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Thread: How old is the Earth?

  1. #1 How old is the Earth? 
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    Ask most people and they'll say 4.5 to 4.6 billion years* but that is the ingredients the Earth is made of. Between a supernova creating radioactive isotopes and them ending up embedded below the surface of our planet, a hundred million years or more could have passed.

    The earliest life we know about is around 3.5 billion years, so I wondered how long after planet formation it took?




    * Latest readings from "Moon rock" tungsten give it as 4.527 billion years.


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  3. #2  
    The Doctor Quantime's Avatar
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    As an estimate I'd say 6 billion. Don't know why. It just feels that old... But parts of the Earth are 4.5 billion.


    "If you wish to make an apple pie from scratch, you must first invent the universe". - Carl Sagan
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  4. #3  
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    The sun is estimated to be 4.57 billion years old (see Wikipedia article "Sun"). The earth has to be younger, so 4.5 billion seems reasonable.
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  5. #4 Re: How old is the Earth? 
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    Quote Originally Posted by Cyberia
    Ask most people and they'll say 4.5 to 4.6 billion years* but that is the ingredients the Earth is made of. Between a supernova creating radioactive isotopes and them ending up embedded below the surface of our planet, a hundred million years or more could have passed.

    The earliest life we know about is around 3.5 billion years, so I wondered how long after planet formation it took?




    * Latest readings from "Moon rock" tungsten give it as 4.527 billion years.
    The oldest radiometric dated rocks on the Earth are ~3.9 - 4 billion years old. This is how long it has been since they were molten (Not how long the original isotopes were created). This sets the lower limit for the age of the Earth's formation. It can't be any younger than this.



    The moon rocks give an older age because the Moon is more geologically stable and hasn't been recycling its crust like the Earth has.
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    The heated mind resents the chill touch & relentless scrutiny of logic"-W.E. Gladstone


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  6. #5  
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    mathman and Janus. It is believed that our solar system had a cold formation as gas giants Jupiter and Saturn would not have formed where they did, so the Sun ignited after most planet formation was completed.

    Would a temperature of maybe 1,000.C affect radioactive decay?

    Moon rocks would give an accurate reading for the Earth also, one that we cannot obtain here because as you put it, the Earth was/is not geologically stable.
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