Freethought & Rationalism Archive

WinAce · 06-20-2002, 09:15 AM

I've been debating with Young-Earth Creationists for a while now at <a href="http://www.blizzforums.com/forumdisplay.php?s=&daysprune=&forumid=18&x=17&y=5 " target="_blank">Blizzforums Serious Discussion</a> (Evolution vs Creationism and various other topics relevant to us infidels). The EvC topic is mostly a bunch of junk about a banned member at first, then takes off about the middle (page 4 for me at 40 posts per page). I'm WinAce.

While I think I did an... adequate job of debunking most of their arguments, one guy in particular (Elric) continues to use a variation of the 'earth's decaying magnetic field' argument for a Young Earth. The other is mostly more reasonable and sticks to irreducible complexity and stuff.

I have only very basic knowledge of geology so I'm in no position to debunk Dr. Humphreys' newest, which appears to challenge the geodynamo theory of earth's magnetism.

<a href="http://www.creationresearch.org/crsq/articles/39/39_1/GeoMag.htm" target="_blank">http://www.creationresearch.org/crsq/articles/39/39_1/GeoMag.htm</a>

Quote:

Abstract

This paper closes a loophole in the case for a young earth based on the loss of energy from various parts of the earth’s magnetic field. Using ambiguous 1967 data, evolutionists had claimed that energy gains in minor (“non-dipole&#8221

parts compensate for the energy loss from the main (“dipole&#8221

part. However, nobody seems to have checked that claim with newer, more accurate data. Using data from the International Geomagnetic Reference Field (IGRF) I show that from 1970 to 2000, the dipole part of the field steadily lost 235 � 5 billion megajoules of energy, while the non-dipole part gained only 129 � 8 billion megajoules. Over that 30-year period, the net loss of energy from all observable parts of the field was 1.41 � 0.16 %. At that rate, the field would lose half its energy every 1465 � 166 years. Combined with my 1990 theory explaining reversals of polarity during the Genesis Flood and intensity fluctuations after that, these new data support the creationist model: the field has rapidly and continuously lost energy ever since God created it about 6,000 years ago.

...

Conclusion: the Earth’s Magnetic Field is Young

The trend in the IGRF data from the most accurate period, 1970 to 2000, is very clear. During that period the total energy - dipole plus non-dipole - in the observable geomagnetic field decreased quite significantly, by 1.4%. Though the data over the previous part of the century are less accurate, there was still an overall decrease of total energy. According to my geomagnetic model, whose general features agree with paleomagnetic and archeomagnetic data, the total field energy has always decreased at least at today’s rate, and it will continue to do so in to the future (Humphreys, 1990).

Today’s energy decay rate is so high that the geomagnetic field could not be more than a few dozen millennia old. Moreover, during the rapid polarity reversals of the Genesis Flood, and during the large fluctuations of surface field B for millennia after the Flood, the rate of energy loss was much greater than today’s rate. That shortens the age of the field even more. In the absence of any workable analytical theory (or data) to the contrary from the evolutionists, these data are quite consistent with the face-value Biblical age of the earth, about 6000 years.

Are there any obvious third grade-level mistakes in that article? That would just be too perfect

Aside from that, what does his hypothesis do that geodynamo theory doesn't?

<a href="http://www.answersingenesis.org/docs/3318.asp" target="_blank">http://www.answersingenesis.org/docs/3318.asp</a>

Quote:

Observational support from the Fields of other planets

Dr Humphreys also calculated the fields of other planets (and the sun) based on this model. The important factors are the mass of the object, the size of the core and how well it conducts electricity, plus the assumption that their original material was water. His model explains features which are deep puzzles to dynamo theorists. For example, evolutionists refer to ‘the enigma of lunar magnetism' — the moon once had a strong magnetic field, although it rotates only once a month. Also, according to evolutionary models of its origin, it never had a molten core, necessary for a dynamo to work. Also, Mercury has a far stronger magnetic field than dynamo theory expects from a planet rotating 59 times slower than Earth.

...

Even more importantly, in 1984, Dr Humphreys made some predictions of the field strengths of Uranus and Neptune, two giant gas planets beyond Saturn. His predictions were about 100,000 times the evolutionary dynamo predictions. The two rival models were inadvertently put to the test when the Voyager 2 spacecraft flew past these planets in 1986 and 1989. The fields for Uranus and Neptune3 were just as Humphreys had predicted.4 Yet many anti-creationists call creation ‘unscientific’ because it supposedly makes no predictions!

Humphreys’ model also explains why the moons of Jupiter that have cores have magnetic fields, while Callisto, which lacks a core, also lacks a field.

So, if his model explains so much data better than geodynamo theory, why haven't actual scientists accepted it? Moreover, why hasn't he published it in a peer-reviewed scientific journal yet?

I've read Mr. Tim Thompson comment that Humphreys' predictions on the fields of Uranus and Neptune are basically useless, but I didn't really understand why except that they were 'on the orders of magnitude' (e.g., vague and easy to 'predict' even with no theory at all?). Could someone elaborate?

I'd appreciate help debunking the other alleged predictions made by his theory that geodynamics 'doesn't account for' (like more rapid energy loss during reversals). Also, anything that his theory would choke on and die over but that geodynamics fit with perfectly would help...

Quote:

Cause of the Earth’s magnetic field

Materials like iron are composed of tiny magnetic domains, which each behave like tiny magnets. The domains themselves are composed of even tinier atoms, which are themselves microscopic magnets, lined up within the domain. Normally the domains cancel each other out. But in magnets, like a compass needle, more of the domains are lined up in the same direction, and so the material has an overall magnetic field.

Earth’s core is mainly iron and nickel, so could its magnetic field be caused the same way as a compass needle’s? No — above a temperature called the Curie point, the magnetic domains are disrupted. The earth’s core at its coolest region is about 3400–4700�C (6100–8500�F), much hotter than the Curie points of all known substances.

But in 1820, the Danish physicist H.C. �rsted discovered that an electric current produces a magnetic field. Without this, there could be no electric motors. So could an electric current be responsible for the earth’s magnetic field? Electric motors have a power source, but electric currents normally decay almost instantly once the power source is switched off (except in superconductors). So how could there be an electric current inside the earth, without a source?

The great creationist physicist Michael Faraday answered this question in 1831 with his discovery that a changing magnetic field induces an electric voltage, the basis of electrical generators.

Imagine the earth soon after creation with a large electrical current in its core. This would produce a strong magnetic field. Without a power source, this current would decay. Thus the magnetic field would decay too. As decay is change, it would induce a current, lower but in the same direction as the original one.

So we have a decaying current producing a decaying field which generates a decaying current … If the circuit dimensions are large enough, the current would take a while to die out. The decay rate can be accurately calculated, and is always exponential. The electrical energy doesn’t disappear — it is turned into heat, a process discovered by the creationist physicist James Joule in 1840.

This is the basis of Dr Barnes’ model.

Addendum: Answering sceptical objections

Exponential Decay?

Some sceptics have claimed that an exponential decay curve is wrong, and a linear decay should have been plotted. Now, both exponential and linear decay curves have two fitted parameters:

Exponential decay (i = Ie-t/t) requires the parameters I and t.

Linear decay of the general form y = mx + c requires the gradient m and y-intercept c.

If the fit were similar, there is no statistical reason to choose one over the other. The fit is very similar for the limited range of data available, with no significant difference between the two.

However, it is a well-accepted procedure in modelling of regression analysis to use meaningful equations to describe physical phenomena, where there is a sound theoretical basis for doing so. This is the case here. Currents in resistance/inductance circuits always decay exponentially, not linearly, after the power source is switched off. For example, in a simple electric circuit at time t with initial current I, resistance R and inductance L, the current is given by i = Ie-t/t, where t is the time constant L/R — the time for the current to decay to 1/e (~37%) of its initial value. For a sphere of radius a, conductivity s and permeability m, t is given by 4sma2/p.

A linear decay might look good on paper, but it’s physically absurd when dealing with the real world of electric circuits. In fact, linear decays are rare in nature in general. Conversely, exponential decay is firmly rooted in electromagnetic theory.

Thomas Barnes, who first pointed out magnetic field decay as a problem for evolutionists, was a specialist in electromagnetism and wrote some well-regarded textbooks on the subject. But most of his critics are crassly ignorant of the subject.

Another important point is that these calculations point to a maximum age of the earth. Even if the sceptics were right about a linear decay, it would still point to an upper limit of 90 million years, and this is far too young for evolution.

A final point is that if the decay really were linear, we haven’t got much time left before the Earth’s magnetic field disappears!

Multipole components of the field
Some sceptics have claimed:

“… only the dipole-field strength has been ‘decaying’ for a century and a half … the strength of the nondipole field (about 15% of the total field) has increased over the same time span, so that the total field has remained almost constant. Barnes’ assumption of a steady decrease in the field’s strength throughout history is also irreconcilable, of course, with the paleomagnetic evidenc of fluctuations and reversals [in the geomagnetic field] (Ecker, 1990, 105)’

The ‘authority’ turns out to be an anti-creationist dictionary compiled by an anti-Christian librarian with, as far as we are aware, no scientific training! Dr Humphreys answered in July 2001:

‘Litany in the Church of Darwin: “The non-dipole part of the earth’s magnetic field shall save us!” That is indeed an old and dismissive evolutionist argument. Tom Barnes discussed it in his papers during the 1970s. I discussed it near the end of my paper “A Physical Mechanism for Reversals of the Earth’s Magnetic Field During the Flood”.6

‘Over 90% of the field is dipolar (two poles, one north and one south), but the rest of it is non-dipolar, or multipolar, such as the quadrupole part (two north and two south poles), the octopole part (four north and four south poles), etc. Just imagine the fields from bar magnets tied together at various angles to one another.

‘In the 1970s, the evolutionists claimed that the very large energy (units are Joules or ergs) disappearing from the dipole part of the field is not really converted into heat, but is somehow being stored in the non-dipole part, later to be resurrected as a new dipole in the reverse direction. Some papers showed that the average field intensity (units are Teslas or Gauss) of some of the non-dipole parts is increasing slightly.7

‘But field intensity is not energy. To get the total energy in a component, one must square the intensity in a small volume around each point, multiply by the volume and a certain constant, and add up all the resulting energies throughout all space. The non-dipole intensities fall off (with increasing distance from the earth’s center) much faster than the dipole intensity, so the non-dipole parts are not able to contribute nearly as much energy to the total as the dipole part. That means the small increase in some non-dipole field intensities does not appear to represent nearly enough energy to compensate for the enormous energy lost year by year from the dipole part.

‘I have my doubts that the paper referred to actually proves the point the evolutionists want to make, that “non-dipole energy gain compensates for dipole energy loss”. Not only does my eyeball estimate above disagree, but the theory of reversals in my 1990 ICC paper disagrees [As shown below, Dr Humphreys no longer has his doubts — he (and anyone who checks the numbers) now knows that the evolutionist claim is fallacious]. It says that some energy will go into non-dipole components, but not nearly enough to compensate for the energy loss from the dipole part. The reversal process I propose is not efficient; it dissipates a large amount of energy as heat. I discussed this, including non-dipole parts by implication, in the second-to-last section (“The Field’s Energy Has Always Decreased&#8221

of my Impact article on the ICR website.

‘As further evidence, I used the authoritative International Geomagnetic Reference Field data — more than 2500 numbers representing the earth’s magnetic field over the whole twentieth century. The bottom line is this:

‘In the most accurately recorded period, from 1970 to 2000, the total (dipole plus non-dipole) energy in the earth’s magnetic field has steadily decreased by 1.41�0.16%. At that rate, the field would lose at least half its energy every 1500 years, give or take a century or so. This supports the creationist model that the field has always been losing energy — even during magnetic polarity reversals during the Genesis flood — ever since God created it about 6000 years ago.

‘The evolutionists, on the other hand, have no workable, mathematically-analyzable theory of reversals. They are claiming that whatever process actually caused the reversals was 100% efficient — that the total energy in their hoped-for future dipole field will be equal to the total energy which was in the dipole field at its last peak (about the time of Christ). That is, their faith in a billion-year age for the field requires them to believe that each cycle is resurrected phoenix-like from the ashes of the previous cycle — with no losses.

‘Put another way, the Church of Darwin requires them to believe that the Second Law of Thermodynamics — that all forms of energy devolve down to heat — does not apply to planetary magnetic fields. Sound familiar?’

Later, Dr Humphreys published ‘The Earth’s magnetic field is still losing energy’, CRSQ 39(1)1–11, March 2002, which explains the above and more in detail (see full article, off site).

Thanks for any help you can provide in debunking this particular piece of claptrap.

Moderators: the reason I posted this in S&S instead of EvC is that technically it's not an evolution issue, but one dealing with geology and possible pseudoscience... If you don't think so, I apologize in advance.

[ June 20, 2002: Message edited by: Allan ]

[ June 20, 2002: Message edited by: Allan ]</p>

Secular Pinoy · 06-20-2002, 03:25 PM

Heh, there are lots of geologists in the EvC forum, so you're missing a lot. There John Solum, Tim Thompson, and others. Don't let the geneticists and biologists in that forum scare you, geology is a legitimate EvC topic.

I haven't had time to read the following URL, but you might find it quite useful: [url=http://www.infidels.org/library/modern/dave_matson/young-earth/specific_arguments/magnetic_field.html]Dave Matson - Magnetic Field
/[url]

Deimos · 06-20-2002, 03:28 PM

Tim Thompson has written a <a href="http://www.talkorigins.org/faqs/magfields.html" target="_blank">talk origins article</a> on this. EDIT - DOH! I skimmed your post a little too fast, I see you've read it

Quote:

The evolutionists, on the other hand, have no workable, mathematically-analyzable theory of reversals. They are claiming that whatever process actually caused the reversals was 100% efficient � that the total energy in their hoped-for future dipole field will be equal to the total energy which was in the dipole field at its last peak (about the time of Christ). That is, their faith in a billion-year age for the field requires them to believe that each cycle is resurrected phoenix-like from the ashes of the previous cycle � with no losses.

Oh really, so what's this then - <a href="http://www.es.ucsc.edu/~glatz/geodynamo.html" target="_blank">Geodynamo</a>

[ June 20, 2002: Message edited by: Deimos ]</p>

Tim Thompson · 06-20-2002, 04:46 PM

Allan: I've read Mr. Tim Thompson comment that Humphreys' predictions on the fields of Uranus and Neptune are basically useless, but I didn't really understand why except that they were 'on the orders of magnitude' (e.g., vague and easy to 'predict' even with no theory at all?). Could someone elaborate? (<a href="http://www.talkorigins.org/faqs/magfields.html" target="_blank">On Creation Science and the Alleged Decay of the Earth's Magnetic Field</a>)

It's because Humphreys' theory is a sham, "window dressing" if you will. His verbatim prediction for the strength of the magnetic fields of Uranus & Neptune was "on the order of 10^24 J/T". Now, if a bright highschool student, bereft of any theoretical knowledge at all were to try to make the same prediction, how would they go about it? It would be easy to guess that since Uranus & Neptune are bigger than Earth, but smaller than Jupiter and Saturn, then the magnetic fields of Uranus & Neptune should likewise be bigger than Earth's, but smaller than those of Jupiter & Saturn.

So our highschool student looks up the field strengths. Earth = 7.9x10^22, Jupiter = 1.6x10^27 and Saturn = 4.3x10^25. The field for Jupiter is the biggest in the solar system, save only that of the sun itself. So, bigger than Earth and smaller than Saturn is roughly everything from 10^23 to 10^25. Split the difference and guess "on the order of 10^24". Voila, Humphreys' "prediction" duplicated by a school kid who does not even know what a magnetic field is. Humphreys could easily have guessed first, and then made up a "theory" with a free parameter that would reproduce his "guess". Just by looking at the numbers, how could anyone imagine that "on the order of 10^24" could ever be anything but right?

Allan Quotes: The evolutionists, on the other hand, have no workable, mathematically-analyzable theory of reversals ...

As usual, the creationist talks about science, but manages to avoid getting it right. Glatzmaier & Roberts managed to construct a realistic computer model of a full field reversal in 1995 (A 3-Dimensional Convective Dynamo Solution with Rotating and Finitely Conducting Inner-Core and Mantle, G.A. Glatzmaier & P.H. Roberts, Physics of the Earth and Planetary Interiors 91(1-3): 63-75, September 1995; A 3-Dimensional, Self Consistent Computer Simulation of a Geomagnetic Field Reversal, G.A. Glatzmaier & P.H. Roberts, Nature 377(6546): 203-209, September 21 1995). Since then there has been quite a bit of work on modeling the geodynamo, with reversals. It's not an effort without its own problems, but it is in fact vastly superior to anything the creationists have mustered forth (Geodynamo theory and simulations, G.A. Glatzmaier, Reviews of Modern Physics 72(4): 1081-1123, October 2000; The geodynamo, past, present and future, P.H. Roberts & G.A. Glatzmaier, Geophysical and Astrophysical Fluid Dynamics 94(1-2): 47-84, 2001; Geodynamo Simulations - How Realistic Are They?, Gary A. Glatzmaier, Annual Review of Earth and Planetary Science 30: 237-257, 2002; also see Gary Glatzmaier's webpage "<a href="http://www.es.ucsc.edu/~glatz/geodynamo.html" target="_blank">The Geodynamo</a>).

The problem for creationists is not that dynamo theory represents an alternative source for Earth's magnetic field, but that it represents a necessary alternative. Fluid motions in Earth's conductive outer core must produce a magnetic field. To claim that is not true is roughly equivalent to claiming that "physics" is not true, a long reach even for creationists.

We find the creationist say, for instance, ... "However, it is a well-accepted procedure in modelling of regression analysis to use meaningful equations to describe physical phenomena, where there is a sound theoretical basis for doing so." True enough, but in fact the creationist is bereft of "theoretical basis", and their treatment of the data is unjustified. Barnes, for instance, appealed to the exponential decay implied by Horace Lamb's study of currents in a solid sphere. That line of reasoning contiunes in the post cited here by Allan. But Earth's interior is not entirely solid, and Lamb's analysis is inapplicable to the fluid outer core.

Besides, what is "sound theoretical justification"? We know that Earth has a turbulent, fluid outer core. We know that the flow of fluid in that core must produce a magnetic field by dynamo process. So we assume that what we know must happen actually happens. That sounds like "sound theoretical justification" to me.

But what about the simple current flow postulated by the creationist? What "natural" process could produce such a current? None that I know of. So there is no "theoretical justifcation", sound or otherwise, for the creationist model. The presence of the current has to be postulated, whereas it can be derived from first prinsiples via dynamo theory.

In short, the value of Humphreys new result is rather overestimated by Humphreys, and the creationist gang. There is no stretch of the imagination that could lead from Humphreys' result (the field is losing energy), to Humphreys' conclusion (the field & Earth are "young"), unless one first postulates that Earth is in fact young (can you say "circular reasoning"?), and uses that postulate to create an ad-hoc model to support the postulate.

Personally, I prefer physics.

[ June 20, 2002: Message edited by: Tim Thompson ]</p>

WinAce · 06-20-2002, 05:11 PM

D'oh... <img src="graemlins/banghead.gif" border="0" alt="[Bang Head]" /> You mean the geologists don't make a habit of frequenting this forum? In that case, I'd like to ask that this topic be transferred over to EvC.

Tim Thompson's article is excellent, however, it doesn't contain a rebuttal to the new version of Humphreys' hypothesis, published in May, although some of it still seems to apply...

I'm unfamiliar with the intricacies of dynamo theory so I don't really understand the implications of it. Are those two articles simply lying when they say geodynamo theory can't account for extra energy loss during a reversal of the field or whatever they're claiming? <img src="graemlins/banghead.gif" border="0" alt="[Bang Head]" />

[edit]And now with Mr. Thompson's reply it seems they were lying, or at least deliberately misrepresenting the predictive power of their theory while hushing up the only alternative that physics agrees with... as usual. Sigh.

Thanks

[ June 20, 2002: Message edited by: Allan ]</p>

Chris_T · 06-21-2002, 06:53 AM

The thing that Dr. Humphrey ignores is that whilst the earths magnetic field really is reducing in field strength rapidly (geographic time scale, i.e time scale of creationist world age) and as such this evidence can be made to suggest that the earth is very young, this is not the whole picture. The magnetic field undergoes reversals on a regular basis. These reversals are not fully understood but are thought to be the result of changing currents in the liquid metal outer core. The changes in the current formations are thought to result in the changes in the earths magentic field.

Whilst these changes are not fully understood, there is a great deal of evidence that they exist. Either side of the mid-atlantic ridge new crust is being formed (at a rate of about 2-3cm's a year). This new crust is magnetised in the same direction as the earths field when it was formed. At regular intervals the magentic field of the crust to either side of the ridge can be seen to reverse. The most sendsible explanation of this is that when this crust was formed the magnetic field was differently aliened than it is now. The width of these zones combined with knowlege of the rate at which new crust forms supports the long term view of earth formation as opposed to the young earth of the creationists. There are other sources of evidence to back up the reversing of the earths field.

On an even shorter time scale the earths field is changing. The magnetic North is slightly off centre from the true geographical north pole. Anyone who reads maps will know this. The magnetic north pole is actually rotating about the true north pole at a rate of a few fraction of a degree per year. This is thought to be due to the corriolis forces acting on the currents in the outer core that cause the magentic field.

The heat that drives the currents in the outer corse is generated by nuclear decay. Any calculation based on heat loss over time of the core is bound to be wrong. Heat loss does occur, but there is no real net loss of heat. Nuclear decay generates new heat. Without this effect the earths core would be solid by now. This nuclear activity is unusual for planets. The moon and mars have solid inert interiors.

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06-20-2002, 03:25 PM	#2
Secular Pinoy Veteran Member Join Date: Feb 2001 Location: Quezon City, Philippines Posts: 1,994	Heh, there are lots of geologists in the EvC forum, so you're missing a lot. There John Solum, Tim Thompson, and others. Don't let the geneticists and biologists in that forum scare you, geology is a legitimate EvC topic. I haven't had time to read the following URL, but you might find it quite useful: [url=http://www.infidels.org/library/modern/dave_matson/young-earth/specific_arguments/magnetic_field.html]Dave Matson - Magnetic Field /[url]

06-20-2002, 04:46 PM	#4
Tim Thompson Regular Member Join Date: Sep 2000 Location: Pasadena, CA, USA Posts: 455	Allan: I've read Mr. Tim Thompson comment that Humphreys' predictions on the fields of Uranus and Neptune are basically useless, but I didn't really understand why except that they were 'on the orders of magnitude' (e.g., vague and easy to 'predict' even with no theory at all?). Could someone elaborate? (<a href="http://www.talkorigins.org/faqs/magfields.html" target="_blank">On Creation Science and the Alleged Decay of the Earth's Magnetic Field</a>) It's because Humphreys' theory is a sham, "window dressing" if you will. His verbatim prediction for the strength of the magnetic fields of Uranus & Neptune was "on the order of 10^24 J/T". Now, if a bright highschool student, bereft of any theoretical knowledge at all were to try to make the same prediction, how would they go about it? It would be easy to guess that since Uranus & Neptune are bigger than Earth, but smaller than Jupiter and Saturn, then the magnetic fields of Uranus & Neptune should likewise be bigger than Earth's, but smaller than those of Jupiter & Saturn. So our highschool student looks up the field strengths. Earth = 7.9x10^22, Jupiter = 1.6x10^27 and Saturn = 4.3x10^25. The field for Jupiter is the biggest in the solar system, save only that of the sun itself. So, bigger than Earth and smaller than Saturn is roughly everything from 10^23 to 10^25. Split the difference and guess "on the order of 10^24". Voila, Humphreys' "prediction" duplicated by a school kid who does not even know what a magnetic field is. Humphreys could easily have guessed first, and then made up a "theory" with a free parameter that would reproduce his "guess". Just by looking at the numbers, how could anyone imagine that "on the order of 10^24" could ever be anything but right? Allan Quotes: The evolutionists, on the other hand, have no workable, mathematically-analyzable theory of reversals ... As usual, the creationist talks about science, but manages to avoid getting it right. Glatzmaier & Roberts managed to construct a realistic computer model of a full field reversal in 1995 (A 3-Dimensional Convective Dynamo Solution with Rotating and Finitely Conducting Inner-Core and Mantle, G.A. Glatzmaier & P.H. Roberts, Physics of the Earth and Planetary Interiors 91(1-3): 63-75, September 1995; A 3-Dimensional, Self Consistent Computer Simulation of a Geomagnetic Field Reversal, G.A. Glatzmaier & P.H. Roberts, Nature 377(6546): 203-209, September 21 1995). Since then there has been quite a bit of work on modeling the geodynamo, with reversals. It's not an effort without its own problems, but it is in fact vastly superior to anything the creationists have mustered forth (Geodynamo theory and simulations, G.A. Glatzmaier, Reviews of Modern Physics 72(4): 1081-1123, October 2000; The geodynamo, past, present and future, P.H. Roberts & G.A. Glatzmaier, Geophysical and Astrophysical Fluid Dynamics 94(1-2): 47-84, 2001; Geodynamo Simulations - How Realistic Are They?, Gary A. Glatzmaier, Annual Review of Earth and Planetary Science 30: 237-257, 2002; also see Gary Glatzmaier's webpage "<a href="http://www.es.ucsc.edu/~glatz/geodynamo.html" target="_blank">The Geodynamo</a>). The problem for creationists is not that dynamo theory represents an alternative source for Earth's magnetic field, but that it represents a necessary alternative. Fluid motions in Earth's conductive outer core must produce a magnetic field. To claim that is not true is roughly equivalent to claiming that "physics" is not true, a long reach even for creationists. We find the creationist say, for instance, ... "However, it is a well-accepted procedure in modelling of regression analysis to use meaningful equations to describe physical phenomena, where there is a sound theoretical basis for doing so." True enough, but in fact the creationist is bereft of "theoretical basis", and their treatment of the data is unjustified. Barnes, for instance, appealed to the exponential decay implied by Horace Lamb's study of currents in a solid sphere. That line of reasoning contiunes in the post cited here by Allan. But Earth's interior is not entirely solid, and Lamb's analysis is inapplicable to the fluid outer core. Besides, what is "sound theoretical justification"? We know that Earth has a turbulent, fluid outer core. We know that the flow of fluid in that core must produce a magnetic field by dynamo process. So we assume that what we know must happen actually happens. That sounds like "sound theoretical justification" to me. But what about the simple current flow postulated by the creationist? What "natural" process could produce such a current? None that I know of. So there is no "theoretical justifcation", sound or otherwise, for the creationist model. The presence of the current has to be postulated, whereas it can be derived from first prinsiples via dynamo theory. In short, the value of Humphreys new result is rather overestimated by Humphreys, and the creationist gang. There is no stretch of the imagination that could lead from Humphreys' result (the field is losing energy), to Humphreys' conclusion (the field & Earth are "young"), unless one first postulates that Earth is in fact young (can you say "circular reasoning"?), and uses that postulate to create an ad-hoc model to support the postulate. Personally, I prefer physics. [ June 20, 2002: Message edited by: Tim Thompson ]</p>

06-20-2002, 05:11 PM	#5
WinAce Beloved Deceased Join Date: Feb 2002 Location: Carrboro, NC Posts: 1,539	D'oh... <img src="graemlins/banghead.gif" border="0" alt="[Bang Head]" /> You mean the geologists don't make a habit of frequenting this forum? In that case, I'd like to ask that this topic be transferred over to EvC. Tim Thompson's article is excellent, however, it doesn't contain a rebuttal to the new version of Humphreys' hypothesis, published in May, although some of it still seems to apply... I'm unfamiliar with the intricacies of dynamo theory so I don't really understand the implications of it. Are those two articles simply lying when they say geodynamo theory can't account for extra energy loss during a reversal of the field or whatever they're claiming? <img src="graemlins/banghead.gif" border="0" alt="[Bang Head]" /> [edit]And now with Mr. Thompson's reply it seems they were lying, or at least deliberately misrepresenting the predictive power of their theory while hushing up the only alternative that physics agrees with... as usual. Sigh. Thanks [ June 20, 2002: Message edited by: Allan ]</p>

06-21-2002, 06:53 AM	#6
Chris_T New Member Join Date: Jun 2002 Location: UK Posts: 1	The thing that Dr. Humphrey ignores is that whilst the earths magnetic field really is reducing in field strength rapidly (geographic time scale, i.e time scale of creationist world age) and as such this evidence can be made to suggest that the earth is very young, this is not the whole picture. The magnetic field undergoes reversals on a regular basis. These reversals are not fully understood but are thought to be the result of changing currents in the liquid metal outer core. The changes in the current formations are thought to result in the changes in the earths magentic field. Whilst these changes are not fully understood, there is a great deal of evidence that they exist. Either side of the mid-atlantic ridge new crust is being formed (at a rate of about 2-3cm's a year). This new crust is magnetised in the same direction as the earths field when it was formed. At regular intervals the magentic field of the crust to either side of the ridge can be seen to reverse. The most sendsible explanation of this is that when this crust was formed the magnetic field was differently aliened than it is now. The width of these zones combined with knowlege of the rate at which new crust forms supports the long term view of earth formation as opposed to the young earth of the creationists. There are other sources of evidence to back up the reversing of the earths field. On an even shorter time scale the earths field is changing. The magnetic North is slightly off centre from the true geographical north pole. Anyone who reads maps will know this. The magnetic north pole is actually rotating about the true north pole at a rate of a few fraction of a degree per year. This is thought to be due to the corriolis forces acting on the currents in the outer core that cause the magentic field. The heat that drives the currents in the outer corse is generated by nuclear decay. Any calculation based on heat loss over time of the core is bound to be wrong. Heat loss does occur, but there is no real net loss of heat. Nuclear decay generates new heat. Without this effect the earths core would be solid by now. This nuclear activity is unusual for planets. The moon and mars have solid inert interiors.

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