The article "Observational Probes of Cosmic Acceleration" by David H. Weinberg et al. reviews the methods used to study the accelerating expansion of the universe, which is attributed to either dark energy or a breakdown of Einstein's theory of gravity. The authors focus on four well-established methods: Type Ia supernovae, baryon acoustic oscillations (BAO), weak gravitational lensing, and galaxy cluster abundance. They discuss the systematic uncertainties in these techniques and strategies to control them, particularly for future "Stage IV" dark energy facilities like BigBOSS, LSST, *Euclid*, and *WFIRST*. The article also covers other approaches such as redshift-space distortions, the Alcock-Paczynski effect, and direct measurements of the Hubble constant. Extensive forecasts are presented for constraints on the dark energy equation of state and deviations from General Relativity, achievable with ambitious experimental programs. The authors emphasize the value of a balanced program that combines multiple methods to cross-check systematic uncertainties and leverage complementary information. The article concludes with a discussion of the implications for future observational efforts and the importance of a comprehensive approach to understanding cosmic acceleration.The article "Observational Probes of Cosmic Acceleration" by David H. Weinberg et al. reviews the methods used to study the accelerating expansion of the universe, which is attributed to either dark energy or a breakdown of Einstein's theory of gravity. The authors focus on four well-established methods: Type Ia supernovae, baryon acoustic oscillations (BAO), weak gravitational lensing, and galaxy cluster abundance. They discuss the systematic uncertainties in these techniques and strategies to control them, particularly for future "Stage IV" dark energy facilities like BigBOSS, LSST, *Euclid*, and *WFIRST*. The article also covers other approaches such as redshift-space distortions, the Alcock-Paczynski effect, and direct measurements of the Hubble constant. Extensive forecasts are presented for constraints on the dark energy equation of state and deviations from General Relativity, achievable with ambitious experimental programs. The authors emphasize the value of a balanced program that combines multiple methods to cross-check systematic uncertainties and leverage complementary information. The article concludes with a discussion of the implications for future observational efforts and the importance of a comprehensive approach to understanding cosmic acceleration.