10. The earth itself is a huge magnet that exhibits * Retardation Magnetism Reflection Refraction Association Deflection Retardation. Magnetism
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Answer:
Lately there has been a lot of discussion about the migration of the magnetic north pole. The magnetic north pole is different from the geographic North Pole and is part of the much larger magnetic field of the Earth. Not only do the magnetic poles shift, they reverse so that north becomes south and south becomes north! Some information we read seems dire, especially when taken at face value. But in order to understand the significance of that movement, we need to understand how the magnetic field of the Earth operates and has changed over time.
Title page of De Magnete by William Gilbert. This tome helped to reshape how Europeans viewed the Earth and magnetism.
William Gilbert famously wrote “Magnus magnes ipse est globus terrestris,” or “The Earth itself is a great magnet.” This is due to the inner workings of the place we call home. The structure of the Earth, moving up from the center, is as follows: 1) the solid inner core, believed to be composed primarily of iron; 2) the liquid outer core, also believed to be composed primarily of iron; 3) the mantle, composed of silicate rocks; and 4) an outer silicate crust. The part that comes into play for the Earth’s magnetic field is the liquid outer core, that sloshing molten iron that is still cooling from the formation of the planet. Today it is generally accepted that the Earth is what is known as a geodynamo, where an electrically conductive fluid, through thermal convection, circulates around the solid inner core. This fluid circulation becomes a corkscrew due to the rotation of the Earth by what is known as the Coriolis Effect, which also causes the helical spin of hurricanes on the surface. The best way to picture what happens in the outer core is to watch a lava lamp, where the mineralized oil in the center is heated by the light source and travels to the top of the lamp, cooling on its journey. Once it cools past a particular temperature, it sinks back to the bottom and is reheated by the light source only to circulate once again. In the outer core, it is this very movement that creates the magnetic field.
This magnetic field has been one of the most misunderstood phenomena throughout recorded history. Many theories on magnetism have been around since the ancient Greeks, and the ancient Chinese even used magnetized rocks, called lodestones, shaped into spoons to harmonize their environments and lives and began using the compass for navigational purposes as early as the 11th century CE. Europeans followed suit shortly and by Columbus’ voyage of 1492 had figured out that when the compass pointed north, it wasn’t necessarily pointing to the geographic North Pole. In fact, according to Campbell, Columbus’ voyage was “probably the first documented observation of the change in declination with changing longitude,” declination being the angle between magnetic north and geographic north that changes as you move either east or west.
Answer:
The magnetic north pole is different from the geographic North Pole and is part of the much larger magnetic field of the Earth. Not only do the magnetic poles shift, they reverse so that north becomes south and south becomes north! Some information we read seems dire, especially when taken at face value. But in order to understand the significance of that movement, we need to understand how the magnetic field of the Earth operates and has changed over time.
Title page of De Magnete by William Gilbert. This tome helped to reshape how Europeans viewed the Earth and magnetism.
William Gilbert famously wrote “Magnus magnes ipse est globus terrestris,” or “The Earth itself is a great magnet.” This is due to the inner workings of the place we call home. The structure of the Earth, moving up from the center, is as follows: 1) the solid inner core, believed to be composed primarily of iron; 2) the liquid outer core, also believed to be composed primarily of iron; 3) the mantle, composed of silicate rocks; and 4) an outer silicate crust. The part that comes into play for the Earth’s magnetic field is the liquid outer core, that sloshing molten iron that is still cooling from the formation of the planet. Today it is generally accepted that the Earth is what is known as a geodynamo, where an electrically conductive fluid, through thermal convection, circulates around the solid inner core. This fluid circulation becomes a corkscrew due to the rotation of the Earth by what is known as the Coriolis Effect, which also causes the helical spin of hurricanes on the surface. The best way to picture what happens in the outer core is to watch a lava lamp, where the mineralized oil in the center is heated by the light source and travels to the top of the lamp, cooling on its journey. Once it cools past a particular temperature, it sinks back to the bottom and is reheated by the light source only to circulate once again. In the outer core, it is this very movement that creates the magnetic field.