Baryon Acoustic Oscillations with galaxies, combined with Cosmic Microwave Background data (in the framework of the Friedman-Lemaitre-Robertson-Walker solution to Einstein's General Relativity) provide today the most precise determination of cosmological parameters.
The Universe is a big expanding Void in which matter, dark and luminous has grown from initial density perturbations to the observed pattern in the sky. Galaxies as observed in redshift space, display a web-like structure, the Cosmic Web, with clusters, filaments, sheets and voids.
I will discuss our evidence for a Baryonic Acoustic Oscillation signal with voids from SDSS BOSS data, and how we can combine with galaxy information to improve cosmological parameter determination.