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How old is the Earth, and how do we know?

  1. profile image47
    linkupposted 7 years ago

    How old is the Earth, and how do we know?

  2. BaliMermaid profile image55
    BaliMermaidposted 7 years ago

    Scientists feel that the earth is 4.55 billion years old but from physical evidence, such as rocks the oldest that they can derive is about 3.8 billion years old. This is because the earth was molten or semi molten for much of its early history.

    Some of these rocks are sedimentary, and include minerals which are themselves as old as 4.1 to 4.2 billion years. Rocks of this age are relatively rare, however rocks that are at least 3.5 billion years in age have been found on North America, Greenland, Australia, Africa, and Asia.

  3. internett1t3 profile image57
    internett1t3posted 7 years ago

    The clocks are naturally radioactive elements, called isotopes, such as uranium.

    Radioactive elements change spontaneously to non-radioactive elements. For example, radioactive uranium changes, or decays, to non-radioactive lead. If you start with a certain amount of radioactive uranium (100% U) it takes a certain amount of time for one half of the uranium to become lead (50% U,50% Pb). Then it takes the same amount of time for that half to become one half lead (25% U, 75% Pb), and so on. This is called the half-life, or decay constant; it never changes inside rocks.

    Different radioactive elements decay at different rates. Some radioactive isotopes have short half-lives, others have very long half-lives, such as millions or billions of years. This is where you need a fancy machine and laboratory to find out how old Earth is; it is done by actually measuring the very tiny amounts of radioactive elements and their decay products, called the parent and daughter, in rocks.

  4. profile image53
    longfelllow3983posted 4 years ago


    Radiometric dating has a lot of assumptions built into it and there is no real way to test those assumptions.

    And if man has been on the earth for as long as secular scientists claim, there would be a lot more people on the earth.