Cosmology: Understanding the Evolution of the Universe
INTRODUCTION SIPTI Rio POI CENO RE v T 1 CV SY STEMATIS PT OLE A ST I vus TRO P C vs A DA PT HYDER NVS TROP CVS CAPR TAR C v L vs MITH Ptolemaic diagram of a geocentric system from the star atlas Harmonia Macrocosmica by the cartographer Andreas Cellarius 1660 Photos com Thinkstock
INTRODUCTION GRAPHIA MVND ANI MAICI ave you ever thought about how our universe came to be Do you sup pose that it happened all at once Do you think that it evolved over time Was there a major event that was responsible for its existence What is the age of the universe How big is it What will the universe be like in the future The truth is we do not have definitive answers to any of these questions However these questions are so important that an entire branch of astronomy known as cosmol ogy is devoted to attempting to answer them The following pages will chronicle the devel opment of this fascinating field Cosmology is a branch of astronomy that specifically deals with the origin structure and space time relationships of the universe It is not the same thing as astronomy which deals with the evolution physics chemistry meteorology and motion of celestial objects as well as the formation and development of the universe Thus cosmology is only one seg ment of astronomy The basic assumptions of modern cosmology are that the universe is homogeneous in space on the average all places are alike at any time and that the laws of physics are the same everywhere Sal
CoSMOLOGY UNDERSTANDING THE EVOLUTION OF THE UNIVERSE The first great age of scientific cosmology began in Greece in the 6th century BCE when the Pythagoreans introduced the concept of a spherical Earth In approximately 170 CE one predominant theory espoused by the Greek culture and Ptolemy of Alexandria in par ticular was a geocentric one This theory was based upon the concept that the Earth was at the center of the universe A number of scientists and deep thinkers offered a variety of theories over the ensuing years Of particular significance was 16th century astronomer Nicolaus Copernicus who ushered in the second great age of cos mology when he developed the heliocentric concept of the solar system which placed the Sun at the center with Earth and the other planets continually orbiting it Albert Einstein one of the most brilliant scientists of the 2oth century is another individual who contributed much to our understanding of cosmology At the top of the list was his approach to thinking about time matter space energy and gravity He pub lished his revolutionary theory of relativity in 1916 which marked the beginning of the third great age of cosmology The most popular answer to the question about how our universe came to be is known 10
INTRODUCTION as the big bang theory Proponents of this the ory believe that between 13 and 14 billion years ago from an infinitely hot incredibly tiny supercondensed state the universe exploded Then in a moment following this event the universe began expanding For the following billions of years the expansion continued but at a slower pace Over thousands of years the intensely hot energy mixture of the early universe began to cool down After millions of years gas stars and galaxies were formed And in about 8 to 10 billion years our solar system including Earth appeared Many other notable figures made substan tial contributions to the world of cosmology in the 20th and 21st centuries They include Edwin Hubble Georges Lemaitre Aleksandre Friedmann George Gamow Edward Teller Hans Bethe Arno Penzias Alan Guth and George Smoot among others Current areas of research in cosmology include the nature of dark matter dark energy antimatter and more After reading this book you will see that while much about the nature and evolution of the universe remains to be discovered the works of many individuals over the centuries have gone a long way toward answering some of our most fundamental questions 11
