Toshiya Ueta is an Associate Professor of Physics and Astronomy at the University of Denver.

His research concerns the evolution of stars like the Sun, and for more than 25 years he has worked with data from ground- and space-based telescopes. Lately he has become interested in observational methods themselves, because of how convolved they are: to learn about a target, an observer must first pin down the properties of everything that happens to lie in between -- precisely the things he did not set out to study.

This book grew out of that interest. We are used to public outreach that celebrates spectacular events somewhere in the Universe, and are rarely invited to ask how any of it came to be known in the first place. That prior question is what this book is about: what it means to see something you can never visit, and how a measurement becomes knowledge.

The chapters follow the order in which the argument actually has to be built -- light, matter, their interaction, and the instruments that let us read the result.