Abstract: Dark energy is a phenomena causing the Universe to expand more rapidly than can be explained by Einstein's laws of gravity. Its discovery merited the 2011 Nobel Prize in Physics. The effects of dark energy imprint on large galaxy maps. The Baryon Oscillation Spectroscopic Survey (BOSS) on the Sloan Telescope has mapped 200 million galaxies in 2-D, and 1.5 million galaxies and quasars in 3-D. We measure the scale of the universe to percent-level precision at redshifts z=2.4, z=0.6 and z=0.3, from the deceleration to acceleration driven by dark energy. Recent maps are consistent with the "simplest" modification of Einstein's laws, the additional of a cosmological constant.