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junior06
2010-Dec-05, 04:03 AM
I wish to propose an alternative model of the Earth which could accomodate a void at its' centre.
Let me right away dissasociate myself from those unfortunate misinformed and dissalusioned individuals who advocate a hollow Earth peopled by lost civilisations and aliens etc. and anyone of their ilk.

With regard to the initial formation and subsequent evolution of planets, the understanding of the effect of gravity in this process is pretty much 'sewn up'. We know that the more matter a body draws to itself in its' formative phase, the greater its' mass becomes and also as a consequence, the wider its' gravitational 'envelope' becomes. This being the case, we know that the mass of any particular celestial body,(Let's be specific and call it the Earth), determines its' gravitational pull on any matter in its' vicinity determined by the distance of the matter from the mass.

The present understanding of the composition of the Earth is analgous to the following model;
( Thanks to the author of the model 'PZKPFW' for their erudite contribution and explanation of same as outlined in a previous thread. I have altered it slightly).The adapted model appears thus:
'123456789X987654321' The numbers represent the mass of the Earth,( in 3d of course), either side of 'X'( The centre of the planet). It is the accepted norm that the enormous pressure exerted on the core from the mass of the planet will be sufficient to prevent the formation of any void at the centre.It is also the accepted norm that the centre of the planet 'X' has zero gravity as a sum result of all the mass around it creating a gravitational equilibrium.

With regard to accretion, the question arises of when, in the formation of a planet, would a central void begin to develop? A legitimate answer to this is when the increasing internal friction created from the accumulating pressure exerted by the matter which is being added to the fledgling mass of the planet, starts to turn the interior molten. Irrespective of its' size, the zero gravity equilibrium at the centre is a state which is established from an early age. This, in combination with the early planets' centrifugal force of rotation,( the young evolving planet would have a much smaller diameter than the present size, so the core rotation would be much faster than the rotation as it is at present), could initiate the formation of the central void. Early massive and frequent volcanoes would further purge this central magma and would create the subsequent layers which would later dictate the subsequent composition of the adult planet,( crust, mantle, outer core etc.)

Following on from the creation of this early void is where I wish to introduce an alternative 'void accomodating' model where the effect of gravity has more influence on the composition of the planet than the effect of, ( and counteracting), the pressure of the mass of the planet 'squeezing' on the core. The alternative model is explained as follows:

'123456789......X.......987654321' The numbers represent the mass of the Earth either side of the centre 'X'.(In 3 dimensions of course).'.......' represent the diameter of the void. ( For the purposes of brevity, when discussing this model, we can assume that when describing the layers '123456789......X' on one side will also automatically relate to the opposite side 'X......987654321').

The final diameter of the void is determined when the pressure of the internal layers of the model have squeezed the mass 'above' them as much as they can. ( Much in the same way as the diameter of the Earth is determined by the limit external layers can squeeze down on the the layers below them). If you regard this heaviest densist region of the Earth's interior (3,4,5,6,7), as having,( by natural implication),a stronger, greater gravitational pull than the lighter less dense regions,it is important to remember that the layers '8,9 and 9,8', represent the INTERIOR surface layers of the model.(Layers '1,2' and '2,1', represent the EXTERIOR surface layers).The gravitational pull from the heavy dense regions of the model, exert equal pressure on both the lighter, less dense '1,2' and '2,1' external layers,(and also more significantly),the internal '8,9' and '9,8' lighter less dense layers.

The equilibrium for the ultimate diameter of the void is achieved through the effects of gravity as it would exist in the 'void accomodating' model as already described above. This regards the effect of gravity as being of greater influence than the 'squeeze' effect of pressure from the mass of the planet in the composition of the model. To explain further, if we look at the 'void' model 123456789.......X........987654321 The extenal layers 1,2,3,4, exert a gravitational pull on the internal layers 5,6,7,8,9. The internal layers 6,7,8,9 however, are also exerting an equal gravitational pull on the external 1,2,3,4,5 layers. The combined gravitational effects of both the internal and external layers exert the greatest squeeze on the molten middle 5 layer.

It is important not to underestimate the strength of the force of gravity and the role that it has in the composition of the model.This is the same force of gravity which holds the trillions X's ? of tons of Jupiter in orbit 483780000 miles distant from the sun.

PetersCreek
2010-Dec-05, 09:06 AM
It is important not to underestimate the strength of the force of gravity and the role that it has in the composition of the model.

But it seems to me, that is exactly what you are doing...underestimating the gravity brought to bear by the all of Earth's mass. You are selectively focusing on the effect 1234 and 6789 have on 5, while neglecting the effect of 987654321 and every other bit and piece of surrounding matter. And remember, the zero gravity equilibrium you mentioned is a point, not a region.

Garrison
2010-Dec-05, 02:22 PM
Sorry but wouldn't the measurements made by mapping seismic waves (http://www.sciencebuddies.org/science-fair-projects/project_ideas/Geo_p022.shtml)have indicated the existence of such such a void? Those measurements are based on the density of the material the different types of wave pass through, a void would, I imagine, produce some quite distinctive results. Sorry if the linked article is a little simplistic but it had the clearest illustrations. :)

Strange
2010-Dec-05, 03:00 PM
I wish to propose an alternative model of the Earth which could accomodate a void at its' centre.
Let me right away dissasociate myself from those unfortunate misinformed and dissalusioned individuals who advocate a hollow Earth peopled by lost civilisations and aliens etc. and anyone of their ilk.

The only difference seems to be that you are not claiming there is a civilization in this void.


This, in combination with the early planets' centrifugal force of rotation,( the young evolving planet would have a much smaller diameter than the present size, so the core rotation would be much faster than the rotation as it is at present), could initiate the formation of the central void.

Wouldn't the centrifugal force due to rotation also be zero at the center?

Why wouldn't any material that started to move away from the center be immediately be pulled back as it is no longer in a position of zero gravity?


The gravitational pull from the heavy dense regions of the model, exert equal pressure on both the lighter, less dense '1,2' and '2,1' external layers,(and also more significantly),the internal '8,9' and '9,8' lighter less dense layers.

Do the math. This is wrong.


The equilibrium for the ultimate diameter of the void is achieved through the effects of gravity as it would exist in the 'void accomodating' model as already described above.

As gravity only ever exerts a force towards the center, the stable equilibrium position is with no void.


It is important not to underestimate the strength of the force of gravity and the role that it has in the composition of the model.

I don't think you understand the way gravity works.

Both pressure and gravity will push things towards the center so your system is unstable. Especially if the inner part is liquid. Which we know it is. We also know, from seismic data, that there is no such void.

R.A.F.
2010-Dec-05, 05:02 PM
I wish to propose an alternative model of the Earth which could accomodate a void at its' centre. Let me right away dissasociate myself from those unfortunate misinformed and dissalusioned individuals who advocate a hollow Earth peopled by lost civilisations and aliens etc. and anyone of their ilk.

Yet your model "disassociates" itself from what is commonly accepted understanding concerning the interior of the Earth. You place yourself in their "ilk" by ignoring the same mainstream evidence as "they" do.


Sorry but wouldn't the measurements made by mapping seismic waves (http://www.sciencebuddies.org/science-fair-projects/project_ideas/Geo_p022.shtml)have indicated the existence of such such a void? Those measurements are based on the density of the material the different types of wave pass through, a void would, I imagine, produce some quite distinctive results. Sorry if the linked article is a little simplistic but it had the clearest illustrations. :)

I like the clarity of that page...we should keep that link "handy" for the next hollow Earth "proponent".

grapes
2010-Dec-05, 06:18 PM
I like the clarity of that page...we should keep that link "handy" for the next hollow Earth "proponent".Interesting "science fair" page.

I was intrigued by their reference "Robertson, date unknown" on the very first diagram, and I tracked it down (through the link at in the middle of the webpage) to this USGS circular: The interior of the Earth, an elementary description (http://pubs.er.usgs.gov/publication/cir532), first published in 1966, and reprinted many times. Unfortunately, that link clearly has the wrong abstract. It should be (from the circular itself):
Evidence on the structure and composition of the earth's interior comes from (1) observations of surface rocks, (2) geophysical data from earthquakes, flow of heat from the interior, the magnetic field, and gravity, (3) laboratory experiments on surface rocks and minerals, and (4) comparison of the earth with other planets, the sun, stars, and meteorites.

The major structural components in the earth that are separated by sharp discontinuities are the crust, the mantle, and the core. The crust forms a very thin surface skin, the mantle is a thick shell that extends half the radius down into the earth, and the core occupies the central part. The crust and upper mantle are known to vary in physical and chemical characteristics, both horizontally and vertically; the lower mantle and core are generally assumed to be uniform because their diagnostic geophysical phenomena are masked by the physical properties of the upper layers.I sent a msg to that effect to the usgs, but routed it through the librarians, they'd probably be the only ones who care :)

But it seems to me, that is exactly what you are doing...underestimating the gravity brought to bear by the all of Earth's mass. You are selectively focusing on the effect 1234 and 6789 have on 5, Worse, junior06 is assuming that that effect is important, when it is actually very nearly zero. It's a common misconception, but that should've been one of the lessons from reading the posts at that other thread: in a spherically symmetric situation, the gravitational effect of mass above a given radius is zero on points closer to the center.

junior06
2010-Dec-05, 11:48 PM
Sorry but wouldn't the measurements made by mapping seismic waves (http://www.sciencebuddies.org/science-fair-projects/project_ideas/Geo_p022.shtml)have indicated the existence of such such a void? Those measurements are based on the density of the material the different types of wave pass through, a void would, I imagine, produce some quite distinctive results. Sorry if the linked article is a little simplistic but it had the clearest illustrations. :)
Seismology utilises 2 types of bodywaves, P and S. Neither of these waves actually pass through the inner core. The existence of of a solid inner core is inferred from the readings from the seismographs. It is not primary evidence for the existence of a solid core.

junior06
2010-Dec-06, 12:26 AM
Wouldn't the centrifugal force due to rotation also be zero at the center?

Why wouldn't any material that started to move away from the center be immediately be pulled back as it is no longer in a position of zero gravity?

This would be true if the centre had a constant stable position. However, this is only a notional idea. In reality, the position of zero gravity at the centre wobbles around a central region influenced by the gravitational effects of 'local' masses in the vicinity of the earth. With regard to the fledgling planet, wasn't the moon the result of a collision with another neighbouring planet? Wouldn't the existence of this rogue mass have a major influence on this wobble? That notwithstanding the effect the subsequent cataclysmic collision would also have had on the position of zero gravity at the centre.


As gravity only ever exerts a force towards the center, the stable equilibrium position is with no void.

The equilibrium for the ultimate diameter of the void is achieved through the effects of gravity as it would exist in the 'void accomodating' model as already described above. This regards the effect of gravity as being of greater influence than the 'squeeze' effect of pressure from the mass of the planet in the composition of the model. To explain further, if we look at the 'void' model 123456789.......X........987654321 The extenal layers 1,2,3,4, exert a gravitational pull on the internal layers 5,6,7,8,9. The internal layers 6,7,8,9 however, are also exerting an equal gravitational pull on the external 1,2,3,4,5 layers. The combined gravitational effects of both the internal and external layers exert the greatest squeeze on the molten middle 5 layer.

The final diameter of the void is determined when the pressure of the internal layers of the model have squeezed the mass 'above' them as much as they can. ( Much in the same way as the diameter of the Earth is determined by the limit external layers can squeeze down on the the layers below them).

Both pressure and gravity will push things towards the center so your system is unstable. Especially if the inner part is liquid. Which we know it is. We also know, from seismic data, that there is no such void.

Geo Kaplan
2010-Dec-06, 02:27 AM
Please learn to use the quote function properly, and please reformat your previous post once you do. It's very hard to figure out who said what in the way you've formatted things.

grapes
2010-Dec-06, 03:41 AM
Seismology utilises 2 types of bodywaves, P and S. Neither of these waves actually pass through the inner core. The existence of of a solid inner core is inferred from the readings from the seismographs. It is not primary evidence for the existence of a solid core.Here's a wiki on seismic waves (http://en.wikipedia.org/wiki/Seismic_wave). The I wave is a P-wave in the inner core, the J wave is an S-wave in the inner core. So, the example at that webpage, sPKIKP is an s-wave that is reflected from the surface as a p-wave, which travels through the mantle, the outer core, the inner core, out the outer core, then back to the surface.

To explain further, if we look at the 'void' model 123456789.......X........987654321 The extenal layers 1,2,3,4, exert a gravitational pull on the internal layers 5,6,7,8,9. No. The net effect of layers 1,2,3,4 on each point interior to the 1,2,3,4 layers is zero, or reasonably close to zero, if we ignore the oblateness.

Garrison
2010-Dec-06, 06:31 PM
Seismology utilises 2 types of bodywaves, P and S. Neither of these waves actually pass through the inner core. The existence of of a solid inner core is inferred from the readings from the seismographs. It is not primary evidence for the existence of a solid core.

Well it appears from Grapes post #10 that it statement is incorrect, and it is regardless evidence that you must deal with. In essence junior06 the burden is on you to provide a coherent theoretical model for your proposal, fit the available evidence to it(or provide a valid reason to ignore the evidence), and demonstrate some reason why your model should be considered superior to the existing model.

junior06
2010-Dec-06, 07:45 PM
Having looked at all the current information regarding the composition of the earths' core, the evidence is incontravertable that it is pretty much impossible that a void could possibly be accomodated at the centre. Having seen the light, thanks to everyone who have contributed to the discussion,( some may say 'humoured me').This whole excersise has tought me not to try to prove a theory based on an 'intuitive hunch', without doing the proper research first. I apologise if anyone feels I have wasted their time. I have also learned I am not as smart as I thought I was and that some of you guys are very learned indeed. Thanks again for your input.

PetersCreek
2010-Dec-06, 08:16 PM
Having looked at all the current information regarding the composition of the earths' core, the evidence is incontravertable that it is pretty much impossible that a void could possibly be accomodated at the centre. Having seen the light, thanks to everyone who have contributed to the discussion,( some may say 'humoured me').This whole excersise has tought me not to try to prove a theory based on an 'intuitive hunch', without doing the proper research first. I apologise if anyone feels I have wasted their time. I have also learned I am not as smart as I thought I was and that some of you guys are very learned indeed. Thanks again for your input.

Yes, indeed, there are some very learned folks here (most far more than I, that's for sure) but we all still learn from discussions here. Thank you for ending the thread on a positive note of acknowledgement. We get them far too rarely here. With that, I am closing this thread as a done deal. If you or anyone else thinks of a good reason to reopen, please report this post.