Sunyaev-Zeldovich Effect (IMAGE) University of Chicago Caption The South Pole Telescope uses a phenomenon called the Sunyaev-Zeldovich effect to pinpoint when dark energy became important in the history of the universe. The SPT measures the slight temperature difference associated with the SZ effect to produce an image of the gas in a galaxy cluster. The deep dark spot in the middle of the images is the SZ effect from a cluster of galaxies. Credit John Carlstrom/South Pole Collaboration Usage Restrictions News organizations may use this image in connection with reports about the University of Chicago's Kavli Institute for Cosmological Physics and the South Pole Telescope. License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.