The standard model of cosmology says that the strength of dark energy should be constant, but tentative hints are emerging that it may have weakened recently
By Leah Crane
4 April 2024
A slice of the largest 3D map of the universe showing the underlying structure of matter
laire Lamman/DESI collaboration; custom colormap package by cmastro
The largest 3D map of the universe ever created is providing hints about the evolution of the cosmos, and they suggest that we may be wrong about the behaviour of dark energy, which makes up most of the universe. It seems that this mysterious force may be weakening over time.
“If it holds up, this is a very big deal,” says Adam Riess at Johns Hopkins University in Maryland, who found the first evidence for dark energy 25 years ago. That is because the standard model of cosmology, called lambda-CDM, suggests that the strength of dark energy should be static over time.
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Dark energy is thought to cause the accelerating expansion of the cosmos – if it is not static, that could also have huge implications for our ideas about the beginning of the universe, its size and its ultimate fate. Reiss, who was not involved in the new work, says the implications could mean “we will have to do some serious soul-searching regarding [our understanding of] gravity and fields”.
The strange findings come from the Dark Energy Spectroscopic Instrument (DESI) in Arizona – and even DESI collaborators are not quite sure what to make of the fact that their data suggests dark energy may have recently gotten weaker. “It’s all we’ve been talking in the collaboration about for months… whether this is interesting or not,” says DESI spokesperson Kyle Dawson at the University of Utah.
DESI researchers examined the strength of dark energy by measuring the large-scale structure and distribution of galaxies in the cosmos, which illuminates how the universe has expanded over time. The researchers then combined this information with three sets of data on supernovae, which act as so-called “standard candles” to determine the distances to cosmic objects thanks to their predictable brightnesses.