'Why' Why is the world, the Universe the way it is Is space infinitely large How small is small What happens when one continues to divide matter into ever smaller pieces Indeed, what is matter Is there anything else besides what can be seen Pursuing the questions employing the leading notions of physics, one soon finds that the tangible and visible world dissolves -- rather unexpectedly -- into invisible things and domains that are beyond direct perception. A remarkable feature of our Universe is that most of its constituents turn out to be invisible, and this fact is brought out with great force by this book.Exploring the Invisible Universe covers the gamut of topics in advanced modern physics and provides extensive and well substantiated answers to these questions and many more. Discussed in a non-technical, yet also non-trivial manner, are topics dominated by invisible things -- such as Black Holes and Superstrings as well as Fields, Gravitation, the Standard Model, Cosmology, Relat