Thomas G. Barnes, Emeritus Professor of Physics at the University of Texas, El Paso, and a creationist, argues that the geomagnetic field was created by unknown processes at the time of creation of the earth and has been decaying irreversibly and exponentially, with a half-life of about 1400 years, since then. He calculates that the field would have been impossibly large in 8000 BC and concludes that the earth, therefore, is less than 10,000 years old. He denies that the earth's field has reversed polarity in the past, and attempts to refute the dynamo theory of the origin of the field. Barnes' arguments and conclusions are commonly cited in creationist literature as definitive proof that the earth is very young. Barnes is wrong, and has ignored or misrepresented much of the data on the earth's magnetic field. Paleomagnetic evidence shows that the earth's field has existed for more than three billion years, and that the dipole field both fluctuates in strength and irregularly reverses polarity. There are no properties of the magnetic field that can be used to place an upper limit on the earth's age. - Author
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Can the earth be dated from decay of its magnetic field?.