The Nature paper claimed DESI data revealed billion-light-year filaments with preferred orientations that would contradict the cosmological principle. Cosmologist Till Sawala says the authors used luminosity distance instead of comoving distance and failed to rescale for cosmic expansion; his reanalysis finds no large-scale alignments. Co-authors and other experts note peer-review limits, while the absence of a preprint highlights tensions between embargo-driven publicity and open scientific scrutiny.
Physicist Challenges High-Profile Nature Paper, Says 'Elemental' Distance Error Explains Claimed Cosmic Alignment
Physicist says splashy new cosmology study made ‘elemental’ mistake
Two weeks ago, cosmologist Till Sawala reacted skeptically to headlines about a peer-reviewed paper in Nature that appeared to upend long-standing ideas in cosmology. The study analyzed a massive dataset from the Dark Energy Spectroscopic Instrument (DESI) and claimed that galaxy filaments extended across billions of light-years and showed preferred orientations—an observation that, if correct, would violate the cosmological principle that the universe is homogeneous and isotropic on the largest scales.
"If something this big had been missed, it would have been quite an embarrassment to the community," Sawala, of the University of Helsinki, says. "So I thought it was important to correct the record."
Where The Analysis Went Wrong
On closer inspection, Sawala identified what he describes as an "elemental" error in the paper's distance handling. He argues the authors used luminosity distance where the analysis required comoving distance, and they did not properly rescale distances to account for the universe's expansion rate. Those technical choices can substantially alter inferred spatial separations at cosmological scales.
"I thought, 'Okay, this is either one of the most important results in cosmology in the last 10 years, or it's wrong,'" Sawala says. "And my instinct is that it was wrong."
After correcting the unit and rescaling issues in an independent reanalysis, Sawala reports that the DESI structures are consistent with the prevailing consensus: there is no strong evidence for enormous, coherently aligned filaments and no clear violation of the cosmological principle.
Responses and Peer-Review Questions
Francesco Sylos Labini, a co-author of the Nature paper and a physicist at the Enrico Fermi Research Center, notes that Sawala's critique emphasizes the patchiness of large-scale structure rather than the original team's orientation-focused claim. Sawala counters that the technical mistakes he identified would affect conclusions about either the patchiness or orientation of structures.
Prominent scientists worry about how the mistake passed peer review. David Spergel, president of the Simons Foundation, calls it "disappointing" that the error was not caught before publication. At the same time, experts such as Harvard cosmologist Daniel Eisenstein caution that subtle coding or unit-conversion bugs can persist unnoticed and may be hard for a small set of referees to detect.
Preprints, Embargoes, and Scientific Openness
Sawala has submitted his rebuttal for peer review and circulated a preprint within the cosmology community. The original Nature paper was not posted to preprint servers such as arXiv.org before publication. Many scientists argue that open preprint posting allows broader community scrutiny and makes it more likely that such issues will be found quickly.
Journals and researchers often use embargoes—keeping results confidential until synchronized publication—to maximize media impact. Critics say that practice can reduce early scientific transparency. "I think these embargoes serve the publication more than the science," Sawala says. "And I think the science should come first."
In short, the episode underscores both the importance of careful technical choices in cosmological analyses and the limits of relying solely on traditional peer review for detecting subtle but consequential errors.
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