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 »

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According to Encyclopædia Britannica, Earth is classified as a terrestrial planet. A terrestrial planet is rocky, in contrast to the predominantly gas planets found in the outer solar system. More »

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 »

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 »

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 »

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 »

As the only known planet that is habitable for human beings, the Earth’s importance is self-evident. Every living organism known to science obtains all of its resources from Earth, and has very few other options availabl... More »