Wednesday, October 16, 2019

Wondering About Chapter 3

Wondering About Reality
 
In the 1999 motion picture film The Matrix, the actor Keanu Reeves plays a character, Neo, who is forced into the horrific realization that the world he lives in – indeed, that everyone he has ever known and loves lives in – is not the objective real universe at all, but only a virtual reality created by an artificial intelligence, an intelligence that has enslaved humanity for its own purposes. Neo’s realization of this truth is the result of his liberation from the Matrix by an individual known as Morpheus (played by Laurence Fishburne). Upon ingesting a red pill, Neo awakens in his own, true, body; a body which is naked and hairless and is curled up in a fetal position in an artificial womb, kept alive via tubes and cables leading into important orifices. More important and unbelievable than this however, is the fact that he is but one body, one virtually identical to the billions that surround him in a vast menagerie of wombs, stretching as far as the eye can see.
Well, what do you think? Could it be true? Could we all be living inside a virtual universe created by an intelligent entity? Could the seeming solidity of the world around us be merely an illusion created by a computer program, and we unfortunate souls slaves to the master programmer who has created this mirage?
I’m guessing your answer to these questions is an unqualified NO! That The Matrix, as entertaining as it was in the movie theater or in your home, or even as compelling, is the paranoid fantasy of any mind bizarre enough to think it even possible. Sure, logically it could be true; but that can be said about any paranoid delusion.
No, there is no Matrix, no master programmer, and we are not slaves except to the extent that we are ignorant of our true condition. But what is true is that the world we experience and perceive is not actually an objective existence “out there” but a virtual reality simulation of that existence, one that is going on inside our own heads, in our fabulously complex and wondrous brains, twenty-four hours a day, throughout our entire lives. The only difference between this simple fact and science fiction is that, as I said, there is no master programmer: all the programming is done by a combination of our genes and experiences working together, each blind to what it is doing and without any plan at all, yet together a combination far more powerful and brilliant that the greatest software engineer in the world.
This statement may astound you, but in fact there is nothing either particularly original or controversial about it; not, at least, to any philosopher or biologist or neuroscientist you might care to mention it to. That is why I say you can go through the process of digesting it and retain your sanity. The only question is, why do so? What purpose beyond an abstract, and somewhat macabre exercise in philosophical musing could it possibly serve? Moreover, given the theme of this book, what does it have to do with curiosity and our capacity to comprehend the universe?
Before answering these questions, it is worthwhile to examine this concept of living inside a virtual reality of the mind in more detail. I need to convince you that, all your experience and perceptions to the contrary, it is true beyond any reasonable doubt. At the same time, and perhaps even more importantly, I also need to make clear just what I mean by it and, just as critical, don’t mean by it. Here, in fact, might be the best place to begin the examination.
A good way to describe anything is by means of an analogy, or metaphor, and the most natural one that suggests itself here, to me at any rate, is the so-called “desktop” of a modern personal computer. I am assuming that you have experience with this phenomenon, whether in the form of a Windows PC, a Macintosh, or one of the several flavors of graphical desktops available on UNIX or other machines. If you do not, the example below (taken from my own PC, naturally) ought to give you the general flavor of what I am talking about:
This is an example of what you might see, looking at the monitor screen of my computer. The first thing that might strike you is that the term “desktop” is indeed a fairly apt one: we see a background of blue as a true desktop might actually have, covered with things you might expect to find on a desktop. For example, there are what are known as “icons” in the upper left hand corner; these could be considered as kinds of folders, or perhaps drawers containing folders and files. The center is dominated by the four open “folder windows” (hence the name Windows, although other graphical interfaces sport the same appearance), each appearing exactly like that; an open folder some of which containing list of still more folders (the rectangular, yellow icons) and open files (e.g., “Chapter 1.doc, Chapter 2.doc, which incidentally are the chapters of this book at the time of writing). There are also two windows representing open and running programs or “applications”: the Notepad Editor, and the Calculator program; you probably find them easy to think of as an open paper notepad and calculator on a real desktop for they really appear as physical applications you might have on a true desktop.
I will ignore the bar at the bottom of the screen, although this does provide more interesting information as well. Basically, what we see are things, or at least by the appearances of things, that we can interact with in an intuitively obvious manner. By using the mouse ( a handheld instrument which you manipulate across your actual desktop) for example, when I maneuver a small arrow (not shown) over any of the icons or windows, or parts of windows, and either singly or doubly clicking a button on the mouse, I cause something to happen. If, for example, I position the arrow over the “file” that says Chapter 3.doc and double-click, a program called Microsoft Word will start, and will load the Chapter 3.doc file so that I can read and or edit it, rather like conjuring up a (very powerful!) typewriter with loaded pages. Double-clicking any of the folder shaped icons on the “My Documents” window will likewise “open” the folder to reveal its contents: most likely, a mixture of more folders and files. Double-clicking any of the upper left corner icons will open a window showing their contents, usually a collection of folders, files, and other icons. Clicking on the calculator program will allow me to enter numbers in the top white bar and perform all sorts of mathematics on them just as with a “real” calculator, while the notepad application allows me to type in text and save it to a file.
I do not want to belabor the point here, for if you have any experience with a modern computer – which I am assuming you do – you are quite familiar with the kinds of actions I am talking about. You are familiar with how you genuinely appear to be working with a real desktop, one containing icons, windows, and applications you can interact with in a way so intuitive and simple a manner it is almost childlike. The point I want to emphasize is that despite this it is nevertheless no more than a virtual reality simulation, one designed to conceal the details of what is really going on while making using the computer so simple and easy. In truth, the desktop and all its icons and windows and toolbars (at the bottom) are but phantoms for the eye; useful phantoms, as they make the computer easy to use, but misleading ones, as they conceal from us and seriously mislead us as to what is actually going on inside that humming box of dumb electronics and other gizmos we are working with. We see a bunch of icons and folders and files, just as we might on an actual desktop. We might even be fooled into thinking that is what we are working with. But it is not, not at all. It is a mirage, through and through.
For what we are really working with are patterns of bits (basically, on / off type switches) which make up two primary parts of the computer physically: its working memory, and its permanent storage, or disk drives. The point is, if we were to study those patterns of on / off switches and try to decipher what they are saying directly, let alone work with them in any direct fashion, we should very quickly find ourselves hopelessly and helplessly overwhelmed by the complexity and non-intuitiveness of the task (to instill some appreciate and admiration in you, however, that is pretty much just what the users of the original computers, some fifty plus years ago, had to do). Designers of an earlier generation of computers, before the graphical interfaces so common today, would simplify using computer by providing a “command console” in which you would type, via a keyboard, the names of programs you wished to run, the files you wanted to work on, or any other commands the computer understood. Even this was no easy task, so when the first graphical interfaces came out in the early / mid 1980s (by the Apple Macintosh), it revolutionized the personal computer, making it a household object much like the television or telephone. Other companies followed suit with their own graphical interfaces, such as Microsoft Windows and the various UNIX interfaces, and the computer revolution was in full steam. With the advent of the internet in the 1990s, and high speed permanent connections in the 2000s, most of us now regard our desktop or laptop machine as indispensible and valuable as our refrigerators. Life, indeed, seems hardly conceivable anymore without it.
* * *
If I keep going on this way, I will stray too far from my subject and my point. Let us recapitulate: there is reality, and there is, or can be, a virtual simulation of that reality such that it has the effect of making it much easier to interact with that reality than directly. The virtual simulation is a model which corresponds to objective reality, but in a way that allows us to interact with it much more effectively. If you can imagine setting bits in a computer memory or disk off or on, instead of working with icons, windows, folders, and files, you should have no problem grasping the advantage of this.
What I am saying goes further, however. Just as the desktop of your computer provides a useful, albeit inaccurate description of its objective reality, your brain does the same with the objective world all around you.
Let’s take a few moments to let that sink in. I am saying that the “objective world” that we all deal with and handle every day as we move through our busy lives is in fact a simulated reality in our own brains. If you find that impossible to believe then, allow me to prove it with a sensual (in this case, optical, but you can fool your other senses as well) illusion, one of the usual stock in trade in books on how the brain works. Have a good look at the object below:
Perhaps you have seen this illusion before. Here’s the upshot: the squares marked “A” and “B” are, all irresistible appearances to the contrary, exactly the same shade of grey. Don’t believe it? Good, don’t take my word: cover the entire image with a cutout which conceals all parts of the figure except these two squares and see what happens. You will see that they immediately jump out as the exact same shade of grey, improbable as that seems. Improble? No, impossible, for take the cutout away and it literally is impossible to not perceive B as much brighter than A.
What is going on here? Quite simply, your brain, which has nothing more to go on than a pattern of photons on your retinas, is creating a model of reality as best as it can, based on rules wired into it by your genes and experience. That model insists that square B must be brighter than square A, despite the actual facts as demonstrated by applying our cutout.
As illusions go, however, this is small potatoes for something as complex and sophisticated as your brain. For a better example – in truth, and the basic point of this chapter –take a look at one of your hands. Make it your left hand (if for no better reason than I’m left-handed). What do you perceive? Solid flesh overlying even more solid bone, if you are like me. Press it against the surface on an object, such as a real desktop, and that perception is made all the more stronger. Now wiggle your fingers. What has happened? No doubt, you feel as though you simply just decided to wiggle your fingers, and then did so. Same if you clench and unclench your hand in a fist, or scratch your nose, or write (oops – if you are right-handed this probably isn’t easy), or deftly pick up an object such as a pen and manipulate it in some way, such as twirling it like a baton. In each case, you are aware of what a marvel of engineering your hand is, and you sense the seemingly miraculous gift of being able to use it the many myriad ways that you do.
As marvelous and miraculous and real as it seems, though, it too is an illusion; a virtual reality created inside your brain for you to interact with. Furthermore, this is true not only of your hands, or any other part of your body, but of the entire – yes, a lá The Matrix – objective world you live and function in. You do not interact with the universe in any direct sense at all, but only through models of that universe created by your brain using the rather limited sensory information it gets from your eyes, ears, sense of touch, and so on. As much as it seems that you are indeed interacting directly with the universe the fact is that you are not; do not, and can not, because the data taken in by your senses is quite insufficient to allow you to do so.
Precisely then, what is going on? The virtual model created in your brain is obviously not arbitrary. On the contrary, it bears a very close correlation to the actual universe around you, as indeed it must if you are not to walk into trees or off cliffs, fail to run away or hide from tigers, feed and take care of yourself, interact with the other human beings, fall in love and procreate, and raise children; all the things, in other words, that we and our ancestors stretching back millions of years have had to do to survive and pass on their genes in the great experiment known as Evolution by Natural Selection. The fact that you have genes that code for a brain that models the world so effectively is no accident. Nature has been honing those genes a long, long time, under relentless and unforgiving evolutionary pressure.
* * *
The problem with this model in your head, and the reason I mention is, is that it can seriously interfere with your understanding the scientific explanation of things. I discovered this often during my own education: sometimes my problems understanding a subject were due to an “intuitively natural” concept of things, a concept that in fact wasn’t true. Or to give a specific example: when studying optics as an undergraduate, a fellow student was hopelessly and distressingly lost trying to follow the subject material. It took a little conversation to reveal that the problem was due to the basic concept of optics that she had; instead of light from the sun and other sources bouncing off objects and entering our eyes, she viewed the light as emanating from her own eyes to illuminate objects, much as the ancient Greeks did. Once she erased this false concept from her mind and adopted the correct one, her problems diminished greatly.
To emphasize this in our current situation, look at your hand again. It appears solid and continuous, which is why it doesn’t pass through whatever it is resting on. But you know, even from your elementary school education, that that isn’t really true. Matter isn’t solid or continuous at all, not even the heaviest and densest of things we normally encounter. All things, as you learned in school, are composed of extremely tiny elemental motes of matter known as atoms. You may even have learned that atoms consist mostly of empty space; an extremely dense but small nucleus of protons and neutron, around which tiny things called electrons orbit.
* * *
I recall my father introducing me to the concept of atoms over the dinner table when I was about seven or eight. He sat at the head of the table, and I was the first one on his right (at the left end because, as I have just mentioned, I’m left-handed). The details are lost to me now but I’m quite clear that one day, as we were all sitting down to dinner, he introduced the concept to me. Mind you, my father was not a highly educated man. I don’t believe he ever even finished high school. But he worked for a chemical company, and had picked up enough science to give me my first taste of the subject. That first taste was that everything – yes, everything – is made of atoms (a story I later learned was not entirely true).
Look upon your hand again. Yes, it is made of atoms. If you are curious (and if you are not I cannot imagine why you are reading this book), the atoms are mostly carbon, oxygen, hydrogen, and nitrogen, with some phosphorus and sulfur thrown in, along with a smattering of iron, calcium, sodium, potassium, chlorine … you get the idea. My hope is that you begin to see why I began this chapter as I did: your perception of your hand and what your hand actually is are quite different things. The perception is for the purposes of your survival and reproduction. The is is what science tells us: the objective reality. Do you begin to see why satisfying our curiosity as to the nature of things is so difficult? Because it so often requires we think about things in a way that is utterly foreign to our normal experiences. We do not experience atoms, either in our hand or, for that matter, as what air is made of. We have this built-in concept of matter as being solid and continuous. But that concept, or instinct if you prefer, is wrong. It is misleading. It blocks the path to comprehension. So if we are to comprehend, very often we are required to cast our instincts and concepts aside, and look at the world with fresh eyes. One of the ambitions of this book is to help you to do precisely that.
Again, stare at your hand and try to see it, not as the solid, continuous thing it appears to be, but as a vast collection of exquisitely small but exquisitely alive, vibrating atoms, interacting with each other and with the environment around them. If you find this difficult to do at first, don’t worry, or give up. You are not being asked to hallucinate (fascinating as such an hallucination would be), only to imagine it – remembering that you cannot truly picture it, you can only simulate the image by making the atoms much larger in your mind than they actually are. So just relax and imagine you are some Lilliputian being transported into this world, observing what such a tiny creature would imagine. Do you have it? Good.
(I can’t resist. There is a scene in the original The Matrix movie, in which Neo at last directly perceives the artificial reality people live in as a stream of symbolic logic symbols; this is truly his moment of liberation, more than anything else. What I am talking about here roughly corresponds to that moment in the movie.)
Now that you have this image before your eyes, I am going to do something cruel: I am going to take a sledge hammer and … no, I am not that cruel. Besides, I don’t need to completely smash that image, however; just enough to let us begin on the next leg of our long journey toward truth – a journey which never actually ends but does take us to the most fantastic worlds and universes. Actually, the general picture you probably absorbed from your schooling is, in the basics, correct: the atom is composed of a a tiny, dense nucleus composed of protons and neutrons, and a cloud of electrons which are somehow around the nucleus – probably you picture them as orbiting the nucleus, in much the same way as Earth orbits the sun, but that is the part I am going to smash, so I won’t emphasize it. The essential picture is, in many ways, correct, especially the part about the atom being almost entirely empty space, meaning that ordinary matter is almost entirely empty space, our perceptions notwithstanding.
It is correct enough to explain why your hand seems solid and cannot pass through walls or desktops. The electrons at the outer edges of your hands encounter the electrons on the wall or surface, where they electrically repel each other so strongly that you would have to rend the matter of your hand and / or the surface of the wall into tiny shreds to make your hand pass through it. That’s right, the apparent solidity is in fact just electrons repelling each other via the electromagnetic force, which is astonishingly powerful – some 1039 times as powerful as gravity (no doubt this seems hard to believe; why gravity appears to be the stronger force is something we will explore later). Your sense of solidity has nothing to due with understanding what is really going on. Nothing to do whatsoever. Remember this. The world is not what it seems. Implant this in your mind, and nourish it like a rich garden. It the key to satisfying curiosity.
* * *
Actually, perhaps you think that atoms are obvious. After all, you went to school where the subject was introduced, and now it may seem as commonplace as other unlikely truths, such as the sphericity of Earth, or the fact that Earth is orbiting the sun and not, as your eyes plainly tell you, vice-versa. But it is not obvious at all. Reflect on the fact that, for a century after John Dalton first proposed the modern concept of atoms in the early 1800s, using the reasoning of the whole number proportions of elements that went into reactions, the great majority of scientists rejected the idea of atoms being real right up to the early 1900s. Nor were they fools for doing so, because the idea of atoms leads to serious conflicts with Newton’s Laws of Motion and the Laws of Thermodynamics as they were then understood. The reason for this is that Newton’s Laws of Motion are time reversible – that is, you cannot distinguish between a process happening in forward time as from one happening backwards; while the Laws of Thermodynamics, in particular the famous Second Law, and its greatest creation, the concept of entropy, state that energy – in the 1800s regarded as a form of fluid – moved inexorably from regions of low entropy / high order in time to regions of high entropy / low order at later times. The bottom line of this view was the so-called “heat death” of the universe, which appeared inevitable, at least from 19’th century perspectives. But if matter were indeed composed of atoms, the reasoning went, then their interactions, as derived from Newton’s Laws, would be time reversible, in violation of the Second Law, which says that entropy – disorder – must always increase. There appeared to be an irreconcilable contradiction here, one that led most scientists, and philosophers, to dismiss the actual existence of atoms as a phantom, despite the increasing evidence from the work of men such as Rutherford and J. J. Thompson that they did indeed exist.
* * *
It took the brilliance of one Ludwig Boltzmann to reconcile the seemingly unreconcilible, which he did by devising a new, subtly different definition of entropy, or disorder. Assuming atoms were real, Boltzmann deduced that the Second Law still held if one took a statistical view of entropy, rather than an absolute view of it. To appreciate Boltzmann’s insight, consider a deck of cards. If the deck is perfectly ordered – i.e., ace of spades, king of spades, queen of spades, etc., down through all the other houses in similar order – then obviously any shuffling of the cards will invariably destroy that order. The order is unlikely to be completely destroyed, however; if we examine the deck after one shuffling, we will still find that isolated pockets of order have survived, both large and small. One might say that the deck is still semi-ordered; that its entropy, while not zero any longer, is still fairly low. It is certainly much lower than a deck of cards that has been shuffled many times, so that all order is lost, but much higher than our original, perfectly ordered deck.
Now consider the second, or third, shuffling. Again, we regard it as likely that the cards will be in less order with each shuffling; or conversely, will possess more entropy. But the key word here is “likely”; it is possible that, purely through the vagaries of chance, that a shuffling will result in an increase of order. In truth, a truly random shuffling will result in a completely unpredictable order of the cards; this in fact is practically the definition of random. But if the order is truly unpredictable, than it very well can be a more ordered arrangement of the cards than before the shuffling! Here is where the key insight lies. It can be, but is unlikely to be, more ordered, simply because if one examines all possible arrangements of the cards, there are many more disordered arrangements than ordered ones. This is why we expect shuffling to decrease the disorder; it is purely a statistical assumption, yet an excellent one simply because there are so many cards. If, instead of fifty-two cards, there were fifty-two thousand, the ratio of disordered arrangements to ordered arrangements would be vastly greater and the likelihood of increasing disorder / entropy by shuffling proportionately greater.
Let us move from card decks to actual, ordinary realities. A single cubic centimeter of air contains not fifty-two thousand but over ten million trillion molecules of various gasses. Thus, the odds of any random process decreasing its entropy (increasing its order) is so infinitesimally small that we regard it as essentially certain not to happen. Indeed, it is so small that we simply say that entropy always increases.
But we are wrong. Entropy doesn’t always increase. It is a purely probabilistic law, which says that order is almost certainly likely to decrease, especially in a system with more than a few dozen or so parts. But almost certainly isn’t always. It may be so often that in the entire lifetime of the universe we never observe its overall order decrease. But nothing says that it can’t happen. It is just overwhelmingly unlikely to happen.
Boltzmann’s insight neatly resolved the apparent conflict between the Second Law and Newton’s Laws of Motions. The evidence coming out of Rutherford’s and Thompson’s laboratories, among others, convinced the scientific world of the truth of atoms in the early nineteen hundreds. Sure, entropy almost always increases, so almost that we never observe the opposite however long we observe, but it is not impossible. For tiny systems, however, it can and has been observed to happen. Newton’s laws and thermodynamics agree after all.
* * *
This book is not meant primarily as the history of scientific ideas. But sometimes it is impossible to both pique and gratify our curiosity without covering the grounds that minds before us have covered. The atom is a perfect case in point. It is both obvious (mainly because we are taught it) yet devilishly elusive at the same time. The above discussions shows a part of the reason why this is true. But – and now we enter Alice in Wonderland territory – it is not the only reason. If anything, in fact, things become truly strange from here on. So buckle your mental seat belts and lets prepare for a wild ride.
Even as atoms were being accepted as real in the early twentieth century – for the record, Einstein’s experiments on Brownian motion probably clinched the case as much any other work – physicists were still in an utter quandary over just how they could be real. By all known laws of physics up to the twentieth century, atoms were simply impossible. Just that: impossible.
The reason for this has to do with the well known analogy between atoms and solar systems, what atoms were modeled from. Earth and the other tiny planets orbit the massive sun, in a seemingly infinitely stable manner, in much the same way as the tiny electrons were proposed to orbit the massive nucleus of protons and neutrons. It is a very natural analogy, which Rutherford initially proposed. And which everyone saw at once could not possibly work.
Analogies are tricky things. We humans naturally employ them when explaining phenomena hitherto unexplained. Analogies can be very powerful, and often form the basis for new insights and explanations in the natural world. Scientists and laymen alike have been using them with wonderful successes for centuries. But there is a nasty snare in this whole process of analogizing, which is why, as Richard Dawkins laments in The Blind Watchmaker “… analogies can be immensely fruitful, but it is easy to push analogies to far, and get overexcited by analogies that are so tenuous as to be unhelpful or even downright harmful. I have become accustomed to receiving my share of crank mail, and have learned that one of the hallmarks of futile crankiness is overenthusiastic analogizing.”
The main reason for this, I suspect, lies in the fact that analogies are just that: compendia of likenesses between something we do understand with the phenomena we are struggling to make sense of. The problem is, almost nothing is really exactly like something else. The appearances of similarity may in fact be purely superficial, and so lead us nowhere (the “Argument from Design”, so often employed by people who reject evolution is, I think, a good example of this). More often however, and this is where the snares are baited and waiting and the unwary are in greatest danger of being caught, come from analogies that work quite well to a certain depth of understanding, but fail at a deeper level of analysis. The analogy between atoms and solar systems fall right into the middle of this dangerous pit; so enticing to the casual eye, but lethally flawed to those who have looked deeper.
Here is the problem as concisely as I can give it. The planets orbit the sun in what appear to be eternally stable orbits, but that it is not actually true. According to classical physics, any object accelerating through a force field (in this case, a gravitational field), where accelerating means either speeding up, slowing down, or changing direction, gradually but inexorably radiates energy away. In the case of planets, the energy lost is in the form of gravitational waves, which are extraordinarily weak. The net result is that the planets’ orbits about the sun are only approximately stable; eventually they will fall into the sun, but not for many trillions of years and more, a time period in which much more serious things are going to happen to the solar system, such as the sun running out of hydrogen fuel and blowing up into a red giant, roasting or destroying all the inner planets, then contracting to a white dwarf, leaving all remaining planets in an eternal deep freeze.
For a single electron orbiting a single proton, the simplest atomic model, the hydrogen atom, the same physics apply, but the time scales are vastly different. Remember the 1039 difference between gravity and the electromagnetic force, the force which attracts the electron in the hydrogen atom to its proton nucleus? Do the necessary calculations and you find the electron radiating away all its energy as electromagnetic radiation and crashing into the nucleus in a tiny fraction of a second. All the other atoms must suffer the same fate, and if indeed this is how physics works at this level, then matter as we know simply could not exist.
And so, by the early twentieth century it was clear from indirect and direct experiments on the nature of atoms that there was no choice but to conclude that, in fact, physics was incomplete, and did not provide a true description of nature at this scale. A new model and new laws were needed, laws that might seem counter-intuitive to common sense (always the bane of science) and even to the known laws of physics. Of course it couldn’t completely overthrow those laws, as they had explained so much as about how reality works, but it must give a deeper, subtler, and more complete description of those laws.
The first attempt to square the now accepted reality of atoms with physics was made by Neils Bohr, in 1913. Bohr accepted the basic Rutherford model of the atoms, of electrons orbiting a tiny, dense nucleus, but added a caveat to the system, based on work previously done by Max Plank and Einstein: He arbitrarily decided that the electrons, unlike planets orbiting the sun, couldn’t have any energy but were restricted to certain, “quantized” values. Atoms didn’t collapse because the lowest allowed quantized level was not zero (an assumption Bohr had no justification for except that it made his model work). To speak strictly correctly, Bohr didn’t quantize the energy of the electrons but their angular momenta, but the difference need not concern us here; what is important is that he was able, for the hydrogen atom, to construct a model with quantized electron orbits, which perfectly explained all the properties of this atom, especially its spectral lines, which were the result of electrons “jumping” (Bohr had no concept for what actually happened when an electron switched orbits) from outer to inner orbits, and releasing the energy in the form of light photons of a specific wavelength.
Bohr’s model for the hydrogen atom was a stunning success and showed the world he was on the right track, but many puzzling problems remained. First, Bohr could not make a working model for any other atom in the periodic table, or any molecule, which are combintations of atoms bound together. Second, his arbitrary assumption of quantized energy levels was just that: arbitrary. It made his model work in an ad hoc fashion, but there was no deep, underlying physical explanation which lay beneath it, an explanation which was satisfying to physicists of the day. Clearly, something more was required. It was that something more, however, which was to set the scientific – indeed the philosophical – world on its heels. For what was required was nothing less than a reevaluation of the very nature of physical reality itself; a reevaluation which still has scientists and philosophers debating to this day.
* * *
In a book about curiosity, it is fitting that what follows is probably the most curious thing scientists have ever uncovered about nature. Echoing the theme from chapter one, it demonstrates just how amazing and profound and unexpected our discoveries will be whenever we are overcome by our desire to know and just have to peek under the covers a little to see how nature genuinely works. It also extends the theme with which I began this chapter, on how scientific understanding undermines and even obliterates our cozy and seemingly so real perceptions of reality and shows that we must look at the world with fresh eyes and imaginations if we are to have any chance of comprehending it. For the world of quantum physics, the bizarre Alice-In-Wonderland world we are about to enter, not only obliterates our perceptions; it challenges our capacity to think at all. It is like a dream in which nothing makes sense, and fades instantly the moment the dreamer awakens.
It is probably the ultimate irony that in the human quest to satisfy our curiosity, we have been ultimately humbled by the inescapable fact that our answers shall always be inherently uncertain. The quest for knowledge has yielded the knowledge of the limitations of that quest. Perhaps we should have seen it coming. We can certainly enjoy the cosmic joke it has played on us. I have no words to match those of Jacob Bronowski, who captured the new view of reality in chapter 11 (“Knowledge or Certainty”) of The Ascent of Man:
One of the aims of the physical sciences has been to give an exact picture of the material world. One achievement of physics in the twentieth century has been to prove that aim is unattainable.
Take a good, concrete object, the human face. I am listening to a blind woman as she runs her fingertips over the face of a man she senses, thinking aloud. ‘I would say that he is elderly. I think, obviously, that he is not English. He has a rounder face than most English people. And I should say that he is probably Continental, if not Eastern-Continental. The lines in his face would be lines of possible agony, I though at first they were scars. It is not a happy face.
This is the face of Stephan Borgrajewicz, who like me was born in Poland. In plate 175 it is seen by the Polish artist Feliks Topolski. We are aware that the these pictures do not so much fix the face as explore it; and that each line that is added strengthens the picture but never makes it final. We accept that as the method of the artist.
But what physics has now done is to show that that is the only method to knowledge. There is no absolute knowledge. And those who claim it, whether they are scientists or dogmatists, open the door to tragedy. All information is imperfect. We have to treat it with humility. That is the human condition; and that is what quantum physics says. I mean that literally.

No absolute knowledge? All information imperfect, to be treated with humility? The only method to knowledge that of the artist? Just what is going on here? Hasn’t all our curiosity been about getting to the ultimate and final truth? Yet what we seem to be hearing here is that there is no so such thing; worse, that we are in danger of falling into dogmatism and even tragedy if we insist on pursuing it to that end.
* * *
Partly by design, partly by accident, this chapter has meandered through several different, though interrelated, themes, the main one being science, our best and in my opinion only realistic hope of satisfying curiosity, repeatedly demanding that we use our imaginations to view reality in ways we had never considered, and which often seem counter-intuitive. Part of that imaginative use means accepting that things are often not at all what we perceive them to be. Another part, the part we are coming to, is that what must even be careful about relying on any intuitions or “common-sense” if we are to understand the way the universe works. I do not mean to say, however, that intuition, perceptions, and common-sense are always wrong or useless; by no means is this so. But we must proceed cautiously and with open minds and eyes if we are to make progress.
Once again, look at your hand and visualize the tiny, vibrating atoms which compose it, much the same way that the tiny, vibrating bees constitute a hive. We left off with Bohr’s description of these atoms, which said that the electrons did indeed orbit their nuclei, albeit in fixed, quantized orbits. We noted that Bohr himself had no explanation why nature should work this way at this scale, instead of continuous orbits like those of the planets around the sun. This was a weakness in Bohr’s original visions, which of course he realized; Bohr understood only too well that what he was suggesting was nature was something more bizarre and counter-intuitive than our senses captured for us.
* * *
This is not a history on the development of quantum mechanics, so I will leave out quite a bit of interesting detail here (like de Broglie’s wave model of electrons, which was actually quite critical to the final vision). What I’d like to do at this point is use the cherished method of analogy again, to help you appreciate the true situation of how electrons behave in atoms and molecules. Again, I think this is more helpful for the layman to start this way.
My analogy is that of a tennis match. Imagine that you are watching the ball sail back and forth between the players (this could be a bit tough if you are picturing modern professional players, who hit those seemingly impossibly hard shots from all angles; so try to make it a friendly game on a local court somewhere). As you watch the ball, even in this friendly match, you are aware that it still seems a blur much of them time. At no particular moment can you make out exactly where the ball is, or how fast it is moving, or its precise direction.
That’s fine. What you are experiencing is simply the limits of your visual acuity system, involving your eyes, optics nerves, and the parts of your brain which process the information. They can follow the situation only so quickly, and the result is that things seem somewhat blurred to you. Still, and despite this, you accept the proposition that, at any given moment in time, the ball has an exact location, and has an exact speed and direction. You can’t pick it up, but certainly a sensitive enough piece of equipment – say a strobe camera operating at high speed – could do so easily. You take that as given. It is just “common sense” you might say.
Yet – and here is the part where you must starting thinking in as unorthodox a manner as possible – you would be wrong. However, in our hypothetical tennis match, not even the most sensitive instrument ever built would show you that you are wrong. That is because the mass of a tennis ball is simply too overwhelmingly huge. Indeed, the mass of a dust mote would be too overwhelmingly huge as well. This is why we don’t ordinarily notice our error; from the viewpoint of creatures our size moving amongst objects that we can see and touch, the error is so small it would never show up. Thus, our brains and sensory systems, which have been attuned by natural selection to deal with objects of approximately our sizes, has a hard time grasping the concept what I am about to tell you. But electrons, which are vastly smaller in mass than anything we shall ever come in contact with, don’t behave the way that the analogy with tennis balls would suggest. They don’t behave that way at all, simply because they are so small in mass. The most concise way of expressing their real behavior is, with all due apologies because I want to avoid math as much as possible, is with an equation:
x × s ≤  / m
Hopefully, this is not too complicated a piece of math to throw at you if you are tucked way in front of a roaring fireplace, all comfy and cozy. Or reading it over your three minute egg at breakfast. But I am going to ask that you look at this equation and drill into your mind, for you shall miss much of what is to come if you don’t. Oh, and before proceeding, this equation is just one version of what is commonly referred to as the Heisenberg Uncertainty Principle, after Werner Heisenberg, who first elucidated it in the 1920s. Some definitions are in order here. First, the sign refers to an uncertainty. In the case of x, what it means is that there is an inherent uncertainty of the position of a particle (tennis ball, dust mote, or electron) at any given moment. Understand something very clearly here: we do NOT mean an uncertainty due to the limitations of any measuring devices; we mean that nature herself does not allow us to say exactly where in the region of uncertainty the particle is – it is as though the particle doesn’t even have an exact position in the region of uncertainty, it is just somewhere within it. Take some time and let that sink in, odd as it sounds, for it is contrary to all your intuitive, common-sense view of how the world works; yet it is critical to understanding the ideas that will be developed here and later. Yes, I am saying that there is inherit uncertainty, and no measurement can reduce or eliminate it; it is built into the foundation of nature’s laws as strongly as the law of gravity or the laws of thermodynamics.
Likewise, the symbol s is an expression of the uncertainty in the speed of the particle, tennis ball, dust mote, or electron, at any given instant. We do not know exactly how fast it is travelling; we can only determine it’s speed within certain limits. Again, this is another oddly-shaped brick in the foundation of natural law. Accept it, strange and counter-intuitive though it might sound as well.
One thing you should see that comes out of the equation is that as x increases, s must grow smaller, and vice-versa. Why? Because their product is a constant, the [ / m] part on the right side of the equation. Thus, if we could measure the position of a particle exactly (x = 0) then s would become infinitely large, while if we measured its speed with perfect precision (s = 0) then x becomes infinite . The second salient point I must mention here is that the product of the two uncertainties, x × s, is always equal to or less than the quantity / m, whatever that is. It turns out that is exceedingly small, on the order of 10-34 newton-seconds, which, I assure you, is a minuscule quantity. It is, for all you scientific pedants out there, a symbol representing the so-called Planck’s constant, which Planck devised around 1900 while working with blackbody radiation, and which Einstein used later to explain the photoelectric effect and Bohr to construct his model of the hydrogen atom (actually, the real constant is h, while is h divided by 2π). m, on the other hand, which is the mass of the object being measured, makes this ratio smaller or larger, depending on its own size. You will all breathe a sigh of relief when I tell you that for m on the scale of a tennis ball or even a dust mote, x × s or / m is so infinitesimally small that, as I have said, it is to small to be measured with even our most powerful and sensitive instruments. Hence, in the world we experience, tennis balls and dust motes and cars and planets, the equation x × s ≤  / m for all practical purposes might as well not even exist. Whew! What a relief, I suspect you are saying, for if it were significant the world would be fantastically different from what we actually experience. Here’s the important point, however, and why I harp on the equation and demand that you absorb and digest it. For an electron, where m (mass) is excruciatingly tiny indeed, this equation – Heisenberg’s Uncertainly Principle -- dominates its behavior. In the next chapter, the one on matter and chemistry, we will explore the consequences of being at the low mass end of things.
And so on to matter and chemistry, and how all this uncertainly stuff fits in.

Wondering About Chapter 2

Wondering About The Sky

Starting at the beginning of our journey, I believe that the human child, looking at the world beneath his feet and the sky overhead, and wondering about it, is as good place to begin it as any. The child is not merely curious about the color of the daytime sky (see Appendix B) of course, but also the blackness of the night. But it is not just the blackness which attracts him but the things that shine within it and take that otherwise monotone of darkness away, revealing the full glory of the universe through the tapestry of night.
When the child gazes upwards at the night sky he sees not only the blackness but the many myriad of points of lights sprinkled against that inky backdrop. How many and how bright the points are depends upon from where he gazes, but they are spectacular nonetheless. Some of the lights stand out as special, or so he notices if he is keen enough an observer over many nights. They are generally brighter than the rest and appear to move slowly, thought stately, across the sky. Some appear only in the evening or the morning skies, while others traverse the entire arc of night, yet are not always there. They appear to ride, more or less, along a single line, which is known to astronomers as the ecliptic. The ecliptic, though our child does not know it, is simply the path the sun takes throughout the sky as a result of Earth orbiting her. The special lights seem to trail in her wake like fireflies.
These lights have special names. The ancient Greeks called them planetes, or wanderers, from which we derive the term planets. Of those visible to the naked eye, they include Mercury, Venus, Mars, Jupiter, and Saturn. One might add the moon and the sun to the list, and speak of the seven stars (although only one, the sun, is truly a star) as did the fool to the king in King Lear: (Fool: “The reason why the seven Starres are no mo then seuen, is a pretty reason”. King: “Because they are not eight.” Fool: “Yes indeed, thou wouldn’t make a good Foole.”).
What are these wandering “stars” that stand out so spectacularly in the night sky, and why do I begin my journey there? Certainly, they have piqued our curiosity as much as anything else in the natural world. The child eventually learns that the reason they wander against the seemingly fixed backdrop of stars is that they are members of our own solar system, planets in their own rights like our own, and so are relatively close by compared to the stars. He – by which, I mean I – also learns of two more planets, discovered over the last two hundred plus years, mighty in their own respects but too dim to be seen clearly from here on Earth: Uranus (which actually is just barely visible under the most optimum seeing conditions) and Neptune. And indeed, Earth we stand on is a planet as well, which we would easily see from the sky of any of the others should any of us be fortunate enough (and I believe some of us will have that fortune) to stand on one of them some day. But from whence does this knowledge come?
To the ancient Greeks and Romans the planets were the gods who inhabited Mount Olympus, but when people began in earnest to explore the natural world within the last few centuries, men like Galileo first pointed his primitive telescopes at them and discovered, lo and behold, that they were not the bright points of light the stars remained under even the highest magnifications, but showed clear discs which nobody, even the Catholic clergy of the day, could deny. Some of them even had small bright objects (which we call moons, or satellites) orbiting them, while others, such as Venus and Mercury, showed phases much like our own moon. The results of these simple observations was that the Earth-centered universe of Ptolemy was forever and at last obliterated and a new model of the heavens had to be found, one in which the Earth and the other planets circled the sun and not the other way around (though, as noted, some objects also orbited the planets themselves, such as our own moon or the four satellites orbiting Jupiter that Galileo discovered).
For me, the planets, and their moons, and the myriad other bodies of rock and metal and ice which form our solar system are such a marvelous beginning along our quest into curiosity, if only because so much has been learned about them in my lifetime. Also, as a boy it seemed my clear mandate to become an astronomer when I grew up (instead of the chemist and general scientific dilettante I actually became), so the night sky held a special fascination, perhaps because more than anything else it made me realize just how inconceivably vast the very concept of everything is.
In the early 1960s, when I was a small child just learning how to read and write, very little was known about the other worlds which inhabited our solar system. What was known was largely from the blurry images of ground-based telescopes and the simple spectroscopic and photographic equipment which was all that was available then. We also had some information from microwave and radio astronomy. So we knew some basic stuff; for example, that Jupiter and Saturn were huge gas giant worlds, Uranus and Neptune more modest gaseous worlds (still considerably larger than the Earth), that Mercury was almost certainly a sun-baked ball of rock as tidally locked to the sun as our moon is to Earth – indeed, it was probably a slightly larger version of our moon. Of Pluto, discovered only in 1930 by Clyde Tombaugh, virtually nothing was known for certain, even its mass and size. Finally, of all these worlds, only thirty two natural satellites were known, with essentially nothing known about any of them except that Titan, Saturn’s largest moon and probably the largest moon in the entire solar system, was the only one showing evidence of a substantial atmosphere, the nature of which was little more than speculation.
* * *
You could not fail to notice that I have overlooked two planets, the two of our most particular interest at that. Venus and Mars capture our imaginations and hopes precisely because they are the nearest worlds to our own, and thus, or so we thought / hoped, were also the nearest in their natures. Even without the benefit of interplanetary probes and the crude, atmosphere befogged instruments we possessed circa 1960, we could see how much promise they held. Rocky worlds like our own, with substantial atmospheres and possibly decent living conditions as good if not better than ours (albeit Mars probably on the cold side, and Venus a tad warm even for the hardiest frontiersmen), they invigorated our imaginations with tales of life and even intelligent beings which even the most skeptical could find believable. Percival Lowell could convincingly describe the “canals” he was certain he spied on Mars (a word which, in fact, is a mistranslation of the Italian word for channels, which their original, equally deluded, discoverer Schiaparelli called them), and the civilization which built them to keep their dying world alive was so believable that when Orson Welles broadcast H. G. Wells novel The War of the Worlds in 1938 thousands were panicked, convinced the invading Martians were all too real. Even well into the 1950s and 60s it was possible to populate the Red Planet with sentient beings with little in the way of scientific rebuke, as Ray Bradbury did in The Martian Chronicles.
Venus somehow inspired less creativity than Mars, perhaps because the dense foggy atmosphere that perpetually hid its surface from view made it seem less hospitable, at least to advanced, intelligent life such as our own. Still, and despite microwave measurements which suggested the planet too hot to be amenable to any life, legions of minds had no problem envisioning all sorts of exotic scenarios for our “sister” world (unlike the smaller Mars, Venus is almost exactly the Earth’s diameter and mass). From vast, swampy jungles, to an ocean-girdling world, to thick seas of hydrocarbons larger than anything on Earth, Venus was often envisioned as a planet as alive as our own.
* * *
All of these visions seemed plausible, even compelling, to imaginative minds right up until the 1960s, when the initial phase of the Great Age of Planetary Exploration blew them all into dust. We – or more precisely our robotic probes, launched into interplanetary space by Cold War ICBMs designed to drop nuclear bombs onto cities teeming with human life – learned that Venus was a searing carbon dioxide encased hell, hot enough to melt lead and with a surface atmospheric pressure equal to almost one kilometer beneath our oceans. Forget life: even our hardiest robots barely lasted an hour under such conditions. As for Mars, our smaller, brother world turned out to be positively welcoming in comparison to our sister, but Schiaparelli and Lowell were shown to be hopeless wishful thinkers; there were no civilizations, no canals, no sentient beings, no beings at all, not even simple plants.
Sometimes what curiosity discovers is that imagination has overreached itself. This is often considered to be curiosity’s downside; I suspect that much of the antagonism towards science comes from just this fact, that in collecting data about the universe we are to some degree destroying our creativity. Thinking about this complaint, I have come to the conclusion that it is not an entirely unfair one. Why do I say this? Because it is true, that in satisfying our curiosity we narrow the range of what “could have been” down into what is, and that is a real loss to real human beings in the real universe. There is no denying this.
At the same time, however, there is an opposite phenomenon which has to be added to the stew. In satisfying our curiosity, we just as often – indeed, perhaps more often – find that our imaginations have been in fact impoverished. It turns out that “there are more things in heaven and earth” than we ever came close to dreaming; that the ocean of actual realities extends far beyond the limiting horizons, out to lands and seas and possibilities we never suspected were out there. The reason I started this chapter with what the last forty years of planetary exploration has found is that nothing could be a better example of this discovery process in action.
Take Mars. The first Mariner photographs were crushing disappointments. Far from being a verdant world, the Red Planet looked more like our moon: crater-pocked, barren, lifeless. There were no signs either of life or any kind of intelligence. Even the atmosphere was less than what we’d hoped: a bare one percent of Earth’s surface pressure, and worse, composed almost entirely our of carbon dioxide, with no free oxygen or water vapor.
But those were just the initial impressions. More Mariner missions, two Viking orbiters and landers, and a slew of other robots hurled at Mars over the last twenty years, not to forget images from the space-based Hubble telescope, have shown it to be a world even more remarkable than we had thought. For one thing, there are amazing geological structures, some of the largest in the solar system: Olympus Mons, the giant shield volcano, is larger than any mountain on Earth several times over, and Cannis Marineris, a Grand Canyon like our own but which would stretch the entire breadth of North America. As for life, Mars now is probably (but not certainly) dead, but it once clearly once had all the elements for life, if several billions of years ago: a thicker atmosphere, warmer temperatures, flowing surface water, a likely abundance of organic or pre-organic molecules. The photographic and chemical evidence, returned from our probes and telescopes, have shown us this past and opened the door to our understanding of it. With some hard work and a little luck, in the coming decade or two we will finally have the answer to the question of whether life on Earth is unique or not, and, by implication, is common in the universe or not. Or if not, why not. Either way, at the very least the ramifications for our own existence are staggering.
This alone could justify the time and energy, and money, spent to satisfy our curiosity about other worlds. But this turns out to be just the beginning. The solar system’s biggest surprises have come in the exploration of the outer planets. It turns out that we knew pathetically little about these worlds and their moons, or the forces that have shaped their evolution. We had a few hints, but we mostly dwelled in ignorance and speculation. Starting in the late 1970s with the Pioneer 10 and 11 missions, then the Voyager and other probes, that ignorance was stripped away in the most spectacular fashion. Pioneer and Voyager returned pictures of worlds far more dynamic than what we had expected, in ways we had not foreseen.
Consider tides. Here on Earth the tidal effects of the moon and, to a lesser degree, the sun, make our oceans rise and fall in gentle cycles. The reasons for tides is a straightforward application of the inverse square law of gravity: the closer two objects are to each other, the more strongly they are pulled together, and so the faster they have to move in their respective orbits to avoid falling into each other. The net result of this dynamic is that the near sides of such objects are moving too slowly and try to fall together, while the far sides are moving too fast and thus want to pull away. On Earth, that means that the oceans on the side facing the moon fall toward it ever so slightly, while the oceans on the opposite side try to drift away. It is a very humble effect, just a few feet, or tens or feet, either way. Nothing to write home about.
Tides can do much than rock the seas of a world, however. The rock comprising Jupiter’s innermost large moon, Io, is largely molten, thanks to the heat generated by tidal forces by both the parent planet Jupiter and the other Galilean satellites. The result is the most volcanically active world in the solar system by far, not excluding Earth. Io’s surface is liberally pocketed by volcanic calderas of all different sizes, which spout sulfur and other molten minerals tens to hundreds of kilometers above and across its surface in a steady rain of debris; a surface so new that it contains not a single impact crater. If the tidal stresses in Io’s guts were just a smidgeon stronger than they are, the world would be literally torn apart by them. That indeed might be Io’s ultimate fate, to be fractured and rendered into a new ring for the giant planet.
The tides are cruelest to Io because it is closest to Jupiter, but they do not leave the other large moons at peace either. The next Galilean satellite, Europa, may prove to be the most intriguing place in the entire solar system outside of our own planet. I must make a brief digression to explain why. Most of the solar system’s matter does not consist of rock and metal but of light elements, such as hydrogen, helium, carbon, nitrogen, and oxygen, and their various chemical combinations – water, ammonia, methane and a variety of small hydrocarbons – chemicals composed of carbon and hydrogen. In the inner solar system these substances are largely in gaseous or liquid form, making it a challenge for the small worlds (including ours) inhabiting this region to even maintain a hold on them in the teeth of the sun’s fierce radiations and her perhaps fiercer solar wind (a steady stream of electrons, protons, and other particles constantly being blown out by the sun, which can easily blow away weakly held atmospheres) , but starting at the distance of Jupiter the sun’s output is diluted enough to let these substances condense into their solid phases: ices. Starting with Jupiter, ice is not merely a thin coating over rocky worlds and moons but comprises the bulk of these bodies. The most predominant of them is water ice, which at the temperatures prevalent in the outer solar system essentially is rock, albeit a low density kind.
The cores of three of the Galilean satellites, Europa, Ganymede, and Callisto, are normal rock like the inner, “terrestrial” planets’, but they are covered with mantles of liquid and solid water many tens to hundreds of kilometers deep. Europa in particular consists of a relatively thin skin of cue ball smooth water ice over an abyssal ocean far, far deeper than any sea on Earth. Again, it is the tidal kneading of Jupiter and its other moons which generate the internal warmth which keeps this ocean in a liquid phase.
Liquid water is one of the most important ingredients to life on Earth, so wherever else in the universe we encounter it we are also encountering the possibility of life. On Mars the presence of flowing water billions of years ago raises that possibility. What Pioneer and Voyager and later missions have done is show how parochial our thinking on this subject has been. The kilometers-thick water ocean beneath Europa’s and other satellites’ icy surfaces no doubt contain their share of organic and other pre-biotic chemicals, as well as free oxygen, and over the eons of being warmed and mixed in this lightless abode who can say what might have assembled itself? We know little enough about life’s origins here to make all kinds of speculation plausible, speculation that will be answered only by sending more and better probes to that world. By, in short, satisfying our curiosity.
Which leads me again to the most important lesson once again, which is in how in satisfying our curiosity we often broaden our perspectives, not narrow them as critics claim. In reaching out, we find more than we ever thought we would, and our lives become immeasurably richer. This is what our science, our passion to know, has given us.
* * *
The fundamental premise, and primary lesson, of science is that there are no magic fountains of truth. There are no books with all the answers, no machines to solve every problem, no authorities with all the answers, no voices in our heads, no golden compasses or other devices waiting to be opened to spoken to in just the right way. All we have are our own limited senses, our own seemingly unlimited minds, our own hard work and perseverance. And this we find true whatever our questions or whatever mysteries the universe puts before us. Actually, there are no mysteries either: there is only what we have not yet understood, because we have not yet figured out how to explain it.
So we press on resolutely, our feet on the ground and heads down but our eyes always facing forward. And we take the pleasure of learning what we learn, in the steps and pieces that we learn it. It is a process that is, at times, grim. But what it yields is pure treasure.
As amazing as the moons of Jupiter have turned out to be, you have to go out still further to find the most amazing moon of them all. The somewhat smaller planet Saturn and its entourage of satellites orbits the sun at a distance twice that of Jupiter’s and ten times further out than Earth’s from the sun. Still a glare too fierce to be gazed at directly, the sun only provides one percent of the warmth and light here that it shines down on us. Furthermore, the effects of tidal interaction between Saturn and its moons is not as potent a force as it is in the Jovian system: there are no raging volcanoes or vast underground oceans of liquid water (with one possible exception). If anything, compared to Jupiter, the Saturnian system would seem to be a quiet backwater where little of interest might be found. Yet something of the most enormous interest is found right here: Titan.
Titan was known to be unique long before we sent any robots to explore it. Unlike all other moons in the solar system, a star passing behind Titan (an “occultation” in astronomer language) will fade and twinkle briefly before disappearing completely, similar to the way the stars twinkle when seen from Earth’s surface. The reason for both phenomena is the same. Atmospheres will refract and scatter the light that passes through them. Titan is the only satellite in our solar system with a substantial atmosphere; one that is, in fact, considerably more substantial than our own.
This in itself would have made it an object worthy of our curiosity. Atmospheres are living things. They continuously grow and regenerate themselves lest they escape away into space, courtesy of the lightness of their molecules, the temperature, the strength of the solar wind, and other factors. They eventually dissipate when left on their own, though this may take billions of years. On Earth, for example, the nitrogen and oxygen which comprise ninety-nine percent of our atmosphere go through chemical and biological cycles which keep them ever fresh throughout geologic time.
Titan’s atmosphere is not only substantial, it is several times as dense as our own. Also, like Earth’s, it is largely nitrogen: ninety-eight point four percent of it is this gas, as compared to seventy-eight percent here. Even more interesting is the other one point six percent, which is largely hydrocarbons – simple, organic molecules – like methane and ethane. Thanks to the sun’s ultraviolet rays, which are still potent at this far reach in the solar system, these hydrocarbons have given rise to even more complicated molecules which comprise the orange smog which permanently hides Titan’s surface from all outside eyes. They also form the basis for clouds and various kinds of precipitation which rain down on this moon’s icy surface, forming the terrestrial equivalent of lakes and rivers.
As a possible womb for life, however, Titan has a problem. Its distance from the sun and shielding cover of hydrocarbon smog mean that the surface temperature here is almost three hundred degrees below zero Fahrenheit. This is so cold that even the nitrogen comprising the bulk of its atmosphere is on the edge of liquefying. Not only is the water so crucial to life on Earth completely frozen into a thick mantle as on other outer moons, but other molecules important to the life’s beginnings here, such as ammonia and carbon dioxide, would be rock-hard solids at these temperatures as well. Moreover, any chemistry which could happen would occur at a pace that would make a snail look like a jack-rabbit on caffeine. Looking over all these factors, biology would seem to be a non-existing subject on Titan.
We shouldn’t think so narrowly, however. Life does not require water so much as it needs some liquid medium, and as noted, compounds like methane and ethane, gasses on Earth, do exist in liquid form both on Titan’s surface and in its atmosphere. True, any biochemistry would proceed with agonizing slowness, but the solar system has been around for almost five billion years, and that might be just enough time for something to happen. We won’t find anything resembling a … well, even a bacterium is probably pushing it … on Titan, but some kinds of self-replicating entities – the most basic definition of life – might exist there. Or whatever could lead up to such entities under more favorable conditions. Either way, when we do find out, we will certainly learn some lessons applicable to how life came to exist on Earth, what that requires and what must be forbidden for that grand event to occur. All of which makes the time and energy and resources necessary to do the finding out worth it.
* * *
Our robotic exploration of the solar system has rewarded us with much more than volcanoes and canyons and possible new possible niches for life. For one thing, knowing about a place is often the first step to going there; it is certainly a necessary step. I call the last forty plus years the initial phase of the Great Age of Planetary Exploration, and there should be little doubt anymore that that is what it is. The twenty-first century will assuredly see us plant our footsteps on our neighboring worlds, the moon and Mars for certain, and the centuries to come will see their thorough colonization and exploitation.
What about beyond? We have come a long way in our travels in my lifetime, but at the same time, we have hardly begun to crack the door open. I loved astronomy as a child, but what excited me the most were not the planets but the stars. In reading about them, I learned that the stars were other suns like our own, possibly with their own worlds and God-knew-what on them, perhaps, one dared hope, some of them even people like ourselves: either way, it was and is an overwhelmingly staggering thought, especially when you contemplate how many stars there are.
Curiosity will eventually take us to the stars, but this is a journey that will take far longer and require much more resources than exploring our own solar system, because the distances involved are so much vaster, by a factor of a million and more. So much greater that it will change what it means to be human in some ways – though our passion to know will hopefully remain intact. We cannot travel to the stars yet, but their light comes to us, rains down on us in fact from every direction we look. And light is a code which, when unlocked, reveals a universe more amazing than dreams.
The six inch Newtonian reflector telescope I received for my eleventh birthday was a wondrous, magical device. With it, I could easily make out mountains and craters on the moon, view the planets as multi-colored discs along with their larger moons, resolve multiple star systems into their components, and in general enjoy many things of the nighttime sky which the naked eye alone can never see. And yet still the stars are so distant that they remained points of light in the blackness, brighter and more variously colored yes, but points nevertheless. Yet even had that telescope been more powerful a device, the miles of air and dust and water vapor I would still have had to peer through would have smeared my vision with unending twinkling and wavering, rendering it of maddeningly limited use. Even the simple question of whether other stars besides our own possessed planetary systems – and so, possibly, life and intelligence – would have been forever beyond its capacities.
The most powerful telescopes humans have ever built can collect a thousand times and more as much light as my childhood toy. They are perhaps the ultimate monuments to our lust for knowledge and understanding, sitting on their mountaintops above much of our world’s blurring atmosphere and now, in the form of the Hubble Space Telescope, even floating in space entirely beyond it. The ones on Earth wield corrective optics and sophisticated computer software to compensate for atmospheric disturbances. Not only do they gather much more light, but that light can be gathered it over hours, even days, of viewing times and stored it on sensitive electronics to be analyzed and manipulated using other ingenious software packages running on other powerful computers.
Light. It is a substance far more valuable than the most precious of metals (it is also far more mysterious, as Appendix A explains). It’s greatest value is not merely allowing us to see the universe around us, however. If you know how to decipher and decode it, and understand what comes out of doing so, light can tell you almost anything you could ever want to know about whatever you are gazing upon. I’m serious: it is that amazing a substance. For example, the science of spectroscopy, the analysis of light by wavelength, allows us to deduce the chemical composition of an object or substance simply by the light it creates, reflects, or transmits. This feature of light, discovered in the nineteenth century, has given us the elemental compositions of the stars and other astronomical objects, a gift we once thought we would never be granted. Light can also tell us the temperature of things and the ways its constituent atoms are chemically bonded together. Not a bad day’s work for something we take so much for granted.
Human ingenuity and the laws of physics are a dynamic combination which seems to have no limits. The question of whether life and intelligence exist elsewhere in the universe hinges partly on whether planetary systems are common or a unique aberration of our own star. Unfortunately, merely looking through our telescopes, or even recording what comes from them with our most powerful technology, can’t answer this most critical of questions: the light from even the dimmest star is so overpowering that it completely masks the feeble reflected glow of any planets it might own. It’s like trying to pick out a the tiny twinkle of a lit match sitting astride a lighthouse beacon’s full fury.
Until the 1990s, that would have been the beginning and end of the quest. But light holds other secrets for the mind clever enough and determined enough to pry them out and exploit them. One of those secrets, which Edwin Hubble used in the 1920s to show that the universe is indeed expanding as Einstein’s General Relativity (but not Einstein himself) predicted, is the ability to tell how fast an object is moving either toward or away from us. The so-called Doppler effect (see Appendix C for a fuller explanation) is easier described using sound rather than light, but the principle is the same: when a sound-emitting object is approaching us, the distance between sound wave peaks and troughs is shortened because the object has moved part of that distance toward us in the meantime; when moving away from us, the distance is increased for the same reason. Thus, in a standard example, a train whistle’s pitch drops suddenly as the train swoops by us.
The same modification of wavelength happens with light, although it is much smaller (because light travels so much faster). It is also trickier to use in an astronomical setting because, after all, we don’t know what the wavelength of the light is when the object is at rest! This is not a problem in planet-hunting, however, as we shall see. The other piece of cleverness in our scheme lies in the fact that, according to Newtonian physics, two gravitationally bound objects revolve around their common center of mass, a point not precisely at the center of either object; the common notion that the moon revolves about Earth, or Earth about the sun, arises because in these cases the larger object is so much more massive than the smaller that the center of gravity of the system is very close to the center of the larger object.
The basic picture starts to emerge: if a star has planets, then the star itself is revolving around the system’s center of mass. This causes the star to wobble about ever so slightly as its planet(s) revolves about it. We may or may not be able to detect this wobble; it depends on how large it is and, more importantly, the angle of the wobble with respect to us. If the angle causes the star to alternately approach and recede from us, this will give rise to a, albeit very small, Doppler shift of its light from our vantage point. It is this regular, cyclic change in the shift we are interested in, which is why the rest wavelength is not important; from its size and other details, we can infer not only the existence of planets, but their masses and orbits. This, needless to say, is where the main difficulty of the technique comes into play, in the “ever so slightly” aspect of the wobble. Only the most resourceful analysis of a sufficiently large enough set of observational data has a prayer of picking this wobble out from all the other motions of a star and everything else in its vicinity.
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Resourcefulness is something Homo sapiens sapiens has never been in short supply of, and thanks to modern technology data can be almost as astronomical as the stars themselves. Assuming you can get enough time on the instruments, that is. The most powerful telescopes in the world are difficult to get that time with; curiosity combined plus the size of the universe makes for far more research proposals than time will ever permit conducting. As a result, the powers that control access to them must be convinced that it will be spent on something that is both worthwhile and possible to do, and convincing them is itself a challenge for the resourceful.
Whether our solar system, and by implication life and intelligence, is unique in the universe or not is a question that, at the end of the 1980s, appeared to be unanswerable in my lifetime.
Besides, ours was the only solar system we knew of. Straightforward physics suggests that the inner planets of a system should be terrestrial – composed of rock and metal, like Earth – and that the larger, gas and ice worlds will be found further out. Gas / ice worlds such as Jupiter, Saturn, Uranus, and Neptune are largely made from small molecules like hydrogen, helium, water, ammonia, and methane; these substances are volatile and are boiled off a newly forming world if it is too close to its sun, while further out they can condense in enormous quantities as they are by far the most common materials in the solar nebula.
So you expect Jovian worlds to be found only in stately orbits far from a star, if it has any. Nature, happily, has a way of not cooperating with our expectations – and of rewarding our willingness to test them. When the first extra-solar planet was discovered orbiting a sun-like star, 51 Pegasi, only some fifty light-years from our own solar system, it stunned the astronomical community only by showing a mass approximately half of our Jupiter’s, while at the same time being in an orbit which was only some five million miles from its sun (as opposed to Earth’s 93 million miles), with an orbital period of only some four and a quarter days. Similar systems were discovered in the ensuing years, also of gas giants in very close proximity to their stars.
In one sense, this should not have surprised us at all. Such planetary systems ought to be the first discovered as they are the easiest to detect: a large planet orbiting close to its sun will produce the largest Doppler shift effect, and hence be easiest to detect. It was just that no one had suspected such systems to exist at all, or at most, to be exceedingly rare. Gas giants, after all, could only form far from their parent stars, otherwise as mentioned the intense stellar radiation and stellar wind will blow the light elements away. Clearly, that was what had happened with Earth’s solar system. So what had gone awry in systems such as 51 Pegasi?
The basic physics of planetary formation are likely to be correct. Therefore, 51 Pegasi b (the official designation of the planet) must have formed at more Jovian-like distances: a good one hundred or so times further out from the present position. Various interactions with other bodies in the system, or even with other stars, have since gradually spiraled 51 Pegasi b in to its current orbit, very close to its sun. This hypothesis is not unreasonable; it was known that planetary orbits could be highly unstable over time spans of billions of years. No doubt, catastrophic interactions with other bodies in the 51 Pegasi system had occurred in this time: smaller, closer, possibly terrestrial (even Earthlike) planets had been bulldozed out of the system permanently, into cold interstellar space.
This just leads to the next question, however. Why has our own solar system been apparently so stable during its four and a half billion years of existence? If anything, the gas giants such as Jupiter and Saturn have done us a good turn by sweeping smaller bodies out of the system which otherwise might have collided with us, or herded them into relatively stable asteroid belts. Have we been just incredibly fortunate in this regard? Why didn’t Jupiter eject our own world, not to mention Mercury, Venus, Mars, and the moon into the interstellar abyss?
The number of additionally discovered systems similar to 51 Pegasi have made this question more than a trifling compelling. It suggests that systems harboring life-bearing worlds are rarer than we had supposed, relying on a mixture of luck and physical laws which we still have but an inkling as to their workings. It seems that once again, in our attempts to gratify our curiosity, we have only given it more fodder to feed on. One thing is for certain: repeatedly, we find our attempts to uncover the secret orderings of things to humble us again and again as to how little we still understand. We think we are taking the Russian dolls apart one by one, into ever deeper levels of understanding, only to find ourselves as baffled as when we had begun.
* * *
I am not trying to sound defeated. I do not believe that we are, or will be defeated. Progress in knowledge, in science, does proceed. Little by little, our curiosity is satisfied. It is merely that it never proceeds in the nice, round, little steps we always expect it to. No, there are fits and starts, backtrackings where we seem worse off than when we had begun, strategic retreats here and there before we make the next jump forward. If anything, this makes the whole journey that much more exciting, and fulfilling. At the end of each day, we can sit and watch the sunset, happy in what we have achieved and that much more edgy and restless for what tomorrow might bring. For we know that, like today, it will bring something, just not the nice, neat packages of knowledge that, actually, would have been quite boring to receive, but a mixture of new questions and mysteries with which we can set out for further explorations – with just enough genuine new understanding to leave us feeling satisfied. That is the way of knowledge, the path that curiosity invariably takes us down. Isn’t it one filled with restless throbbing and hope? I believe that it is.
Furthermore, since the discovery of the 51 Pegasi planet, almost fifteen years ago, astronomers have been aiming their instruments at the sky with the hopes finding more planetary systems, and not only that, planetary systems more like our own solar system. And they have been successful well beyond anyone’s expectations. Over the last few years systems have been found with planets more similar to our own; these includes “super-Earths”, which are rocky terrestrial worlds akin to our own, only much larger, and other large planets, similar to our own gas giants but smaller. Some of these worlds have even revealed the tantalizing tastes of substances such as oxygen and water, absolutely essential to life as we know it. It seems quite likely now that over the next ten-twenty years we will discover Earth-like planets circling other stars in our galactic neighborhood. And where there is life, there is certainly the possibility of intelligence.
* * *
Well, I certainly hope I have whetted your appetite for what is to come. At this point, I myself must admit that it is uncertain just what ground I will cover, what areas will be explored, what mysteries will be unveiled. Perhaps that is as it should be. Curiosity is a passion which you never know for certain where it may lead you. You only know it will go somewhere; that there will be a resting spot somewhere in the future you can perch upon and gaze at the territory covered, while the campfire dims and the last of the evening meal lingers on your palette.

Wondering About Chapter 3

Wondering About Reality   In the 1999 motion picture film The Matrix , the actor Keanu Reeves plays a character, Neo, who is forced i...