Baryon acoustic oscillation

Investigating the nature of the “dark” vacuum energy (DE) that’s presumed to drive the present acceleration of the cosmic Hubble expansion requires tying the redshifts z of distant objects to independent measurements of their distances. One such method involves measuring both z and celestial position for large numbers of galaxies, in search of a spatial-correlation feature of known length at different values of z. That baryon-acoustic-oscillation (BAO) correlation length is attributed to sound-like waves in the early universe’s hot-plasma epoch. At the epoch’s abrupt end, the plasma waves became density fluctuations of ordinary “baryonic” matter that remain imprinted on the spatial distribution of galaxies (see Physics Today, April 2008, page 44). How the BAO correlation length at any particular z looks from here and now (z = 0) measures our distance from that z. The Baryon Oscillation Spectroscopic Survey (BOSS) collaboration has now reported its...