Light from the Depths of Time

Although this book has been available for some time, it is only now appearing in an English edition. This gives me the opportunity of adding a few explanations. I have not struggled to include the very latest, tentative results. I have, instead, concentrated on presenting cosmological ideas to interested non­ experts. They often encounter considerable difficulties when attempts are made to explain even long-established results in this field, so the aim of this book is to provide them with help. Naturally, I have also tried to include modern findings. To help with the explanation I have made use of the fictitious inhabi­ tants of Flatland, occasional historical digressions, and the dreams of Herr Meyer. Incidentally, I chose this name, which is very common in German­ speaking countries, to suggest an average citizen, just like the man next door. I should like to thank Springer-Verlag for deciding to publish this book in the language in which many of the discoveries described here were first formulated. I also thank my translator, Mr Storm Dunlop. Finally I thank Hanna Tettenborn for compiling the index.

1. Anatomy of the Milky Way.- Cosmic Yardsticks.- Herr Meyer Solves a Riddle.- Approaching the Milky Way.- In the Virgo Cluster.- The Stars of the Milky Way Make Their Appearance.- Inside the Milky Way.- The Centre of the Milky Way.- 2. Light.- Waves in Empty Space.- Herr Meyer Dreams About the Electromagnetic Spectrum.- The Spectrum.- How the Spectral Lines Are Formed.- Hydrogen as a Radio Transmitter.- Thermal Radiation.- Spectra from the Depths of Space.- A Millionth of a Gramme of Light.- Radiation into Matter; Matter into Radiation.- Energy in Light and Matter.- 3. Speeding Up the Milky Way.- Novae and Supernovae.- The Rotating Disk.- Two Populations.- Motion Revealed by Light and Radio Waves.- Herr Meyer and His Bicycle.- The Doppler Effect.- The Pattern of Movement Within the Milky Way.- 4. Plumbing the Depths of the Milky Way.- Stellar Proper Motions.- Radial Velocities.- Star Streams.- The Hyades Cluster.- Beyond the Hyades Farther Out into Space.- Pulsating Stars and the Cosmic Distance Scale.- How Far Away Are the Globular Clusters?.- Harlow Shapley Ousts Us from the Galactic Centre.- The Hyades Stars Determine the Size of the Universe.- 5. The Island Universe Debate.- The Problem of the Nebulae.- Stars Erupt in the Nebulae.- “Secondary Nuclei” Within the Andromeda Nebula.- The 26th of April 1920.- Walter Baade Increases the Distance of the Andromeda Nebula.- 6. The Universe Is Expanding.- The High Velocities of the Spiral Nebulae.- Are We in the Centre of the Universe?.- Expansion and Olbers’ Paradox.- When Did It Begin?.- Galaxies That Are Approaching.- Doubts About the Expansion.- What Lies Farther Out?.- 7. The Big Bang in Flatland.- Herr Meyer’s Dream of Flatland.- The World of the Flatmen.- A Two-Dimensional World’s Astronomy.- Geometry in Flatland.- True Curved Surfaces.- Is Our Three-Dimensional Space Curved?.- Ghosts from the Fourth Dimension.- 8. Expansion and Gravity.- It Is the Same Everywhere in the Universe as It Is Here.- Which Curved Universe Do We Inhabit?.- The Expansion Slows Down.- Expanding Flat Universes.- From Flatland to Our Universe.- Gravitational Repulsion?.- Which Came First, the Chicken or the Egg?.- The Russian Balloonist and Einstein’s Mistakes.- The Theory of the Steady-State Universe.- 9. The Realm of the Nebulae.- Galaxies Rotate.- The Invisible Material.- The Zoo of Galaxies.- Galactic Nuclei.- Seyfert Galaxies.- Clusters of Galaxies.- Cannibalism Among Galaxies.- Clusters of Clusters.- 10. The Radio Sky.- The Birth of Radio Astronomy.- Radio Waves from the Milky Way.- The Story of Cygnus A.- Radio Galaxies.- The Twin Exhaust Model.- “Tadpole” Galaxies and Aperture Synthesis.- 11. The Mysterious Quasars.- The Classification of Radio Sources.- Stars That Are Utterly Unlike Anything Ever Seen Before.- The Recession Velocities of Radio Stars.- Are Quasars Really Distant?.- Black Holes in Quasars?.- The Absorption Lines in Quasars.- The Problem of Superluminal Velocities.- Herr Meyer and the Firework Display.- A Counter-Example.- Are There Quasars in the Centres of Galaxies?.- The Double Quasar.- 12. ... and There Was Light.- Radio Emission from Our Bodies.- Searching for Faint Radiation from the Milky Way.- The Radiation Remaining from the Big Bang.- Cold Radiation from the Hot Big Bang.- Our Slipstream in Space.- The Cosmic Mixture of Matter and Radiation.- Cosmic Material in the Laboratory.- When Radiation and Matter Separated.- Radiation Becomes Dominant.- Where Is the Antimatter?.- The First Chemical Elements.- Are Neutrinos Sufficient to Close the Universe?.- Our Universe’s Luminous Boundary.- Olbers’ Paradox, for the Last Time.- 13. The Intelligent Universe.- Where Did Galaxies and Quasars Come from?.- Why Is the Universe so Smooth?.- We Are Here Because the Universe Is Uniform.- What Came Before?.- At the Origin of Time.- When the Universe Was Tossed into Physics.- Do Natural Laws Determine the Form of the Universe?.- A Time-Lapse Film of the Universe.- Appendices.- A. Frequency and Wavelength.- B. How the Distance of the Hyades Is Determined.- C. The Space Telescope and Stellar Parallaxes.- D. Distances by Dead Reckoning.- Author and Subject Index.