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1. How do scientists know the age of the earth?

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1. How do scientists know the age of the earth?

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This is a question that is often asked and here is a broken down version of the answer...

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Approximately 4.5 billion years ago a planet covered in hot molten rock and no atmosphere. This ball of flaming rock has now developed into the gorgeous planet we live on now.

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3. What scientist use to determine the age of Earth

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3. What scientist use to determine the age of Earth

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If there is one thing we have a surplus amount of on earth, it's rocks. And these rocks are the tool to figuring out the age of our planet.

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Radiometric dating is when the scientist take what they think is the oldest rock they can find and break down the rock and figure out what it is made up of. They can then tell by the makeup of the rock how old it is.

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http://www.smithsonianmag.com/smart-news/how-do-we-know-earth-46-billion-years-old-180951483/
https://www.youtube.com/watch?v=YSau4HTNjkE
http://www.mineralminers.com/html/zircon-crystals.stm
http://news.nationalgeographic.com/news/2014/02/140224-oldest-crust-australia-zircon-science/

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This mineral is especially important. It takes  lot longer to weather so after everything else is broken down you are left with these minerals. Since they last longer and are older than other rocks, these minerals is are key to figuring out the age of rocks.

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Zircon has small traces of uranium which is very similar to zirconium (the main element in zircon). So similar that in some cases the uranium will replace the zirconium. The uranium will eventually decay into lead. So the more lead in these rocks, the older they are.

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There is a rock (the oldest rock that can be found on earth) in Australia that has been said to be 4.5 billion years old, and even though this is rock-solid (no pun intended)  evidence that the earth is at least  4.5 billion years old, we still don't know the definite age.

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The reason we will never have a definite age of our planet is because rocks on earth recycle themselves and when they are melted down and then made a rock again they lose all the data that was stored inside.