illions of lucky people in Africa and Asia had the opportunity to witness an unusual celestial event on January 15 2010 Using special dark glasses pinhole cameras and other devices so that they would not be blinded by the Sun they saw a rare annular solar eclipse This kind of eclipse takes place when the Sun is clos est to Earth and the Moon is farthest away so the Moon does not completely cover the Sun This means that at the peak phase of the eclipse the rim of the Sun is visible all around the disk of the Moon The peak phase of the January 15 eclipse lasted 11 minutes and 8 sec onds Such a duration for an annular solar eclipse will not be exceeded until the year 3043 The subject of eclipses is just one of the many fascinating topics you will learn more about in this volume Early Egyptians and Chinese used their eyes to study the annual patterns of the sky carefully enough to make accurate calendars During the 2nd century AD the Egyptian astronomer Ptolemy formulated his geocen tric Earth centered model of the universe now known as the Ptolemaic system It was not until the 1500s that the Polish astrono mer Nicolaus Copernicus determined that OIO
INTROpUCTION A IN Observers watch the January 15 2010 annular solar eclipse at the central stadium in Thiruvananthapuram Kerala South India Eyes WideOpen Getty Images
AsTRONOMY UNDERSTANDING THE UNIVERSE Ptolemy's notion that the Sun revolves around Earth was invalid instead he con cluded that Earth and the other planets actually orbit around the Sun But there was no way to prove Copernicus idea until the invention of the telescope This revolutionary new piece of technology allowed Italian astronomer Galileo Galilei in the early 1600s to carefully record the move ment of different heavenly bodies including four moons which he observed revolving around Jupiter Galileo's findings paved the way for the confirmation of Copernicus theory Over time telescopes have been get ting larger and more powerful Now there are even telescopes in space NASA s Kepler space telescope recently revealed a rocky planet named Kepler 1ob that astronomers believe to be the smallest planet ever discov ered outside our solar system In the 20th century scientists deepened their understanding not only of astronomy but also cosmology the study of the universe and its laws Along with technology scien tists use mathematics and physics to make discoveries Albert Einstein revolutionized cosmology in 1905 with his special theory of relativity which stated that space and time
INTRODUCTION could be seen as parts of a deeper structure space time and that mass and energy are really the same thing Scientists later devel oped the big bang theory According to this theory the universe started some 13 billion years ago with a sudden expansion of mat ter and antimatter Many scientific tests have confirmed the validity of this theory In this book you will learn about impor tant advances that astronomers have made through time But you will also learn that astronomy is one of the few sciences in which amateurs can play a significant role You do not need your own Kepler telescope or a Ph D in physics to make a significant con tribution With the proper tools including knowledge and a sharp eye even an amateur can make an important discovery In 1995 two amateur astronomers Alan Hale and Thomas Bopp working independently of each other spotted a comet beyond the orbit of Jupiter Comet Hale Bopp as it came to be known reached perihelion the closest distance to the Sun on April 1 1997 without ever coming very close to Earth It was however spec tacularly visible to the naked eye and became perhaps the most widely witnessed comet of the 20th
