In DepthAstronomy

Robot detector to map cosmos for clues to dark energy's force

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Science  13 Sep 2019:
Vol. 365, Issue 6458, pp. 1066
DOI: 10.1126/science.365.6458.1066

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Summary

In 1998, astronomers discovered something astonishing: Some antigravitational force was speeding up the expansion of the universe. Two decades later, "dark energy" is still a mystery. But next month, a veteran telescope in Arizona, retrofitted with a robotic system to map an unprecedented 35 million galaxies, will begin to hunt for clues. That huge sample, spanning much of the visible universe, will allow the Dark Energy Spectroscopic Instrument to look for fluctuations in the clumping patterns of galaxies that might betray the nature of dark energy. So far, dark energy appears to have the same effects everywhere, across most of the history of the universe. That suggests it is a constant pressure associated with the fabric of space itself—a so-called cosmological constant. But if dark energy turns out to vary over time, it could require a more exotic explanation, such as an additional force field, sometimes dubbed quintessence. Or it could point to the need for a more fundamental rewrite of general relativity, Einstein's theory of gravity.

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