Calendars Of The World

This is a spin off from The oldest religion topic. Lynx gave me the idea.

I read somewhere that the most accurate calendar is the Mayan calendar. I dont know exactly how it works but it is apparently incredibly accurate. Is there anyone who can explain it?
There is a Mayan profecy that this current cycle shall reach its end approx 2012, after which a new sun shall be born. That's in about nine Years!!!!! I hope their prophecies are not as accurate as their calendar!
Edit: typo LYNX

The news is worse than I thought:

They reveal that the Mayan calendar prophesies the end of our own "Age of the Jaguar", the fifth and final "sun" in 2012 AD. This, according to Cotterell's sun-spot theories, will be brought about by a sudden reversal in the earth's magnetic field.

http://www.knowledge.co.uk/xxx/cat/mayan/

So the film "The Core" is prophetic? :o

Hello Rat-Faced, back on duty?

Not having seen the film I cannot comment!

I have just placed a link to that Mayan calendar article.

If this is prophetic, there might not be anyone around to say!

However I have heard of the earth magnetic flux reversal in the past. These seem to follow a periode of no flux whatsoever. Records of the direction of Earths magnetic field seemed to be found at the bottom of the Atlantic oceaan along the mid Atlantic ridge.

I get a calendar from the milkman every year.

I have found it to be 100% accurate - every day and date as it should be.

No mention of the end of the world, so you are probably okay.

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Originally posted by nigel123@24 July 2003 - 17:29
Records of the direction of Earths magnetic field seemed to be found at the bottom of the Atlantic oceaan along the mid Atlantic ridge.

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I guess there must be something in it if they are going to those lengths to keep the records hidden.

Magnetic Flip-Flops
Considering that ships, planes and Boy Scouts steer by it, Earth's magnetic field is less reliable than you'd think. Rocks in an ancient lava flow in Oregon suggest that for a brief erratic span about 16 million years ago magnetic north shifted as much as 6 degrees per day. After little more than a week, a compass needle would have pointed toward Mexico City.
The lava catches Earth's magnetic field in the act of reversing itself. Magnetic north heads south, and -- over about 1,000 years -- the field does a complete flip-flop. While the Oregon data is controversial, Earth scientists agree that the geological evidence as a whole -- the "paleomagnetic" record -- proves such reversals happened many times over the past billion years.

"Some reversals occurred within a few 10,000 years of each other," says Los Alamos scientist Gary Glatzmaier, "and there are other periods where no reversals occurred for tens of millions of years." How do these flip-flops happen, and why at such irregular intervals? The geological data, invaluable to show what happened, registers only a mute shrug when it comes to the deeper questions.

For that matter, why is it that instead of quietly fading away, as magnetic fields do when left to their own devices, Earth's magnetic field is still going strong after billions of years? Einstein is said to have considered it one of the most important unsolved problems in physics. With a year of computing on Pittsburgh's CRAY C90, 2,000 hours of processing, Glatzmaier and collaborator Paul Roberts of UCLA took a big step toward some answers. Their numerical model of the electromagnetic, fluid dynamical processes of Earth's interior reproduced key features of the magnetic field over more than 40,000 years of simulated time. To top it off, the computer-generated field reversed itself.

"We weren't expecting it," says Roberts, "and were delighted. This gives us confidence we've built a credible bridge between theory and the paleomagnetic data." Their surprising results, reported as a cover story in Nature (Sept. 21, 1995), provide an inner-Earth view of geomagnetic phenomena that have not been observed or anticipated by theory. Furthermore, the Glatzmaier-Roberts model offers, for the first time, a coherent explanation of magnetic field reversal.


Journey to the Center of the Earth
Roughly speaking, Earth is like a chocolate-covered cherry -- layered, with liquid beneath the surface and a solid inner core. Beneath the planet's relatively thin crust is a thick, solid layer called the mantle. Between the mantle and the inner core is a fluid layer, the outer core. According to generally accepted theory -- the dynamo theory -- interactions between the churning, twisting flow of molten material in the outer core and the magnetic field generate electrical current that, in turn, creates new magnetic energy that sustains the field. "The typical lifetime of a magnetic field like Earth's," says Glatzmaier, "is several tens of thousands of years. The fact that it's existed for billions of years means something must be regenerating it all the time."
How do we know if the dynamo theory is right? To the consternation of our desire to understand what's happening inside the planet we live on, Jules Verne's Journey to the Center of the Earth is still fiction. There's no way to penetrate 4,000 miles to Earth's center, nor to monitor fluid motions or magnetism in the outer core.

The Glatzmaier-Roberts computational model may be the next best thing to a guided tour of inner Earth. While other models have given good clues that theory is on track, they have been limited by a two-dimensional approach that required simplifying assumptions. Roberts and Glatzmaier set out to implement a fully three-dimensional model, based on a computer program Glatzmaier developed over many years, that would allow the complex feedbacks between fluid motion and the magnetic field to evolve on their own -- in other words, to be solved "self consistently."

Simulated three-dimensional structure of Earth's magnetic field, with inward (blue) and outward (yellow) directed field lines. Field lines extend two Earth radii from the core. The location of the core-mantle boundary is evident where the structure becomes complex.
Their objectives, in retrospect, were modest. "Mainly," says Roberts, "we wanted to get a geomagnetic field that would maintain itself longer than the decay time. No one's ever done that in a self-consistent manner." After nearly a year running almost daily, as allocated computing time was about to expire, the model produced its Eureka moment.

By itself, the reversal is strong confirmation of the model, and other details -- magnitude and structure of the field -- also agree well with surface features of Earth's field. The simulation also offers precious insight into the dynamics that sustain the magnetic field and generate reversals. Contrary to what anyone guessed till now, the model shows that in the inner core the magnetic field has an opposite polarity from the outer core, and this stabilizes the field against a tendency to reverse more frequently.

"No one even dreamed about this," says Glatzmaier. "That's the nice thing about a supercomputer. You can just let it do its thing, solve these equations over and over -- a large set of variables affecting each other with nonlinear feedback, very hard to figure out. It's a beautiful problem for a supercomputer, and it's really exciting to see this structure and dynamics that no one imagined."











Reversal of Earth's Magnetic Field
Earth's magnetic field evolving for about 9,000 years before, during and after the simulated reversal. The outer circle indicates the fluid outer core boundary; the inner circle, the solid inner core. The left hemisphere shows magnetic field contours directed clockwise (green) and counterclockwise (yellow). The right hemisphere shows contours directed westward (blue) and eastward (red), out of and into the plane of the paper.

The left hemisphere shows that the field penetrating the inner core is opposed in polarity to the outer core, a feature completely unanticipated by theory. "The outer core polarity," explains Glatzmaier, "is continually trying to invade the inner core. Only when the whole field almost decays away, however [middle], does it finally have a chance to diffuse in. Once it does, the opposite polarity gets established. The inner core polarity is the stabilizing force, like an anchor, the slowest thing that can change."


Animation
1.62 MB
At about 36,000 years into the simulation the magnetic field reversed its dipole polarity over a period of only 1200 years. The image below is from an animated sequence showing how the field's structure changed.

Click on the image to the left to download the animation (1.62 MB).




--------------------------------------------------------------------------------
Researchers: Gary Glatzmaier, Los Alamos National Laboratory.
Paul Roberts, University of California-Los Angeles.
Hardware: Cray C90
Software: User-developed code.
Keywords: magnetic field reversal, lava, paleomagnetic record, geomagnetic phenomena, dynamo theory, outer core, inner core, polarity, Earth.

Related Material on the Web:
Los Alamos National Laboratory
Generation and Evolution of the Earth's Magnetic Field further information on the research by Gary Glatzmaier
Geodynamo -- The first self-consistent 3D numercial simulation of the "geodynamo".
Projects in Scientific Computing, PSC's annual research report.
PSC Scientific Visualisation Animations and Images

References, Acknowledgements & Credits

http://www.psc.edu/science/Glatzmaier/glatzmaier.html

http://www.isourcecom.com/maya/themaya/calendar.htm

The Core


On topic,

I have no idea which Calendar is the most accurate.

I do know that the Gregorian isnt, however.

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Originally posted by JPaul@24 July 2003 - 16:35
I get a calendar from the milkman every year.

I have found it to be 100% accurate - every day and date as it should be.

No mention of the end of the world, so you are probably okay.

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Thanks JPAUL, I do feel relieved!

Re Magnetic Flip-Flops

That paper doesn't appear to take into account that the earth is also passing through a rather large electric current (the solar wind) which would itself have an inductive effect not only on the iron core but also on the much more prevalent aluminium oxide deposits dotted around the world.
The earth also sits in the magnetic field of the sun, although due to it's distance this probably has much less effect.

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why is it that instead of quietly fading away, as magnetic fields do when left to their own devices, Earth's magnetic field is still going strong after billions of years? Einstein is said to have considered it one of the most important unsolved problems in physics.

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Einstein was unaware of the solar wind.

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According to generally accepted theory -- the dynamo theory -- interactions between the churning, twisting flow of molten material in the outer core and the magnetic field generate electrical current that, in turn, creates new magnetic energy that sustains the field.

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Hooray for perpetual motion.
It is believed that the magnetic field of the sun is also subject to frequent reversals, and the sun doesn't have the same physical properties (with the exception of the iron core).

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After nearly a year running almost daily, as allocated computing time was about to expire, the model produced its Eureka moment.

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Phew, that was lucky, wasn't it.

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"That's the nice thing about a supercomputer. You can just let it do its thing, solve these equations over and over -- a large set of variables affecting each other with nonlinear feedback, very hard to figure out. It's a beautiful problem for a supercomputer, and it's really exciting to see this structure and dynamics that no one imagined."

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Another nice thing about supercomputers is that you can mess about with variables until you get near the solution you are looking for, then lock off the awkward ones and let the computer generate lots of useful results.

I'm sure there is a lot more to it than is explained in this document, but there are also some glaring holes which haven't been explained.

I don't like knocking theories without providing an alternative, but so far I haven't had the chance. I'll try to do so.

@Lynx: I am sure it would be totally out of character if you did't try to.

Right, here we go then, first a word from NASA:

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We do not completely understand this process either in the sun or in the earth, BUT one of the prevailing theories called the Parker Dynamo Theory predicts that in a rotating, conductive system where magnetic fields are subject to 'cyclonic convestion', you end up with field flips with a time interval that depends on the density, conductivity and rotation rate of the system. I am not an expert in this area, but at least there is a theory to start from that SEEMS to explain some of this, and it works for both the sun and the earth! But there are many unsettled issues about just how the magnetic field is generated in the first place, and several observations that do not support this theory very well.

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(my underscoring)

Then a link because this one is a bit too long to quote here.

It is interesting to note that none of these theories seem to wish to take into account the basic theory of electromagnetism, which given the present direction of the solar wind and the rotation of the earth would by it's very nature create a magnetic field similar to that found surrounding our planet, although not of the same magnitude. However, it could provide a type of 'excitor' field.
The properties of excitor fields are well known in commercial power production where they used to create much greater magnetic fields at the heart of modern generators. Interestingly, in power generation it is the necessity to keep excitor fields in phase with the power being generated. Of course this is easy to do, since the field generator is simply a feedback from the power generated in the first place.
But there is no direct feedback in the case of the earth, so it is possible for phase slip to occur. And the side effect of phase slip is...

...field reversal.