DESI is an ambitious project using 5000 tiny robotic fibers to map the cosmos back 11 billion years. It is collecting light from distant galaxies and quasars to create the largest 3D map of the universe’s structure and expansion history.

DESI’s first year data provides unprecedented precision in measuring how fast the universe expanded over time. Understanding how our universe has evolved is linked to how it ends, and to one of the greatest mysteries of physics: dark energy, the unknown ingredient that makes our universe expand faster and faster.

However, subtle differences are seen when combined with other data, compared to what our main Lambda CDM model predicts. As DESI gathers more data, these results will help show if we need to modify the model.

The Lambda CDM model includes both normal and dark matter, which slow expansion, as well as dark energy that accelerates it. But dark energy’s physical nature remains a mystery. DESI’s precision may offer new insights into dark energy’s behavior and help solve this key puzzle.

Researchers also hope to better measure the Hubble constant and neutrino masses. Understanding neutrinos’ tiny masses could reveal new physics, since they subtly affected the early universe despite rarely interacting. DESI may provide the most stringent limits yet on their masses from cosmological data alone.

DESI involves over 900 scientists worldwide. Its robotic positioners each night map galaxies and quasars farther than ever before seen. Spectra reveal objects’ velocities and distances, allowing expansion measurements over time. Researchers use subtle galaxy clustering patterns like baryon acoustic oscillations as a “cosmic ruler” across billions of years.

Future goals include mapping 3 million quasars and 37 million galaxies. Quasars illuminate gas clouds farther than galaxies, extending measurements to the earliest epoch. Careful analyses account for uncertainties to enable robust model comparisons. Statistical techniques extract the tightest cosmological constraints possible from DESI’s unprecedented data volume and resolution.

DESI promises to characterize the universe’s evolution with unmatched fidelity. Its wealth of information on dark energy, dark matter, and neutrinos will test physics at the grandest scales.

By charting cosmic history with greater power and precision than ever thought possible, DESI aims to resolve lingering mysteries and shed light on the ultimate fate of the universe.


Lauren Biron, The most precise measurement of our expanding universe (University of Michigan) | DESI Early Data Release Studies

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