Wu says these distant galaxy clusters are like houseflies flitting through a dark room--they're incredibly hard to see. But if the wall behind the flies were to emit light, their silhouettes would be revealed. "The CMB acts as this kind of backlight to galaxy clusters," he explains.
吳俊輝形容，這些距離地球非常遙遠的星系團，就如同在黑暗房間飛行的蒼蠅，很難被發現；但如果蒼蠅後面的牆會發光，它的身影就會被背景光所投射出來而無所遁形，「宇宙背景輻射就是照亮這些星系團的『背景光』。」