Why do stars twinkle? Our atmosphere is to blame as pockets of slightly off-temperature air, in constant motion, distort the light paths from distant astronomical objects. Atmospheric turbulence is a problem for astronomers because it blurs the images of the sources they want to study. The telescope featured in this image, located at ESO��������s Paranal Observatory, is equipped with four lasers to combat this turbulence. The lasers are tuned to a color that excites atoms floating high in Earth’s atmosphere — sodium left by passing meteors. These glowing sodium spots act as artificial stars whose twinkling is immediately recorded and passed to a flexible mirror that deforms hundreds of times per second, counteracting atmospheric turbulence and resulting in crisper images. The de-twinkling of stars is a developing field of technology and allows, in some cases, Hubble–class images to be taken from the ground. This technique has also led to spin-off applications in human vision science, where it is used to obtain very sharp images of the retina.