Scientists and other keen observers of the natural world sometimes make or write a statement pertaining to scientific activity that is destined to live on beyond the brief period of time for which it was intended. This book serves as a collection of these statements from great philosophers and thought-influencers of science, past and present. Gaither's Dictionary of Scientific Quotations allows the reader quickly to find relevant quotations or citations to spearhead an oral or written presentation of their research. Organized thematically and indexed alphabetically by author, this work makes readily available an unprecedented collection of approximately 18,000 quotations related to a broad range of scientific topics including astronomy, biology, chemistry, engineering, and physics. With its unique thematic organization of the quotations, this book accomplishes its goal of presenting a large array of entries in each discipline and enabling the reader to choose a quotation on a particular subject from a variety of sources and perspectives. The resulting compendium allows the reader to conceptualize and embrace the written images of scientists, laymen, politicians, novelists, playwrights, and poets about humankind's scientific achievements. Quotations are listed with the credited author, title, chapter, page number, birth/death date and occupation where possible.