The Magnetic Declination: A History of the Compass

Description

This book aims then to describe in a comprehensible way efforts made over centuries of measuring and understanding the magnetic declination. The book also highlights some important characteristics of the Earth’s magnetic field thanks to the declination measurements. Some applications and societal implications are also underlined. Anyone living in the 21st century knows the best way to navigate is by using a smartphone App.  Decades and centuries ago, in order to find the same way a magnificent instrument was used: the compass.  Despite many being aware of the compass, not everyone appreciates that throughout the ages of exploration, sailors and explorers linked their lives and great discoveries to the  magnetic needle.  Furthermore, is there an awareness of  the Earth’s physical mechanism behind the changes in time and space of the direction indicated by the compass? The magnetic declination is at the center of this book and it helps the reader to understand how to navigate in time and space. The book provides the history of the compass and magnetic declination leading the reader to the understanding of our magnetic planet. This book is designed for those who are fascinated by the long history of geomagnetism. This book relies on reader’s knowledge of elementary scientific concepts, and introduces the geomagnetism concepts as they evaluated in time. The focus is on some basic concepts and physical processes in order to understand the evolution of a specific element of the geomagnetic field, the declination. The primary audience may have just started an interest in the geomagnetism and history of science, as students and researchers. Some readers may have an interest that only touches the geomagnetism, as navigators, geophysicists, historians.                      Preface Contents Part I Introduction 1 Some Introductory Notions 1.1 Back in Time 1.2 Geomagnetic Field Components 1.3 Geomagnetic Field Sources 1.4 Geomagnetism, Archaeomagnetism and Palaeomagnetism References Part II The Beginning of Magnetism 2 The Poetry and Philosophy of the Beginnings 2.1 From Floating Ideas to Floating Needles 2.1.1 Mesopotamia 2.1.2 Mesoamerica 2.1.3 China 2.1.4 Greece 2.2 The Greatest of Centuries References 3 The First Attempts to Observe the Magnetic Declination 3.1 Empirical Theories 3.2 The First Observations 3.2.1 Magnetic Declination 3.2.2 Magnetic Dip 3.3 Spatial and Temporal Variations 3.3.1 Spatial Variations 3.3.2 Temporal Variations 3.4 Early Ideas About the Sources References Part III Magnetic Declination–From the Age of Sail to the First Modern Observations 4 Ancient Declination Maps 4.1 The First Maps Including Magnetic Information 4.1.1 Erhard Etzlaub – 1492 Map 4.1.2 Jean Guérard – 1631 Map 4.2 From Declination Measurements to Magnetic Elements 4.2.1 Cabot Map – 1544 4.2.2 Gerardus Mercator – 1569 Map 4.3 From One to Two Magnetic Poles 4.3.1 Guillaume Le Nautonier – 1603 Map 4.4 The Earliest Magnetic Charts 4.4.1 Edmond Halley – 1700 Map 4.4.2 Charts and Atlases Before the Vector Field Measurements References Part IV Magnetic Declination from the First Continuous Observations to the Satellite Era 5 Long-Series of Declination Observations 5.1 London Series 5.2 Paris Series 5.3 Munich Series References 6 Geomagnetic Vector Field: From Ground to Satellite Measurements 6.1 The First Geomagnetic Observatories 6.2 Geomagnetic Observatories: From Analog to Digital Era 6.2.1 Absolute Instruments 6.2.2 Variometers 6.2.3 Automatic Observatories 6.3 Space Measurements: Magnetic Satellites References Part V Some Specific Features of the Magnetic Declination 7 Maps of Magnetic Declination Over the Last Centuries References 8 Spatial Evolution: Westward Drift References 9 Temporal Evolution: Geomagnetic Jerks References 10 Geomagnetic and Magnetic Poles 10.1 The Geomagnetic Poles 10.2 The Magnetic Poles 10.2.1 The North Magnetic Pole 10.2.2 The South Magnetic Pole References 11 What Next? 11.1 Magnetic Declination at the Space Era 11.2 Magnetic Fields Beyond the Earth References