CONTENTS INTRODUCTION CHAPTER 1 PLANET EARTH CHAPTER 2 THE STRUCTURE OF EARTH 23 CHAPTER EARTH s SPHERES 38 CHAPTER 4EARTH S CYCLES 55 CHAPTER SEARTH's SATELLITE THE Moon 65 CHAPTER A PHYSICAL CHA RCTERISTICS OF THE Moon 76 88 89 CONCLUSION GoSSARY For MORE INFORMATION BIBLIOGRAPHY 94 INDEX 95
OJ ong ago Earth was the subject of great speculation Ancient astronomers such las Ptolemy thought that Earth was the center of the universe Likewise there have been all sorts of assumptions about Earth s satellite the Moon One of the most inter esting beliefs was that moonlight was capable of driving a person crazy Using a telescope Galileo Galilei went on to show that the Sun was actually the center of the universe And while some folks still believe that a full Moon brings out the weird in people they have plenty of solid evidence that proves the Moon has real natural effects on Earth For instance the gravitational pull of the Moon dur ing its many phases influences ocean tides Many additional facts about Earth and the Moon have been discovered over the years The results of years of research into the nature of Earth and the Moon are the subject of this book More is known about Earth than any other planet in the solar system mainly because scientists have had the advantage of living here Even before the advent of helpful tech nology such as the telescope and computers scientists managed to find ways to figure out certain characteristics of the planet These included its size shape and movement For instance ancient Egyptians measured
INTRODUCTION shadow length and factored in the distance between cities to obtain a rough estimate of Earth's circumference To find out about Earth s physical struc ture scientists test and observe the planet s surface layer known as the crust Using mate rial from this and the top of the next deepest layer the mantle they can work out formu las that tell them what s happening all the way down to Earth's center the core To study the atmosphere the envelope of gases surrounding Earth scientists have an array of other tech niques and tools including radar and tethered balloons that carry sophisticated instruments Manned space missions have provided scientists with plenty of information about the Moon s physical characteristics Testing of Moon rocks revealed the age and composi tion of the satellite s surface Long before the rocket age ancient astronomers used math observation and simple deduction to guess timate measurements of the Moon's size and its distance from Earth Exploration observation and experimen tation have answered many questions and dispelled many myths concerning Earth and its satellite Yet there are still many myster ies to be solved regarding this ever evolving planet and its
