BREAKING in cosmology: the Dark Energy Spectroscopic Instrument (DESI) has completed its primary five-year survey, delivering the most detailed 3D map of the Universe ever constructed. Mounted on the NSF Nicholas U. Mayall 4-meter Telescope at Kitt Peak, DESI uses multi-object spectroscopy to measure the redshifts of tens of millions of galaxies and quasars. Each observation captures spectra from up to 5,000 objects simultaneously via robotically positioned optical fibers, enabling an unprecedented data collection rate. So what does “3D map” actually mean here? Astronomers combine two key measurements: * Angular position on the sky (2D) * Redshift (z), which encodes distance via cosmic expansion This converts sky coordinates into a full 3D distribution of matter across billions of light-years. Key scale: DESI mapped more than 47 million galaxies and quasars, tracing structure over roughly 11 billion years of cosmic history. That means we are not just seeing where galaxies are, but...