Modern Cosmology can lay a defensible claim to the title "The Grandest Science", for no other field has so vast an object of study: the Universe in its entirety.

But what is meant by the "Universe"? One might define the Universe as "the sum of all that exists," but this is insufficient, for existence draws its meaning from the universe. The Universe exists independent of any, or all, of its contents.

A complete definition of the "Universe" may not be possible, for it may be that some aspects of the cosmos are forever beyond our limited understanding. However, we can start with some possible working definitions.

The Universe can be defined as that contains and subsumes all the laws of nature and everything subject to these laws; that, is all that is physical. This definition encompasses structures that may not be observable to us. Alternatively, we can define the Universe as the physical system that is potentially observable.

Regardless of which definition one adopts, one faces the problem that i is too broad to be useful. Is cosmology, then, the study of everything? Are all sciences cosmology? We therefore restrict our definition of cosmology to the study of the formation, structure, and evolution of the universe as a whole.

Cosmology is sometimes regarded as a subfield of astronomy, but this is not an accurate division. Astronomy is the study of the contents of the universe. Although modern cosmology is intimately linked with astronomy, as our only way to observe the universe is to observe the objects it contains, it is also closely tied to physics. The universe consists not only of bodies, but also of forces and laws which govern their interactions. Indeed, we shall find that physics plays a much greater role than astronomy in describing the earliest moments of the universe. Cosmology draws upon many fields, and itself contributes to other sciences, sometimes in unexpected ways.

Finally, we have noted that modern cosmology has truly come into its own only in the last century. This period, and particularly in the last half-century, has seen astonishing progress culminating, at the end of the twentieth century with the emergence of a coherent view of the universe. And as 20th century draws to an end, Cosmology is entering an exciting new phase. The first decade of the new millennium promises a crescendo of discoveries -- heralded by ever-improving detectors and bigger, better telescopes -- bringing "the big picture" into focus. For the first time in the history of mankind, we stand at the threshold of being able to answer some of the most profound question about the Universe:

• How did it all begin?
• Was there a beginning at all, or have the heavens and Earth existed forever?
• Will the Universe come an end?
• How will it end?

The triumph of scientific cosmologies over the anthropocentric worldviews has not always been welcome; many people mourn the ancient universes in which humans played a clear and important role. The new universe seems, to some, a bleak and sterile place, while the ineffable universes of the past seemed awesome and meaningful.

But this attitude often results from a confusion of the knowledge of a thing, or more precisely, the model that allows us to know it better, with the thing itself. Science knows that crystals are highly ordered arrangements of atoms; quartz, for example, is simply a chunk of a common mineral, a major component of sand, which happens to have an ordered structure. It is the unusual large-scale symmetry of crystals, compared to most objects, that accounts not only for their rarity in nature, but also for their beauty. But this leaves many people dissatisfied; they feel that the ability of polished crystals to refract light, which sometimes even makes the light appear to originate within the crystal itself, must mean that these humble rocks possess mysterious powers. Others, while not so extreme, still find the description of a diamond as a tightly bound collection of carbon atoms repugnant, as though this knowledge somehow takes away from the beauty of the gem.

In reality, a diamond's sparkle depends mostly upon human knowledge and artifice to find its expression. A rough diamond is hardly more than a dull, gray pebble, with perhaps a bit of sheen. The trial-and-error experience gained over the centuries by diamond cutters has now been augmented by technology; a diamond to be cut is often subjected to a micrograph to determine planes along which it will most readily fracture. The various standard cuts must be carefully prepared in order that the stone show its greatest fire. It is knowledge that elicits the greatest beauty of a diamond.

Thus the knowledge that we acquire need not preclude awe. Rather than the constricted, unchanging universe imagined by our ancestors, we now find ourselves in a dynamic and evolving universe too large for any real comprehension of its size. If some people might be distressed that humans now seem so small and insignificant, science can only respond that we are nevertheless a part of this grand cosmos, and we should feel privileged to have the ability to appreciate its true majesty. If we have been forced to abandon our anthropocentric models, in return we have gained a far grander home.