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How Do We Know Something Has Changed Over Time?

The Earth is like a big, old tree. We can count its rings to see how old it is. Scientists use rocks and fossils, like clues in the ground, to figure out when things happened long ago.

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Examples

  1. A tree grows rings every year, and we count them to know how old it is. Scientists use rocks like zircon crystals to do the same thing, but over billions of years.
  2. Fossils in layers of rock are like clues left by ancient animals. If a fossil is buried deeper, it might be older than one closer to the surface.
  3. Some rocks have tiny clocks inside them that tick for millions of years, scientists can read those clocks to figure out how old the Earth is.

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Categories: History · geology,fossils,age of the earth