The mysterious dark energy makes up 68% of our universe. Experimental evidence for dark energy comes from astronomical observations and are a focus point of the astronomy program. Darren DePoy and Jennifer Marshall build astronomical instruments for observatories including the Dark Energy Survey, Giant Magellan Telescope, and Large Synoptic Survey Telescope. Nicholas Suntzeff and Lifan Wang use supernovae to probe dark energy directly, and astronomer Lucas Macri calibrates the cosmic distance scale by using precision measurements of the Hubble Constant. High energy theorists Bhaskar Dutta and Dmitri Nanopolous investigate the theoretical underpinning and potential source of dark energy.