A project to produce more than double the number of galaxy distance measurements than all other previous surveys combined, could lead to an explanation of one of nature’s biggest mysteries.
In 1998, astronomers announced that the expansion of the universe is not slowing down as many people had thought, but rather is speeding up. To account for this, scientists have invoked an invisible force called “dark energy”, which makes up 75% of the cosmos’ total of energy and matter in the cosmos. Dark energy opposes gravity, and makes the universe want to spread out.
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It was the surprise of the decade. In 1998, two teams of astronomers independently reached the same conclusion: the expansion of the Universe was not slowing down or petering out, as most people had assumed. It’s accelerating. And that means there’s something wrong with our theories.
The ANU’s Prof. Brian Schmidt was leader of one of the teams. “It initially seemed a crazy result, but we were confident we’d eliminated any errors,” he says.
Both teams studied Type Ia supernovae—distant stellar explosions that all appear to have the same intrinsic brightness—to measure how far away they are. By combining those figures with redshifts, where light from receding stars is shifted to the red end of the spectrum, the astronomers could gauge how fast the Universe was expanding at different stages of its life. The answer was that it is speeding up.
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