WENDY FREEDMAN is staring down the universe. For 40 years, she has been digging into the biggest secrets of the cosmos, patiently whittling down uncertainties to find the value of a number that defines the expansion of the universe, determines its age and seals its ultimate fate.
Freedman, who works at the University of Chicago, studies the Hubble constant, a number that represents how fast the expansion of the universe is accelerating. We have known about this escalating expansion since 1929, when US astronomer Edwin Hubble found that the more distant an object was, the faster it seemed to be moving away from us.
That is when things got tricky. Pinning down the numbers requires accurate measurements of astronomical distances. In Hubble’s era, astronomical images were taken by shining light through a telescope onto a photographic plate. Calculating distances from those images was difficult and imprecise.
