The fundamental outlines of the physical world, from its tiniest particles to massive galaxy clusters, have been apparent for decades. Does this mean physicists are about to tie it all up into a neat package? Not at all. Just when you think you’re figuring it out, the universe begins to look its strangest. This eBook, “Ultimate Physics: From Quarks to the Cosmos,” illustrates clearly how answers often lead to more questions and open up new paths to insight. We open with “The Higgs at Last,” which looks behind the scenes of one of the most anticipated discoveries in physics and examines how this “Higgs-like” particle both confirmed and confounded expectations. In “The Inner Life of Quarks,” author Don Lincoln discusses evidence that quarks and leptons may not be the smallest building blocks of matter. Section Two switches from the smallest to the largest of scales, and in “Origin of the Universe,” Michael Turner analyzes a number of speculative scenarios about how it all began. Another two articles examine the mystery of dark energy and some doubts as to whether it exists at all. In the last section, we look at one of the most compelling problems in physics: how to tie together the very small and the very large – quantum mechanics and general relativity. In one article, Stephen Hawking and Leonard Mlodinow argue that a so-called “theory of everything” may be out of reach, and in another, David Deutsch and Artur Ekert question the view that quantum mechanics imposes limits on knowledge, arguing instead that the theory has an intricacy that allows for new, practical technologies, including powerful computers that can reach their true potential.