Sounding the dark cosmos

Sound waves travelling through the relativistic plasma during the first million years of the universe imprinted a preferred scale in the density of matter. We now have the ability to detect this characteristic fingerprint in the clustering of galaxies at various redshifts and use it to measure the acceleration of the expansion of the universe. A proposed new instrument, the Wide-Field Multi-Object Spectrograph (WFMOS), would use this test to shed significant light on the true nature of dark energy, the mysterious source of this cosmic acceleration. WFMOS would also revolutionize studies of the kinematics of the Milky Way and provide deep insights into the clustering of galaxies at redshifts up to z similar to 4. In this article we discuss the recent progress in large galaxy redshift surveys and detail how WFMOS will help unravel the mystery of dark energy.