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Earth and the moon.
- Article from:
- The Handy Astronomy Answer Book
- Article date:
- January 1, 2008
- Author:
CopyrightCOPYRIGHT 2008 Visible Ink Press. This material is published under license from the publisher through the Gale Group, Farmington Hills, Michigan. All inquiries regarding rights should be directed to the Gale Group. (Hide copyright information)
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EARTH
What is Earth?
Earth is the third planet in the solar system, orbiting at a distance of about 93 million miles (150 million kilometers) from the Sun. It is the largest and most massive of the terrestrial planets. Its interior structure consists of a metallic core, which has both a liquid and solid compenent; a thick rocky mantle; and a thin rocky crust.
How was Earth first measured?
The study of the size and shape of Earth is called geodesy. People have studied geodesy for millennia. As early as 2,000 years ago, the Greek-Egyptian astronomer and mathematician Eratosthenes used the shadow of the Sun to compute that Earth was a ...