Ever since its infancy, humankind has been seeking answers to some very
basic and profound questions. Did the Universe begin? If it did, how old
is it, and where did it come from? What is its shape? What is it made
of? Fascinating myths and brilliant in- itions attempting to solve such
enigmas can be found all through the history of human thought. Every
culture has its own legends, itsownworldcreationtales,
itsphilosophicalspeculations, itsre- gious beliefs. Modern science,
however, cannot content itself with fanciful explanations, no matter how
suggestive they are. No- days, our theories about the Universe, built
upon rational ded- tion, have to survive the hard test of experiment and
observation. Cosmology, the science which studies the origin and evo-
tion of the Universe, had to overcome enormous dif?culties before it
could achieve the same level of dignity as other physical dis- plines.
At ?rst, it had no serious physical model and mathematical tools that
could be used to address the complexity of the problems it had to face.
Then, it suffered from a chronic lack of experim- tal data, which made
it almost impossible to test the theoretical speculations. Given this
situation, answering rigorously the many questions on the nature of the
Universe seemed nothing more than a delusion. Today, however, things
have changed. We live in the golden age of cosmology: an exciting
moment, when, for the ?rst time, we are able to scienti?cally understand
our Univers
