NASA’s New Telescope Will Test Whether Scientists Got Dark Energy Wrong

For nearly three decades, dark energy has helped explain why the universe’s expansion is accelerating. NASA’s newly launched Nancy Grace Roman Space Telescope may now test whether that explanation still holds.

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Roman will be a discovery machine that will bring us closer than ever before to answering humanity’s most profound questions about our cosmic history.

The discovery of cosmic acceleration in the late 1990s overturned the earlier view that expansion was slowing. Observations from the Hubble Space Telescope and ground-based instruments showed the opposite. The scientists involved, including Australian astrophysicist Brian Schmidt, received the 2011 Nobel Prize.

More recent maps of the universe have introduced doubt about the standard picture. Researchers using the Dark Energy Spectroscopic Instrument and the Dark Energy Survey have found tentative hints that dark energy may vary over time. Cullan Howlett, an astrophysicist at the University of Queensland, said the evidence suggests it could be weakening rather than remaining constant.

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Dark matter and dark energy are mysterious enough that it’s really helpful to have these different views.

Roman will give scientists another way to check those results. Its mission includes studying dark energy and dark matter, neither of which interacts with ordinary matter in ways that make direct observation easy. Scientists instead study their effects on the movement and distribution of galaxies.

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We basically found some tentative hints, I would say, of time variation.

Those galaxies form clusters connected by filaments across vast voids, a structure researchers call the cosmic web. Three-dimensional maps of that web record how the universe has changed since the Big Bang. If Roman confirms that dark energy has evolved, predictions about the universe’s future could change dramatically, and physicists would need to replace their current working model.

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We call it the cosmic web.