ARlogo Annu. Rev. Astron. Astrophys. 2010. 48: 673-710
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The authors are not aware of any potential biases that might be perceived as affecting the objectivity of this review.


We thank the Carnegie Institution for Science, which, through its support of astronomical facilities and research for over a century, enabled the original discovery of the expansion of the Universe, as well as continued efforts to measure accurately the expansion of the universe over cosmic time. Many dedicated individuals have made contributions to solving the problems encountered in accurately calibrating the extragalactic distance scale; it has been a community effort spanning the better part of a century, but it remained a problem that could not have been solved without NASA and its vision in supporting space astrophysics. We thank Chris Burns for producing Figure 12. We also thank Fritz Benedict, Laura Ferrarese, Robert Kirshner, James Moran, Jeremy Mould, and Adam Riess for their many constructive suggestions on an earlier draft of this article. And finally, our sincere thanks to John Kormendy, our ARAA Editor, for his patience and his insightful and helpful comments on the final version of this review as it went to press.