Earth's Magnetic field
This confirms the age of the earth. The Dynamo Theory describes exactly the origin of Earth’s magnetic field.
The strength of Earth’s magnetic field is constant, and proves that the earth is billions of years old. The magnetic field measurements of rocks prove that the direction of Earth’s magnetic field has gone through about 50 reversals.
The Facts Are .....
There are basically two ages for the earth based on the strength of Earth's magnetic field and rock magnetic polarity. The calculated ages are - a young age (6,000 - 10,000 years) and an old age (over 600 million years). As there are two interpretations of the same data, neither calculations can be used as 'proof' of the age of the earth. [based on logic]
Over the past 1,000 years, the energy stored in the earth's magnetic field has decreased by a factor of 2.7. If this rate of decay has continued since the beginning, then the earth could be no more than 10,000 years old. 
The NASA Magsat satellite launched in 1979 has produced data which indicates that the earth's magnetic field has a half-life of only 830 years. This totally contradicts the uniformatarian evolutionary idea that the earth's magnetic field has remained largely unchanged during geological time. 
As the earth’s magnetic field is decaying, evolutionary theories relying on a constant field strength are erroneous. For example, as the magnetic field was stronger in the past, less cosmic radiation would have entered the atmosphere. This would have resulted in lower Carbon-14 production. Any estimates of age based on Carbon-14 are therefore grossly over estimated. 
Evolutionary theory tries to overcome the fact that the weakening strength of the earth's magnetic field is evidence for its very young age by inventing the reversal hypothesis. This says that the weakening magnetic field is part of a normal cycle of changes in the earth's poles. This hypothesis is not based on any observed or tested fact, and it has no valid scientific basis. Rock magnetism cannot be used to verify this theory as there is a self-reversal process known to exist in rocks which is completely independent of the earth's magnetic field. [based on logic]
Under evolutionary assumptions and time frames, the 50 or so reversals of magnetic polarity found in rocks are assigned a period of 600 million years. However, palaeomagnetic measurements of a lava flow at Steens Mountain (Oregon, USA) show that magnetic polarity reversals can take place in two weeks - the time period during which the lava cooled. 
Dynamo theorists acknowledge that their theories concerning the source of the earth's magnetic field are incomplete, very complex, and not very successful in making predictions. 
"... you would have thought we would have given up guessing about planetary magnetic fields after being wrong at nearly every planet in the solar system". Written by F. Bagenal in "The Emptiest Magnetosphere"
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