a jar.
  3. If you had a clock that ticked once every billion years, it would take 4.6 ticks to reach today.

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