Atom: An Odyssey from the Big Bang to Life on Earth ... and Beyondby Lawrence M. Krauss
Now in paperback, the story of matter and the history of the cosmosfrom the perspective of a single oxygen atomis told with the insight and wit of one of the most dynamic physicists and writers working today.
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Now in paperback, the story of matter and the history of the cosmosfrom the perspective of a single oxygen atomis told with the insight and wit of one of the most dynamic physicists and writers working today.
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The Universe in an Atom
Many are called, but few are chosen.
In the year 1281, the second Mongol invasion of Japan began, and ended. The invaders were defeated as much by the force of nature as by the Japanese warriors, as the Mongol ships suffered grievous losses due to the Kamikaze, or "divine wind". This routed the invaders and boosted Japanese pride in their island's invincibility, much as the storms that helped repel the Spanish Armada from British shores 307 years later immortalized in a commemorative medal with the words "God Blew, and they were"helped affirm the sense of Divine Right harbored by Mother England for centuries thereafter.
Those Mongol ships that survived the crossing of the Sea of Japan may have noticed the range of mountains that rise sharply from the water near the town of Toyama. These are known by some as the Japanese Alps a popular skiing attraction today. Deep below these snowy peaks, where the sun never shines, indeed has never shone, may lie the secret of our existence, forged from a fiery wind, not necessarily divine, but more intense than any that has ever swept the Earth and as old as creation itself.
In the deep Mozumi mine in the town of Kamioka lies an immense tank of pure, clear water, recycled daily to remove contaminants. Forty meters in diameter and over 40 meters high, the Super-Kamiokande detector, as it is known, containes 50,000 tons of waterenough to quench the thirst of everyone in a city the size of Chicago for a day. Yet this device, located in a working mine, is maintained with the spotless cleanliness of an ultra-purified laboratory clean room. It has to be. The slightest radioactive contaminants could mask the frustratingly small signal being searched for by the scores of scientists who monitor the tank with 11,200 phototubeseerily resembling television tubeslining the outside of the tank. If the scientists' attention wavers for even a second, they could miss an event that might not occur again in the lifetime of the detector, or the scientists. A single event could explain why we live in a universe of matter, and how long the universe as we know it may survive. The signal they are searching for has been hidden for at least 10 billion years older than the Earth, older than the sun, and older than the galaxy. Yet compared to the timescale of the process behind the event being searched for, even this stretch is just the blink of a cosmic eye.
We are about to embark on a journey through space and time, traversing scales unimaginable even a generation ago. A tank of water located in the dark may seem an odd place to begin, but it is singularly appropriate on several grounds. The mammoth detector contains more atoms by a factor of 1 billion or sothan there are stars in the visible universe. Yet amid the 10 (1 followed by 34 zeroes) or so identical atoms in the tank is a single oxygen atom whose history is about to become of unique interest to us. We do not know which one. Nothing about its external appearance can give us any clue to the processes that may be occurring deep inside. Thus we must be ready to treat each atom in the tank as an individual.
The vast expanse of scale separating the huge Super-Kamiokande tank and the minute objects within it is a prelude to a voyage inward where we will leave all that is familiar. The possible sudden death of a single atom within the tank might hearken back to events at the begin-ning of time.
But beginnings and endings are often inextricably tied. Indeed, each Sunday one can hear proclaimed loudly in churches across the land: "As it was in the beginning, is now, and ever shall be, world without end." But do those who recite these words expect that they refer to our world of human experience? Surely not. Our Earth had a beginning. Life had a beginning. And as sure as the sun shines, our world will end.
Can we nevertheless accept this prayer as metaphor? Our world will end, but our world is merely one of a seemingly infinite number of worlds, surrounding an unfathomable number of stars located in each of an even larger number of galaxies. This state of affairs was suspected as early as 1584 when the Italian philosopher Giordano Bruno penned his De l'infinito universo e mondi. He wrote:
There are countless suns and countless earths all rotating around their suns in exactly the same way as the seven planets of our system. We see only the suns because they are the largest bodies and are luminous, but their planets remain invisible to us because they are smaller and non-luminous. The countless worlds in the universe are no worse, and no less inhabited than our Earth.
If, in the context of this grander set of possibilities, we contemplate eternity, what exactly is it that we hope will go on forever? Do we mean life? Matter? Light? Consciousness? Are even our very atoms eternally perdurable?
And so that is ultimately why our journey begins in the water in this dark mineshaft. If we explore deeply enough into even a drop of water, perhaps located in the Super-Kamiokande tank, we may eventually make out the shadows of creation, and the foreshadows of our future.
The water is calm, clear, and colorless, but this apparent serenity is a sham. Probe deeper plop a speck of dust into a drop of water under a microscope, say and the violent agitation of nature on small scales becomes apparent. The dust speck will jump around mysteriously, as if alive. This phenomenon is called Brownian motion, after the Scottish botanist Robert Brown, who observed this motion in tiny pollen grains suspended in water under a microscope in 1827, and who at first thought that this exotic activity might signal the existence of some hidden life force on this scale. He soon realized that the random motions occurred for all small objects, inorganic as well as organic, and he thus discarded the notion that the phenomenon had anything to do with life at all. By the 1860s, physicists were beginning to suggest that these movements were due to internal motions of the fluid itself. In his miracle year of activity, 1905, Albert Einstein proved, within months of his famous paper on relativity, that Brownian motion could be understood in terms of the motion of the individual bound groups of atoms making up molecules of water. Moreover, he showed that simple observations of Brownian motion allowed a direct determination of the number of molecules in a drop of water. For the first time, the reality of the previously hidden atomic world was beginning to make itself manifest.
It is difficult today to fully appreciate how recent is the notion that atoms are real physical entities, and not mere mathematical or philosophical constructs. Even in 1906, scientists did not yet generally accept the view that atoms were real. In that year the renowned Austrian physicist Ludwig Boltzmann took his own life, in despair over his self-perceived failure to convince his colleagues that the world of our experience could be determined by the random behavior of these "mathematical inventions."
But atoms are real, and even at room temperature they live a more turbulent existence than a farmhouse in a tornado, continually pulled and pushed, moving at speeds of hundreds of kilometers an hour. At this rate a single atom could in principle travel in 1 second a distance 10 trillion times its own size. But real atoms in materials change their direction at least 100 billion times each second due to collisions with their neighbors. Thus in the course of one minute, a single water molecule, containing two hydrogen and one oxygen atoms, might wander only one-thousandth of a meter from where it began, just as a drunk emerging from a bar might wander randomly back and forth all night without reaching the end of the block on which the bar is located.
Imagine, then, the chained energy! A natural speed of 100 meters per second is reduced to an effective speed of one-thousandth of a meter per minute! The immensity of the forces that ensure the stability of the world of our experience is something we rarely get to witness directly. In fact, it is usually reserved for occasions of great disaster.
You can get some feeling for the impact that tiny atoms can have on one another by inflating a balloon and tying the end, then squeezing the balloon between your hands. Feel the pressure. What is holding your hands back, stopping them from touching? Most of the space inside the balloon is empty, after all. The average distance between atoms in a gas at room temperature and room pressure is more than ten times their individual size. As the nineteenth-century Scottish physicist James Clerk Maxwell, the greatest theoretical physicist of that time, first explained, the pressure you feel is the result of the continual bombardment of billions and billions of individual atoms in the air on the walls of the balloon. As the atoms bounce off the wall, they impart an impulse to the wall, impeding its natural tendency to contract. So when you feel the pressure, you are "feeling" the combined force of the random collisions of countless atoms against the walls of the balloon.
Although this collective behavior of atoms is familiar, the world of our direct experience almost never involves the behavior of a single atom. But attempting to visualize the world from an atomic perspective opens up remarkable vistas, and gives us an opportunity to understand more deeply our own circumstances. The eighteenth-century British essayist Jonathan Swift recognized the inherent myopia governing our worldview when he penned Gulliver's Travels, which noted that the rituals and traditions of any society may seem perfectly rational for one who has grown up with them. Swift's Lilliputians fought wars over the requirement that eggs be broken from their smaller ends. From our vantage point, the requirement seems ridiculous. The same may be true for our view of the physical world, which is colored by a lifetime of sensory experience.
And so, as we approach the beginning of our oxygen atom's journey forward, we have to stretch our minds in the tradition of Swift. The atoms getting thrashed today in a drop of water may have a hard life, but this can't even begin to compare to the difficulties associated with their birth. To imagine these moments, we must go back to a time before water existed in the universe. We must venture back to when things were vastly more violent, back to a time more than 10 billion years ago, and perhaps less than 1 billionth of a billionth of a second after the beginning of time itself. We must visualize the universe on a scale that is so small, words cannot capture it. Indeed, we must go back to a time when there were no atoms ...or Eves.
We begin when what is now the entire visible universe of over 400 billion galaxies, each containing over 400 billion stars, each 1 million times more massive than the Earth, encompassed a volume about the size of a baseball. The simplicity of this statement belies its outrageousness. It is impossible to intuitively appreciate this era by making the leap from here to there in one giant step. But it is possible to imagine a series of smaller steps, each of which itself pushes the limits of visualization, but each of which gets us closer to fathoming the truly extreme environments we are about to enter.
Our first step begins with our own sun. Almost a million times as massive as the Earth, at its center the temperature is almost 15 million degrees, cooling by more than a factor of 1,000 at the surface to a mere 6,000 degrees, about twice the temperature of boiling iron. Nevertheless, the sun's average density is only marginally greater than that of water, not much different than the average density of the Earth, in fact. If we squeeze the sun in radius by a factor of 10, so that it is now 10 times the radius of the Earth, it is now much denser than any planet in the solar system. A teaspoon of its material would, on average, now weigh several pounds. Compress the sun by an additional factor of 10. Now the size of the Earth, with a mass 1 million times as great, each teaspoon of its material weighs almost 10 tons. Compress the sun now by another factor of 1,000. It is now about 6 kilometers in radius, the size of a small city. A single teaspoon of its material weighs 1 billion tons! (The amount of work required to perform this feat of compression, by the way, is equivalent to the total radiant energy released by the sun over the course of 3 billion years!)
At this density, the atoms in the sun lose their individual identity. Under normal conditions, a single atom is composed of a dense nucleus, made up of the elementary particles called protons and neutrons, which are themselves made up of smaller fundamental particles called quarks. The nucleus contains more than 99.9 percent of the total mass of the atom. It is surrounded by a "cloud" of electrons that occupy a space more than 10,000 times larger in radius than the nucleus but carrying almost none of the mass of the atom.
By "cloud" I actually mean nothing of the sort. "Cloud" is simply a name we give to the electron distribution because we have no really appropriate label. It is impossible to describe in words what the electrons "do" as they surround the nucleus. At this scale they are described by the laws of quantum mechanics, under which material objects behave completely unlike they do on human scales so that our normal experience is no guide whatsoever. Individual elementary particles such as electrons do not behave like "particles." They are not localized in space when they are orbiting the nucleus, as planets are when they orbit the sun rather, they are "spread out." I say this even though we know that electrons can, under certain carefully controlled conditions, be localized on scales so small that we have not yet been able to put a lower limit on its intrinsic size, with no evidence whatsoever of any internal structure. Our language, derived from our intuitive experience of the world, has no place for such behavior.
But the electrons in an atom are not spread out over all space, merely in a volume approximately 1,000 billion times larger than the volume of the nucleus. When we compress the sun to the size of downtown Washington, D.C., we squish the atoms to the point where their electron clouds are essentially pushed inside the nuclei, which in turn are touching each other. The entire mass of the sun is then essentially like one huge atomic nucleus.
(As bizarrely unrealistic as such a scenario for an object like the sun may seem, it actually happens about a hundred times every second in the visible universe. In our own galaxy, about once every thirty years the inner core of a star ends its life in such a state after a massive stellar ex-plosiona supernova of the type that created us.)
Let us keep on compressing. Take this gigantic solar atomic nucleus of mass 10 times the mass of a hydrogen nucleus, and compress it further by another factor of 100,000, so that a single teaspoonful of material now weighs a million billion billion tons the mass of 1,000 Earths! The sun is now the size of a basketball.
However, there are about 400 billion suns in our galaxy, and at least as many galaxies in the visible universe. Even if every star was compressed down to the size described above and all the stars in all the galaxies were packed closely together, they would still encompass a volume as large as that of the Earth. (Implying, by the way, in case it ever proves useful to you to know it, that one can fit as many basketballs inside the Earth as there are stars in the visible universe.)
We have one more large step to take. Compress all of this mass, 160,000 billion billion times the mass of the sun, down by another factor of 10 million in radius. The matter in the entire presently visible universe is now contained in a space the size of a baseball. The mass of a teaspoonful of this matter alone equals as much as a million galaxies, containing a total mass of a billion billion of our sun! In the space traditionally occupied by a single atomic nucleus, the amount of matter contained would be more than enough to construct all of New York City! In the space traditionally occupied by a single atom, including the region in which the electrons normally orbit, the amount of matter would be almost the mass of the entire Earth!
These numbers may seem staggering, but they do not tell the whole story. In fact, they miss the most important part of it. As one compresses matter, the energy exerted heats the material up. A larger and larger fraction of the total energy of a closed system is contained in the radiant energy emitted and absorbed by the hot particles. Well before the whole system is compressed to the unfathomable levels I have described abovein fact, when the observable universe is compressed by merely a factor of 10,000, about a million light-years acrossits energy would be dominated not by matter, but by the energy of radiation.
The radiation at this point is so hot and dense that it beats out the gravitational pull of all 160,000 billion billion stars! But by the time we compress the visible universe down to the size of a baseball, the fraction of the total energy associated with the mass of all the matter making up all galaxies today is only about 10, or about 1 part in 10 million billion billion! (This radiation has a huge pressure and it does work on an expanding universe, so that after a few thousand years, its energy dwindles away and becomes negligible, leaving just the matter contribution to dominate the universe today.) Thus, while in the region normally occupied today by a single atom the matter contained at that time would have a rest mass comparable to that of the Earth, the actual amount of energy contained in this region, including radiation energy, would have been much larger. In fact, it would correspond to the energy of the entire presently visible universe!
The universe in an atom!
Let's pause and reflect on our voyage. Even after the baby steps, it is still mind-boggling to try to picture what conditions are like when each atomic volume contains an amount of energy equivalent to that contained in our whole visible universe today. But you may wonder whether it is even worth trying. After all, under such conditions the whole meaning of "atoms," the protagonists of our story, dissolves. How can we connect individual entities like the oxygen atoms that help make up the molecules of our DNA with anything in that incredible morass?
You also might have wondered why, if we are going to go back this far, we don't go back all the way, and begin our story at the infinitely dense Big Bang itself. Let's address this second concern first. The reason we do not take our story all the way back to t=0 is that this instant is still shrouded in mysteries beyond our scientific purview, so there is nothing concrete to say. But we do not think we have to go all the way back to t=0 in order to understand the origin of our atoms. We believe that the Super-Kamiokande experiment, or a larger one that may follow it, may allow us to infer the events that would have had to occur at the precise moment when the existence of atoms in our universe first became a real possibility. And, to respond to the first concern, that moment occurred very early in the history of the universe. It is appropriate to argue that each atom in our bodies began life precisely then, even though atoms themselves would not exist for what would seem like an eternity at that moment.
Although no events have yet been observed in the Super-Kamiokande tank that would let us re-create with some certainty the events at that time, we know that a specific, if subtle, series of events had to occur in that primordial baseball in order for our oxygen atom to exist today. So subtle and rare, in fact, that had anyone been around then to notice what was taking place, they probably wouldn't have.
Indeed, it seems that without an early series of rare events at least as rare as a single person buying two winning lottery tickets for two different state lotteries in the same year no one should be around today to celebrate creation, or lotteries.
Nevertheless, there is a maxim I am constantly reminded of in my work: Because the universe is big and old, no matter how unlikely something is, if it can happen it will happen. Accidents more remote than anything that might occur during our lifetime occur every second somewhere in the vast reaches of the cosmos. The most important question of modern science, and perhaps theology as well, is then: Are we merely one such accident?
Because Super-Kamiokande has not yet given us the empirical evidence we need to infer precisely what series of events occurred at this early time, we only know that some specific challenges, which I shall describe, had to have been met in order for our oxygen atom to exist today. In this sense the story of our atom takes on a Rashomon-like quality. In his famous film, Akira Kurosawa followed three different versions of the same event, a rape and murder, as remembered by three participants. Because of their different vantage points, and their different past experiences, each describes a different story. None is universally accurate, but each contains at least a germ of truth....
What People are saying about this
(Frank Wilczek, Professor of Physics at MIT)
(Martin Rees, author of Just Six Numbers and Before the Beginning)
Meet the Author
Lawrence M. Krauss is the best selling author of The Physics of Star Trek. He received his Ph.D. in physics from MIT and now chairs the Department of Physics at Case Western Reserve University.
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