The Lyman-Alpha Forest is a series of Absorption Lines in Electromagnetic Radiation (EMR) from distant galaxies and Quasars (QSO) consisting of Lyman Alpha (Ly-α), the first Spectral Line of the Lyman Series (121.6 nm), Redshifted (z) to various degrees. As light passes through intervening Intergalactic Medium (IGM) clouds including neutral Hydrogen (H) (HI Region (HI)), radiation is absorbed, and by recognizing and measuring the shifted Lyman-alpha lines, characteristics of the intervening clouds can be determined including location and size. This is useful for studying the Large Scale Structure (LSS) of the universe. The Baryon Oscillation Spectroscopic Survey (BOSS) survey uses this technique to find evidence of Baryon Acoustic Oscillations (BAO).
Large Scale Structure (LSS)