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Earth’s Magnetic Field Decay

April 20, 2007

In the previous article I talked about the irregular movement of the poles and how many magnetic pole reversals are known to have happened throughout history.

Physics Lesson
Something that I haven’t seen many people acknowledge is that these pole reversals require energy. I poked around on YouTube looking for a demo video of the nerdy professor flinging himself off his chair by reversing a gyroscope. Unfortunately, I’ll have to post that later. I did find this video which shows how much gyroscopes resist change when the gyroscope bends sideways over empty space without falling. The reason for this is Newton’s first law of motion, “An object in motion will remain in motion unless acted upon by a net force.” Change in motion requires energy and energy has a tendency to dissipate, not concentrate. This is the second law of thermodynamics “The total entropy of any isolated thermodynamic system tends to increase over time, approaching a maximum value.” In English that means things tend to go from a state of higher order to greater disorder. Things fall apart, wind down, break down, and grind to a halt.

Our magnetic field is no exception. The Canadian Geologic Survey says “Magnetic fields decay, and we can show that the existing geomagnetic field would disappear in about 15,000 years unless there were a mechanism to continually regenerate it.” This is a reference to the current theory of where our magnetic field comes from. The restriction that the system must be sustained over the course of billions of years is applied to any proposed model. This ensures that it lines up with our geologic time scale, which in turn lines up with the evolutionary biology model, which is measured by radioisotope dating. “Many mechanisms have been postulated to explain how the magnetic field is generated, but the only one that is now considered plausible is analogous to a dynamo”. It makes sense to make scientific theories line up with existing models, I just want people to understand the chain of assumptions and contingent truths. The data is not allowed to speak for itself, it is not examined in a vacuum. So let’s just look at the data.

Data
“For example, the total intensity at Toronto has decreased 14%, from approximately 64,000 nT to 55,000 nT, during the last 160 years. ” – Canadian Geologic Survey – Secular Variation

“Archeomagnetic evidence shows that this decrease has, in fact, been going on for the last two thousand years, and that the strength of the dipole now is only about half of what it was two millenia ago. The dipole strength is currently decreasing at a rate of about 6.3% per century, and were it to continue to decrease at that rate, the strength would reach zero in approximately 1,600 years.”

” It appears that only about five percent of neutron stars, the most strongly magnetized, undergo significant field decay;” – Neutron Star Field Decay could impact what we know.

“We also know from studies of the magnetisation of minerals in ancient clay pots that the Earth’s magnetic field was approximately twice as strong in Roman times as it is now.” – British Geologic Survey, Magnetic Flip

“Human beings have been on the Earth for a number of million years, during which there have been many reversals, and there is no obvious correlation between human development and reversals. Similarly, reversal patterns do not match patterns in species extinction during geological history.” – same as above.

“Satellites in low-Earth orbit over Southern Africa are already showing signs of radiation damage suffered as a result of the Earth’s magnetic field weakening above our part of the planet.” – Sunday Times, New Zealand (quoted in archive).

Amateur Project to track magnetic field change – http://www.rense.com/general51/mag.htm

Conclusions
Well, I’m not really drawing a definite conclusion. Just think about the possibilities and the underlying assumptions that hold them up. Does obscure subjects like geomagnetism really matter to you personally? Well, if you walk outside one day and see an aurora borealis above your head in the middle of the day, then suddenly it becomes the most relevant thing in the world. You’ll be able to tan in no time.

No matter what the generation mechanism of the magnetic field it is still subject to entropy and thus decay. Even if the field is able to wondrously re-generate itself, that regeneration takes energy on a global scale. The field would naturally decay by itself if it were static, such as the iron core being a giant bar magnet. The fact that it flips, moves, and jerks around means it’s using up even more energy. Some day that energy is going to run out.

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One comment

  1. I think I may have pointed out to you a while ago that your chart only goes back to 1840. This means that even with your 6000 year old earth you would have one hell of a magnetic field. I do not know the effects of long term exposure to extremely high amounts of magnetism, but I am sure it is not healthy.

    Furthermore I find it a little odd that the chart stops at 1840. Especially considering we know quite a lot about our magnetic field. This seems to be more of an indication of a field reversal than a young earth creationist reason for why the earth can’t be millions of years old.

    For further reading
    http://en.wikipedia.org/wiki/Earth's_magnetic_field#Magnetic_field_reversals



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