Hubble Constant Discrepancies – Implications for Our Expanding Universe

October 2019

Briefing date: October 23, 2019 (3:30pm EDT)


Dr. Chris Britt (STScI)


  • Dr. Wendy Freedman (U Chicago)

  • Dr. Charles Lawrence (JPL / Calitech)

  • Dr. Adam Riess (Johns Hopkins University, STScI)

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Please join us for this special edition of the Universe of Learning Science Briefings! We will hear about disagreements in measurements of the expansion of the universe and what that implies for our understanding of cosmology.

In this briefing, speakers will share content about how the rate of the universe is measured in different cosmological epochs and what the differences in those measures can tell us. Dr. Wendy Freedman will discuss the cosmic distance ladder and how to measure the expansion of the universe. Dr. Charles Lawrence will present how the Planck mission uses fine measurements of the afterglow of the Big Bang to infer the value of the Hubble Constant. Dr. Adam Riess will discuss the discrepancy between the present and predicted expansion rate of the Universe and the broader implications that could have for cosmology. In addition to these, we will highlight several resources relating to this content.


Wendy Freedman is the John & Marion Sullivan University Professor of Astronomy and Astrophysics at The University of Chicago. She received her PhD from the University of Toronto in 1984 and has done groundbreaking work on distances to the local universe. She led the Hubble Key Project to measure the Hubble Constant. She has served as the Director of the Carnegie Observatories, was the founding chair of the board of directors for the Giant Magellan Telescope, and is a member of the National Academy of Sciences and a fellow of the American Physical Society. She has received numerous awards for her work, including the Gruber Cosmology Prize and the Dannie Heineman Prize for Astrophysics

Charles Lawrence is the Chief Scientist for Astronomy and Physics at the Jet Propulsion Laboratory. He is the Project Scientist for the U.S. Plank Project and Deputy Project Scientist for the Spitzer Space Observatory. His research interests include measurement and analysis of the cosmic microwave background, extragalactic radio sources, and gravitational lensing. He is the recipient of two Exceptional Achievement Medals, two Outstanding Leadership Medals, and a Distinguished Public Service Medal, all from NASA, and was part of the Planck team awarded the 2018 Gruber Prize in Cosmology. Dr. Lawrence earned his Ph.D. in physics from the Massachusetts Institute of Technology.

Adam Riess is a Bloomberg Distinguished Professor, the Thomas J. Barber Professor in Space Studies at the Krieger School of Arts and Sciences, the Krieger Eisenhower Professor of Physics and Astronomy, a distinguished astronomer at the Space Telescope Science Institute and a member of the National Academy of Sciences. He received his bachelor’s degree in physics from the Massachusetts Institute of Technology in 1992 and his PhD from Harvard University in 1996. His research involves measurements of the cosmological framework with supernovae (exploding stars) and Cepheids (pulsating stars). He leads the SHOES Team in efforts to improve the measurement of the Hubble Constant and the HIgher-z Team to find and measure the most distant type Ia supernovae known to probe the origin of cosmic acceleration. In 2011, he was named a co-winner of the Nobel Prize in Physics and was awarded the Albert Einstein Medal for his leadership in the High-z Supernova Search Team’s discovery that the expansion rate of the universe is accelerating, a phenomenon widely attributed to a mysterious, unexplained "dark energy" filling the universe. The discovery was named by Science magazine in 1998 as "the Breakthrough Discovery of the Year." His accomplishments have been recognized with a number of other awards, including a MacArthur Fellowship in 2008, the Gruber Foundation Cosmology Prize in 2007 (shared), and the Shaw Prize in Astronomy in 2006.

FACILITATOR: Dr. Chris Britt received his BS and PhD in astrophysics from Louisiana State University. He was a postdoctoral researcher at Texas Tech University and at Michigan State University before joining the Space Telescope Science Institute in Baltimore as an Education and Outreach Scientist, where he works with the Hubble and James Webb Space Telescopes to bring cutting edge astronomical research to public audiences.