earth-sciences

"... You can imagine the Earth as an enormous battery whose magnetic field is formed by the movement of molten metal (caused by the Earth's rotation) around the solid metal inner core. At present the positive terminal is at the , but in times past the orientation has switched so that the positive terminal is at the . Over the past 76 million years the Earth's magnetic field has reversed 171 times. No-one knows exactly why this happens, but at present the magnetic field is weakening a little each decade. Many researchers think that this presages another shift. Just how long before the reversal happens, however, is unknown."

"Since the development of simple compasses, the Earth's magnetic field has been an important aid for navigation, enabling travelers to find their way in uncharted regions. It became an essential tool in the exploration of the planet and facilitated the great voyages of discovery in the late 15th century that established links between the continents. It is one of the central properties of the Earth and has been studied with purpose-built equipment on land, at sea, and in the past half-century from satellites. The magnetic field extends far into space around the planet, where it interacts with the energetic particles from the Sun and interstellar space that impact on the Earth. It produces sideways forces on the rapidly moving, electrically charged particles and deflects them around the planet. In this way, the magnetic field acts as a protective shield against harmful radiation and enables life to exist on the planet."

"Mining is a uniquely political enterprise. It requires permits and capital, as well as legal and moral defenses strong enough to withstand inevitable litigation."

"Bad ventilation, deep excavation, defective supports, etc., etc., annually bring death to thousands of miners, but this system of operation saves expenses, therefore augments the gains, and gives the mine owners no occasion to be sorry. Neither does the factory-pasha care how many of "his" laborers are torn and rent apart by machinery, poisoned by chemicals, or slowly suffocated by dirt and dust. Profit is the main thing."

"All minerals are limited and especially limited at an affordable rate. Since a techno-industrial civilisation needs minerals, any such civilisation is bound to reach a point where it can’t continue."