The Old Theory Until now, there was only one theory regarding the source of Earth's magnetic field, which is the internal dynamo theory. This theory was accepted because it offered the best explanation at the time. Also, much research has been done to support the theory. According to the internal dynamo theory, a dynamo near the center of the planet generates the current that produces the magnetic field. This dynamo would be in the liquid outer core of the planet. It would produce the magnetic axis and project it from the planet. The axis would expand and spread the magnetic field around the planet. This theory also suggests that the internal dynamo is sustaining itself by using fuel from Earth's core. The internal dynamo theory has changed over the years. At first scientists thought that a bar magnet was in the center of the planet and the compass needle pointed to the poles of that magnet. This made perfect sense at the time because we can see that the same thing happens when we put a compass near a bar magnet. The Bar Magnet In The Sun image demonstrates the idea of the bar magnet theory. However, this example shows the bar magnet imbedded within the sun because just like the planets, the sun also has a magnetic field, which is more complex than Earth's magnetic field. Scientists have tried to use the internal dynamo theory to explain the magnetic fields of all the planets, some moons, and the sun. However, the old model does not work for the sun, moon, and other planets. The bar magnet concept lasted a long time as the main theory regarding the source of Earth's magnetic field. However, while trying to apply it to other cases, scientists found problems with the theory. Over the years, they discovered that a bar magnet could not hold magnetism above the temperature of 770 degrees centigrade because high heat destroys magnetism. This caused the theory to gradually evolve over time.

This “fantastic story” of one of physics’ great riddles takes us through centuries of scientific history (Simon Lamb, author of Devil in the Mountain). Why do compass needles point north—but not quite north? What guides the migration of birds, whales, and fish across the world’s oceans? How is Earth able to sustain life under an onslaught of solar wind and cosmic radiation? For centuries, the world’s great scientists have grappled with these questions, all rooted in the same phenomenon: Earth’s magnetism. Over two thousand years after the invention of the compass, Einstein called the source of Earth’s magnetic field one of greatest unsolved mysteries of physics. Here, for the first time, is the complete history of the quest to understand the planet’s attractive pull—from the ancient Greeks’ fascination with lodestone to the geological discovery that the North Pole has not always been in the North—and to the astonishing modern conclusions that finally revealed the true source. Richly illustrated and skillfully told, North Pole, South Pole unfolds the human story behind the science: that of the inquisitive, persevering, and often dissenting thinkers who unlocked the secrets at our planet’s core. “In recent years, many very good books for interested non-scientists have been published: Richard Dawkins’s Climbing Mount Improbable and The Ancestor’s Tale, Stephen Jay Gould’s The Lying Stones of Marrakech, and Dava Sobel’s Longitude and The Planets, to name some of them. North Pole, South Pole . . . is a worthy addition to that list . . . Turner has a great story to tell, and she tells it well.” —The Press (New Zealand)

The mystery of Earth's invisible, life-supporting power Alanna Mitchell's globe-trotting history of the science of electromagnetism and the Earth's magnetic field--right up to the latest indications that the North and South Poles may soon reverse, with apocalyptic results--will soon change the way you think about our planet. Award-winning journalist Alanna Mitchell's science storytelling introduce intriguing characters--from the thirteenth-century French investigations into magnetism and the Victorian-era discover that electricity and magnetism emerge from the same fundamental force to the latest research. No one has ever told so eloquently how the Earth itself came to be seen as a magnet, spinning in space with two poles, and that those poles have dramatically reversed many time, often coinciding with mass extinctions. The most recent reversal was 780,000 years ago. Mitchell explores indications that the Earth's magnetic force field is decaying faster than previously thought. When the poles switch, a process that takes many years, the Earth is unprotected from solar radiation storms that would, among other disturbances, wipe out much and possible all of our electromagnetic technology. Navigation for all kinds of animals is disrupted without a stable, magnetic North Pole. But can you imagine no satellites, no Internet, no smartphones--maybe no power grids at all? Alanna Mitchell offers a beautifully crafted narrative history of surprising ideas and science, illuminating invisible parts of our own planet that are constantly changing around us.

In Hidden Attraction Gerrit L. Verschuur traces the history of our fascination with magnetism, from the first discovery of magnets in Greece, to state-of-the-art theories that see magnetism as a basic force in the universe.

Ancient and indigenous peoples have insisted their knowledge of plant medicines came from the plants themselves, perceived through a heart-centered mode of perception, not trial-and-error experimentation. Author Stephen Harrod Buhner explores this heart-centered mode of perception, helping readers learn about the medicinal uses of plants and gather information directly from the heart of Nature.

In Mysteries of Terra Firma, James Lawrence Powell tells an engrossing three-part tale of how we came to understand the ground on which we walk, and how that ground holds the key to the greatest secrets of deep space and time. Naming his profound stories Time, Drift, and Chance, he tells of the three twentieth-century revolutions in thought that created the amazing science of Earth -- and of all planets to the edge of the universe. The riddle that drove the first revolution is obvious and yet in 1904 remained impenetrable: how old is Earth? An encounter between the imperious Lord Kelvin and a New Zealand farm-boy-turned-physicist, Ernest Rutherford, set the stage for the solution and launched a golden century of geology. As a result, scientists learned that if the 4.5 billion years of geologic time were compressed into a single twenty-four-hour period, Homo sapiens would have arrived only in the last second. The geological Revolution of Time reveals how long the ground on which we walk has existed, and how briefly we have trod that ground. In the early twentieth century, German meteorologist and polar explorer Alfred Wegener proposed a counterintuitive, heretical theory: that terra firma is not so firm; instead of being fixed in place, continents drift. In 1926, petroleum geologists convened in New York City to discuss Wegener's radical idea, where it was met with outrage and skepticism: "If we are to believe Wegener's hypothesis we must forget everything which has been learned in the last seventy years and start all over again," one attendee said. Forty years later, a new generation did exactly that. The Revolution of Drift, the second part of Powell's narrative, showed us how the ground on which we walk moves. Throughout geologic time, meteorites have incessantly bombarded everything in the solar system. Far from serene and predictable, the planets are ruled by random violence on an unimaginable scale. Once a mountain-sized meteorite flew through space, struck the Earth, killed the dinosaurs and two-thirds of all species, and spared the small hamster-sized creature that happened to be our ancestor. The chance of that happening again is essentially zero. So, the final revolution in Powell's history of a golden century of geology is the Revolution of Chance. Simply put, this revolution in thought has transformed our understanding of how lucky we really are. If we can learn so much from considering no more than the rocks beneath our feet, what will we learn when we begin walking on other planets? Mysteries of Terra Firma is both charming in its storytelling and staggering in its implications. Discovering the ground on which we stand is a fascinating journey into our past -- and our future.

This book describes the history of the progress made in auroral science and magnetospheric physics by providing examples of ideas, controversies, struggles, acceptance, and success in some instances. The author, a distinguished auroral scientist, fully describes his experiences in characterizing and explaining auroral phenomena. The volume also includes beautiful full-color photos of the aurora.