4 A SPECIAL PLACE Earth is the third planet from the sun and one of eight planets in our solar system Earth orbits or travels around the sun at an average distance of about 93 million miles 150 kilometers Earth appears bright blue and white when viewed from outer space Earth is a special planet It is the only planet in the uni verse known to support life Life is possible on Earth thanks to the oxygen in its air and water on its surface A satellite flying 435 miles 700 km over Earth captured this beau tiful image of our unique planet
5 Earthʼs average temperature can change How might rising average temperatures affect humans THINK ABOUT IT Earth’s atmosphere also is the perfect temperature for life averaging about 59 F 15 C It is not too hot like Venus or too cold like Neptune But Earth is always changing due to its many cycles and systems Understand ing how these cycles and systems work is important because human activities conti nue to affect the plan et’s surface oceans and atmosphere A photograph taken at night shows the lights of the populated areas of Taiwan and mainland China
6 EARTH’S AMAZING FEATURES Earth is the fifth largest planet in the solar system Scientists have figured out that Earth’s mass is about 5,972,000,000,000,000,000,000 tons Land covers about 30 per cent of Earth’s surface Seven large continents make up Earth’s landmass They are Africa Antarc tica Asia Australia Europe North America and South America Asia is the largest continent and Austra lia is the smallest Water covers about 70 per cent of the planet’s surface The This sheet of ice and snow is known as a glacier Most of Earthʼs surface is covered with water or ice
7 THINK ABOUT IT Which continent do you live on and what is the closest ocean to you four major water bodies on Earth are the Arctic Atlantic Pa cific and Indian oceans They surround the continents Some of the water on Earth is frozen For example there are large ice sheets in the Arctic and Antarctic regions The layer of gases surround ing Earth is the atmosphere This is the air that living things need to breathe Earth’s atmosphere reaches up to several hundred miles above the surface Other planets also have atmospheres Unlike Earth though most other planets atmospheres cannot sup port life These Alaskan mountains are part of the landmass that makes up the North American continent
