EARTH S MAGNETIC FIELD Module 6
MAGNETIC FIELD A Magnetic field is generated by current or the flow of electrical charge Resistance a material s opposition to the flow of electric current. II = VV RR I = current V = voltage R = resistance
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EARTH S MAGNETIC FIELD Earth s magnetic field is necessary for life Protects us from harmful cosmic rays (UV-radiation) by deflecting solar winds whose particles destroy the ozone (O 3 ). Layer of the earth s atmosphere that absorbs UV radiation from the sun If magnetic field were any weaker, these winds would not be deflected effectively If magnetic field were any stronger, magnetic storms would make life on earth impossible
FLUID CONVECTION Convection occurs when particles with a lot of heat energy in a liquid or gas move and take the place of particles with less heat energy. Fluid in hot areas is less dense than fluid in cold areas, so it rises into the cold areas. The denser cold fluid falls into the warm areas. Liquids and gases expand when they are heated.
MAGNETIC FIELD THEORIES Dynamo Theory Magnetic field created by flow of liquid iron in the core. Rapid Decay Theory Electrical current of the earth is a consequence of how it was created Differences in temperature, pressure and composition produce current in the core Rotation of the earth causes current to move in one general direction. Magnetic field strength fluctuates over time May be due to flow of material in the core, but exact mechanism is unknown Current is slowing down over time due to natural resistance in the core Magnetic Field strength is decaying over time
OBSERVATIONS OF THE MAGNETIC FIELD 1. Over the past 175 years, data indicates that the earth s magnetic field is decaying Dynamo theory predicts a changing magnetic field as temperature differences in the core change Rapid-decay theory predicts a general decrease in the field strength over time Due to the natural resistance in the core Consequence of how God created the earth
OBSERVATIONS OF THE MAGNETIC FIELD 2. Throughout history the direction of the magnetic field has reversed a many times Direction of magnetic field changes as the direction of the current in the core changes Fossil layers all over the earth contain strong evidence the earth s magnetic field has reversed directions many times Magnetic materials within layers are pointed in opposite directions
MAGNETIC FIELD REVERSALS Dynamo Theory Predicts that these reversals are a natural occurrence According to this theory, reversal is a SLOW process A minimum of 2,000 years for a reversal to occur Rapid-decay Theory Does not predict reversals, BUT Rapid reversals may have occurred during the flood Powerful release of energy in the earth s core during the flood caused a disturbance to the flow of electric current Disturbances would continue to affect the flow of current for a period of time after the flood
OBSERVATIONS OF THE MAGNETIC FIELD 3. We can observe the magnetic fields of other planets. Dynamo theory incorrectly predicts the magnetic fields of other planets Predicts a MF on Mars, but mars does not currently have one Predicts no MF on Mercury, but Mercury does have one Off by a factor of 100,000 with the fields of Uranus and Neptune Rapid-decay theory accurately predicts the magnetic fields of all planets
COMPARING THEORIES Rapid-Decay Theory Predicts a steady decay of the earth s magnetic field over time Does not predict magnetic field reversals Does allow for the occurrence of reversals given a catastrophic event Accurately predicts the magnetic fields of other planets Dynamo Theory Predicts a fluctuating magnetic field strength Predicts magnetic field reversals Does not accurately predict the magnetic fields of other planets
CONSEQUENCES OF RAPID DECAY THEORY Theory relies on a global, cataclysmic event to explain reversals Most scientists do not believe any such event has ever occurred Christians can point to the flood as the event responsible for these reversals Given the current magnetic field strength, this theory suggests the earth must have been formed less than 10,000 years ago Magnetic field would have been too strong to sustain life in the past if Earth were older Literal interpretation of genesis is consistent with this claim Other scientific evidence suggests earth is billions of years old