<p>“This is an interesting historical overview of the development of ideas relating to vacuum energy. It is a well-written, easy read, and should appeal to anyone with an interest in dark energy, which should be all of us, since this is often claimed as the biggest mystery in modern physics. Kragh and Overduin have split the story into 12 chapters, tracing relevant ideas from the ancient Greek philosophers up to the present day.” (Douglas Scott, Journal for the History of Astronomy, Vol. 47 (4), November, 2016)</p><p>“This is an exceptionally good, short guide to the history of physicists’ understanding of the energy of empty space. … This is an excellent brief history of cosmology. I expect to cite it many times in my academic papers and books.” (Simon Mitton, The Observatory, Vol. 135 (1245), April, 2015)</p>