One of the many mysterious forces of our planet is its magnetic field. This field is similar to a bar magnet tilted 11 degrees from the Earth’s spin axis, thus true north is not the same as magnetic north. It bows out at the equator and retouches the planet at the poles. Magnetic fields can exert forces on moving electrical charges and helps protect the Earth from projectiles in space, as well as aid in the movement of biological forms on the planet.
The Magnetic Field Originates in the Earth’s Core
The Earth’s magnetic field forms from electric currents that circulate in the molten core of the planet. This field results from a current loop that dips toward the Northern Pole. The speed of rotation of the Earth plays a part in the generating the currents within the core, which is called a “dynamo effect.” This effect is unique to the Earth. For instance, the planet Venus does not have a magnetic field though its core is similar to the Earth’s because Venus rotates more slowly.
Rocks Tell the History of the Magnetic Field
The magnetism within rocks tells the history of the constant changes in the Earth’s magnetic field. Scientists can determine what the magnetic field was when the rock cooled to a sold form. These indicators within the “magnetic fossils” are how they know that the magnetic field of the Earth changes every million years or so.
Solar Winds Affect the Earth’s Magnetic Field
Solar winds are streams of ionized gases that blow outward from the sun’s surface at about 4000 kilometers per second. The Earth’s magnetic field shields the planet from these gases, deflecting them like water deflects around the bow of a ship. The imaginary surface where these solar winds are deflected are called the magnetosphere. Some high-charged particles can leak into the magnetosphere and become trapped in the Van Allen belt, an area of strong radiation that lie within 60,000 kilometers of the Earth’s surface.
Birds and Animals Depend on the Magnetic Field to Navigate
Humans use the Earth’s magnetic field for compasses to navigate their way around the glove and investigate every corner of the planet. Birds, whales, turtles and other animals also use these magnetic forces to return to natal grounds to mate. In many experiments, changes in the magnetic field caused disruptions in animals’ movement and behavior.
The Earth’s Magnetic Field Is Fading
Researchers have determined that the Earth’s magnetic field has decreased since 1845 when Carl Friedrich Gauss began recording data on it. Today, it is about 10 percent weaker than it was then, according to writer John Roach of the National Geographic News. Scientists speculate whether the decrease will continue until the field collapses altogether and then reverses. It that occurs, compasses would then point south instead of north. The magnetic field has reversed many times in the past, without life stopping on the planet. Scientists theorize that animals that depend on the magnetic field for navigation would adapt to the changes.
Information about the Earth’s magnetic field gives the world yet another look at the planet’s continuous state of change and how dependent it is on the forces that make it work.
