The HSC observed the sky for a total of 330 nights over six years, and different teams of researchers analyzed the data in different ways. They obtained S8 (dark matter density) values between 0.763 and 0.776—similar to values found in other weak lensing studies.

The S8 value determined using the cosmic microwave background is significantly higher: 0.832. This contradicts our understanding of the evolution of the Universe; The standard cosmological model assumes that the distribution of matter starts out relatively uniform and then becomes denser as matter clusters into galaxies and cosmic structures.

The results of weak lensing studies are unlikely to be due to errors: different instruments and methods of analysis have repeatedly produced consistent results.

The authors made great efforts to eliminate bias and protect the study results from internal errors.

“I worked on this analysis for a year and was never able to see the values,” says Dalal.

However, there are other cosmological inconsistencies, notably the Hubble tension, which is an unresolved difference in the measurements of the accelerating expansion of the Universe.

What does it mean? Perhaps our cosmological models contain errors. Our understanding of dark matter may be incomplete. We may be doing something wrong when measuring.

Perhaps, having solved one contradiction, we will find a solution for the others. Or we won’t find it. But one thing is clear: there is a fundamental flaw in our efforts to understand the evolution of the universe.

In the future, more powerful equipment will allow larger and more accurate studies. Only through them can we get closer to answers to these exciting problems.