Explore how scientists discovered that the universe is expanding at an increasing rate in this video from NOVA: Invisible Universe Revealed. Saul Perlmutter and Adam Riess describe how their competing investigations into whether gravity would slow the expansion of the universe led to the same surprising finding: the universe was actually speeding up. Images from the Hubble Space Telescope allowed scientists to find and measure the distances to dozens of type 1a supernovae in distant galaxies. That data, combined with redshift data about the galaxies, revealed that the expansion rate of the universe was accelerating.
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