how old is our planet? – Hafnium Zone

Question: how old is our planet?
- Keywords:
  earth,
  solar system,
  universe
Asked by RoRo to Susan on 19 Jun 2015.
- Susan Cartwright answered on 19 Jun 2015:
  
  4.6 billion years. This is worked out using radioactive elements. I’ve answered a question very like this in more detail; it should come up under “related questions”.

jtracy commented on 19 Jun 2015:

How do we know that? (question from the class) 🙂

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Question: how old is our planet?