This all-new and long-awaited sequel to Carl Sagan and Ann Druyan's international bestseller Cosmos takes readers to worlds only now emerging with the advent of new technologies. With lucid prose that recalls the best-selling and beloved Cosmos, Ann Druyan takes readers on an extraordinary journey through the vast and unexplored realms of Earth and space, past and future, fact and imagination. Written and published in coordination with the sensational international television debut of a second season of National Geographic's Cosmos, Cosmos: Possible Worlds travels through more than 14 billion years of cosmic evolution and into an astonishing future where probes travel by light beams to distant stars, helping us solve enduring mysteries of our origins and dream of an unimaginable time ahead. Along the way, we meet the colorful characters who push beyond the boundaries of knowledge—both the little-known but monumental visionaries of the past and the scientists whose work is shaping our future. Color photographs, art, and diagrams based on graphics created for the television series—plus a foreword by Neil deGrasse Tyson, best-selling author, wildly popular science commentator, and host of Cosmos on the National Geographic Channel—complete this highly anticipated package.

1. Introduction.- 2. Observational Data.- 3. Celestial Mechanics Minimum.- 4. Elementary Particle Dynamics. I Rigid Body Collisions.- 5. Elementary Particle Dynamics. II Ring Cosmogony.- 6. Elementary Particle Dynamics. III Wave, Photometric, and Other Effects.- 7. Collective Dynamics of Disc Particles. I Formalism.- 8. Collective Dynamics of Disc Particles. II Stability Analysis.- 9. Resonance Effects in Planetary Rings. I Spiral Waves.- 10. Resonance Effects in Planetary Rings. II Narrow Ringlets and Satellites.- 11. Formation and Stability of the Uranian Rings.- 12. Origin, Dynamics, and Stability of the Neptunian Rings.- 13. Self-organisation of the Solar System.- 14. Space Studies of the Outer Planets.- Conclusion.- Appendices I. The Possibility of Studying the Dynamics of Astrophysical Discs in a Two-Dimensional Approach.- 1. Introduction.- 2. Original Equations for the "Volume" Functions.- 2.1 Initial Dynamic Equations.- 2.2 Equation of State.- 3. Derivation of the Basic Equations for the "Plane" Functions.- 3.1 Order-of-Magnitude Estimates of the Terms in the Initial Equations.- 3.2 The Two Limiting Cases of Astrophysical Discs.- 3.3 Limitations of the Characteristic Times of Processes Studied in the Two-Dimensional Approximation.- 3.4 Closed System of Integro-differential Equations for a Barotropic Disc.- 4. Closed Set of Differential Equations for a Polytropic Disc in an External Gravitational Field.- 4.1 Derivation of the Two-Dimensional Equations.- 5. Closed Set of Differential Equations for a Polytropic Self-gravitating Disc.- 5.1 Derivation of the Two-Dimensional Equations.- 5.2 Why Does the Gradient of the Plane Pressure Not Have the Physical Meaning of a Force?.- 6. Conclusion.- 1. Derivation of a Closed Set of Integro-differential Equations.- 2. Derivation of the Dispersion Equation Describing the Three-Dimensional Perturbations.- 4. Dispersion Relation for Waves in the Plane of the Disc.- 5. The Role of Perturbations Along the Rotation Axis.- 5.1 Condition for Neglecting Mass Transfer Along the Rotation Axis.- 5.1.1 General Case.- 5.1.2 Isothermal Disc.- 6. Conclusion.- III. Derivation of the Linearised Equations for Oscillations of a Viscous Disc.- 1. Derivation of the Linearised Equations for Oscillations of a Viscous Uniformly Rotating Disc.- 2. Derivation of the Linearised Equations for Oscillations of a Viscous Differentially Rotating Disc of Inelastic Particles with Account of External Matter Fluxes.- 3. Derivation of the General Dispersion Equation.- IV. Evaluating the Gravitational Potential Inside and Outside a Triaxial Ellipsoid.- 1. Potential Inside the Ellipsoid.- 2. Potential Outside the Ellipsoid.- V. A Drift Mechanism for the Formation of the Cassini Division.- 1. Introduction.- 2. Statement of the Problem.- 3. Derivation of the Non-linear Momentum Conservation Equations.- 4. Time-Averaged Non-linear Momentum Conservation Equations.- 5. Absence of Averaged Radial Mass Flux in a Dissipationless Disc. Large-Scale Convection.- 6. Radial Mass Transfer in a Viscous Disc.- 7. Evolution of the Surface Density of a Disc.- 8. Conditions for the Formation of Different Types of Resonant Structures: Gaps or Wavetrains?.- 9. Estimate of the Maximum Width of a Gap Produced by a Density Wave.- 10. Some Additional Remarks.- VI. Resonance Structures in Saturn's C Ring.- References.