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Article Contents

ABSTRACT

1.INTRODUCTION

2.EXPANSION OF THE UNIVERSE: THE COSMOLOGICAL CONTEXT

3.MEASUREMENT OF DISTANCES

3.1.Cepheid Distance Scale

3.2.Tip of the Red Giant Branch (TRGB) Method

3.3.Maser Galaxies

3.4.Surface Brightness Fluctuation (SBF) Method

3.5.Tully-Fisher Relation

3.6.Type Ia Supernovae

4.THE HUBBLE SPACE TELESCOPE (HST) KEY PROJECT

4.1.Systematics on H_o at the End of the Key Project and a Decade Later

5.OTHER METHODS FOR DETERMINING H_o

5.1.Gravitational Lens Time Delays and H_o

5.2.The Sunyaev-Zel'dovich (SZ) Effect and H_o

5.3.Measurements of Anisotropies in the Cosmic Microwave Background

6.AGE OF THE UNIVERSE

7.WHY MEASURE H_o TO HIGHER ACCURACY?

7.1.Constraints on Dark Energy

7.2.Constraints on the Neutrino Mass

7.3.Measuring H_o to ± 2%

8.FUTURE IMPROVEMENTS

9.SUMMARY POINTS

10.DISCLOSURE STATEMENT

REFERENCES