Earth's Magnetic Field
If you run a current through a solenoid a magnetic field will be formed running through the centre, out the top and then arching back around the outside to complete the cycle. Remove the current and the magnetic field decays. It gives back the energy it took to create it. Creationists believe that the Earth's magnetic field is an original feature. The field is decaying into electrical energy as in the lab. In the lab the curve produced by a decaying magnetic field is a negative exponential (which has a half-life). The earth's magnetic field data also shows a negative exponential curve with a 1400-year half life. This cannot be sustained for billions of years into the past.
The problem says Ross is that the curve is sinusoidal - it goes up and down like a sine wave. There is a dynamo that provides the energy to sustain this. However, the magnetic field data never shows the curve has gone up. Ross thinks it will increase some time in the future. But is the magnetic field caused by a dynamo? There is no proof of this. Thus Ross is saying without supporting data that the dynamo theory is true and contradicts the magnetic field decay. Yes, and if the magnetic decay theory is true the dynamo theory must be wrong. So what? Well, since the Earth IS old and the magnetic field theory predicts a young Earth it must be wrong and therefore the Earth is OLD. Yes, but this argument begs the question - it was already ASSUMED the Earth was old to begin with. What does that prove?
I said I make an exception for Ross as an apologist. He puts the discussion of creationist thinking under the heading, "Bogus evidences for a young universe." Well, the only thing that is bogus here is the pretense that Ross has a knowledgeable understanding of the science involved. He thinks that his contemptuous attitude is a valid substitute for good science. Creationists are used to this attitude from unbelievers but Ross stands on his Christian faith as he presents this material. Does this fall into "Love thy neighbour as thyself?" You be the judge.