title: Astrophysics is Easy!: An Introduction for the Amateur Astronomer (The Patrick Moore Practical Astronomy Series)
author: Michael Inglis
description: <P>From the reviews: </P> <P></P> <P>"Inglis  offers a handy, useful resource both for amateur astronomers and colleges with small student-oriented observatories. It will be useful for introductory astronomy courses that include some observations.  Many different kinds of stars are discussed with the appropriate physics. In addition, Inglis treats topics such as different kinds of galaxies, gravitational lensing, and Hubbles Law, all done using mathematics no more sophisticated than arithmetic. For all good college libraries. Summing Up: Highly recommended. General readers; lower-division undergraduates; two-year technical program students." (K. L. Schick, CHOICE, Vol. 45 (6), 2006)</P> <P>"Inglis begins by discussing all the fundamental tools of the trade and then moves on to the astrophysics of the interstellar medium stars, and finally galaxies. The texts tone is friendly and conversational, and the author sprinkles in his own anecdotal experiences. The book is generously illustrated with black-and-white figures and a few color photographs.  Astrophysics Is Easy! is a must for any amateur astronomer who desires to learn more about the science of astronomy  ." (Jennifer Birriel, Sky and Telescope, May, 2008)</P> <P>"The author has set himself the goal of writing a book that is useful to the amateur astronomer who wants to know more about the beauty in the sky  . this book is affordable for many young scientists, physicists, or amateur astronomy groups. It will also be useful to professional astrophysicists who have to address a broad audience or prepare a lecture for a non-scientific public.  this book may encourage more young readers to pursue a career in science, maybe even in astrophysics." (Fernande Grandjean and Gary J. Long, Physicalia Magazine, Vol. 30 (4), 2008)</P>
zlib_text: Charles KeetonUndergraduate Lecture Notes in PhysicsPrinciples of
  Astrophysics2014Using Gravity and Stellar Physics to Explore the
  Cosmos10.1007/978-1-4614-9236-8_1
  
  © Springer Science+Business Media New York 2014
  
  # 1\. Introduction: Tools of the Trade
  
  Charles Keeton1
  
  (1)
  
  Department of Physics and Astronomy, Rutgers University, Piscataway, NJ, USA
  
  Abstract
  
  A concise way to state the scientific method in astrophysics is this: We use
  theory to make quantitative predictions that can be compared with
  observations. Sometimes we can solve the relevant equations with pencil and
  paper in a modest number of steps, but other times we cannot. How do we
  proceed? Often we can use physical insight and approximate calculations to
  understand the salient features of a system without sweating the details.
  Before diving into technical material, it is good to see how physical
  reasoning and estimation techniques (such as toy models, scaling relations,
  Taylor series approximations, and dimensional ana