We live in a big universe. Even if we were able to travel across the universe at the speed of light, the journey would take us at least ten billion years. Why is the universe so large? Has the universe always been this big, or was it smaller in the past? If smaller, how small was it? Was there a time when the volume of the universe vanished?

We can ask related questions regarding matter in the universe. Why is the universe not empty? From where do the atoms that make up our bodies originate? When were these atoms created?

Questions such as these lead us inevitably to the origin of the universe. Did the universe have a definite beginning, or has it always existed? If it had a beginning, can we talk meaningfully about what might have happened beforehand? And what caused the universe to come into existence in the first place?

The purpose of this book is to address questions such as these. Moreover, because our own origin is linked with that of the universe as a whole, we are indirectly studying our own past when we investigate the beginning of the universe.

We will see that the structure of the universe is intimately related to the structure of the smallest elementary particles. This relationship between the world of the very large and that of the very small was manifest even during the first second of the universe's history.