Scientists have long known that Earth's core is mostly made of iron, but the density is not high enough for it to be pure iron, meaning lighter elements exist in the core, as well. In particular, it's ...

But Why is a show led by kids. They ask the questions and we find the answers. It’s a big interesting world out there. On But Why, we tackle topics large and small, about nature, words, even the end ...

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Terms apply to American Express benefits and offers. Visit americanexpress.com to learn more. Choosing a rewards credit card can be overwhelming. You don't just have to consider the reward structures, ...

Earth's core is mostly made of the metals iron and nickel, but it also contains lighter elements like hydrogen, oxygen and silicon. CharlesC via Wikimedia Commons under CC-BY-3.0 How Earth got its ...