Preface; Part I. Theory: 1. Dark energy, gravitation and the Copernican principle J.-P. Uzan; 2. Dark energy and modified gravity R. Maartens and R. Durrer; 3. Some views on dark energy D. Polarski; 4. Emergent gravity and dark energy T. Padmanabhan; Part II. Observations: 5. Foundations of supernova cosmology R. P. Kirshner; 6. Dark energy and supernovae P. Ruiz–Lapuente; 7. The future of supernova cosmology M. Wood-Vasey; 8. The space advantage A. Kim; 9. Baryon acoustic oscillations B. Bassett and R. Hlozek; 10. Weak gravitational lensing A. Heavens; Index.