In recent years, thanks to data from Hubble and other telescopes, astronomers found another twist: a discrepancy between the expansion rate as measured in the local universe compared to independent observations from right after the big bang, which predict a different expansion value. In 1998, this led to the discovery of "dark energy," a mysterious repulsive force accelerating the universe's expansion. Pursuit of the universe's expansion rate began in the 1920s with measurements by astronomers Edwin P.
And, finally, reminding us that we have a lot more to learn among the stars.Ĭompleting a nearly 30-year marathon, NASA's Hubble Space Telescope has calibrated more than 40 "milepost markers" of space and time to help scientists precisely measure the expansion rate of the universe - a quest with a plot twist. You think this would frustrate astronomers, but instead it opens the door to discovering new physics, and confronting unanticipated questions about the underlying workings of the universe. To compound things even further, the present expansion rate is different than it is expected to be as the universe appeared shortly after the big bang. In the interim the mystery of dark energy pushing the universe apart was discovered. But it's become more than just refining a number to cosmologists. The measurement is about eight times more precise than Hubble's expected capability. This can be used to predict that the universe will double in size in 10 billion years. When the Hubble Space Telescope was launched in 1990 the universe's expansion rate was so uncertain that its age might only be 8 billion years or as great as 20 billion years.Īfter 30 years of meticulous work using the Hubble telescope's extraordinary observing power, numerous teams of astronomers have narrowed the expansion rate to a precision of just over 1%.
The brightest, and therefore farthest detectable milepost markers are Type Ia supernovae. This required building a string of cosmic distance ladders assembled from sources that astronomers have a reasonable confidence in their intrinsic brightness. He suspected his measurements might be evidence of something else more oddball going on in the universe.įor decades after Hubble, astronomers have toiled to nail down the expansion rate that would yield a true age for the universe. Hubble even said that he studied the galaxies simply as "markers of space." However he was never fully convinced of the idea of a uniformly expanding universe. This could be interpreted as the uniform expansion of space. Hubble found that the farther a galaxy is, the faster it appears to be moving away from us. And, the galaxies weren't standing still. The first act of this revelation came when, a century ago, American astronomer Edwin Hubble discovered myriad galaxies outside of our home galaxy, the Milky Way. What's more, we wouldn't have a clue about its age either – or in fact if the universe was eternal. Without any observational evidence for space expanding, contracting, or standing still, we wouldn't have a clue to whether the universe was coming or going. Science history will record that the search for the expansion rate of the universe was the great Holy Grail of 20th century cosmology.
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