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The planet Earth can sometimes be referred to as terra firma, macrocosm, globe, big blue marble and terrestrial sphere. It is believed that life only exists on Earth since no other planet has the right environment to sup... More »

www.reference.com Science Astronomy Planets

Venus is the planet that is closest to Earth. Venus is about 23.6 million miles away from Earth when it's at its closest, though it can be as far as 162 million miles away. More »

www.reference.com Science Astronomy Planets

A lot of "Earth-like" planets are out there, but not all of them necessarily have landscapes that are identical or similar to Earth's. For example, Mars has been described as "Earth-like" thanks to its rocky surface, des... More »

www.reference.com Science Astronomy Space Travel
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Ptolemy’s theory of the solar system placed the Earth at the center with each planet on an orbit around it and the stars on a celestial sphere. Ptolemy believed that astronomical elements existed in circular, rotating mo... More »

www.reference.com Science Astronomy Planets

From Earth, the planet Saturn looks like a tannish-beige colored sphere famously girdled by rings substantial enough to be seen through a small telescope. Its apparent magnitude of between +1.47 to ?0.24 makes Saturn a f... More »

www.reference.com Science Astronomy Planets

The person who discovered that the Earth is a planet, and not the center of the universe, is the Polish mathematician and astronomer Nicolaus Copernicus. He created the heliocentric view of the solar system, which is the... More »

www.reference.com Science Astronomy Planets

Earth formed around 4.54 billion years ago and is the third planet from the Sun. It is the fifth largest planet in the solar system and the largest of the terrestrial planets. It is also the densest of all the planets. More »

www.reference.com Science Astronomy Planets