1. Early theories
Since the scientific revolution, a small number of notable scientists have proposed the possibility of a hollow earth. One of the first was the famous English astronomer and mathematician, Sir Edmond Halley (1656-1742) . He held that the earth had an outer crust, 500 miles thick, and a hollow interior containing three smaller spheres, one within the other, approximately the size of Venus, Mars, and Mercury, each sphere being separated from the next by 500 miles of atmosphere. The smallest sphere was thought to form a hot, solid core. Halley speculated that the inner spheres might be inhabited, and that light might be produced in a number of ways: the atmosphere might be luminous, or the inner sides of the spheres might emit light, or there might be small suns within the earth.
Halley's theory of concentric spheres largely stemmed from his efforts to explain why the earth's magnetic poles appeared to be wandering. He believed that each sphere had its own set of magnetic poles, and that the outer sphere moved slightly faster than the rest, causing magnetic variations. Halley presented his theory to the Royal Society in 1692; it attracted a great deal of attention and was reprinted several times, though not many scientists took it seriously.
Leonhard Euler (1707-1783), the noted Swiss mathematician and physicist, also speculated about a hollow earth. In 1767 he proposed that the earth's hollow interior contained at its centre a small glowing core which served as a miniature sun for the inner world's hypothetical inhabitants . Sir John Leslie (1766-1832), a Scottish physicist and mathematician, proposed that the earth had a hollow interior containing twosuns, Pluto and Proserpina . Jules Verne's classic tale Journey to the Centre of the Earth (1864) was partly inspired by Leslie's ideas.
The idea of a hollow earth has received little interest from scientists since then, but there have been occasional exceptions. In 1892, C. Lapworth wrote:
everywhere we find evidences of symmetrical crushing-in of the earth-crust by tangential stresses. Everywhere we find proofs that different layers of that crust have been affected differentially, and the outer layers have been folded the most. We seem to be dealing, not with a solid globe, but with a globular shell composed of many layers.
Is it not just possible that our earth is such a hollow shell, or series of concentric shells, on the surface of which gravity is at a maximum, and in whose deepest interior it is practically non-existent? May this not be so, also, in the case of the sun, through whose spot-eddies we possibly look into its hollow interior? 
A name often mentioned in connection with the hollow-earth theory -- usually in order to ridicule it -- is Captain John Cleves Symmes (1779-1829) . He believed that the earth's interior was hollow, containing another four hollow, concentric spheres, with space between each, and habitable on both their concave and convex surfaces. He held that all celestial bodies had a similar structure. He estimated that the earth's outer shell was 1000 miles thick. Unlike Halley, he believed that there were enormous holes at the poles: 4000 miles across (12°) at the north, and 6000 miles (16°) across at the south, both being slightly askew. He argued -- quite wrongly -- that the refraction of sunlight percolating through the holes would be sufficient to cause the whole inner world to be lit with a perpetual day.
It is difficult to see how a newly forming planet could become a series of concentric spheres. But Symmes managed to interpret the rings of Saturn and the cloud belts of Jupiter as evidence for his theory. His arguments for gigantic polar openings were not very compelling either. He cited the supposedly abnormally warm climate in the polar regions, and believed that there was no ice beyond a certain latitude. He also invoked the alleged northerly migration of polar birds and animals, the erratic behaviour of the compass near the poles, and the aurora borealis, which he believed was caused by the sun's rays reflecting off the internal oceans and emerging through the polar holes. He held that polar explorers had probably sailed some distance over the rim of the openings, but not far enough to realize where they were.
Symmes' notion of polar openings earned him a great deal of ridicule. References to 'Symmes' hole' were common in the 1820s. If someone suddenly disappeared, the reply was often: 'Oh, I expect he's gone down into Symmes' hole.' Symmes announced that he was prepared to lead an expedition to the inner world. He said that his only terms were 'the patronage of this and the new world', and that he dedicated his quest to his wife and her ten children. On at least nine occasions, petitions signed by hundreds of Symmes' supporters were presented and debated before the US House of Congress with the goal of financing such an expedition, but without success. However, enthusiasm for Symmes' ideas appears to have been largely responsible for the US Exploring Expedition of 1838-1840, which first determined that the Antarctic was of continental dimensions.
Figure. Symmes' gaping hole.
1871 saw the publication of The Hollow Globe , a book written by Wm.F. Lyon, based on information channelled through M.L. Sherman, a clairvoyant. The central idea of the book is that the earth is a hollow sphere, with a shell some 30 to 40 miles thick, and that the interior surface is a beautiful world, in a more highly developed condition than the exterior, and is accessible by a spirally formed aperture located in the 'unexplored open polar sea'. The earth's inner concave surface is said to be habitable. The book presents various arguments against the then widely-held theory that beneath its thin crust the earth was filled with molten lava. It suggests that spiritual powers or 'world-builders' made all planets hollow, because that is the simplest and most economical shape, providing the greatest amount of strength compatible with the smallest amount of material.
The book by Lyon and Sherman was reviewed in the July 1884 issue of The Theosophist . The article is unsigned, implying that it was written by the editor, H.P. Blavatsky. She says that the book shows a high grade of intelligence and that the 'spirit' which inspired it was probably an adept, and possibly one of the adepts behind the founding of the Theosophical Society. She concludes that 'like other works of a similar character this book has appeared, before the world was ripe enough to understand it, and it is therefore known and appreciated by only comparatively few'. She expresses the hope that the author will fulfil his desire to enter the earth's interior, 'if not in his present incarnation, then in the next, as a member of the sixth race, forerunners of which have already made their appearance upon this, the exterior surface of our hollow globe'.*
*For an overview of the paradoxical statements on this subject found in modern theosophical literature, see Theosophy and the hollow earth,http://ourworld.compuserve.com/homepages/dp5/hollow.htm.
Another notable book is Etidorhpa or The End of Earth by John Uri Lloyd, first published in 1895 . Written in the form of a novel -- a story within a story -- it appears to contain a certain amount of scientific and esoteric information.* The earth is depicted as hollow, with an outer shell 800 miles (1280 km) thick. (This is certainly more plausible than the figure of 30-40 miles (50-65 km) given by Lyon and Sherman; some hollow-earthers suggest a figure of 1000 miles or even 2000 or more miles.) The shell is said to be honeycombed with caverns, containing a wide variety of plant and animal life. At a certain depth below the earth's surface, the earth begins to generate its own luminosity. Gravity is said to increase to a depth of about 10 miles (16 km) below sea level, and then to steadily decrease, reaching zero at the 'sphere of rest', 700 miles (1120 km) below the outer surface, and 100 miles (160 km) from the inner surface. No details are given of the inner world, or inner circle, but the implication is that it is habitable.
*In his book debunking the hollow-earth theory, Kafton-Minkel describes Etidorhpa as a unique work and the most remarkable of the inner-world novels. ('Etidorhpa' is 'Aphrodite' spelt backwards.)
The book was formerly sold by the publishing company of the Point Loma Theosophical Society, and the following notice appeared in the May 1896 issue of its journal, Theosophy (p. 62): 'One of the most fascinating books which has appeared for years is Etidorhpa. It is fiction of the most scientific kind, full of facts as well as, to the average man, full of theories, and a vein of the most serious occultism runs through its 360 pages. The author, John Neri [Uri] Lloyd, is one of the best-known chemists in America, and his book has aroused wonderful interest among scientific and literary people. It is safe to say that no book on such lines has set so many people hard a-thinking in years. It will possess additional interest to members of the T.S. by reason of the many illustrations by one of our devoted members, J. Augustus Knapp of Cincinnati.'
In Living Energies (Bath: Gateway Books, 1996), Callum Coates draws attention to the important information provided in Etidorhpa on the functioning of springs and artesian wells (pp. 133-4). He also writes: 'in keeping with all other globular cell-structures, the Earth [may be] hollower than we presently think, which may be why it resonates like a bell when seismic charges are set off. Solid bodies do not resonate so readily' (p. 86).
The Phantom of the Poles by William Reed was published in 1906 , and A Journey to the Earth's Interior by Marshall B. Gardner was first published in 1913 . These two books have had an enormous influence on virtually all subsequent writers on the hollow earth. On the basis of the accounts of polar explorers, both authors came to the conclusion, quite independently of each other, that at the north and south poles there were large entrances to the earth's interior. Reed held that the earth's shell was 1000 miles thick, and that the southern polar opening was 1500 miles in diameter and the northern one 1000 miles in diameter. Gardner believed that the earth's shell was 800 miles thick, and both openings 1400 miles across. Reed, like Symmes, seemed to think that sunlight shining into the polar openings would be sufficient to illuminate the interior, while Gardner revived Euler's idea of a central sun, which he thought was 600 miles in diameter. Like Symmes, Gardner was an evangelist, and mailed scores of copies of his book to professors, legislators, presidents, and kings.
Figure. The earth according to Gardner.
If a gigantic polar hole did exist, and if the earth's convex outer surface curved smoothly inward until it became the inner concave surface, it would in theory be possible to walk or sail from the earth's exterior to the interior and back. The highest point of the rim or verge around the entire hole would be the 'north pole' in the sense that the polestar would be directly above the head of a person standing there. As the rim was approached, a degree of latitude would become ever shorter, giving explorers the impression that they had travelled much further than expected.
Many of the arguments for large polar holes presented by Gardner and Reed are the same as Symmes'. Most are very feeble and some are patently ridiculous. Reed, for example, argued that the flattening of the poles (which he apparently understood to mean that the poles were literally flat!) proved that there must be a polar opening, as this would detract from the earth's roundness. As a example of how the hollow earth with its central sun may have formed, Gardner cited the Ring Nebula in the constellation Lyra, which looks like shells of gas surrounding a star, and which he believed would eventually contract into a planet with a central sun. Such nebulae were in fact called 'planetary nebulae' in the astronomy texts of that day because they look much like planets in low-powered telescopes. However, the central star of the Ring Nebula is much larger than any known planet, and the shell of gas surrounding it, millions of miles across, is expanding, not contracting, as the Ring Nebula is the remnant of a nova or exploding star. Gardner also believed that the Andromeda Nebula was in the early stages of becoming a planet, whereas it is now known to be a galaxy larger than the Milky Way!
Reed, writing in 1906, argued that the reason the north pole had not been discovered was because it did not exist on the earth's surface but in midair, in the centre of the polar opening. Gardner, on the other hand, published his book several years after the north pole had apparently been reached: Dr Frederick A. Cook claimed to have reached it in April 1908, and Commander Robert E. Peary in April 1909. However, Gardner highlighted the bitter dispute that erupted between these two explorers and their supporters (see part 3). He suggested that both had spent weeks wandering lost on the verge of the northern polar hole, and that Peary in particular may have had a problem telling the truth.
Both Reed and Gardner assumed that the inner world had a warm climate and that warm air escaping through the northern polar hole caused the Arctic to be abnormally warm. However, while carefully selecting examples of polar explorers encountering warm conditions in certain parts of the Arctic, they tend to ignore the bitter cold that is far more prevalent. It is well known that the climate within the arctic circle varies greatly depending on latitude, proximity of the sea, elevation, and topography, and that warm ocean currents around some of the arctic coasts allow an abundance of marine life.
In the northern hemisphere the zone of lowest temperature (the 'cold pole') lies in eastern Siberia, several hundred kilometres south of the arctic circle, in a region far removed from the moderating influence of the ocean. Here temperatures as low as -71°C have been recorded. At Olekminsk, which lies some 1100 km from the nearest ocean, the temperature can be as low as -60°C in the winter but as high as 45°C in the summer -- the greatest temperature range in the world; its all-year average is about 0°C. The lowest all-year temperatures are found in the Greenland interior, with an all-year average of -29°C. This is because, in contrast to the thin ice cover in Siberia, the Greenland ice sheet never completely melts in summer . On 5 April 1969 Wally Herbert and his Transarctic Expedition team found the temperature at the north pole to be -37.2°C. Obviously Reed and Gardner's hot air must have been blowing in the wrong direction at the time!
Reed and Gardner propagated the view that instead of an ice-covered ocean in the far north, there was an open polar sea. This view was held by many 19th-century explorers but was disproven by Fridtjof Nansen's epic voyage in the Fram from 1893 to 1896, though Reed and Gardner managed to convince themselves otherwise (see part 3).
Reed argued that polar meteor showers, and the dust and stones found in arctic ice were the debris of volcanic eruptions in the interior world, and that coloured snow was caused by massive amounts of pollen originating from lush plant and flower growth inside the earth. Gardner claimed that the frozen mammoths found in Alaska and Siberia were from the earth's interior; they had allegedly died while searching for food, fallen into the ice and been quick-frozen, and had then been carried over the verge of the opening by ocean currents. The reason they were often well-preserved was because they had died only recently. However, many mammoth carcasses have been found frozen into the tundra hundreds of miles from the ocean and the vast majority are not well preserved.
Reed and Gardner drew attention to the fact that birds, polar bears, foxes, and musk oxen in the Arctic had been seen moving north for the winter, and that this had given many polar explorers the impression that a warm continent must exist near the north pole. Reed and Gardner believed the land actually lay inside the earth. Debunkers of the hollow-earth theory dismiss polar explorers' anomalous observations of animal movements as fragmentary and unreliable .
Reed and Gardner speculated that the earth's interior was probably inhabited. Gardner believed it was the original home of both the Eskimos and all the East Asian peoples. He even suggested that the 'up and outward position' of Chinese eyes may be 'a modification of the ordinary eye position induced by the fact that in the interior the sun is always in the zenith'! He called on all fellow-patriots to urge the American government to mount an expedition to colonize the inner world, as this 'would add the most glorious page yet written to the annals of the United States'.
Much of what was written on the hollow earth during the 20th century is of little or no value. Many of Reed and Gardners' arguments have been trotted out time and again, while the results of later exploration have been largely ignored. Perhaps the most widely-read book on the subject is The Hollow Earth (1963), written by Dr Raymond Bernard , which rehashes most of the flimsiest and silliest arguments for a hollow earth with large polar openings. Many explorers have now walked or sledged to the poles, flown over them, satellites have photographed them, and there is a permanently manned base at the south pole. A number of expeditions have crossed directly across the north and south poles, and some have approached each other from different parts of Antarctica and met at the correct spot. But no polar openings have apparently been discovered. At least, none are marked on maps. This is seen by many hollow-earthers as evidence of a vast international conspiracy !
1998 saw the publication of Jan Lamprecht's book Hollow Planets , which attempts to tackle the issue from a more scientific angle. But he, too, believes that there is a massive coverup taking place to conceal smaller polar holes, measuring perhaps 200 miles across, and offset from the geographic poles (see part 3). Lamprecht at least puts paid to the idea that a large northern polar opening can be seen on certain satellite photos  -- which some writers claim were released to the public before the authorities realized what they showed and before the photos could be falsified or suppressed. The 'holes' mostly turn out to be storms and temporary circular air currents. What's more, they are found in all manner of locations: for instance, one satellite photo shows a feature 900 miles in diameter over the Kamchatka Peninsula in Russia (see figure below), while another shows a feature 800 miles across over Greenland. But it seems that for some hollow-earthers even a polar opening that changes size and jumps from place to place is preferable to none at all!
Figure. A hole in the pole? 
Although mainstream scientific interest in the possibility of a hollow earth is nonexistent, there has been a small amount of speculation about hollow moons. In 1959, Soviet scientist Iosif Shklovsky argued that the acceleration of Phobos (the inner moon of Mars) was so large that it had to be hollow, given the calculated drag force and mass, and might therefore be artificial. However, he later discarded this theory as the acceleration proved to be much smaller and the atmospheric model incorrect .
In the mid-1970s, two senior Soviet scientists, Mikhail Vasin and Alexander Shcherbakov, suggested that the earth's moon was partially hollow. Unable to believe that it could be naturally hollow, they argued that it had been partially hollowed out by an alien civilization, which turned it into a huge spaceship and steered it into orbit around the earth. This theory was then elaborated upon by Don Wilson .
One of their arguments was that the chance of the earth capturing the moon by accident is extremely tiny, and the chances of this resulting in a circular orbit such as the moon now has are even tinier. Another argument was that the moon's (theoretical) density is much less that the earth's (3.3 as opposed to 5.5 g/cm³). They also pointed out that moon craters, even those 100 miles or more across, are only a mile or two deep whereas the largest ought to be 24-30 miles deep. They argued that the consistently shallow depth of craters (most of which are assumed to be due to impacts) was the result of the moon having a 20-mile layer of metallic armour plating beneath the 2.5-mile-thick outer layer of rock. Another argument was that when lunar modules and spent rocket stages were made to crash into the moon, it rang like a bell (or a huge hollow sphere) for up to four hours; moreover, the shock waves started small, then built up to a peak, before dying away. This was completely unexpected.
Several other scientists have pointed to facts that could indicate that our moon is hollow, though this possibility has never been entertained very seriously. For instance, in 1962, a NASA scientist, Dr G. McDonald, wrote in Astronautics: 'If the astronomical data are reduced, it is found that the data require that the interior of the Moon be less dense than the outer parts. Indeed, it would seem that the Moon is more like a hollow than a h***genous sphere' . McDonald did not accept this conclusion and assumed that either the data or the calculations must be wrong. Dr S.C. Solomon of MIT claimed that a study of the gravitational field of the moon indicated that it could be hollow. He concluded his study, published in The Moon, An International Journal of Lunar Studies, as follows: 'The Lunar Orbiter experiments vastly improved our knowledge of the Moon's gravitational field . . . indicating the frightening possibility that the Moon might be hollow' . On the basis of seismic data, various models of the moon were produced. In 1974 Science News reported that 'Some such models would have made for a rather bizarre Moon, such as a hollow titanium ball' . The moon's seismic behaviour is now considered to be compatible with its solidity.
According to a modern geological textbook: 'Geologists could be wrong about the earth's interior, but the current model of a solid rock mantle and a liquid metallic core with a solid inner core is widely accepted because it is consistent with all available knowledge. A hollow earth is not' . Three objections to a hollow earth are mentioned:
1) it would not have seismic-wave shadow zones;
2) it would not have an average density of 5.5 g/cm³;
3) it would not have a magnetic field.
All these objections make the convenient assumption that current theories of seismicity, gravity, and geomagnetism are correct, but as shown in part 1, there is good reason to doubt this. The solid-earth model is based on assumption upon assumption about every parameter.
Regarding the second objection, it has already been shown that the true mass and density of the earth are unknown. The other two objections are considered below.
The dominant boundary in the earth's interior is believed to be that between the mantle and outer core. The vast majority of seismic waves are thought to travel through the mantle and many bounce back and forth between the earth's outer core and the surface. Very few are believed to penetrate the outer core, and even fewer pass through the inner core. The depth of the core-mantle boundary is said to be 2900 km, but this is likely to be wrong if scientists are wrong about the density distribution within the earth. As shown in part 1, seismologists are known to be making systematic errors in their interpretations of seismic data even in the outer few kilometres of the earth's crust.
As mentioned earlier, there are two main types of seismic waves that pass through the body of the earth: P waves and S waves. P waves can travel through solids, liquids, and gases, while S waves can only travel through a solid medium. Because no S waves appear beyond 103° from an earthquake epicentre, scientists have concluded that S waves do not penetrate the core. P waves, on the other hand, are almost entirely absent between approx. 103° and 142° from the epicentre of an earthquake, from which it is concluded that they do penetrate the outer core, but are sharply refracted when entering and leaving, thus creating the 'shadow zone'. Scientists infer from this that the outer core is liquid. Theoretically, it could be gaseous, but this is regarded as impossible.
It could be argued that what scientists call the crust and mantle corresponds to the outer solid shell of a hollow earth, while the outer core is the 'hollow' cavity, and the inner core is the central sun. Scientists maintain that P waves, but not S waves, pass through the liquid 'outer core'. But would this be possible if the outer core were really a 'hollow' cavity? Clearly, hollow-earthers would not argue that the earth's interior is an absolute void. The earth's outer surface is covered by a gaseous atmosphere, the outer regions of which are an ionized gas (plasma), which thins until it merges into the interplanetary medium (an even more attenuated plasma), which stretches to the sun (believed to be a ball of plasma). The space between the earth's inner surface and an inner sun may contain similar grades of matter.
But would such a model be able to reproduce the travel times of P waves that in the current model are thought to have travelled through the dense 'outer core'? At the outer core, P-wave velocity is said to fall from about 13.6 to 8.1 km/s. This need not be exactly true, for although the overall travel times of seismic waves are known with a high degree of precision, the exact path and varying velocities of seismic waves within the earth are impossible to determine. However if, in the hollow-earth model, we place a thin atmosphere above the inner surface, then seismic-wave speeds in it may be only a fraction of the 'scientific' value; in the outer atmosphere the speed of sound is only 331 metres per second! So this model will probably only work if we assume that the inner cavity contains an etheric medium through which seismic waves can propagate at much faster speeds. Although the existence of an all-pervading medium of subtler, etheric matter is a logical necessity, whether it would allow the effects described here is unknown.*
*Substituting 'empty space' and field equations for an all-pervading medium is unsatisfactory; abstract mathematical descriptions explain nothing (seeSpace, time, and relativity, http://ourworld.compuserve.com/homepages/dp5/relativ.htm).
Light propagates through the ether rather than an absolute void. It is known that certain electromagnetic waves in the atmosphere can produce sound waves when they strike the earth. But the speed of light is some 33,000 times greater than the theoretical seismic velocities in the 'outer core'.
If the force of gravity on both the outer and inner surfaces of the earth's solid shell is directed 'downward', i.e. into the shell, there must be a zone of zero gravity somewhere within the shell, where these two forces cancel. Etidorhpa places this 'energy shell' or 'sphere of rest' at a depth seven eighths of the distance from the outer to the inner surface. Such a zone might reflect S waves and most P waves. Some of the P waves that pass through it, or perhaps the vast majority, might then be channelled around the earth between the inner surface and the energy sphere, with most of them being refocused on the other side of the earth, thereby creating the P-wave shadow zones. In this model, rather than P waves travelling more slowly through the 'outer core' than through the mantle, most may not travel through the cavity at all but make a detour around it, so that their slower speed is only apparent. However, if virtually no P waves travel through the cavity, some explanation other than a central sun would be needed to account for the seismic data that suggest an 'inner core'.
Seismic data alone cannot determine whether the earth is solid or hollow, because they cannot be interpreted without making certain fundamental assumptions. As indicated in part 1, the conventional assumptions about gravitational acceleration, density, and pressure within the earth are open to doubt. It is therefore possible that seismic waves follow different paths and have different velocities than scientists think, and that the standard earth model is far removed from reality.
A hollow earth would require a new theory of geomagnetism since it would rule out the present dynamo model -- which, as shown in part 1, is highly dubious anyway. A number of alternative mechanisms have been put forward, but none has won widespread support . Magnetism is caused by charged particles in motion, and an alternative theory is that the earth's magnetic field is generated by charges in the earth's atmosphere and the crust, which are carried with the earth as it rotates. The main objection to this theory is that planets would have to have enormous electric fields in their atmospheres and there is no evidence of this. But nor is there any evidence disproving it; the earth's background electric charge cannot be measured directly from the earth itself .
A rotating planet can be compared to an electrical solenoid . A solenoid consists of a coil of wire, and when a current is passed through it, a magnetic force is generated at right angles to the direction of the wire. Since planets carry charges with them in their atmosphere and crust, this generates electrical currents in the direction of rotation, or east-west. The magnetic field is generated at right angles to this, i.e. north-south.
The most detailed alternative model of the geomagnetic field has been developed by Harold Aspden, who argues that the field is generated mainly by ether spin . More specifically, it arises from charge displacement caused by the spinning ether sphere located within the earth and extending about 100 km above its surface, in conjunction with a balancing charge displacement in the matter constituting the physical earth. Aspden explains that, with a distributed core charge of one polarity and a compensating surface charge of opposite polarity, the earth's rotation would produce a magnetic field that matches what is observed. The reason the magnetic poles are offset from the geographic poles is because the ether sphere spins about an axis that is tilted with respect to the earth's spin axis. And the reason the magnetic poles move around the geographic poles earth is because the ether spin axis precesses around the earth's spin axis.
In the light of Aspden's theory, a spinning, ethereal central sun could play a key role in generating the main magnetic field. Other factors contributing to the irregular and varying nature of the overall geomagnetic field includd electric currents in the ionosphere and magnetosphere, magnetized rocks in the earth's crust, electric currents in the earth's crust (telluric currents), subterranean flows of brines and other conducting fluids, and ocean current effects . The concentration of charges in the atmosphere fluctuates according to a 24-hour cycle, just as the magnetic field undergoes daily fluctuations. The field increases during solar flares and sunspot activity, when the earth receives more charged particles.
Rocks cannot retain magnetism when the temperature is above the Curie point (about 500°C for most magnetic materials), and in the standard earth model, this restricts magnetic rocks to the upper 40 km of the earth's interior. In the hollow-earth model, on the other hand, only certain parts of the earth's outer shell would probably be above the Curie temperature, and metallic deposits would make a far greater contribution to the earth's permanent magnetism and to regional magnetic anomalies.
Palaeomagnetic studies show that some ancient rocks have been magnetized in a direction opposite to that of the present magnetic field. The scientific consensus today is that the global geomagnetic field at the time these rocks formed had a reversed polarity. In at least some cases, however, rocks with inverse magnetism may have undergone self-reversal at a later stage, or reflect a regional magnetic anomaly. Even today there are isolated spots of opposite magnetic polarity in both the northern and southern hemispheres.
If global magnetic reversals have occurred, they could be caused by the sign of the electric charge of the earth or its atmosphere, or the direction of electric currents in the crust or atmosphere being reversed by some mechanism. Aspden suggests that geomagnetic reversals could be due to the solar system periodically entering space domains in which electric polarities are reversed. In addition, an electrochemical cell can self-reverse, and the earth may contain giant electrochemical cells . One of the exernal sources of the earth's magnetic field is the ring current in the outer Van Allen radiation belt. Paul LaViolette argues that very intense solar activity could strengthen the ring-current magnetic field to such an extent that it could reverse the polarity of the earth's main magnetic field . Furthermore, the sunspots of the outer sun are known to undergo polarity reversals in a cycle of about 22 years, and something similar might happen with an inner sun, contributing to magnetic anomalies at the earth's surface.
Given the problems faced by the dynamo theory and the existence of other ways of generating a planetary magnetic field, geomagnetism does not rule out the possibility of a hollow earth.
Gravity and isostasy
If the newtonian theory of gravity were correct, there could be no huge caverns in the earth's outer shell and no tunnels connecting the outer and inner worlds. Even a few kilometres beneath the earth's surface the immense pressures would cause any cavities to collapse. Moreover, a habitable inner surface, with gravitational forces holding inhabitants 'down', would be impossible, because the gravitational attraction of the matter beneath their feet would be counteracted by the gravity of the matter forming the earth's shell above their heads -- i.e. on the opposite side of the 'cavity' -- and by the attraction of the inner sun.
However, if, as several experiments suggest, the newtonian assumption that gravity has unlimited penetrability is incorrect, and negative particles and ions can screen or counteract the attractive force of gravity , pressures (and temperatures) would not increase steadily with depth, the earth's shell could be honeycombed with cavities and tunnels, and the force of gravity on the inner concave surface would be compatible with life.
Isostasy is the theoretical balance of all large portions of the earth's crust as though they were floating on a denser underlying layer, about 110 km (70 miles) below the surface. Theoretically, if a section of lithosphere is loaded, e.g. by ice, it will slowly subside to a new equilibrium position; and if a section of lithosphere is reduced in mass, e.g. by erosion, it will slowly rise to a new equilibrium position. It might be argued that without a superheated, viscous mantle below the Moho boundary, isostasy would not work. In actual fact, whether the traditional 'mantle' exists or not, the simplistic theory of isostasy has already been shown to have serious shortcomings.
Much of the evidence to support isostasy has come from observations of the apparent rebound of the crust following the retreat of the late Pleistocene ice sheets from northwest Europe and Canada. However, while the north of Sweden appears to be in the process of uplift, as ideas on isostasy require, the southern parts of the country are sinking. Since scientists largely base their estimates of mantle viscosity on selective data on 'postglacial rebound', their estimates are unlikely to be correct.
Antarctica is thought to have supported massive ice sheets for most of the past 15 million years. If the mantle were subject to deformation under such loading, even at a nominal rate of 1 mm/year, the crust there should have subsided by 15 km -- which has obviously not happened. In fact, the Trans-Antarctic mountains, only several million years old, are elevated more than a kilometre above sea level, showing that the lithosphere/mantle is capable of lifting continental ice sheets, rather than being depressed by them. The most concentrated crustal loading of the earth's lithosphere probably occurs beneath large seamounts, since the ocean crust is fairly thin. However, on the basis of the current earth model, Peter James has calculated that the bearing capacity at the Moho is an order of magnitude greater than the imposed loading of a seamount, so that isostasy cannot explain their subsidence .
The theory of isostasy is tested by making gravity measurements over the earth's surface. On the assumption that gravity is proportional to inert mass, positive or negative gravity anomalies are interpreted as indicating an excess or deficiency of mass, and therefore departures from isostatic equilibrium. Gravity measurements reveal many large-scale 'isostatic' anomalies. For instance, an enormous area of 'negative mass' covers part of India and most of the adjacent Arabian Sea, yet there is no evidence that the lithosphere there is being upwarped. Moreover, in regions of tectonic activity vertical crustal movements often intensify gravity anomalies rather than acting to restore isostatic equilibrium. For example, the Greater Caucasus shows a positive gravity anomaly (usually interpreted to mean it is overloaded), yet it is rising rather than subsiding. The greatest anomaly of all is the triaxial deformation of the earth. In addition to the rotation axis and the (43-km-longer) equatorial axis, the earth has a third axis, roughly through the equator; as a result, the equator is a little flattened, being oval rather than truly circular. The earth's shape is distorted by protuberances of various shapes and sizes, equivalent to about 2000 feet of rock, or over a mile of ice, and the anomalies have spans of the order of thousands of miles .
The fact that there is no empirical basis for the common assumption that gravity is proportional to mass casts doubt on the standard interpretation of gravity measurements; rather than being a direct function of the quantity of matter, the strength of the gravitational force may depend on the electrical and other properties of matter. The defective theory of isostasy can certainly not be used to lend weight to the orthodox picture of the 'mantle'.
The earth's crust has undergone oscillating uplifts and subsidences throughout geologic history. Most of the sediments forming the continents were laid down under the sea, and the total thickness of sediments is sometimes as much as 20 km, showing that vertical movements of about the same magnitude have taken place. There is also mounting evidence for submerged continental landmasses in the present oceans. It is widely believed that 'mantle' heat flow and vertical and horizontal movements of mantle material can cause significant changes in crustal thickness, composition, and density, resulting in substantial uplifts and subsidences.
Neither vertical crustal movements nor earthquakes and volcanoes require a solid earth, with a high-density, permanently superhot 'mantle'. However, there must certainly be zones within the earth's shell where very high temperatures exist. The theory of surge tectonics postulates that all the major features of the earth's surface, including rifts, foldbelts, metamorphic belts, and strike-slip zones, are underlain by shallow (less than 80-km-deep) magma chambers and channels, known as 'surge channels' . Surge channels and complexes are believed to correspond to linear lenses of anomalous (low-velocity) upper mantle that are commonly overlain by shallower, smaller low-velocity zones. Seismotomographic data suggest that surge channels may form an interconnected worldwide network, which has been dubbed 'the earth's cardiovascular system'. Magma is said to flow horizontally and vertically through active channels at the rate of a few centimetres a year, and due to the earth's rotation the preferred direction of flow is eastward. Horizontal flow is demonstrated by two major surface features: linear, belt-parallel faults, fractures, and fissures; and the division of tectonic belts into fairly uniform segments. The magma is believed to originate in the asthenosphere, which is generally believed to consist of partially melted rock. Rather than being a global layer, the asthenosphere consists of disconnected zones, extending from about 60 to 150 km in depth.
Interpretations of seismic data generally assume that lower velocities mean higher temperatures while higher velocities mean lower temperatures. For instance, the high-velocity 'roots' of ancient continental nuclei are assumed to consist of cooler rock, while low-velocity zones (such as the asthenosphere) are usually assumed to consist of hotter, perhaps partially melted rock. However, differences in seismic velocity can also reflect differences in pressures, chemical composition, or mineralogical phases, and it is therefore wrong to assume that all low-velocity zones must be areas of incipient melting. V. Sánchez Cela argues that asthenospheric zones are better explained as zones where phase changes are taking place .
Drilling tens of kilometres into the crust to check seismic interpretations is technologically unfeasible at present. However, further information on the lower crust and upper 'mantle' could also come from the future discovery of tunnels and caverns extending to 'impossible' depths. The Veronja (or Krubera) Cave in Georgia, Abkhazia, is currently the deepest known cave in the world, with a depth of 1710 metres . South African gold mines are by far the deepest mines in the world, reaching depths of over 2 miles (3.2 km).
Basalts have erupted on earth throughout geologic history, and cover some 63% of the ocean basins and at least 5% of the continents. Giant flood-basalt fields, such as the Deccan Traps in India and the Siberian Traps, have volumes of 100,000 to 10,000,000 km³. In plate tectonics, flood basalts, large igneous provinces, and all intraplate magmatism are usually ascribed to 'mantle plumes' -- upwellings of hot material allegedly originating at the core-mantle boundary. The movement of plates over the plumes is said to give rise to hotspot trails, i.e. chains of volcanic islands and seamounts. Such trails should therefore show an age progression from one end to the other, but a large majority show little or no age progression. In a detailed critique, H.C. Sheth has argued that there is no geological evidence of any kind requiring mantle plumes, and that the concept is ill-founded, contrived, and invalid, and has led earth scientists up a blind alley. He shows that shallower processes could produce basaltic volcanism .
While cylindrical upwellings of mantle material (not necessarily from great depths) might account for isolated volcanoes, they cannot account for the massive ovate and linear flood-basalt provinces found in many parts of the world. Some geologists argue that volcanism in the midocean ridges, linear islands and seamount chains, ocean plateaus, island arcs, and continental interiors is more readily explained by the rupturing of individual or colliding surge channels . V. Sánchez Cela has proposed that the upper mantle is far more sialic than current models assume, and believes that the ultramafic rocks currently assumed to come from the upper mantle, together with their partial melting products (basalts), can be formed in the upper crust in suitable dynamic and chemical conditions .
80% of all earthquakes are said to take place in the upper 100 km, while the rest occur at depths of up to 700 km.* Most deep-focus earthquakes occur in Benioff zones, which are probably deep contraction fractures that formed early in the earth's history. Moreover, as mentioned in part 1, such earthquakes suggest the existence of solid, brittle rocks at such depths, contrary to the conventional earth model.
*It should be noted that all estimates of depth based on the interpretation of seismic data are likely to be wrong if the underlying assumptions concerning the earth's interior are wrong. However, such estimates can be used as a relative indication of depth.
Electrical disturbances have been noted both preceding and during earthquakes, volcanic eruptions, and hurricanes. It has been suggested that changes in geoelectric currents may precede major mechanical stress relief that appears afterwards in the form of an earthquake . In addition to the observation of anomalous earth currents in the vicinity of earthquake epicentres, changes in the magnetic field, both local and global, before, during, and after earthquakes and volcanic eruptions have been observed .
In the 19th century, earthquakes, volcanoes, and many other geological phenomena were believed to be caused by great currents of electricity in the earth and atmosphere. Nowadays, electrical and magnetic phenomena have been demoted to mere byproducts of crustal stresses and the movement of internal fluids. Nevertheless, electromagnetic forces may play a far more prominent role in geological activity than is currently believed. Joseph Cater suggests that the fault lines crisscrossing the earth's rocky shell could act as condensers allowing a significant buildup of electric charges, resulting in tremendous repulsive electrostatic forces and explosive discharges when the concentration reaches a critical state. The ensuing stresses and strains and accumulating heat could help to generate pockets of molten rock, and trigger vertical and horizontal crustal movements .
If scientific estimates of the temperature far below the earth's surface are grossly exaggerated, the earth's shell may contain far more liquid water than is currently believed. If water (from either surface or subterranean sources) comes into contact with locally superhot rocks, this would have explosive effects.Etidorhpa suggests that large quantities of water periodically come into contact with huge deposits of sodium and other metallic bases, and the violent chemical reaction that ensues forces melted rock and steam to the surface, resulting in earthquake or volcanic activity. As indicated in part 1, the movement of subterranean gases might also play an important role in such activity.
In short, none of the geological activity observed at the earth's surface proves the standard earth model or rules out a hollow earth.
Several researchers have suggested that a spinning sphere might become hollow naturally. If the earth was initially in a more molten or plastic state and rotated faster than today, centrifugal forces could have partially counteracted the gravitational force, causing the highest-density matter to migrate to the outer zones, thereby 'hollowing out' the planet's interior.
Scientists believe that stars and planets formed from huge clouds of dust and gas, which condensed into spinning spheres under the force of gravity. John Flora states that such stars and planets should have spun ever faster as they contracted, in accordance with the law of conservation of angular momentum. In reality, however, larger stars spin faster than smaller ones, and in our solar system larger planets spin faster than smaller ones. For instance, the earth rotates in 24 hours, while Jupiter, the largest planet, with a diameter over 11 times that of earth, spins about its axis in just under 10 hours. This is not what we would expect of condensed, solid planets. Flora argues that a high rate of rotation would cause a spherical body to expand until it reaches a point of maximum inertial stability, thereby becoming hollow .
Dr Gordeev, a mathematician, argues that if a h***geneous globe begins to spin, the centrifugal force will cause light elements to move outwards, leaving behind a core at the centre, where centrifugal force is zero. Assuming there is an initial crust, when the light materials reach it, it will become increasingly 'solid', while the rest of the globe becomes 'hollow'. Gordeev disagrees with Flora's argument that some kind of polar holes would be produced during the formation of a hollow sphere .
According to theosophy, instead of condensing out of molten physical matter our globe has crystallized out of a more ethereal state of matter, described as 'fiery, cool and radiant'. The Stanzas of Dzyan (6:4) describe in figurative language how 'fohat' -- electric, vital force, guided by the universal mind -- builds planets ('wheels') by generating vorticular motion ('whirlwinds') in the primordial matter or 'fire-mist': 'He collects the fiery dust. He makes balls of fire, runs through them, and round them, infusing life thereinto, then sets them into motion' . The 'germs of wheels' are described as 'centres of force, around which primordial Cosmic matter expands, and, passing through all the six stages of consolidation, becomes spheroidal and ends by being transformed into globes or spheres'. The earth thereby 'passed from a soft plastic body into a rock-bound globe'. The 'rocky crust' or 'body shell' is said to have reached its most material state at the midpoint of our planet's evolution, several million years ago, and has since begun to return slowly to a more ethereal state . At the centre of any globe there is said to be an 'inner kingdom' composed of the lowest of the three kingdoms of elementals (ethereal, submineral nature-forces). The earth's core is described as 'concreted electricity', and is said to be analogous to the nucleus of an atom .
Whereas science regards the sun as a ball of plasma, or fourth-state matter, theosophy asserts that the sun's interior consists largely of matter in its fifth, sixth, and seventh states -- states unknown to scientists on earth . It also asserts that sunspots do not prove the solidity of the 'central mass' of the sun, any more than storm clouds prove the solid mass of the atmosphere behind them, and that the sun's visible outer robes of condensed vital electricity merely form an outer shell . According to the scientific model, a photon takes about a million years to travel from the sun's centre to its surface. According to theosophical literature, on the other hand, the sun's energies take only a year to pass through the sun, and there are bodies circling in the interior of the sun, around its core .
Although scientists cannot be certain of the real masses and average densities of the planets, they do have a good idea of their relative masses and densities. That means that if the earth is hollow, it is highly likely that all the other planets, and also the sun, are hollow as well, otherwise astronomical predictions of celestial motions would fail, and the space programme would be impossible. Even the conventional values for the mass and average density of celestial bodies do not rule out their being hollow, since there could be a super-dense type of energy-substance concentrated at their centres.
As far as a hypothetical central sun is concerned, an analogy can perhaps be drawn with the external sun. The theory that the sun is powered exclusively by thermonuclear reactions faces serious problems, the main one being that the sun only produces about a third as many neutrinos as the model requires. The fact that the sun undergoes periodic fluctuations in output and size is also difficult to reconcile with thermonuclear theory .
To account for the neutrino shortage, it has been proposed that electron-neutrinos from the sun change into muon-neutrinos and tauon-neutrinos on their way to the earth, these two neutrino 'flavours' being more difficult to detect. In June 2001 the Sudbury Neutrino Observatory (SNO) in Canada announced that it had confirmed this theory. However, the only way to truly confirm it would be to make neutrino measurements at the sun and at several points between sun and earth. Since the experiments in question only involved measurements on earth, the joyful acceptance of the SNO's pronouncements by other mainstream scientists merely confirms how uncritical and unprofessional they can be when orthodox theories are at stake .
Harold Aspden is one of the scientists who rejects the hypothesis that the sun derives its power from fusion of colliding protons in its allegedly super-hot interior. He argues that gravity close to the sun's surface squeezes hydrogen atoms so close together that they ionize. And since the gravitational interaction between two free protons is 1836 times greater than that between two free electrons, the net repulsion of the protons in the sun's interior balances gravitational forces and prevents further compaction. As a result the sun has a uniform mass density and temperature that is insufficient to trigger fusion - 'and if it were,' says Aspden, 'the sun would have been blown to pieces long ago'! He continues:
The energy the sun radiates is sustained because free electrons recombine with protons and when they do, this imports energy from the quantum underworld (the aether) to get those electrons back into their quantum state orbits. The sun's energy is not fusion energy but simple energy drawn from the aether by gravity squeezing hydrogen atoms close together to cause ionization. 
Paul LaViolette argues that the cores of both planets and stars produce what he calls 'genic energy', because they are supercritical regions of space where photons draw energy from the underlying ether. He argues that 15% of the sun's energy could be supplied by genic energy, while the rest comes from nuclear fusion. He shows that the sun and low-mass stars (red and brown dwarfs) have the same mass-luminosity relation as the four gas giants (Jupiter, Saturn, Neptune, and Uranus), suggesting that they are powered chiefly by the same energy generation mechanism. He maintains that genic energy can account for 73% of the earth's entire thermal output, including all of the core heat flux. This would render unnecessary the current speculations that this heat comes from the gradual release of heat trapped since primordial times, or from the gradual solidification of a molten core, or from radioactive decay .
Jones et al. have proposed that cold nuclear fusion might be an important source of the heat emanated by the earth . They argue that the fusion of deuterium and hydrogen deep within the earth would explain the high levels of helium-3 found in rocks, liquids, and gases from volcanoes and in active tectonic regions of the earth's crust. They point out that Jupiter radiates twice as much heat as it receives from the sun, and suggest that the excess heat could come from cold fusion in Jupiter's core, which is believed to consist of metallic hydrogen together with iron silicates. LaViolette argues that while cold fusion might be feasible for planet-sized bodies, stars would exhaust their deuterium supply within a few million years due to their much higher luminosities, so that cold fusion does not explain why the planets share a common mass-luminosity relation with lower main-sequence stars.
That there may be unrecognized sources of radiation deep within the earth is shown by the phenomenon of 'anomalous cascades' -- huge showers of nuclear particles that have been measured in a deep mine coming from the sides and even from below. Neutrinos are the only known particles capable of penetrating the entire earth to create the upwardly directed showers, but ordinary neutrinos from the sun do not seem to have enough energy to produce them .
On the question of what powers the stars, G. de Purucker writes:
the interiors of the various suns are not at all existing in conditions of incomprehensibly intense heat, although it is probably true enough that the outermost ethereal layers of the suns possess a certain amount of heat of their own, as a result of chemical processes. The heart of any sun is a most marvellous alchemical laboratory in which occur molecular, atomic, and electronic changes which it would be utterly impossible to reproduce in any of our chemical workshops. 
He states that although some degree of atomic dissociation may be taking place in the sun, this does not explain the origin of the energies that it ceaselessly emanates. Every star, he says, is 'the outward vehicle of an indwelling spiritual and intellectual presence'; at their core resides 'a divine monad of stellar origin and character'. And this solar logos or 'god' should not be thought of as being solely at the core of the physical sun, but rather as being in the invisible astral, mental, and spiritual realms of the sun . Purucker is here voicing a central tenet of the ancient wisdom: that every physical organism is the outer manifestation of a series of inner 'energy fields' or 'souls' of increasing subtlety and power.
On earth, too, a series of chemical and alchemical processes are said to be constantly in progress, which differ from those taking place in stars and nebulae only in degree.
The interior of the Earth is another of Nature's marvelous laboratories wherein wonderful and to us men almost unknown things are constantly happening; and, indeed, the same may be said of the unceasing laboratorial work of Nature in the higher and highest ranges or strata of the Earth's atmosphere, and its unceasing interplay of forces and substances with the fields of outer space, whether this be done through the medium of radiation of various kinds, or partly by radiation and partly by as yet undiscovered natural means. 
Modern science is often inclined to adopt a sledgehammer approach in its study of nature. For instance, physicists widely believe that by smashing subatomic particles together at ultrahigh energies in particle accelerators and then studying the debris, they will be able to wrench from nature some of her deepest secrets! It is also commonly believed that nuclear fusion, whereby light elements combine into heavier ones, can take place only at temperatures of millions of degrees, such as are thought to exist in stars. Yet numerous experiments have shown that anomalous excess heat can be produced by a variety of poorly understood nuclear reactions, possibly involving fusion, at low temperatures and in relatively simple devices, instead of in reactors costing millions of dollars. 'Cold fusion' has generally been derided by the scientific establishment , though as noted above, some scientists have speculated that it may be taking place within the earth and other planets.
Biologist Louis Kervran and a number of other researchers have demonstrated that, in plants, animals, humans, and even minerals, common elements can be transmuted into heavier or lighter elements without the need for extremely high temperatures and pressures . These transmutations are often reversible, and most involve hydrogen, which has 1 proton (1H), or oxygen, which has 8 (8O). Examples are:
11Na + 8O -->
|(Na = sodium; K = potassium)|
19K + 1H -->
|(Ca = calcium)|
12Mg + 8O -->
|(Mg = magnesium)|
14Si + 6C -->
|(Si = silicon; C = carbon)|
25Mn + 1H -->
|(Mn = manganese; Fe = iron)|
Mainstream scientists dismiss the possibility of such alchemical transformations, as they believe that protons and neutrons can only be added to or removed from atomic nuclei by violent methods and under extreme conditions. But nature can apparently accomplish such things by gentler means as well.
A reviewer of one of Kervran's books wrote:
Hundreds of experiments in reputable laboratories undoubtedly demonstrate that transmutations of atomic nuclei occur in living matter. It may be impossible, but it seems to happen. Sodium changes to potassium, calcium to potassium and vice versa. In certain cases silicon plus carbon gives calcium. Nitrogen is transformed to carbon monoxide. All of which is quite contrary to all know natural laws; but the experiments exist, and I know of no serious refutation of them. 
In 1959, French chemist Pierre Baranger stated that, after many years of experiments, 'we have to submit to the evidence: plants know the old secret of the alchemists. Every day under our very gaze they are transmuting elements' .
Kervran argued that the occurrence of low-energy transmutations, sometimes with the help of bacteria, helps to explain the origin of metals and the composition of successive geological strata.
In a series of experiments with seedlings placed in air-tight glass vessels, Rudolf Hauschka found that their mineral content both increased and decreased, and he concluded that plants could not only transmute physical substances, but could also generate physical matter out of the ether and dematerialize it again. He noted an emergence and disappearance of matter in rhythmic sequence, often in conjunction with the phases of the moon .
It would seem that no model of the earth and its evolution can be correct or complete if it ignores the evidence for subtler states of matter and alchemical transmutations.