What does this equation mean?

A third, independent method has entered the field in the past two decades: baryon acoustic oscillations imprinted not on the CMB but on the later, three-dimensional distribution of galaxies themselves. The same sound waves that set the CMB’s acoustic scale also left a faint, statistically detectable preferred separation between galaxies — a standard ruler that can be measured at many different cosmic epochs by surveying galaxy positions and redshifts in bulk. The Dark Energy Spectroscopic Instrument, operating at Kitt Peak with roughly five thousand robotically positioned optical fibers that can each be aimed at a separate pre-selected galaxy or quasar every exposure, released its first-year cosmological results in 2024 from more than six million extragalactic objects across redshifts from 0.1 to 4.2. Combined with a Big Bang nucleosynthesis prior on the baryon density and the CMB-measured acoustic angular scale, DESI’s first-year analysis returned a matter density of $\Omega_m$ = 0.295 $\pm$ 0.015 and $H_0$ = 68.52 $\pm$ 0.62 kilometers per second per megaparsec [ 8 ] — a value between the CMB-only and local-ladder numbers, and, notably, mild evidence favoring a dark energy equation of state that evolves with time rather than the constant value assumed by the simplest Lambda-CDM model. That evolving-dark-energy hint is preliminary: it depends on which combination of datasets is used and has not reached the standard of evidence the field applies to a genuine model revision. It is reported here as exactly that — an early, statistically interesting signal under active follow-up, not a settled result.