Astronomy has been associated with the detection of electromagnetic waves or photons from within and beyond the solar system, ranging from Radio to Gamma-ray Astronomy. Particle Astrophysics, including Neutrino and Dark-Matter Astrophysics today, started with the discovery of cosmic rays in 1911. The Space Age expanded particle observations to in-situ studies of lower energy electrons and ions with a variety of charge states in space plasmas traversed by spacecraft. Remote observation of space plasmas became possible only after the discovery of energetic neutral atom (ENAs) in space in 1950.This book is a primer for those who wish to learn more about the origins of ENAs, related detection techniques, and how ENA images and spectra can be used to study space plasmas beyond the reach of spacecraft. It tells a comprehensive story from the first encounters with ENAs in the Earth's magnetosphere to Neutral-Atom Astronomy of the edge of the heliosphere and the interstellar medium. This story includes how ion mass spectrographs evolved into ENA imagers, overcoming the technical challenges, how to extract information from ENA data, and a variety of diagnostic applications on the magnetosphere, interplanetary space, other solar-system objects, the heliospheric boundary, the local interstellar medium, and a glimpse into the future of Neutral-Atom Astronomy.The authors hope to inform and inspire readers to further enrich this field of study.

Astronomy has been associated with the detection of electromagnetic waves or photons from within and beyond the solar system, ranging from Radio to Gamma-ray Astronomy. Particle Astrophysics, including Neutrino and Dark-Matter Astrophysics today, started with the discovery of cosmic rays in 1911. The Space Age expanded particle observations to in-situ studies of lower energy electrons and ions with a variety of charge states in space plasmas traversed by spacecraft. Remote observation of space plasmas became possible only after the discovery of energetic neutral atoms (ENAs) in space in 1950.This book is a primer for those who wish to learn more about the origins of ENAs, related detection techniques, and how ENA images and spectra can be used to study space plasmas beyond the reach of spacecraft. It tells a comprehensive story from the first encounters with ENAs in the Earth's magnetosphere to Neutral-Atom Astronomy of the edge of the heliosphere and the interstellar medium. This story includes how ion mass spectrographs evolved into ENA imagers, overcoming the technical challenges, how to extract information from ENA data, and a variety of diagnostic applications on the magnetosphere, interplanetary space, other solar-system objects, the heliospheric boundary, the local interstellar medium, and a glimpse into the future of Neutral-Atom Astronomy.The authors hope to inform and inspire readers to further enrich this field of study.

Quantum cosmology has gradually emerged as the focus of devoted research, mostly within the second half of last century. As we entered the 21st century, the subject is still very much alive. The outcome of results and templates for investigation have been enlarged, some very recent and fascinating. Hence this book, where the authors bequeath some of their views, as they believe this current century is the one where quantum cosmology will be fully accomplished.Though some aspects are not discussed (namely, supersymmetry or loop structures), there are perhaps a set of challenges that in the authors' opinion remain, some since the dawn of quantum mechanics and applications to cosmology. Others could have been selected, at the readers' discretion and opinion. The authors put herewith a chart and directions to explore, some of which they have worked on or aimed to work more, in the twilight of their current efforts. Their confidence is that someone will follow in their trails, venturing in discovering the proper answer, by being able to formulate the right questions beforehand. The authors' shared foresight is that such discoveries, from those formulations, will be attained upon endorsing the routes within the challenges herewith indicated.

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