A representation of the evolution of the universe over 13.77 billion years. The far left depicts the earliest moment we can now probe, when a period of “inflation” produced a burst of exponential growth in the universe. (Size is depicted by the vertical extent of the grid in this graphic.) For the next several billion years, the expansion of the universe gradually slowed down as the matter in the universe pulled on itself via gravity. More recently, the expansion has begun to speed up again as the repulsive effects of dark energy have come to dominate the expansion of the universe. Credit: NASA’s Goddard Space Flight Center
Three Decades of Space Telescope Observations Converge on a Precise Value for the Hubble Constant
Science history will record that the search for the expansion rate of the universe was the great Holy Grail of 20th-century cosmology. Without any observational evidence for space expanding, contracting, or standing still, we wouldn’t have a clue as to whether the universe was coming or going. Furthermore, we wouldn’t have any idea about its age either – or in fact, if the universe was eternal.
The first act of this revelation came when, a century ago, American astronomer Edwin Hubble discovered myriad galaxies outside of our home galaxy, the
“You are getting the most precise measure of the expansion rate for the universe from the gold standard of telescopes and cosmic mile markers.” — Nobel Laureate Adam Riess
For decades after Hubble, astronomers have toiled to nail down the expansion rate that would yield a true age for the universe. This required building a string of cosmic distance ladders assembled from sources that astronomers have a reasonable confidence in their intrinsic brightness. The brightest, and therefore farthest detectable milepost markers are Type Ia supernovae.
When the Mystery of Universe’s Expansion Rate: Hubble Data Shows That “Something Weird” Is
