How Do Scientists Know How Old the Earth Is?

Scientists use a special kind of clock that’s hidden inside rocks and fossils. It’s like having a really, really slow timer, so slow it takes millions of years to tick once! They call this process radiometric dating, and it helps them know when the Earth was born.

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Examples

  1. If you had a clock that took one million years to tick once, and it had been ticking for 4.5 billion years, you'd have counted 4,500 ticks!
  2. Imagine your grandma’s old birthday cake, if each layer represents 100 million years, the Earth is like a cake with 45 layers!

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