Planet Earth Help

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By — McGraw-Hill Professional
Updated on Aug 30, 2011

Introduction to Planet Earth

From space, our world looks like a brilliant blue marble. Sometimes called the “blue planet,” the Earth is over 70% water and is unique in our solar system. Clouds, fires, hurricanes, tornadoes, and other natural characters may change the Earth’s face at times, but in our solar system, this world is the only one capable of life as we know it.

Native peoples, completely dependent on Mother Earth for everything in their lives, worshipped the Earth as a nurturing goddess that provided for all their needs. From the soil, came plants and growing things that provided clothing and food. From the rivers and seas, came fish and shellfish for food, trade articles, and tools. From the air, came rain, snow, and wind to grow crops and alter the seasons. The Earth was never stagnant or dull, but always provided for those in her care. Ancient people thought Mother Earth worked together with Father Sun to provide for those who honored her.

Today, astronauts orbit the Earth in spaceships and scientific laboratories, 465 km above the Earth, marvel at the Earth’s beauty, and work toward her care. Former astronaut Alan Bean communicates this beauty by painting from experience and imagination. Astronaut Tom Jones publishes books for young and old of his space experiences. Other NASA astronauts, scientists, engineers, and test pilots have communicated their wonder and appreciation for our fragile world through environmental efforts that address earth science issues. The study of geology includes many areas of global concern.

Geology is the study of the Earth, its origin, development, composition, structure, and history.

But how did it all start? What of the Earth’s earliest beginnings? Many scientists believe the Sun was formed from an enormous rotating cloud of dust and gases pulled by gravity toward an ever denser center of mass. The constant rotation flattened things out and allowed debris (some the size of oranges and others the size of North America) to form planets, the Moon, and comets.

The larger pieces of matter in this debris field had enough gravity to grab up smaller cosmic chunks, glob them together, and allow them to grow larger. When the gathering debris got to be over 350 km across, it was slowly shaped into a sphere by gravity. Figure 1-1 illustrates the steps this formation might have taken.

Planet Earth

Fig. 1-1. Gravity shaped space debris into a sphere depending on weight and size.

Other scientists think that everything came about in one gigantic explosion, the Big Bang. Everything was pretty much developed and just simply spiraled out to take the places that we know today. In fact, some astronomers believe that the Universe is expanding. They think all the galaxies are getting further and further apart to almost unimaginable distances. Seems like it would be tough to study something that is moving further away from you all the time!

For the study of Earth Science, though, that is not a problem. The entire planet is a laboratory and provides a lot of great samples.

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