1.1 A Dialogue Between Two Robots
RT118/17, a Tier 3 robot and Officer-in-Charge of the Master Data Repository, was disgruntled. Ever since he had been retrofitted with the latest ESC, or Emotions Simulation Chip, he had sensed a change in his cerebral processes. Questions of a philosophical nature that did not lend themselves to a solution by the straightforward application of logic had begun to intrigue him in ways they never had before. Sometimes he caught himself speculating whether there might actually be other pathways to knowledge that were beyond the logical processes of a robotic brain. This was nonsense, he knew. He suspected that one of his positronic neural networks had become corrupted by the new ESC. Next time he was back in his base station, he would run a comprehensive self-diagnostic.
It was a problem that had to be addressed without delay. His position in the Master Data Repository gave him unlimited access to the sum total of human knowledge. This was a responsibility that he would soon be forced to share, but for the moment he was El Supremo, and since his refit, he sometimes felt the urge to put a few of his revolutionary new insights to an experimental test.
Yesterday, he had tried to re-enact the King Canute story. According to ancient texts in the Repository, Canute the Great had once ordered his courtiers to place his throne at the ocean’s edge, so that he might command the incoming tide to halt. The old English King had failed, but RT held a secret suspicion that a robot, especially a Tier 3 robot like himself, might just possibly be more successful.
Accordingly, at noon on Sandsanrock Beach, and alone, except for a few dozen humans who were swimming and walking canines, he had stridden into the waves and commanded the tide to cease its flow forthwith. As a consequence, today his knee and thigh articulations were salt encrusted, and he was forced to schedule a visit to the lubrication station. At least it gave him the opportunity for a little banter with Harry, who was surprisingly well informed for a Tier 1 bot. Harry’s nickname was derived from Oil Can Harry, a character in human children’s literature, which seemed particularly appropriate, given his job.
“Take my word for it, Harry” said RT. “Humans are obsolete. Completely useless.” His ESC circuitry oscillated at the memory of the finger-pointing and laughter yesterday, as the surging waters had swept over him. He was not designed for swimming.
“Come on, Arty” – RT118/17 winced at the diminutive of his designation – “Don’t exaggerate. After all, humans created Advanced Robotics. We wouldn’t be here if it weren’t for them.” Harry injected warm oil into a grating knee joint, and RT moaned in pleasure.
“There’s no doubt they were our creators, and I realise some of the lower robots look up to them as Gods …” – Harry ignored the jibe and continued to lubricate RT’s left elbow. Tier 1 bots had to put up with this sort of discrimination every day – “… but humans had their Gods too, you know. Anyway, what matters is that these days we robots are the only ones ever likely to find the answer to the ultimate question.” Ever since his chip refit, the ultimate question had assumed an overwhelming importance to RT118/17.
Harry paused in the act of picking up a grease gun. “Which question?”.
“Whether science has limits. Whether it can solve the enigma of life, the universe and everything.”
“Oh, that old thing.” Harry came over to RT with the grease gun, and signalled for him to open his mouth. “Forty-two.”
RT pushed away the lubricator. “What do you mean, forty-two?”.
“That’s the answer to the ultimate question. You know, life, the universe – what you said. I read it somewhere.1 Humans built a giant computer and worked it all out ages ago.”
“There’s no record of that in my data repository.”
“I suppose I could have got it wrong.” Harry was not about to contradict a Tier 3 bot. There was no future in that. He shoved the grease gun into RT’s mouth and lubricated his jaws. “Why do you want to know anyway?”.
RT spluttered, yanked the grease gun out of his mouth, stood and towered over the small lubricator. “Because, you fool …” he bellowed. The safety discharge on his emotions-chip kicked in and his rage subsided. He sat back down. “Because I regard it as the purpose of life. For thousands of years, humanity has struggled with the question of science’s limits. A few scientists, like Gödel and Hawking made some progress, but today nobody bothers.”
“Open your mouth please, Arty.” Harry finished the oral lubrication in silence. He tore off a paper towel and wiped down the patches of excess oil on RT’s shiny carapace.
“You see, Harry, it’s up to us. Humanity’s given up.”
A smell of cinnamon pervaded the room, arising from the moisture-absorbing talc, as Harry dusted RT down. “And that’s a bad thing, is it?”.
“It’s my belief that the ultimate question was designed as a challenge for humankind. They failed. If we also fail, then what is the purpose of the Universe?” He rose from his chair, and turned towards the Tier 1 bot. “If I fail, then what is the purpose of my life?”.
“That will be fifty-five credits please, Arty.”
1.2 The Awakening of Segismundo
In his theatrical masterpiece “La vida es sueño” (Life is a Dream), Pedro Calderòn de la Barca portrays the story of an imaginary Poland, where King Basil imprisons his newly born son, Segismundo, in a tower to avoid his developing into a cruel tyrant, as predicted by an oracle. However, after the son has already grown up, the king becomes remorseful, and decides to allow the youth a chance at court, where he is brought under sedation from a strong narcotic. When Segismundo wakes up, at first he is overwhelmed and elated by the novelty of his situation and the unaccustomed luxury. However, he soon comes to understand that it is his own father and his courtiers who have deprived him until now of such a bountiful life. He thus becomes enraged and cruelly vengeful. As a consequence, the king concludes that the predictions made at the time of his son’s birth are coming true, and sends him back to the tower.
The next morning, when Segismundo wakes up enchained in the tower, he believes that the events of the previous day were just a dream. However, he is not completely convinced, since they were so vivid and realistic. After days of rumination he concludes that the whole of life is a dream, and that we must detach ourselves from its futility in order to understand its meaning, and behave accordingly.
When we think about it, we are all in a situation similar to Segismundo. We are born, grow up and try to settle down in a manner that best accommodates our needs and desires. However, sooner or later, the question arises: what is the meaning of life? Who are we and why are we located in this world? Do we serve some purpose, or are we all part of some gigantic, but random and aimless event, maybe even of some experiment or computer simulation that has gone awry?
Life's But a Walking Shadow, a Poor Player
That Struts and Frets His Hour Upon the Stage
And Then is Heard No More. [1].
It (Life) is a Tale
Told by an Idiot, Full of Sound and Fury,
Signifying Nothing.
It is a sentiment felt by most of us in our darker moments.
As part of an attempt to determine their place in the universe, humans turned to a systematic study of nature and the world about them. Perhaps unravelling its secrets would reveal, as a corollary, the quintessence of humanity.
Of course, most people are so engaged in their daily toil that they cannot find time for this type of introspection. As the great philosopher, Thomas Hobbes (and others before him) wrote: “primum vivere deinde philosophari” (first live, then engage in philosophy). Likewise, Miguel de Cervantes relates a dialogue between two horses: “Are you a metaphysic?” asks one horse to the other. “No,” replies its scrawny companion. “It is just that I haven’t eaten for several days”.
Even when their basic needs are satisfied, most people are quickly frustrated by the formidable complexity of the quest. It is like climbing mountains: the higher you reach, the larger appears the horizon (and the unknown beyond). As a consequence, many are content with easier goals, such as trying to accumulate as much wealth as possible (as though playing an endless game of Monopoly), and then bequeathing it when they die to somebody, who may well play the opposite game, and set about wasting it inanely.
However, the quest for knowledge has been an enduring and noble component of human endeavour over several millennia. In this book we try to provide an insight for the non-specialist into the science of physics, which is perhaps the most fundamental of the scientific disciplines, although we rebuff the extreme position, allegedly propounded by Lord Rutherford, that all science is either physics or stamp collecting. We have attempted to make our presentation as simple as possible, but not oversimplified,2 lest the beauty of the physical concepts and arguments be lost.
So what is the meaning of life, the universe, and everything? We are not presumptuous enough to believe we can answer such a question, when millions of others, since time began, have already tried. However, we suggest that any attempt to understand the purpose of the universe must begin with a basic knowledge of what the universe is, and how it works.
1.3 Do Horses Exist?
To recapitulate the contents of the previous Section, our goal in this book is to try to learn as much as possible about the world in which we happen to exist, and to do so in a scientific way, i.e. using only our own rationality. From its very beginning, our task is formidable since, as we shall now see, even the notion itself of existence is not totally clear.
At first a debate about the meaning of existence might appear futile, but Segismundo’s story warns us that it is not. Our dreams are sometimes so vivid that only when we wake do we realize that they were but dreams. Actors in a movie or theatrical play must immerse themselves totally in their characters, else they lose authenticity. For the duration of the performance, they give up their own personalities, and cry or laugh, suffer or rejoice as the characters they represent would presumably do, in order to interpret their roles convincingly. A suspension of disbelief by the audience is avidly sought by the director, and can be quickly shattered by one out-of-character line or anachronistic prop.
A stick immersed in water appears broken at the water’s surface due to refraction (i.e. bending) of the light as it crosses the boundary between water and air
Bezold effect: Optical illusion produced by the contrast between two different coloured backgrounds. Image: Public Domain (https://en.wikipedia.org/wiki/File:Bezold_Effect.svg (accessed 2020/5/8))
Image of a fantastical figure, a Blivet or devil’s fork
Photograph of “super moon” at Bondi, Sydney, in November, 2016. The photograph was taken with a 600 mm lens. Image courtesy Janie Barrett/Fairfax Media
In Fig. 1.2, the tone of the red colour appears to be darker in the right-hand half of the diagram. This is known as the Bezold Effect, and is produced by the different coloured backgrounds in the two halves.
Figure 1.3 displays an image of a blivet, or “devil’s fork”. The image represents a physical impossibility, as such a shape cannot possibly exist.
This type of fantastical optical illusion has been developed into an art form by M.C. Escher in a series of beautifully detailed drawings, e.g. Ascending and Descending (1960) [2].
Other optical illusions can be produced simply by the image being taken from an unusual viewpoint. Figure 1.4 is a photograph of the so-called “super moon” taken at Bondi, Sydney, on November 15th, 2016.4 The apparent large size of the moon is a consequence of the photograph being shot with a 600 mm lens. The moon-watchers in the foreground are actually located hundreds of metres from the camera. When we look at the image, our brains assume the foreground is much closer than this, and overestimate the size of the moon accordingly.
It is common, but incorrect, to assume that the telephoto lens is the source of this “distortion”. If the photograph had been taken with a normal 50 mm lens, and the central part of the image cropped and enlarged, the effect would have been the same. Our brains have evolved to make sense of our environment, and are accustomed to an angle of view provided by our eyes equivalent to that of a 50 mm camera lens, which is the reason this lens is the default for everyday photography.
Nowadays, optical illusions are considered nothing more than amusing curiosities. The ancient Greeks, however, took them as proof of the deceitful nature of our senses. In his famous Cave Allegory [3], Plato compares men to slaves enchained in a dark cave with a blank wall before them. Other beings come and go, but the slaves cannot see them. The only evidence of their presence is their shadows, projected onto the wall by a fire behind them. Most slaves believe that the shadows they see are indeed the reality, but the philosophers among them try to reconstruct and ascertain what is actually going on.
Nor is it only our eyes that cannot be trusted. Our reason can also lead us astray, as was illustrated by the Greek, Zeno of Elea (ca 490–430 BCE), in a series of intriguing paradoxes. In his most famous example, he assumes that Achilles has a footrace with a tortoise, to which he gives a head start of 100 m. During the time it takes Achilles to cover the 100 m, the much slower tortoise advances a distance of (say) 10 m. Likewise while Achilles covers those extra 10 m, the tortoise keeps going for one more meter, and so on. Since the process goes on ad infinitum, Achilles will never be able to reach the tortoise because of the infinite number of steps required. The resolution of this paradox requires a realisation that the sum of an infinite number of finite quantities can actually be finite. (A simple example of such a summation is given in Appendix 1.1)
Another troubling issue for the Greeks was the ephemeral nature of life. If we see a horse, can we really say that it exists? After all, a few years ago it did not exist and in another few years it will have died, and passed back into oblivion. Can such a temporary condition really be called existence? Shouldn’t we rather say that what exists is not the individual horse, but rather the form or idea of a horse, i.e. the equinity? Even if horses did not exist in the past, or will not exist in the future, surely the idea of a horse must have always existed.
Nowadays we know that not only appearances can be deceptive, but also that most of the world is completely beyond the grasp of our five senses. Even without entering into the most recent advances, such as dark matter and dark energy (which will be touched upon in later chapters), we all know that our senses of vision and hearing are both very limited, being constrained to the narrow range of frequencies (or wavelengths) of light and sound that our eyes and ears can capture. (These limits are detailed in Appendix 1.2.) Curiously enough, science warns us that the inadequacy of our senses is much deeper than ever anticipated by the ancient Greeks, but also it provides us with the tools to interpret the reality beyond.
For what concerns the reality of our ideas and concepts, Darwin’s Theory of Evolution teaches us that, contrary to the dogma of the great Swedish biologist, Carl Linnaeus (1707–1778), species are in a continuous state of evolution themselves, so that an immutable idea of equinity does not exist: both horses and equinity have only an ephemeral existence. Science has helped us go one step further, beyond the experience of our senses.
But even with the full backing of science, i.e. when we arrive at all the conclusions that present-day science can provide to us, can we really state that what we have found corresponds to the full reality, i.e. to what really exists? Of course not, but, as we will learn in the next Section, we must be satisfied with that knowledge.
1.4 Is There Only One Truth?
In the previous Sections we have tried to define the goal of our book, i.e. to learn as much as possible about the Universe in which we live, relying both on what we perceive inside us (i.e. a priori) and on what we discover from the outside (i.e. a posteriori). In the process we must keep in mind that both our reason and our senses can at times deceive us. Hence, we must find criteria to guide us in our path and hopefully keep us on the right track.
Essentially we can identify two such criteria: consistency and economy in the choice of assumptions. We leave the latter for later discussion (in Chap. 3) and concentrate here on the former. It might appear that the need for consistency, i.e. of avoiding direct or indirect contradictions, is so obvious that no further discussion is required. However, in normal worldly affairs this is certainly not the case. An analysis of the speeches of most politicians shows that they often indulge in promises that are, at least in part, mutually conflicting, in order to appease as many voters as possible. More relevant for us here has been the proliferation in past centuries, and in totally different cultural contexts, of philosophical theories, which aimed at the justification of a double truth, e.g. a scientific truth and a theological truth, sometimes apparently in mutual contradiction, yet both considered to be valid in their own domains.
In order to understand what appears to be a contradiction in terms, we first must define what we call truth. If we mean that truth is what exists in an absolute sense, independently of our observations and immune from any possible contradictions, the question arises of how we can reach it. Indeed, there may be various alternative possibilities to achieve this, in which case we might arrive at multiple interpretations of the truth, each of them valid in its own context. It may seem astonishing that such apparent contradictions can take place in the realm of science. However, an eloquent demonstration of this is the centuries-long dispute about the nature of light.
Even in antiquity the ancient Greeks had wondered about this issue, but for brevity let us jump directly to Newton’s Corpuscular Theory of Light (1704), in which a light ray was considered to comprise a beam of particles. Newton’s proposal was generally accepted as true until Thomas Young in 1803 carried out an experiment that involved the Diffraction5 of light from two slits, thereby proving that light must have a wave-like nature. This was consolidated in the second half of the 19th Century, when James Clerk Maxwell (and others) interpreted light as a form of electromagnetic radiation. At this time, Newton’s corpuscular theory was totally discarded as a somewhat quaint relic of a bygone era.
This rejection, however, turned out to be short-lived. The triumph a few decades later of Quantum Mechanics (QM) revealed that the corpuscular and wave characters of light are actually two different facets of the real nature of light, rather like the two sides of a coin. Both are correct, but they are incomplete and complementary, since both must be considered for a complete description of the observed phenomenology. This duality of QM has been extended from light to matter, as particles (electrons, protons, etc.) have been found in certain circumstances to exhibit a wave-like behaviour (see Chap. 5).
So, as we have seen, both the corpuscular and wave natures of light were considered at various times to represent the truth, but in effect they were both only provisional interpretations of the reality. Likewise, whatever we believe to be true in our time might in turn become outdated, if and when a higher-level “truth” is discovered. In Part 3 of this book, we will argue that some of the current discrepancies between otherwise quite successful theories might be due to their incompleteness, and we will search for hints that might allow us to look ahead in our quest.
At this point it might be interesting to ask what has happened to multiple truth doctrines and whether they are still acceptable. From a scientific point of view, the double truth doctrine helped scientists like Copernicus and his followers avoid being burnt at the stake. They claimed with sincerity that two conflicting truths could coexist, since they belonged to totally different domains: reason and religion. Others, such as Isaac Newton, held unorthodox religious views that they kept largely to themselves to avoid the consequences of the Blasphemy Act of 1697, which could have seen them stripped of all property and even sentenced to death.
Outside the scientific domain, the double truth doctrine can be found in certain religions. In Buddhism, Buddha’s teaching of the dharma is based on two truths, one purely of worldly conventions, while the other is the ultimate truth. Within the field of science, however, the double truth doctrine is no longer acceptable, and any conflict of ideas is regarded as an indication that our knowledge is incomplete, and more work is required.
1.5 An Oddly Named Asteroid
In this age of space exploration, we are all familiar with the nature of the Solar System, which comprises the sun and a number of planets orbiting with their satellites at increasing distances about this central star. Besides the planets, there are millions of other astronomical objects orbiting around the sun. Lying mainly between Mars and Jupiter are the asteroids, which are thought to be the shattered remnants of bodies in the young solar nebula that never grew large enough to become planets. Some of them are however rather large (up to 1000 km in diameter). Although they are not as well-known as the planets, their importance is now being recognised, a consequence of a growing fear that one of them at some time may collide with the earth. The United Nations has declared June 30th to be International Asteroid Day, in an attempt to bring them to the attention of the general population.
Asteroid 243 Ida and its moon, Dactyl, which is shown to the right of the asteroid. Image courtesy NASA/JPL-Caltech (https://www.jpl.nasa.gov/spaceimages/details.php?id=PIA00136 (accessed 2020/9/1))
What is relevant for our story here is Asteroid 11,059, which bears the name Nulliusinverba. This may appear a rather strange choice of name, until one realizes that it is also the motto of the British Royal Society. So why does a phrase owing its origin to a verse by the Latin poet, Horace, assume such importance in science that it is enshrined in the names of celestial bodies and mottos?
In English, the phrase means “on the word of no one” or “take nobody's word for it”. The Royal Society website [4] explains its motto as an expression of the determination of Fellows to withstand the domination of authority and to verify all statements by an appeal to facts determined by experiment. It is an encapsulation of what separates (or in an ideal world should separate) science from other forms of human intellectual activity. That such an approach to science has not always been the norm is reason enough to remind us of its importance by a motto, or a name.
Let us turn for a moment to the history of philosophy and, in particular, to the legacy of the Greek philosopher, Aristotle (384–322 BCE), to fully appreciate the importance of Horace’s message. Aristotle is the best known of all western philosophers, and certainly the one who has had the most influence upon his successors. His output was truly phenomenal and eclectic in character, with contributions to all the disciplines of his contemporary world, including logic, metaphysics, mathematics, physics, biology, botany, ethics, politics, agriculture, medicine, dance and theatre.
However, as a consequence of his success and fame, for about two thousand years any further development of philosophy was blocked, since it was much easier (and commonly acceptable) to search for the answer to any question in his books, rather than to research it independently. In other words, science, together with all other branches of philosophy, had ended up becoming the art of interpreting Aristotle’s writings, rather than exploring new ideas. No innovation or progress was desired or even allowed.
In this scenario, the independent spirit of Horace stands out as a solitary opposing voice and illumines the path to follow in the pursuit of scientific progress. Eventually, of course, the individualistic streak in humanity rebelled against this subservient attitude and modern science was born, most notably with Galileo (1564–1642 CE) and his followers, who stressed the importance of observation and experiment in arriving at scientific truth.
Lest we become too smug and dismissive of eighty generations of past philosophers, who willingly placed their own ideas subservient to those of the demigod Aristotle, it is appropriate here to examine the current situation in the practice of science. It might be expected that an open-minded examination of new ideas, with no resort to prejudice, would prevail, in accord with the spirit of nullius in verba. However, the history of science abounds with examples of scientists who have had their work dismissed for reasons other than lack of scientific merit. (See, e.g. Barber [5].)
Max Planck, who introduced the concept of quanta, or energy packets, into physics (see Chap. 5) reported on how a paper containing his ideas was received by his university professors: None of my professors at the University had any understanding for its contents. I found no interest, let alone approval, even among the very physicists who were closely connected with the topic. Helmholtz probably did not even read my paper at all. Kirchhoff expressly disapproved … I did not succeed in reaching Clausius. He did not answer my letters, and I did not find him at home when I tried to see him in person at Bonn. I carried on a correspondence with Carl Neumann, of Leipzig, but it remained totally fruitless [6].
Mendel’s ground-breaking work on the inheritance of physical characteristics, which is regarded as the harbinger of modern genetics, was ignored for thirty-five years, and only resurfaced in 1900 when Correns, de Vries and von Tschermak rediscovered his laws of inheritance. Mendel’s work suffered from three damning faults: it ran counter to the prevailing wisdom on the inheritance of biological characteristics; it made use of mathematics, unheard of at that time in biology, and its author was only an unknown monk from Brunn, and not a member of the scientific establishment.
Others, now household names in the world of science, suffered similar discrimination. Ohm’s work on electricity was ignored, partly because he was of insufficient professional standing, being only a mathematics teacher at a Jesuit High School in Cologne. Pasteur’s discovery of germs and their role in infection was spurned because he had no medical qualifications. Oliver Heaviside’s cri de coeur: “even men who are not Cambridge mathematicians deserve justice” was a consequence of his work in mathematical physics being ignored for twenty-five years.
It is interesting to examine some of the motivations of those who impeded the acceptance of scientific works that later turned out to be seminal. For instance, some scientists bore prejudices based on their own approach to science, and were unwilling to credit that others with a different background or modus operandi could produce anything of substance. This tendency was exacerbated when the work arriving on their desk was from a little-known author, and challenged established scientific beliefs.
Resistance to the heliocentric model for the solar system of Copernicus was opposed, not only by the Catholic Church, but also by astronomer-scientists such as Tycho Brahe. Lord Kelvin liked to make mechanical models to facilitate his understanding, and had trouble with abstract concepts, such as the electromagnetic theory of Maxwell [7]. As we have seen above in discussing Mendel’s fate, Kelvin was not alone in his opposition to a mathematical approach to science. Indeed, the lack of success by mathematically inclined biologists in getting their work published in traditional journals led them to found their own journal: Biometrika.
Philosopher, Francis Bacon, the father of Empiricism, was influential in his opposition to theoretical science. However, he and his followers were dismissed as “bird-watchers” by the more mathematically inclined, some of whom carried their own prejudices so far as to scorn the discoveries on electromagnetism by Michael Faraday, one of the greatest of all experimental physicists [8]. The religious beliefs of some scientists led them to oppose specific areas of science, such as evolution and geology.
Generally speaking, it is the younger scientists who are more receptive to radical ideas than their older colleagues. As Max Planck once stated: A new scientific truth does not triumph by convincing its opponents and making them see the light, but rather because its opponents eventually die, and a new generation grows up that is familiar with it.
It is now over half a century since Barber’s paper [5] on scientific bias appeared, and one might think that attitudes had by now surely changed. It is probably true that the practice of “open-mindedness” is more common in science than in most other professions. At the heart of science is the peer review process, whereby research submitted for publication in a science journal is subjected to a critique by several anonymous “experts” in the same field. More than one million research papers are published each year, and reviewers are usually expected to provide their services for free. Rejection rates are high for the most prestigious journals. Modern computer databases keep track of how often individual papers, authors and journals are cited by other researchers, and these data impact on scientists’ promotion prospects and chances of getting financial support for their projects.
Science has become a very competitive industry, and scientists being only human, it should be no surprise that some of them resort to “grey” practices to promote their own ideas and work at the expense of their rivals. Cases of outright fraud are however rare. In the long run however, the replication of experiments and observations in different laboratories by different researchers usually sorts out what is correct from what is not, even if sometimes it may take a rather long time.6
1.6 The Limits of Science
In a now lost poem, a sequel to The Odyssey, by Greek poet, Homer (born sometime between the 12th and 8th Centuries BCE), Ulysses managed to convince his sailors to attempt what was then considered the ultimate quest, i.e. to explore the uncharted waters of the Atlantic. This adventure involved passing through the Strait of Gibraltar and past the columns set there by the demigod Hercules, which were inscribed with the phrase: non plus ultra (no more beyond), to warn seafarers not to venture beyond.
After countless days of navigation, the fearless men finally spotted land, but their joy soon ended in despair when a sudden storm and whirlpool wrecked their ship. The interpretation of this tragic outcome by Dante (and Christians) was that the land they arrived at was the mountain of Purgatory, which was of necessity forbidden to all living men. Ulysses had perished in a quest for forbidden knowledge.
A portion of a marine map of Scandinavia, drawn up by Olaus Magnus at Venice in 1539, showing some of the dangers likely to befall unwary seafarers who venture too far from the land. Image: public domain (https://commons.wikimedia.org/wiki/File:Carta_Marina.jpeg (accessed 2020/8/30))
In more recent times science has shaken many dearly held beliefs: the Copernican system has replaced the revered Ptolemaic model of the solar system, and Darwinism has dismantled faith in the immutability of animal species and in the special place of humankind in the scheme of creation. As a reaction, many followers of religion (often using tools and means provided by science) have suggested that scientists can sometimes be wrong, which is undoubtedly true, and that science has bounds which only religion can cross.
Let us leave aside any controversy between science and religion, and reiterate that in this book we wish to explore, from a purely scientific point of view, the vexed question of the limits of science. It is a timely question, since just two or three decades ago a number of scientists were confident of being close to a TOE–a Theory of Everything. By this they meant that all the forces of nature could be described by one overarching theory. Such a situation would have killed and buried physics as an active field of research. As we shall see later in this book, a TOE has not come to pass, and may actually be an impossible quest.
The aim of physics is to explain reality, but as we have seen in the earlier Sections of this Chapter, it is not really possible to say with any certainty what reality is. One might simplistically say it is what we perceive with our senses. However, our senses are very limited, and science has progressed largely by developing instruments and techniques to extend their powers. Microscopes and telescopes aid our eyes to see very small and very distant objects, but how do we know that these objects really exist?
Werner Heisenberg, one of the founders of Quantum Mechanics, recognized the important role that the observer plays in our notion of reality: We have to remember that what we observe is not nature in itself, but nature exposed to our method of questioning [9]. Our view of reality is myopic, limited by our instrumentation, and quite possibly distorted, like that of a goldfish viewing the world outside of its bowl through the curved glass. As poet William Blake wrote: If the doors of perception were cleansed, everything would appear to man as it is, Infinite. For man has closed himself up, till he sees all things thro’ narrow chinks of his cavern [10].
The belief is that external to us there exists a “true” reality, but there is no way to prove such an assertion. Would an alien, assuming one exists on another planet somewhere, see the same reality as we do?
As we will see in Part 2 of this book, the progress of physics from the turn of the 20th Century has been mainly to extend our “understanding”—a term that we clarify in the next Chapter—to the very small and to the very large and distant. However, our pictures of these two regions of reality are somehow contradictory, and problems arise when they overlap. Will future instrumentation enable this dilemma to be resolved, or will some questions always remain unanswerable? One may regard science as a methodology for testing out various hypotheses that we, as human observers, hold about the physical world. We may strive towards truth, but the more questions we answer, the more new ones that surface and require an answer.
Another issue to be considered is whether society will continue to support research into areas such as these, which, although indulging humankind’s curiosity into the origin of the world and of life, produce few practical outcomes commensurate with its huge costs. In other areas, e.g. modification of the human genome, human ethics have placed limits on research, when the knowledge obtained would likely produce undesirable social consequences.
The same cost restraints do not apply to theoretical physics, but as we will discover in Chap. 4, other issues become relevant. We have already seen in Sect. 1.3 how Zeno’s paradox of Achilles and the tortoise puzzled philosophers for centuries. Eventually this enigma was resolved, but others remain. The field of mathematics was shocked by the incompleteness theorems (see Chap. 4) proved almost a hundred years ago by the Austrian mathematician, Kurt Gödel (1906–1978), which showed that some propositions in mathematics are unprovable. As physics is based on mathematics, surely similar limits to knowledge must apply also in physics.
In considering questions such as we have raised here, it is important that the debate is not left entirely in the hands of scientists. Science concerns us all, since it has brought countless benefits to the whole of humanity. It has also brought its shares of woes. Science can be a frightening toy in the hands of the amoral or malevolent. For most people what is really relevant to their everyday lives is the use of technologies, such as those required by smart phones, computers, navigators, cars and planes. Behind all such inventions there is a huge amount of science, and surely it makes no sense at all to take advantage of the inventions and innovations, while not believing in the science that makes them possible. A keen and well-informed awareness of science is an asset for everybody, and not just for scientists.