Wendy Freedman

Wendy Laurel Freedman (born July 17, 1957) is a Canadian-American astronomer and one of the world’s leading experts on observational cosmology. Her many honors include the Gruber Cosmology Prize (2009), the Dannie Heineman Prize for Astrophysics (2016), and the National Medal of Science (2025). (Her husband and longterm collaborator Barry Madore is known for the Arp-Madore Catalogue.)

Quotes

• The Hubble constant, which measures the expansion rate, together with the total energy density of the Universe, sets the size of the observable Universe, its age, and its radius of curvature. Excellent progress has been made recently toward the measurement of the Hubble constant: a number of different methods for measuring distances have been developed and refined, and a primary project of the Hubble Space Telescope has been the accurate calibration of this difficult-to-measure parameter. The recent progress in these measurements is summarized, and areas where further work is needed are discussed. Currently, for a wide range of possible cosmological models, the Universe appears to have a kinematic age less than about 14±2 billion years. Combined with current estimates of stellar ages, the results favor a low-matter-density universe. They are consistent with either an open universe, or a flat universe with a non-zero value of the cosmological constant.
  • (August 2000) "The Hubble constant and the expansion age of the Universe". Physics Reports: 13–31. DOI:10.1016/S0370-1573(00)00013-2.

• We are at an interesting juncture in cosmology. With new methods and technology, the accuracy in measurement of the Hubble constant has vastly improved, but a recent tension has arisen that is either signaling new physics or as-yet unrecognized uncertainties.
  Just under a century ago, Edwin Hubble revolutionized cosmology with his discovery that the universe is expanding. Hubble found a relationship between radial velocity and the distance to nearby galaxies, determining the proportionality constant Ho (=v/r), that now bears his name. The Hubble constant remains one of the most important parameters in cosmology. An accurate value of Ho can provide a powerful constraint on the cosmological model describing the evolution of the universe. In addition, it characterizes the expansion rate of the Universe at the current time, defines the observable size of the Universe, and its inverse sets the expansion age of the Universe.
  • (2017) . "Cosmology at a Crossroads: Tension with the Hubble Constant". arXiv:1706.02739 [astro-ph.CO]. (preprint for article (2017) . "Cosmology at a crossroads". Nature Astronomy 1 (5): 0121. DOI:10.1038//s41550-017-0121.)

• ... after finishing my postdoc, I became a faculty member at Carnegie, and then ended up being the scientific leader of this project to measure the rate at which the universe is expanding. ... when that project finished, .. we .. resolved the issue. We went from a factor of 2 uncertainty — we measured an uncertainty of 10%.
  • (June 5, 2023) "Our Expanding Universe: Wendy L. Freedman 2023 Ryerson Lecture". University of Chicago, YouTube. (quote at 13:50 of 58:54 in video)

External links

• Oakes, Elizabeth H. (2007). "Freedman, Wendy Laurel". Encyclopedia of World Scientists. Facts on File Science Library (revised ed.). Infobase Publishing. pp. 251–252. ISBN 9781438118826.  (869 pages)
• Drapa, Michael (January 7, 2025). Wendy Freedman awarded National Medal of Science. UChicago cosmologist honored for pioneering research on Hubble constant. UChicago News.