Earth is the third planet from the Sun in the solar system and the only celestial body in the universe known to harbor life. Astronomers have estimated that the Earth formed about 4.54 billion years ago, or about 60 million years after the Sun.
It's not a coincidence that the continents nearly fit into one another, like the pieces of a jigsaw puzzle. The most recent supercontinent, called Pangea, was formed about 335 million years ago and began to separate about 175 million years ago. It was centered near Earth's equator and surrounded by the superocean named Panthalassa, which occupied about 70% of Earth's surface.
Earth is made out of approximately 32.1% iron (Fe), 30.1% oxygen (O), 15.1% silicon (Si), and 13.9% magnesium (Mg).
It really takes about 365.2422 days for the Earth to complete a full orbit around the Sun. Wait a minute—doesn't that mean that, every four years or so, we'll have an entire extra day? Yes! Every four years, we add an extra day to the calendar, February 29th, and the year becomes a leap year.
Although we often think of and depict the Earth as a perfectly round globe, Earth's shape is what's known as an oblate spheroid. Because of the force caused by Earth's rotation, the equator bulges slightly outward. In fact, if you were to travel around the equator, you'd be traveling about 43 km more than if you were to travel around the Earth from pole to pole.
This leads to the strange fact that, although Mount Everest is the tallest mountain on Earth, the point furthest away from Earth's center is actually Mount Chimborazo in Ecuador. Additionally, because the force of gravity is affected by your distance from the center of the Earth, you would weigh slightly less on the equator than at one of Earth's poles.
Though we don't think of it much, land only covers less than a third of Earth's surface. This is why Earth has the nickname the "Blue Planet." About 96.5% of this water is held by Earth's oceans.
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