How heavy is the universe? Conflicting answers hint at new physics.

[Judi Lynn]

By Anil Ananthaswamy - Scientific American 2 hours ago

Standard model of cosmology may need a rewrite.



(Image: © Shutterstock)

Two entirely different ways of "weighing" the cosmos are producing disparate results. If more precise measurements fail to resolve the discrepancy, physicists may have to revise the standard model of cosmology, our best description of the universe.

"If this really is a glimpse of the standard model breaking down, that would be potentially revolutionary," says astronomer Hendrik Hildebrandt of the Ruhr University Bochum in Germany.

Similar concerns over the correctness of the standard model have been raised over the past few years by two independent calculations of the so-called Hubble constant, or the rate at which the universe is expanding today. Those two measurements also disagreed, creating what has been called the Hubble tension.

The new discrepancy — called the sigma-eight tension — involves measuring the density of matter in the universe and the degree to which it is clumped up, as opposed to being uniformly distributed. The result is encapsulated in a parameter called sigma-eight. To calculate sigma-eight, Hildebrandt and his colleagues turned to an effect called weak gravitational lensing, in which the light from distant galaxies is bent ever so slightly toward our telescopes because of the gravitational pull from matter that lies between the galaxies and Earth.

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