It is a known fact, though not well publicised, that the earth’s magnetic field is decaying relatively rapidly. The earth’s magnetic field is considered to be due to circulating currents in the earth’s interior, which is thought to consist of hot liquid metal. The magnetic currents are extremely large and with no known mechanism to sustain them, the earth’s magnetic moment is predicted to be decaying.
Dr Barnes has shown that the magnetic moment of the earth is expected to decay exponentially because it is produced by real currents that dissipate energy through Joule heating.When the measured values of the earth’s magnetic moment are plotted against time over the past 150 years, it is shown to be decaying exponentially as predicted by theory. Furthermore, the half-life of this decay is shown to be about 1,400 years. This means that in 1,400 years time , the value of the earth’s magnetic moment would be half its present value, and 1,400 years ago it was twice its present value.
It also means that if the earth had been in existence 20,000 years ago, then the strength of the magnetic field on the surface of the earth would have been 18,00 gauss – stronger than the field between the pole pieces of the most powerful radar magnets. Dr Barnes has pointed out that it is not very plausible. The core of the earth could not have stayed together with Joule heat that would have been associated with the currents producing such a strong field. From this it can be concluded that the earth must be less than 20,00 years old.
Monty White A.J. Scientific Evidence for a Young Earth.