With 5,000 tiny robots in a mountaintop telescope, researchers can look 11 billion years into the past.

The light from far-flung objects in space is just now reaching the Dark Energy Spectroscopic Instrument, or DESI, enabling us to map our cosmos as it was in its youth and trace its growth to what we see today.

Now, using the largest 3D map of our cosmos ever constructed, the DESI collaboration has made the most precise measurements to date of how fast the universe has expanded throughout its history. Understanding how our universe has evolved is tied to how it ends, and to one of the biggest mysteries in physics: dark energy, the unknown ingredient causing our universe to expand faster and faster.

Researchers, including University of Michigan scientists, shared the analysis of their first year of collected data in multiple studies published on the open-access repository arXiv and in talks at the American Physical Society Meeting in the United States and the Rencontres de Moriond in Italy.

“DESI has mapped out the expansion history of the universe over the past 11 billion years to unprecedented accuracy. In doing so, it has provided new insights about the behavior of dark energy that causes the accelerated expansion today and whose physical nature remains a key mystery,” said U-M physicist Dragan Huterer. “In the years to come, DESI will be providing invaluable new information about how our universe works.”

Our leading model of the universe is known as Lambda CDM. It includes both normal and dark matter (“cold dark matter,” or CDM) and dark energy (Lambda). Both matter and dark energy shape how the universe expands—but in opposing ways. Matter slows the expansion down, while dark energy speeds it up. The amount of each influences how our universe evolves. This model does a good job of describing a wide variety of cosmological observations.

However, when DESI’s first-year results are combined with data from other studies, there are some subtle differences with what Lambda CDM would predict. As DESI gathers more information during its five-year survey, these early results will become more precise, shedding light on whether the data are pointing to different explanations for the results we observe or the need to update our model. More data will also improve DESI’s other early results, which weigh in on the Hubble constant (a measure of how fast the universe is expanding today) and the mass of particles called neutrinos.

​​DESI’s overall precision on the expansion history across all 11 billion years is 0.5%, and the most distant epoch, covering 8 billion to 11 billion years in the past, has a record-setting precision of 0.82%. That measurement of our young universe is incredibly difficult to make, says U-M physicist Gregory Tarlé.

Please read the rest of the news article and watch the videos here.