Prof. James Overduin, Baltimore, MD, USAProf. Helge Kragh, Aarhus University, Denmark

"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)

• Early ideas of space and vacuum.- The active ether.- Planck’s second quantum theory.- Half-quanta and zero-point energy.- Nernst’s cosmic quantum ether.- The Hamburg connection.- The cosmological constant.- From Casimir to Zel’dovich.- Inflation and the false vacuum.- Variable cosmological constants and quintessence.- How heavy is the vacuum?.- The accelerating universe.

Prof. James Overduin, Baltimore, MD, USAProf. Helge Kragh, Aarhus University, Denmark

"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)

• Early ideas of space and vacuum.- The active ether.- Planck’s second quantum theory.- Half-quanta and zero-point energy.- Nernst’s cosmic quantum ether.- The Hamburg connection.- The cosmological constant.- From Casimir to Zel’dovich.- Inflation and the false vacuum.- Variable cosmological constants and quintessence.- How heavy is the vacuum?.- The accelerating universe.