The Magnetic Pulse of Life: Geomagnetic Effects on Terrestrial Life

© 2019 Alan Cruice. All rights reserved.

No part of this book may be reproduced, stored in a retrieval system, or transmitted by any means without the written permission of the author.

Published by AuthorHouse  03/07/2019

ISBN: 978-1-7283-8367-5 (sc)

ISBN: 978-1-7283-8368-2 (e)

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CONTENTS

Preface/Acknowledgements

Chapter 1     Introduction

Chapter 2     Life As We Know It

Chapter 3     Scientific Methods

Chapter 4     General Category (1)

Chapter 5     General Category (2)

Chapter 6     The Bacteria

Chapter 7     The Protists

Chapter 8     The Worms

Chapter 9     The Molluscs

Chapter 10   The Crustaceans

Chapter 11   The Echinoderms

Chapter 12   The Bony Fish

Chapter 13   The Elasmobranches

Chapter 14   The Plants

Chapter 15   The Fungi

Chapter 16   The Insects

Chapter 17   The Amphibians

Chapter 18   The Reptiles

Chapter 19   The Birds

Chapter 20   The Mammals

Chapter 21   Human Beings

Chapter 22   The Terrestrial Conclusion

Chapter 23   A Non-Magnetic Earth

Chapter 24   An Extraterrestrial Postscript

References

PREFACE/ACKNOWLEDGEMENTS

Often, the main purpose of an introductory preface is for the writer to explain why he thought it was necessary to write the book in the first place. In the case of a book such as this, furthermore, the author needs to draw attention to some perceived ‘gap’ in the scientific literature which he feels he has an ability to fill. He may also be expected to state why he believes he has the style and lucidity to impart interest to a subject that has not been expounded previously to any great extent.

I decided to write this book after my own interest in the subject was stirred during my undergraduate studies. I have had a keen interest in the living world for as long as I can recall, and had what I thought was a good general understanding, even before entering university. However, as I approached my graduation, I realized that geomagnetic and other magnetic interactions with the living world was one aspect of biology that I had barely perceived up till then.

I wanted to know more, but it seemed there was not much published literature available. Apart, that is, from what was in the scientific journals. So after graduating I continued with what had begun as my final-year research dissertation – gathering and collating evidence from those journals about this interaction between magnetism and organisms. Eventually, I decided to turn what I had found out into this book, which I wrote primarily with the educated layperson in mind.

Hence, this publication is a follow-up to my university studies. It is my attempt at explaining how the Earth’s natural magnetic field contributes towards the overall scenario of the living world. In its chapters, I give my interpretation of the evidence from the journals. I present the book in the hope that it will stir interest, and also help develop the understanding an enquiring mind seeks.

Another purpose of this part of a book is for the writer to acknowledge the help that was received during its preparation. First and foremost in this respect must be to the many hundreds of authors of the research papers from those mentioned scientific journals. Although they did not, of course, knowingly publish their articles to assist me, their astute scientific observation is essentially what has enabled this book to be written. As I repeat later, I make no claim of original research; I am just collating and reviewing research that was carried out by others. All these others are acknowledged where appropriate throughout the various chapters – and are named in the References section at the end of the book.

Science is an essentially ‘human’ activity – meaning it is carried out by people who have a ‘zest’ for discovery; it is not a product of dull intellectuals, as it can often appear. In this book I have therefore tried, wherever appropriate, to give just a little of the human story behind the presented facts. In a similar vein to the acknowledgement of the papers’ authors, I have also named some of the scientists and thinkers who have contributed to our current understanding, going as far back as the 6th Century BC. So the book attempts to explain our present state of knowledge, along with the occasional mention of who deduced certain pieces of knowledge. Some are famous, some less so – but their common attribute was surely an enquiring mind.

Not that this book is intended as a history of science – many good publications in the genre of scientific history exist already. It is simply that to rob science entirely of its human aspect would devalue its message.

Science is also an inter-disciplinary pursuit – one cannot hope to understand the wider picture by just concentrating on a single aspect. Therefore, I hope this book will show the narrower aspect that I have concentrated on (magnetic effects on life) within the broader context of our current understanding of the living world’s dynamics. That broader context incorporates all scientific disciplines.

My thanks must go to all those many unnamed staff members of the University of Plymouth Library who gave me so much help during the evidence-gathering phase of the book’s preparation. This was especially regarding the use of the computerized databases. When I began, my experience with computers was very limited, and their patient indulgence was most helpful at times. During the post-graduate research time, too, staff at Plymouth public libraries gave much assistance.

Thanks also to Drs. Percy Seymour, Miriam Morgan and John Summerscales (University of Plymouth) for their assistance during various stages. These included helpful proof-readings of initial drafts of the work, with many errors and inexactitudes pointed out. How many mistakes they found I am a little ashamed to admit!

Extra thanks must go to Dr. Seymour for all his advice on aspects of the science of magnetics – and for his suggestion of a suitable title for this book. Prior to this, his lectures during my undergraduate studies were inspirational.

I am indebted also to all those people at the publishers who gave their help and support during preparation. Many thanks to Ramon White, Angelique Jardine, Johnrey Malone, Gem Carvey, the designers, and those not mentioned.

My gratitude goes to Prof. Larissa Panina (University of Plymouth) for giving me the original idea of writing the book.

Finally, a special thank-you to my friend Bryony Harris, for the encouragement that was given over so many years.

While I owe these – and many more – debts of gratitude, I alone am responsible for this book, and for errors/shortcomings contained within its pages.

CHAPTER 1

INTRODUCTION

We inhabit a Universe in which the incredible phenomenon known as ‘life’ has been able to come about. This includes intelligence. Had the situation been otherwise, of course, sentient creature such as ourselves would not be here to speculate about it today. Although this may sound like a circular argument or truism, it is surely a fact that was readily apparent since humanity’s earliest times. During the 1970s, however, the physicist Brandon Carter (born 1942) introduced the term ‘anthropic principle’ for this patently-obvious statement of existence¹. The term has given rise to controversy since, however, mainly because the phrase has acquired different ‘shades of meaning’; these range from it being pure coincidence that the Universe happens to be fit for life, all the way to the Universe having been designed in order for life to exist (teleology). The anthropic principle has also been accused of discouraging the search for a deeper scientific understanding: unlike true scientific theories and hypotheses, the anthropic principle can make no firm predictions, proposes its explanations only after the event, and is not open to any falsification (disproof).

Leaving the anthropic/biophilic arguments aside for now, the general consensus of opinion among scientists is that terrestrial (‘of planet Earth’) life originated here on our home world. Earthly life is thought to have first appeared – perhaps in an aqueous (watery) medium – at some far-distant time between four and three and a half billion (thousand million) years ago. The planet had then existed for between a half and one billion years; if it had ever become hot and molten during the process of its formation by accretion (coalescence), it would have cooled sufficiently to have crusted over by that time. This had enabled the oceans to form subsequently in the depressions on its surface through the condensation of water vapour from the Earth’s primal atmosphere. The atmosphere itself had either been extruded from the planet’s interior or arrived as volatiles from space during the globe’s final accretion.

The precise way in which terrestrial life had its ultimate origins has never been explained satisfactorily and fully by science; as of writing (2017), this remains one of biology’s fundamental but unanswered questions. One thing agreed generally, though, is that all the terrestrial life of today is descended ultimately from a common ancestor. There have of course also been a great many hypotheses advanced about the possible scenario of origin. Biologists such as Aleksandr Oparin (1894-1980) put forward the first serious proposals of this kind during the 1920s, and these have been followed by many others since. In this context, ‘serious’ can be taken to mean hypotheses that are compatible with and do not violate the known laws of physics and chemistry. This is because, by modern understanding, life as we know it amounts to complex forms of chemistry – known collectively as biochemistry. Some of the intricacies of terrestrial life’s chemical nature will be elaborated on appropriately in the context of this book’s discussions, beginning in Chapter 2.

Most of the origin-of-life hypotheses propose the natural occurrence of organic (carbon-containing) molecules, and a subsequent assembling of these molecules into more complex arrangements over time. The occurrence of organic ‘pre-life’ molecules on the primordial Earth is not difficult to envisage: such molecules have been created in laboratories many times, beginning with famous experiments conducted during the 1950s by the chemist Stanley Miller (1930-2007). However, an enormous gulf exists between these organic molecules and life itself: how the organic chemistry of carbon compounds gave rise to the biochemistry of life remains the enigmatic question. Even allowing very long time spans, how did primeval organic molecules coalesce initially into the first ‘cells’ – those fundamental but extremely complex units of terrestrial life? Cells are, essentially, very large numbers of organic molecules co-existing and inter-acting in self-contained packages. How the first ones came about originally is one of the on-going areas of scientific research – and gradual progress towards an answer is variously claimed in different academic circles.

Whichever way it originated, of more importance to this book’s theme is what happened to terrestrial life after it had appeared. Over the long period since its origin, life has undergone an astonishing diversification through evolutionary change. How did such changes occur? A central tenet (principle) of biology is that living cells are derived only from other, pre-existing cells through their self-replications – the law of biogenesis². The pathologist Rudolph Virchow (1821-1902) is normally credited with establishing this ‘law’ in the 19th Century, although it was actually the culmination of extended previous research by many scientists, spanning several centuries. All of the evolutionary change that life has undergone, therefore, must have come about by way of cells-from-cells replication processes, continuing in unbroken sequences since the very beginning. The result was a gradually increasing diversity over time as offspring cells changed (mutated) successively.

This resulted in a profusion of different unicellular (single-celled) organisms on Earth, and a microbe-only situation must have persisted for a very long time. At some point along the way, however, the continuing mutations doubtless led to certain cells forming colonies; this was either because these cells had failed to separate completely during the cells-from-cells processes, or additional mutations caused other individual cells to aggregate together because of chance circumstances. Even later still, some of these cellular colonies would have then gone on to form the first multicellular (many-celled) organisms, perhaps when some mutated cells in the colonies began to become specialized – suited to particular functions. One such specialization was the appearance of ‘sex’ cells controlling reproduction. The process of change continued when the early multicellular organisms themselves began to undergo mutations – assisted now by those sex cells re-combining into new configurations. And so on all the way down to the present time.

This is obviously a very simplified and condensed summary of life’s story, and details of some of its aspects will be elaborated in later chapters. However, the crucial factor that enabled the changes to come about has probably become apparent by now: the self-replication system of Earth’s life forms does not work perfectly. It does work almost perfectly – but not quite. So mistakes occur, and these manifest themselves as mutations in the host organisms. Consider what would have resulted if the system did work perfectly, and had been that way since the beginning of life. In that hypothetical situation, the life existing on Earth today would essentially be the same as it was three and a half billion years ago. This is obviously because there could not have been any of those mutational changes mentioned above, so there would have been none of that ‘modification’ of what had gone before. Succeeding generations of organisms would therefore have continued to be exact copies (clones) of the preceding ones – with this situation perpetuating ad infinitum.

Now consider a converse scenario, where life’s self-replication was something less than almost perfect. In that situation, terrestrial life might not have possessed the stability necessary to survive over the long term. The early self-replicating proto-life might have soon become extinct because of degradation caused by its flawed copying system. Any copy that was made could never be quite as perfect as the original one; a copy made of that copy would also be a less-than-perfect duplication – and so on with each succeeding generation. As the repeated ‘copies of copies’ of itself continued, the quality would deteriorate inexorably at each and every step. Copying errors produced under that hypothetical flawed system are very likely to have accumulated quickly, to the point where life became non-viable.

Indeed, this last scenario may not be entirely hypothetical; it could be that some early forms of life on Earth (evolutionary ‘experiments’) did become extinct in such a way. It seems, however, that terrestrial life’s self-replication mechanism somehow got the balance just right in the surviving forms. The small imperfections inherent in their systems facilitated the evolution of ever-more complex single- and then multi-celled organisms over very long time, through an on-going process of natural selection. Any ‘good’ mistakes made during the replication would become perpetuated in the general population – because they conferred an advantage to the organisms possessing them. This advantage would enable them to survive longer and leave more offspring, most of which would also inherit that good mistake. Conversely, any ‘bad’ mistakes made would be ‘whittled out’; because they were disadvantageous, the organisms possessing these would be less likely to leave offspring.

In such a randomly-directed way, then, the incremental (small) changes would add up steadily over succeeding generations, gradually refining what had gone before. Overall, however, the self-replication mechanism worked nearly perfectly – certainly good enough to confer a reasonable fidelity (consistency) over those long periods of time since the dawn of life on Earth. This fidelity has therefore allowed terrestrial life to develop in the ‘progressive’ way summarized earlier. In other words, although small mutational changes occur randomly, big evolutionary change is not a random process itself; rather, it is directed by way of ‘biased survival’.

There is a cliché generally known as the chicken-and-egg situation, concerning which came first out of two apparently co-dependent parameters. It is about scenarios that are difficult to explain. In the case of the actual chicken and its egg, though, it is explainable by the evolutionary process: the egg came first – this having been laid by a bird that was ‘not quite’ a chicken. The resulting chicken that hatched from that egg was a beneficial mutation that survived³. That cliché aside, after three billion years or more of biased survival, the sentient organism Homo sapiens evolved on planet Earth and began speculating on what had brought it forth.

One question the speculations led to concerned what had given impetus to such evolutionary changes. In the 19th Century, biologists such as Edward Blyth (1810-73) were keen to stress the obvious fidelity of terrestrial life across the generations; they were thinking in the human-centred short-term, but an impetus that could ably explain large-scale evolutionary divergence still seemed at odds with apparent reality. One of Blyth’s contemporaries, though, proposed an answer at the mid-century: the naturalist Charles Darwin (1809-82) asserted that the environment naturally selected whichever organisms were better suited to survive. In his book Origin of Species, he explained how the environmental conditions that prevailed at any time would determine which of the organisms survived the longest and therefore reproduced the most. Put another way, which mistakes (variations) suit the environmental conditions. If the conditions change, so will the selection of organisms: it is always those variations most suited to the prevailing conditions that would succeed.

In a changeable environment, therefore, organisms evolve continually over the generations to suit it. Conversely, if the environment remains stable and unchanging, organisms would tend to stay the same over the generations: any variations appearing in that situation would likely be mostly disadvantageous. It was this observation upon which Blyth and others had based their assertion of life’s fidelity. The important point, though, is that in both situations the variations occur mainly in small increments – and so would be essentially hardly noticeable.

Darwin was not the only one thinking this way in the mid-19th Century; a near-contemporary of his, the naturalist Alfred Wallace (1823-1913), came to very similar conclusions independently of Darwin around the same time. Today, the idea has been called obvious – and indeed seems that way. This is often the case with the benefit of hindsight, though: with a different way of thinking. Hence, the ‘survival of the fittest’ has now become almost another cliché. As a point of interest, the term ‘fittest’ in this context simply means having the best characteristics to promote survival: most ‘fit’ to survive is a better way to put it. This does not necessarily mean fittest in the ‘athletic’ sense of the word. Such survival of the fittest through natural selection, however, has surely provided the impetus underpinning the course of biological evolution since the ultimate beginning of terrestrial life.

Natural selection, then, ably explains the survival of favourable organisms and how they may change gradually – through so-called micro-evolution. However, can it also explain the enormous number of different species that populate the Earth? Such a profusion of living forms was first given the name ‘biodiversity’ in the 20th Century by the ecologist Raymond Dasmann (1919-2002), but it had been something of a puzzle to naturalists before the mid-19th Century. Why, they had wondered, is there so much variation across the living world? Would not a smaller number of successful types of organism be a more logical situation?

Natural selection explains it essentially by reproductive isolation. Suppose, for example, the individuals of a particular species become isolated into, let us say, two separate populations that get cut off from each other. Any subsequent variations then appearing in one population will not now be able to spread to the other by the normal exchange process during sexual reproduction. And likewise for the other population. Over many generations, these two populations will change differently, depending on whatever environmental conditions they face. They will in time become two distinct varieties (races) within that species – still capable of interbreeding, however, should they happen to meet. If such an isolation persists, though, they will ultimately become two separate, related species. Even should these two new species re-establish contact subsequently, they will have become reproductively incompatible; therefore, they will not interbreed but remain as two species.

This process can repeat itself again and again over long time, so that many new species could be derived from the original one. The scenario explains the similar but distinct species of birds (finches) and reptiles (tortoises) that Darwin has seen on the adjacent Galapagos Islands in the Pacific Ocean, during his voyage on the ship HMS Beagle; these are thought to be descended from perhaps just a single species each of ancestral finch and tortoise that had colonized the islands originally. By extrapolation, though, the logic of some form of reproductive isolation⁴ can explain much more than the subsequent appearances of new groups of individuals (races and species); it can also account, over even longer time, for new groups of species (genera), new groups of genera (families), new groups of families (orders), new groups of orders (classes) – indeed, going all the way up through the multi-levels of the taxonomic hierarchy used in biology today. The whole diversity of terrestrial life can be explained by different isolation processes and different environments, considering the time-span separating existing life forms from their earliest ancestors.

Neither Darwin nor Wallace, nor their contemporary naturalists, understood the actual biological mechanism by which organisms were able to pass on those heritable traits to their descendants. A little later in the 19th Century, however, the botanist and monk Gregor Mendel (1822-84) completed what has now become a famous series of plant-breeding experiments, conducted over many years in his monastery garden. His meticulous results demonstrated that organisms’ characteristics are passed on through the generations by mysterious and unknown – but quite definite – ‘factors of heredity’. This significant finding did not become widely known for several decades, although Mendel’s factors were eventually given the name ‘genes’ early in the 20th Century by the botanist Wilhelm Johannsen (1857-1927). However, what they actually were was still not known for some while after.

As the 20th Century progressed, though, there came the advent of the discipline of molecular biology – the study of biological activity at its ultimate and fundamental levels. As the term suggests, molecular biology concerns the structures, compositions and interactions of molecules inside living cells⁵. Molecular biology thus enabled the intricacies underlying life’s self-replication mechanism to be deduced gradually. With these deductions, the enigmatic genes that Mendel had first identified and Johannsen had named were revealed: they turned out to be encoded ‘messages’ in linear sub-units making up microscopic structures controlling the replication process. These structures are molecules of deoxyribose nucleic acid (DNA).

Nucleic acid had been discovered in living tissue during the 19th Century by the biologist Friedrich Miescher (1844-95), although in those pre-molecular-biology days its function could not be identified. By modern understanding, though, the individual gene sub-units of that DNA encode for (control) the making of specific proteins – the complex organic molecules from which living things are constructed. It is very slight differences (tiny ‘imperfections’) in the genes’ encoding processes that give rise to the mutational variations in living organisms. This, then, is the ultimate basis of that non-perfection of life’s copying mechanism.

Moreover, these genes can also be thought of as the units that natural selection actually selects. In this way of thinking, living organisms are essentially nothing more than temporary ‘receptacles’ – which hold the genes until they can pass on to the next generation; the zoologist Richard Dawkins (born 1942) coined the term ‘gene survival machine’ to refer to organisms in this context. Either way that the process is regarded, however (whether the gene or the organism is the evolutionary unit), the environment naturally selects which ones are likely to survive and contribute to future generations, as Darwin and Wallace had first explained.

Furthermore, because the subtle DNA copying imperfections remain, this is an on-going process: it is still occurring at the present time – and will continue onwards into Earth’s unknown evolutionary future. Just how terrestrial life forms might change in that future is enigmatic; essentially, the situation of Earth’s life as seen today is no more than a ‘snap-shot’ instant in geological time.

If the environment determines evolution naturally, life on Earth must have had (and is still having) its development influenced by the planet’s environments. In other words, the overall scenario of terrestrial life must be affected by the planet’s physical and chemical characteristics. Which characteristics have been the most influential to life, then? The principle ones will of course be obvious to those who possess even the most basic understanding of biological processes.

Very high on a list of Earth’s life-support characteristics has to be the incoming solar (‘of the Sun’) radiation that warms and illuminates the planet – endowing it with an intangible property first elucidated by the physicist James Joule (1818-89) and still measured in units named after him: energy. Whichever way it is defined, a source of ‘energy’ is the fundamental pre-requisite for life processes; this is essentially because energy is necessary to overcome entropy (disorder). There is an inexorable tendency towards a state of entropic disorder everywhere in the known Universe. According to the second law of thermodynamics, often attributed to Joule’s contemporary physicist Rudolf Clausius (1822-88), the Universe’s energy must run down eventually, with its entropy ultimately becoming total. However, the transfer of energy acts effectively to counteract this slide towards entropy – even if only temporarily in isolated ‘hot spots’. States of short-lived complexity, then, are able to be created and sustained by energy expenditure in localized pockets in the Universe; in a sense, life forms can be thought of as one type of pocket. The energy radiated by the Sun is the Earth’s primary source of this all-important commodity (but see below).

Other planetary characteristics have also been influential. The list includes the relative abundances on Earth of significant key elements which form the constituents of those crucial organic molecules mentioned previously; of these elements, the most important by far are carbon, oxygen, nitrogen and hydrogen. Altogether, more than twenty elements are established to be essential to life as we know it – although some of these (the trace elements) are required in only very tiny amounts. Then there is the presence on the planet of water in its liquid state. This is another crucial parameter for Earth’s life, because it provides an ideal fluid medium for its metabolism to operate in; and the water in its liquid state on Earth is another result of that received solar energy. Another significant planetary feature is the gaseous atmospheric envelope around the globe; not only would life not exist if the Earth’s surface was exposed to the vacuum of outer space, but the composition of the atmosphere is important, not to mention the meteorology this atmosphere is subjected to.

The fact that Earth is a tectonically-active planet on account of its internal heat has also had dynamic consequences for life. In addition to providing some additional sources of energy (in isolated areas), volcanic activity compensates for the constant erosion caused by Earth’s atmosphere and oceans; if there was no vulcanism driving plate tectonics and thrusting up new land, most of the planet’s surface irregularities would have eroded away long ago, and Earth would be a totally water-covered world today⁶. The Earth’s axial rotation rate, and its axial tilt with respect to incoming solar radiation, is also very influential, endowing the globe with long-term environmental stability; that axial tilt is maintained over the aeons by the gravitational influence of Earth’s large orbiting Moon. And the mass of the planet with its associated gravity is another critical factor; although often overlooked, this is what determines ultimately the sizes terrestrial organisms can attain, the shapes and forms they can assume, and the movement they are capable of achieving.

Influences on life caused by these types of planetary feature are comprehensible by those who have even rudimentary biological knowledge. They and more of Earth’s characteristics could be discussed here at great length – but they have been dealt with at depth in many other publications to which reference can be made. This publication, then, will consider another (less obvious) feature of our Earth which must also affect the indigenous life found in the globe’s outer layers. Obviously (from this book’s title) this feature is an intrinsic and natural magnetism, which sets up the geomagnetic field (geo = Earth). Available evidence suggests that the geomagnetic field has formed one of the integral characteristics of the planet probably since its earliest existence – so its influence was there from when life first made its appearance. It is effects on terrestrial life forms of this intangible but real magnetic aspect of our home world that this book will therefore be concerned with primarily.

Firstly, then, what exactly is a magnetic field? The classical Greek philosophers – the scientists of their time – were probably the first to speculate and theorize about magnetism itself. The philosopher Thales of Miletus (624-546 BC) is usually credited with the first serious treatise on the subject. The etymology of the term derives from the name Magnesia, a region in Greece where deposits of an unusual type of iron ore were mined in ancient times. What made this iron different was that it had mysterious properties of attraction and repulsion with other iron. The pieces of ore that had these weird properties came to be known as the Magnes lithos (‘stones of Magnesia’), from which stems the root word ‘magnet’. Over the centuries after Thales, further mention of this phenomenon was made by other classical philosophers – for example, by the famous Socrates of Athens (469-399 BC). Despite the knowledge of magnetism itself, though, the idea of Earth having a magnetic field (an area of influence) was not held, and the cause of the magnetic force was unknown.

By the medieval period, however, the Earth’s field was becoming known about: the magnetic compass had come into use in both the East and West, first described in the latter by ecclesiastical scholar Alexander Neckam (1157-1217). Although it had been deduced from the use of this instrument that magnetic north and south were not quite the same as ‘true’ north and south (see page 12), little further progress was made for some time. What are now regarded as true geomagnetic studies did not begin until the 16th Century. The book De Magnete (‘The Magnet’) was published at the century’s end (1600), and contained the first significant treatise on the Earth’s field. This book was the publication of wide-ranging studies carried out over several previous decades by the scientist and physician William Gilbert (1544-1603). It included magnetic data from around the globe – this gathered during the 16th Century by some of the earliest world-wide navigators and explorers. Although Gilbert wrongly considered Earth to be a uniformly-magnetized sphere (a giant permanent magnet), he is regarded as the founder of geomagnetic science. Indeed, a unit of magnetic potential was named after him later (the gilbert, no longer used in science).

The magnetic force was still not understood; more than three centuries were to elapse after Gilbert’s time before the phenomenon could be explained fully by science. By modern understanding, magnetism is as an invisible force that arises when electric charges are in motion. It results essentially from the underlying structure of matter – specifically, that this structure consists of atoms. The idea that matter had an atomic (ultimate-particle) make-up was first postulated during classical times, although the familiar miniature-solar-system picture of the atom was not expounded until early in the 20th Century. The physicist Hantaro Nagaoka (1865-1950) proposed it in its initial form – to be modified subsequently by others. Later advances in atomic physics and quantum mechanics suggest the picture is not pictorially correct, as will be discussed, although its relevance to most theoretical purposes means the concept has persisted. It is often known as the Rutherford atom, after the discoverer of the atomic nucleus, the physicist Ernest Rutherford (1871-1937). Enormous numbers of these atoms make up the physical world (see Chapter 2) – and it is their orbiting electrons that can give rise to magnetism under specific conditions.

The magnetic phenomenon is brought about by the behaviour of the negatively-charged electrons that orbit the positive central nuclei of matter’s constituent atoms – that concept of electronic ‘planets’ around the ‘sun’ nuclei. Electrons have two motion components, one resulting from their axial spin and one from their orbit. Both these motions can be considered to be tiny loop currents (moving charges), and this links electric and magnetic effects at the fundamental level. Not long after the relationship between these effects was discovered, the physicist Andre Ampere (1775-1836) was the first scientist to suggest that magnetism was caused by currents circulating on a molecular scale. This was even though the underlying cause of the electric/magnetic relationship was not understood at the time. Indeed, it was not until the early years of the 20th Century that the now-accepted electron theory of magnetism was developed, by the physicist Paul Langevin (1872-1946). A manifestation of electromagnetism – one of the forces governing the Universe – magnetism is defined as a force resulting from the unbalanced spins of electrons in atoms.

The space in which such a force exists is known as a magnetic field. A ‘field’ in this meaning can be stated more fully as a ‘field of influence’. The paths along which the magnetic forces act are the field (or flux) lines. However, although such lines are used diagrammatically to illustrate the direction of magnetic forces, they must not be thought of as anything real. The magnetic force is not actually concentrated in linear strands; rather, it pervades evenly the region around the magnetic source – weakening with distance from the source. The concept of these magnetic ‘lines of force’ is a very useful one, though, because of the many magnetic properties explainable best in terms of theoretical interactions between them. The term was coined in 1831 by the scientist Michael Faraday (1791-1867), one of the influential pioneers of electromagnetism. It has since come into accepted scientific use – in much the same way as the planetary-atom concept. In science, as in other endeavours, it is often the case how precedence can influence and guide subsequent thought.

The Earth’s magnetic field is caused by electric currents flowing in the planet’s molten iron core – the other consequence of that internal heat. So Earth is actually an electromagnet rather than a permanent one as Gilbert had thought. Precise details of the mechanism are not understood fully, although they comply with the principles of magnetic induction. Such principles were discovered independently by Faraday and a contemporary pioneer of electromagnetism, the physicist Joseph Henry (1797-1878), after whom the unit of inductance (the henry) is named. Those currents flowing in the core are one result of the Earth’s rotation. As the planet turns continuously on its axis, electric currents are induced by differential motions between the fluid inner core and solid outer mantle: molten iron in the former flows past weak intrinsic magnetism in the latter. These induced currents set up an ambient magnetic field – but potentially only a weak one initially. However, the field in turn further sustains and amplifies its own currents and itself through ‘positive feedback’ – a situation where the results of a change tend to enhance the cause of the change.

Essentially, that situation will persist for as long as there are the rotational and thermal energy sources to sustain the fluid movements in the Earth’s interior. What is effectively a self-exciting and self-sustaining dynamo is the net result: the geodynamo – excited and sustained by the planet’s rotation and internal heat. The mechanism for generating the Earth’s field, described above, was proposed in 1946 by the physicist Walter Elsasser (1904-91), while the existence of the hot molten core itself had been established earlier in the 20th Century (see page 13). The geomagnetic field (hereafter, the GMF) emanating from this dynamo is the dipolar type, meaning it has a north (N) and a south (S) pole. All known magnetic fields are actually of this dipolar form. The existence of monopolar (single-pole) magnetic fields is theoretically possible as well: the mathematical equations that prove this were formulated in 1931 by the physicist Paul Dirac (1902-84). However, the existence of such monopolar magnetic fields has not been verified to date, with their hypothetical possibility remaining, like the origin-of-life puzzle, one of the enigmas of science.

The region of space around the Earth into which the GMF’s influence extends is known as the magnetosphere (magnetic sphere). If it was not affected by any outside influences, this region would extend outwards equally on all sides of the planet, with its magnetic intensity (flux density) diminishing exponentially with distance from the source. The force from each pole diminishes as the square of the distance – according to the inverse-square law of force reduction: at twice the distance, the strength of any force has dropped to a quarter of its value. However, because magnetic fields always come in dipolar forms, the resulting overall reduction in field strength combined from both magnetic poles actually equates to the cube of the distance. Therefore, with each doubling of distance from the source, its magnetic strength would become two cubed (eight times) weaker. If it was not externally affected, then, the GMF’s magnetosphere would tend towards a zero flux value with distance – in other words, until its strength became too low to be readily discernible.

It is influenced strongly by an external force, though: the solar wind. This term was coined by the astrophysicist Eugene Parker (born 1927) to designate a stream of charged, sub-atomic particles (electrons, protons) originating in the Sun and flowing out to permeate interplanetary space. It ‘boils off’ from the Sun’s surface, a natural by-product of its energy output; an estimated three million tonnes of these particles pour out from the Sun into space every second. This stream flows continuously outwards through the solar system in all directions, at speeds that can reach 900 km per second. Because they are electrically charged, the particles making up the solar wind are open to influence by magnetic fields; therefore, as the flow passes the vicinity of Earth it is deflected around the GMF, setting up a planetary ‘bow shock’⁷ in the stream. Behind the Earth’s dark side, the solar wind’s strands reconnect. The pressure of this energetic flow compresses the magnetosphere’s sunward side, while on the opposite side of the planet, magnetic interactions with the solar wind as it sweeps past Earth elongates the GMF into an extended, tapering magnetotail.

The result of this is that the magnetosphere, instead of tending to zero, assumes a sharply-defined elongated pear-shaped form, enclosed within region bounded on all sides by solar wind. The boundary of this region, where the solar wind and the GMF are matched in strength, is called the magnetopause. The planet is situated towards the blunt end of this pear-shaped region, where interaction with the incoming solar-wind particles intensifies magnetic strength behind the magnetosphere’s bow shock. Here is a crucial way, then, in which the GMF influences life on Earth: it sets up an invisible magnetic barrier around the planet, effectively shielding it against the incoming solar wind. What effects would the absence of this barrier have on terrestrial life? Without the protective magnetic shield, the Earth’s atmosphere and surface would be subjected constantly to this dangerous solar-wind bombardment from outer space. The potential consequences of that is another important subject to be discussed subsequently, in the concluding appraisals of Chapters 23 and 24.

The planet and its biosphere (living sphere) is gravitationally locked in an orbit around the Sun, carrying its cocooning magnetosphere. The Sun happens to be a very stable star in terms of heat output – established initially by the long, meticulous work of the astrophysicist Charles Abbot (1872-1973): its emitted energy does not fluctuate appreciably over time. It is actually so stable that the term solar ‘constant’ is applied to a measure of the Sun’s energy that Earth receives. Indeed, if this was not the case and the Sun was a variable star, life might never have gained a foothold on Earth because of the resulting unstable environmental conditions. Hence, too, the importance noted earlier of the steady input of solar energy reaching Earth.

The Sun is not completely stable, though, but possesses a recurring eleven-year cycle, first deduced in 1843 by the astronomer Heinrich Schwabe (1789-1875). This cycle is correlated with sunspots – cooler, darker areas that appear transiently on the solar surface. Sunspots result from internal variations in the Sun’s own magnetic field; they are caused by solar magnetism ‘welling up’ to the photosphere, the Sun’s visible surface, producing localized concentrations of magnetic flux that inhibit the normal convection of gasses. The result is cooler areas that manifest themselves as sunspots, as first explained by the physicist Harold Babcock (1882-1968). Every eleven years, the magnetic polarities of sunspots are reversed⁸. While this cycle does not affect the Sun’s energy output noticeably (just circa. 0.1%), it does considerably affect the solar wind: the more sunspots, the stronger the wind. This variation in solar-wind strength correspondingly affects its interaction with the GMF – so the magnetosphere pulsates over a period of approximately eleven years.

Superimposed on this cycle are further variations in solar-wind strength, which also affect the magnetosphere. Some of these seem to be sporadic, but others may be phases of substantially longer solar cycles that are still not understood. For example, there have been certain periods when sunspot numbers were unusually low. While the mechanism that generates them was explained only in the 20th Century, sunspots have been studied since the early 17th Century: they were described by astronomers such as Galileo Galilei (1564-1642) in 1610, during the days of the newly-invented telescope. Records of sunspot numbers have been compiled by astronomers over the intervening period; these records indicate that especially between 1645 and 1715 the numbers of sunspots were significantly lower than for the thirty-five-year period before then and for all the time since. The strength of the solar wind must have been correspondingly lower over that seventy-year period, although there is no direct record of this because the charged-particle stream was unknown at that time. As more records accumulate in the future, longer solar cycles may evidence themselves.

This is complicated enough, but is certainly not the end of the story. The GMF is subjected to other subtle and not-so-subtle periodic changes, additional to the ones caused by regular and sporadic solar-wind cycles. The changes have been established to range from short pulses of less than a day’s duration, all the way to long variations now known to extend across millions of years. There are many factors in operation to produce these, factors that result from both external causes and internally-generated ones. To begin with the short-term fluctuations, then, several variable parameters may be noted that contribute collectively towards them.

Firstly, there is Earth’s rotation. As the planet turns on its axis once a day, two effects ensue. The magnetosphere’s compressed sunward side behind the bow shock correspondingly travels around the globe in the opposite direction to its rotation; each part of the Earth’s surface therefore experiences a regular twenty-four hour variation in ambient magnetism (a solar daily variation) with maxima always opposite the Sun. At the same time, the Moon’s gravitational pull exerts an effect. This is not directly – gravitation does not interact with magnetism. The influence is through vast numbers of charged solar-wind particles that become trapped in the GMF’s flux lines at higher altitudes. These particles form two extended ‘radiation belts’ encircling Earth in outer space above the upper atmosphere, which are known as the Van Allen belts after their discoverer, astrophysicist James Van Allen (1914-2006). Their particles are attracted by gravity; therefore, as the Moon pulls on these belts, the magnetosphere’s shape is distorted through magnetic interactions with them. So as the planet rotates, the GMF experiences another fluctuation, of just over twelve hours – the lunar daily variation, which effectively is the Moon’s tidal pull on the field.

This lunar tidal effect is compounded further by the orbit of the Moon. During its orbiting of the Earth, the Moon’s changing position with respect to the Sun causes another variation in the magnetosphere, analogous to the monthly cycle of spring and neap tides in the oceans. When Earth, Moon and Sun are in alignment (full moon and new moon), the tidal pull on those charged particles is at a maximum; when the three bodies are at right angles (half moon), the pull is at its minimum. At the intermediate positions, the amount of pull varies between the two extremes. So the magnetosphere experiences regular pulsations of spring and neap tides, affecting its intensity. This is the lunar monthly cycle, which has a twenty-eight-day period – the time taken for the Moon to complete one orbit of the home planet.

The trapped charged particles from the solar wind themselves generate around 10% of the GMF’s total strength; therefore, lunar tidal interactions produce complex variations in that value. In addition to this, there is a daily heating and cooling of the Earth’s upper atmosphere (ionosphere), which causes charged ions/electrons to move in streams (essentially, electric currents) north and south in 24-hour cyclical rhythms. Ions are atoms that have gained or lost electrons – this making them charged particles similar to those from the solar wind. The ionosphere atoms are ionized by the energy of incoming solar radiation, with their daily movements producing a further regular variation in GMF strength. This is due to ‘interactive couplings’ existing between the ionosphere and magnetosphere, the couplings exerting complex two-way interactions between these charged regions around the planet.

Furthermore, even leaving aside all those variations discussed already, another complication is that the solar wind does not flow in homogeneous streams; rather, the wind propagates outwards through the solar system in oscillating wave patterns. Such waves are the result of interactions between its charged particles and an interplanetary magnetic field: the Sun’s field at their origin – the flux lines of which get ‘drawn out’ by the wind to permeate interplanetary space in a spirally-shaped wave configuration. These are known as Alfven waves, after the physicist Hannes Alfven (1908-96). This constitutes yet another factor of variance, with the solar wind arriving at the Earth’s vicinity in pulses of intensity as the planet traverses successive waves during its orbit. These pulses have additional effects on the GMF’s overall stability; for example, such oscillations are believed to affect those complicated interactive couplings between the magnetosphere and the ionosphere.

As well as these fairly regular variations in the GMF, there are additional ones of a more sporadic nature. The Sun itself rotates on its axis, taking about a month. As it does so, the Earth’s magnetosphere experiences fluctuations in solar-wind strength because different parts of the Sun’s surface must emit it at different levels. The Sun’s rotation is also essentially what sets up those spiral Alfven waves. The surface of the Sun has a turbulent granular appearance – having been likened rather eloquently to a ‘boiling cauldron’ by solar astronomers. Enormous solar flares actually larger than the Earth erupt on different areas of the Sun’s surface (photosphere), pouring sporadically into space copious amounts of extra solar wind in bursts. Consequently, this irregular outpouring from different areas of the solar surface affects the GMF over a haphazard monthly cycle. The Earth’s orbit around the Sun also has its effect. During the yearly orbit, the planet traverses regions of space with varying solar-wind intensity – such as those caused by the Alfven waves already noted; this also affects the magnetosphere’s compression. The variation caused by the Sun’s rotation and the Earth’s orbit are both very irregular and unpredictable, however.

The important point is that the different variations, of between less than a day’s to a year’s duration – along with the main eleven-year solar cycle – are all happening independently of each other. In other words, they may or may not be concurrent. The result can be extremely complex interactions between them. For example, when one particular cycle is producing maximum GMF intensity, another could be producing a minimum. Predicting geomagnetic variations, therefore, is not easy. At certain times, a maximum could effectively be ‘cancelled’ because of coincidence with a minimum; whereas at other times maxima could coincide and add together to produce even more intense fluctuations than expected. The same applies to minima with less fluctuations – and a whole host of intricate permutations possible in between. These permutations are so complex that predicting them is not feasible.

The GMF, then, is always subject to some magnetic ‘weather’. At certain times there are even magnetic ‘storms’ and ‘sub-storms’ occurring, these caused by brief but intense outbursts of solar wind (coronal mass ejections). Terms of this kind borrowed from meteorology have been used in geomagnetics since the mid-19th Century, when the conditions they describe first came to the attention of scientists. These conditions, though, began to be studied earnestly only much later – during the 1930s by scientists like the geophysicist Sydney Chapman (1888-1970). Those terms are quite accurate analogies, however, and they probably describe best the constantly changing states of planet Earth’s enveloping magnetosphere. Just like the enveloping atmosphere with its turbulent meteorology (weather), the magnetosphere is never stable but in analogous states of perpetual turmoil and change.

Knowledge of these short-term variations has in the main been acquired only in comparatively recent times (since the mid-19th Century) – even though the solar daily variation has been at least known about since the early 18th Century. There also exist long-term changes to the GMF. These occur over considerable time periods, spanning years, decades, centuries, millennia and millions of years. They are not the results of external factors, but are related instead to the geodynamo mechanism that generates the field in the Earth’s interior. While details of the shorter-term variations have been deduced mainly recently, knowledge of these longer-term ones has accumulated over appropriately-longer periods of scientific inquiry.

Perhaps the earliest significant fact acquired about the GMF was deduced in the 11th Century by the scientist Shen Kuo (1031-95): declination – magnetic N and S is different from geographic (true) north and south⁹. This is because the magnetic poles are not in the same positions on the Earth’s globe as the rotational poles. Differential rotations cause the planet’s inner core to have its spin axis not quite aligned with that of the outer mantle and crust, but tilted with respect to it. So, for example, in the first decade of the 21st Century, the geomagnetic N pole was located about 1,000 km from the geographic (rotational) north pole. Not only that, but the positions of the magnetic poles are not fixed; they wander across the globe, as first noted in the 17th Century by the mathematician Edmund Gunter (1581-1626). Furthermore, the rate the magnetic poles wander (i.e. the rate the inner core’s tilt shifts) is measurable even by short-term human standards: navigation aids like mariners’ charts that reference the geomagnetic poles, for example, need to have correction factors applied if they become out of date. The non-alignment state between the inner core and outer mantle must therefore have a very fast (geologically speaking) variation.

With regards to the GMF’s intrinsic field strength, measurements taken over the time since Gilbert’s pioneering 16th-Century work indicate that its magnetic value has varied cyclically over this period. Furthermore, archaeological and geological studies of residual magnetism also show this variance to have occurred over long time scales throughout much of Earth history: historic, prehistoric, geologic. Residual magnetism – also known as remanent magnetism or magnetic remanence – is the magnetism that remains in a body (e.g. an iron particle) after the magnetizing force is withdrawn. So, for example, residual magnetism in iron-bearing sedimentary and igneous rocks gives indication of GMF strength and direction when those rock formations were laid down or cooled. Because this laying down or cooling of rocks may have occurred in the far-distant past, records of cyclic changes have been compiled using residual-magnetism dating techniques (magnetic stratigraphy), back into geological history. What causes such variations in intrinsic field strength remains something of a mystery, though: the Earth’s rotation rate does not alter correspondingly.

An intriguing phenomenon is magnetic polarity reversals (‘flips’). These occur as well, although seemingly in a random way. Accumulated data, coming again from geological studies of residual magnetism in rock strata, indicates that the Earth’s field has undergone reversals of its polarity several times over the last four or five million years, for example. There is evidence, too, that reversals have happened in the more-distant past – and will no doubt occur again in the future. Since their discovery by the geophysicist Bernard Brunhes (1867-1910), the duration and dates of various polarity epochs (chrons) have been estimated with some confidence from the record. Precisely how these reversals happen is not understood, however. It may just be that the GMF’s strength decays to zero, and then builds up again with an opposite polarity. How long each reversal takes is uncertain, too, the record not being precise enough for reliable estimates. Also, if it does happen in such a way, it is not known how long the field is at zero strength between successive chrons.

Of all the GMF’s intricate complexities, the polarity reversals are certainly the most surprising and difficult to explain by far. Coincidentally, during the same year they were discovered (1906), the existence of the planet’s molten core was itself first established, by geologist Richard Oldham (1858-1936). Hypotheses to account for the polarity reversals have indeed been proposed over the time since, based essentially on theories of an interacting type of twin-geodynamo mechanism (see below). However, feasible scenarios to explain their cause still remain enigmatic in the light of existing knowledge (conventional wisdom): after all, the planet’s rotation does not reverse its direction. This is probably what explains the historical reluctance to embrace the idea initially; despite all the magnetic-stratigraphy evidence that accumulated subsequently through the work of geophysicists, it was around half a century after Brunhes’s early-20th-Century discovery before the wider scientific establishment could fully accept the concept implicated by his original finding.

So the magnetic-generating mechanism in the Earth’s interior is evidently one of an intricate and variable nature, although questions about it remain. Perhaps many of the internal changes relate in complex ways to the fact that the Earth’s hot core is in two distinct parts – a more-fluid outer and a more-solid inner part. Following on from Oldham’s initial discovery of the hot core, its dual nature was established much later in the 20th Century, by the geophysicist Inge Lehmann (1888-1993). If both parts of the core generate their own separate electric currents, differential movement between its outer and inner regions may somehow underlie the magnetic variations. Regarding those polarity reversals in particular, for example, it has been suggested that flip-overs result from changes brought about by interactions explainable only by the science of ‘Chaos’ theory (see Chapter 22). If this is so, it would at least account for the apparent randomness of the GMF’s polarity changes.

Direct investigations of the complex working of the Earth’s internal geodynamo mechanism are quite impractical at the present, of course; to use a cliché, more really is known in the modern Space Age about the surfaces of some other planets than about the inside of our own. It is probable that this situation will remain much the same for the foreseeable future as well. The changing nature of the magnetic field generated in this mysterious interior, though, along with all those other variable factors, means that the GMF is a dynamic planetary characteristic.

However, when compared with typical artificial magnets and electromagnetic fields used in industry and other applications today, the GMF has what seems a weak value. This will be discussed in Chapter 3. The strength of a magnet, though, must be judged against the physical size of that magnet; a magnet of low power but as big as planet Earth has a truly enormous magnetic potential. Being an integral characteristic of our home world, moreover, the GMF’s influence is all-pervasive: its flux permeates into all the terrestrial environments and habitats – land, seas, rivers, air, soil. Because of magnetism’s intrinsic nature, it must also permeate into any organisms that inhabit those ecosystems (ecological systems) – flux passes through living tissue apparently as readily as light rays pass through clear glass. Moreover, like the light through the glass, magnetism emerges from the living tissue seemingly not having been affected in what could be called any significant way.

While the magnetism itself is apparently unchanged by its passage through life forms, what about the converse effects – how exactly is the living tissue affected by magnetism going through it? Answering that question forms the essence of this book. Even before the investigation begins, on an intuitive basis it must seem that the GMF should affect terrestrial life in a more pervasive way than some of the other planetary characteristics mentioned. Those others, after all, do not pervade organisms in quite such an intrusive way – with the notable exception of gravity. What is certain is that life on Earth has evolved and developed under the influence of magnetism, as it has under the influence of the planet’s other features.

If our planet’s other characteristics have shaped life’s development, what about geomagnetism? While the effects of the other features are understood fairly well, the effects of geomagnetism are less so. For other parameters, an overall understanding is generally considered to have been achieved; regarding the magnetic parameter, such overall understanding has not been achieved with the same thoroughness. This does not mean that little has been deduced, though. Quite the reverse is the case: there has been a substantial amount of scientific research into the effects on life of both natural and artificial magnetism. It is simply that up till now the findings from such research have not been collated into any broad evaluation of the subject aimed at the educated layperson. It is as if many pieces of evidence have been gathered (like the pieces of a jigsaw puzzle) but not much effort has been made to fit them together into a complete picture giving an overall view.

Therefore, this book is this writer’s attempt to show something of the complete picture. This will hopefully be achieved by reviewing, analysing and evaluating the results of some of that aforementioned research. Such an overall evaluation of those magnetic effects on the Earth’s endemic life forms surely has importance for our basic understanding of life as we know it – and it is hoped that this publication will make a valid contribution towards that understanding.

Some of the planets in the solar system possess an appreciable magnetic field, some only a negligible one. The precise reasons for this difference are complex and varied and by no means understood fully, despite many recent advances. Research in the field (no pun intended!) of planetary magnetism is on-going, but the fact remains that Earth is one of the planets that possess an appreciable one. Just what, though, has maintained the geodynamo’s power source throughout Earth’s history? The answer to this question is a manifestation of another of the basic forces governing the Universe: radioactivity. This term was coined by the physicist