Earth is the third planet from the sun. It is the only known planet with life. The earth is the largest of the four rocky planets (Mercury, Venus, and Mars). The earth has one satellite that we call the moon. Earth is also known as Terra.
Photo: Planet earth with it’s distinctive oceans of water that supports life (Creative Commons: NASA)
Facts About the Earth
Size: radius of 6.4 thousand kilometers.
Mass: 5.97 x 1024 kilograms.
Gravity: 9.79 meters/second².
Satellites: one (moon).
Rotation: 24 hours (length of a day).
Surface Temperatures: 180-330 °K.
Surface of the Earth
The surface of the planet is covered by water (71%) and land (29%). The planet’s surface is geologically active. It experiences volcanic activity and earthquakes. The planet’s outer shell is broken into tectonic plates. Mountain systems are created by the collision of tectonic plates.
The earth has an atmosphere composed of nitrogen (78%), oxygen (21%), and other gases (1%). The atmosphere is very active and supports a wide range of climates. Climates range from the very cold to hot tropical climates.
Terra is the only planet known to support life.
Improving Your Reading and Thinking Skills
Think for a few moments. Try to recall the major ideas in this article. When you are done, click the box below for a list of main ideas.
How did you do? With practice, you should be able to identify many of the major ideas. You may even discover some important ideas that aren’t listed.
Solar System Exploration, NASA.