Earth is the third planet in the solar system. Earth orbits the sun at a distance of roughly 93 million miles and is the only known planet capable of supporting life. More »

Earth is considered to be the "third rock from the sun." That phrasing is used because Earth is the third planet from the sun, as well as being a terrestrial (rocky) planet. More »

Mercury, which is the closest planet to the Sun, is 36 million miles from the sun, and Neptune, the eighth planet from the Sun, is approximately 2,790,000,000 miles away. The rest of the planets fall in between that rang... More »

Humans, animals and plants on Earth need the sun because it provides most of the energy required to survive in this solar system. Earth would be a very cold and lifeless planet if it did not get its light and heat from t... More »

Copernicus’ heliocentric model shows how an observer on Earth orbiting the sun would see a planet with a longer orbital period appear to move backward and then forward again. Ptolemy’s model, with the Earth at the center... More »

In the year 1515, Nicolaus Copernicus theorized that the Earth was a planet and discovered the idea of a heliocentric solar system, a system in which all planets revolved around the sun. He built his own observatory in 1... More »

Venus is the second planet from the sun in our solar system, with a size and mass similar to that of Earth. It's easy to identify in the night sky because it's the second-brightest object after the moon. It's named after... More »