This book provides an introduction to the physics of interstellar gas in the Galaxy. It deals with the diffuse interstellar medium which supplies a complex environment for exploring the neutral gas content of a galaxy like the Milky Way and the techniques necessary for studying this non-stellar component. After an initial exposition of the phases of the interstellar medium and the role of gas in a spiral galaxy, the authors discuss the transition from atomic to molecular gas. They then consider basic radiative transfer and molecular spectroscopy with particular emphasis on the molecules useful for studying low-density molecular gas. Observational techniques for investigating the gas and the dust component of the diffuse interstellar medium throughout the electromagnetic spectrum are explored emphasizing results from the recent Herschel and Planck missions. A brief exposition on dust in the diffuse interstellar medium is followed by a discussion of molecular clouds in general and high-latitude molecular clouds in particular. Ways of calibrating CO observations with the molecular hydrogen content of a cloud are examined along with the dark molecular gas controversy. High-latitude molecular clouds are considered in detail as vehicles for applying the techniques developed in the book. Given the transient nature of diffuse and translucent molecular clouds, the role of turbulence in the origin and dynamics of these objects is examined in some detail. The book is targeted at graduate students or postdocs who are entering the field of interstellar medium studies.

This book provides an introduction to the physics of interstellar gas in the Galaxy. It deals with the diffuse interstellar medium which supplies a complex environment for exploring the neutral gas content of a galaxy like the Milky Way and the techniques necessary for studying this non-stellar component. After an initial exposition of the phases of the interstellar medium and the role of gas in a spiral galaxy, the authors discuss the transition from atomic to molecular gas. They then consider basic radiative transfer and molecular spectroscopy with particular emphasis on the molecules useful for studying low-density molecular gas. Observational techniques for investigating the gas and the dust component of the diffuse interstellar medium throughout the electromagnetic spectrum are explored emphasizing results from the recent Herschel and Planck missions. A brief exposition on dust in the diffuse interstellar medium is followed by a discussion of molecular clouds in general and high-latitude molecular clouds in particular. Ways of calibrating CO observations with the molecular hydrogen content of a cloud are examined along with the dark molecular gas controversy. High-latitude molecular clouds are considered in detail as vehicles for applying the techniques developed in the book. Given the transient nature of diffuse and translucent molecular clouds, the role of turbulence in the origin and dynamics of these objects is examined in some detail. The book is targeted at graduate students or postdocs who are entering the field of interstellar medium studies.

Force is one of the most elementary concepts that must be understood in order to understand modern science; it is discussed extensively in textbooks at all levels and is a requirement in most science guidelines. It is also one of the most challenging - how could one idea be involved in such disparate physical phenomena as gravity and radioactivity? Forces in Physics helps the science student by explaining how these ideas originally were developed and provides context to the stunning conclusions that scientists over the centuries have arrived at. It covers the history of all of the four traditional fundamental forces - gravity, electromagnetism, weak nuclear force, and the strong nuclear force - and shows how these forces have, over the years, allowed physicists to better understand the nature of the physical world. Forces in Physics: A Historical Perspective traces the evolution of the concept from the earliest days of the Ancient Greeks to the contemporary attempt to form a GUT (Grand Unified Theory): BLAristotle and others in Ancient Greece who developed ideas about physical laws and the introduction of forces into nature BLNewton and others in the Scientific Revolution who discovered that forces like gravity applied throughout the universe The 19th century examinations of thermodynamics and the forces of the very small BL20th century developments - relativity, quantum mechanics, and more advanced physics - that revolutionized the way we understand force. The volume includes a glossary of terms, a timeline of important events, and a bibliography of resources useful for further research.