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.

Atoms are Real

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.

The Journey of an Oxygen Atom

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.