Our leading model of the universe is known as Lambda CDM. It includes both a weakly interacting type of 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 and dark matter slow 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 results from previous experiments and how the universe looks throughout time.
But, with just its first year of data, Dark Energy Spectroscopic Instrument (DESI) has been able to analyze the expansion history of the young universe with over 99% accuracy. The data from DESI has provided unprecedented measurements of the expanding universe, offering new insights into dark energy. When results are combined with data from other studies, there are some subtle differences with what Lambda CDM would predict. There are some hints pointing at small temporal variations in the density of dark energy.
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.
