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The Magnetic Field of the Earth

18 December 2010

At www.wired.com/wiredscience/2-1-/12/magnetic-copper-slag/ …. it seems that copper slag from Iron Age smelting activities at Khirbet es/Nahu in NE Jordan and from Timna in what is now southern Israel has been C14 dated to the 10 and 9th centuries BC, and a magnetic field that spike twice during the 180 years they studied, has been dated at 980 and 890BC. On both occasions the magnetic field jumped up in strength but within 20 years had fallen back down again. Such geomagnetic spikes do not seem to be happening nowadays. One scientist claimed this did not occur anywhere else in the world and as such it might be caused by a small piece of magnetic molten iron that just happened to be sitting under the Levant. As strained as that sounds the researchers are intrigued enough to next visit copper mines on Cyprus to see if similar spikes can be found there. The discovery is vexing scientists as it is thought the earth's magnetic field comes from the movement of molten iron in the core. Palaeomagneticists have thought such movements in the field were small and slow, fluctuating a little in the course of a century – sort of uniformitarian. The Israeli study seems to prove otherwise – and the findings were presented in a poster display at the American Geophysical Union meeting on December 16th and are due to be published in a paper in Earth and Planetary Science Letters. An interesting aside to this story is that the Timna mines were exploited by the Egyptians – and it is perhaps possible the slag comes from the Late Bronze Age. However, the article presumes the slag is dated to the Iron Age – might this be as a result of the C14 dates achieved. The 10th and 9th centuries are firmly attached to the Iron Age in the orthodox chronology – but what if the C14 dates were right but the Iron Age came somewhat later. Just a thought.

On a similar subject we have a story at http://wattsupwiththat.com/2010/12/17/first-measurement-of-magnetic-field-in-earths-core/ and it is all about a paper in Nature (December 16th) by geophysicist Bruce Buffett – which has caused a bit of a stir. The magnetic field strength at the core is 50 times stronger than at the surface, he claims – but it is not as strong as predicted in the orthodox consensus theory. The strength, in this paper, is based on observations, he says, not by inference from a model. A strong magnetic field in the outer core was thought to be responsible for convection and a lot of heat. Some of this heat is thought to be a residue from 4 billion years ago when the earth was very hot and molten, from radioactive decay of long lived elements such as potassium, uranium, and thorium, and even the release of gravitational energy. A weak field would have implied little heat supplied from radioactive decay while a very strong field would have implied a large contribution from radioactive decay. Neither appears to be true. The cooling earth is thought to have captured its magnetic field from the planetary disc in which the solar system formed. The internal dynamo, so it is said, regenerates the field thanks to heat produced inside the earth. The heat makes the liquid outer core boil, or convect, and as conducting metals rise and sink throught the existing magnetic field they create electrical currents that maintain the magnetic field.

Buffett is a theories man but he also uses observations to improve computer models of the internal dynamo. A lack of information about conditions inside the interior of the earth is a hindrance, he says, in the making of an accurate model. He thinks the tug of the moon on the tilt of the earth's spin axis may provide information on the magnetic field within the earth. The tug of the moon, he suggests, makes the spin axis slowly rotate in the opposite direction which then produces magnetic changes in the outer core that damp down the precession. Radio observation of distant qasars, he continues, provides very precise measurements of changes in the earth's rotational axis as required to calculate the damping effect. The moon is continually forcing the rotation axis of the core to precess so the response of the fluid outer core to the precession of the inner core has an important role. Buffett goes on to describe the 'observed evidence' – which is extremely clever. However, the commenters to the piece, and there are lots of them, mostly impressed by Buffett, does include some dissent which makes interesting reading – but members and readers can make up their own minds.

A Chris Reeve makes the point that Buffett is a proponent of New Physics. The idea that the magnetic field would have disappeared without an internal dynamo, he says, is a problem created by the theory – and it ignores the fact that lightning has been observed passing from the earth into space and each time a stroke occurs upstairs the Van Allen Radiation Belt blinks. He adds, electrical processes are always second order effects in conventional theories.

Vukcevic (see also www.vukcevic.talktalk.net/LFC9.htm ) points out a number of anomalies as far as its magnetic field is concerned – for example, the magnetic field in the northern hemisphere behaves differently to what it does in the southern hemisphere. He goes on to say it would be strange if the moon was able to modulate the sun spot cycle but ends up by saying he has no idea how the earth's magnetic field is generated but I am sceptical of people who claim they do know. This is a bit of science that is a long way from being settled.

Tapperofspines (what a lovely pseudonym) points to another Nature paper published a few months ago with a different conclusion on the strength of the magnetic field within the core. He adds, this is not a measurement of the earth's core magnetic field but an inference based on other measurements. Not the same thing.

Chris Reeve returned with another blast sparked by a commenter on the practise of science. After a bit of a tirade he provided an example of what he meant – the cosmic microwave background. A philosophical approach to science dictates that the theorists must be willing to consider all the potential inferences which are physical before considering those which are meta-physical. However, when cosmologists saw an electromagnetic fury of microwaves coming at the earth from all directions they opted to infer that this was a relic of a primordial Big Bang explosion. If they had stepped into a plasma laboratory and looked at experiments on plasma beams they would have seen they always emit microwaves. He goes on to praise James Maxwell.

In a further comment he came back to say that in a plasma based cosmology two cosmic bodies which approach one another could eventualy charge-neutralise with each other. Such electrical charges should show up in the geological record as dramatic changes in the magnetism of earth's rocks. Hence, we might wonder how this might affect the first post (above) and the spikes in copper slag.

PS … do we know Chris Reeve? Yes, by googling his name and electric universe (combined) a number of sites pop up, especially comments made on www.thunderbolts.info – if inclined you might find this an interesting exercise. At the same web site there is a video clip of Wal Thornhill addressing some of the common points of criticism aimed at the Electric Universe theory at pro-orthodox web site such as Bad Astronomy and Physics Forums. There is also a post (December 16th) on Helios Awakens with the NASA image of an eruption on the surface of the sun from a week or so ago.

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