Helge Kragh gained doctoral degrees in physics (1981) and in philosophy (2007). He was a high school teacher in physics and chemistry (1970- 87), and then later a professor of history of science at Cornell University, USA; University of Oslo, Norway; and University of Aarhus, Denmark (1987-2015). After retiring, he is now emeritus professor at the Niels Bohr Institute, University of Copenhagen, Denmark.Malcolm Longair is Director of Development and Outreach, Jacksonian Professor Emeritus of Natural Philosophy at the Cavendish Laboratory, University of Cambridge, UK. He also holds the position of Editor-in-Chief of the Biographical Memoirs of Fellows of the Royal Society (2016-2020). Longair has previously held positions as a university lecturer in the Department of Physics, University of Cambridge (1970—80); Astronomer Royal for Scotland, Regius Professor of Astronomy, University of Edinburgh, Director of the Royal Observatory, Edinburgh (1980—90); Jacksonian Professor of Natural Philosophy, University of Cambridge (1991—2008); and Head of Cavendish Laboratory (1997—2005).

• 1: Cosmological theories before and without Einstein 2: Observations and the universe 3: Relativistic models and the expanding universe 4: Alternative cosmological theories 5: Steady state theory and the cosmological controversy 6: Observational and astrophysical cosmology: 1940 to 1980 7: Relativistic astrophysics and cosmology 8: The cosmic microwave background: From discovery to precision cosmology 9: Space science and technological progress: Testing theories of relativistic gravity and cosmology during the Cold War 10: Observational and astrophysical cosmology: 1980 to 2018 11: Inflation, dark matter, and dark energy 12: Stranger things: Multiverse, string theory, physical eschatology 13: Philosophical aspects of cosmology

Helge Kragh gained doctoral degrees in physics (1981) and in philosophy (2007). He was a high school teacher in physics and chemistry (1970- 87), and then later a professor of history of science at Cornell University, USA; University of Oslo, Norway; and University of Aarhus, Denmark (1987-2015). After retiring, he is now emeritus professor at the Niels Bohr Institute, University of Copenhagen, Denmark.Malcolm Longair is Director of Development and Outreach, Jacksonian Professor Emeritus of Natural Philosophy at the Cavendish Laboratory, University of Cambridge, UK. He also holds the position of Editor-in-Chief of the Biographical Memoirs of Fellows of the Royal Society (2016-2020). Longair has previously held positions as a university lecturer in the Department of Physics, University of Cambridge (1970—80); Astronomer Royal for Scotland, Regius Professor of Astronomy, University of Edinburgh, Director of the Royal Observatory, Edinburgh (1980—90); Jacksonian Professor of Natural Philosophy, University of Cambridge (1991—2008); and Head of Cavendish Laboratory (1997—2005).

• 1: Cosmological theories before and without Einstein 2: Observations and the universe 3: Relativistic models and the expanding universe 4: Alternative cosmological theories 5: Steady state theory and the cosmological controversy 6: Observational and astrophysical cosmology: 1940 to 1980 7: Relativistic astrophysics and cosmology 8: The cosmic microwave background: From discovery to precision cosmology 9: Space science and technological progress: Testing theories of relativistic gravity and cosmology during the Cold War 10: Observational and astrophysical cosmology: 1980 to 2018 11: Inflation, dark matter, and dark energy 12: Stranger things: Multiverse, string theory, physical eschatology 13: Philosophical aspects of cosmology

Helge Kragh gained doctoral degrees in physics (1981) and in philosophy (2007). He was a high school teacher in physics and chemistry (1970- 87), and then later a professor of history of science at Cornell University, USA; University of Oslo, Norway; and University of Aarhus, Denmark (1987-2015). After retiring, he is now emeritus professor at the Niels Bohr Institute, University of Copenhagen, Denmark.Malcolm Longair is Director of Development and Outreach, Jacksonian Professor Emeritus of Natural Philosophy at the Cavendish Laboratory, University of Cambridge, UK. He also holds the position of Editor-in-Chief of the Biographical Memoirs of Fellows of the Royal Society (2016-2020). Longair has previously held positions as a university lecturer in the Department of Physics, University of Cambridge (1970—80); Astronomer Royal for Scotland, Regius Professor of Astronomy, University of Edinburgh, Director of the Royal Observatory, Edinburgh (1980—90); Jacksonian Professor of Natural Philosophy, University of Cambridge (1991—2008); and Head of Cavendish Laboratory (1997—2005).

• 1: Cosmological theories before and without Einstein 2: Observations and the universe 3: Relativistic models and the expanding universe 4: Alternative cosmological theories 5: Steady state theory and the cosmological controversy 6: Observational and astrophysical cosmology: 1940 to 1980 7: Relativistic astrophysics and cosmology 8: The cosmic microwave background: From discovery to precision cosmology 9: Space science and technological progress: Testing theories of relativistic gravity and cosmology during the Cold War 10: Observational and astrophysical cosmology: 1980 to 2018 11: Inflation, dark matter, and dark energy 12: Stranger things: Multiverse, string theory, physical eschatology 13: Philosophical aspects of cosmology