Carol was absent-minded and a little slow on the uptake.卡萝尔心不在焉，反应有点迟钝。I often do absent-minded things, particularly when I'm worried.我常做些心不在焉的事，尤其是在我焦虑不安时。In his later life he became even more absent-minded.他晚年变得愈加...
By measuring the motion of the galaxies in a cluster, astronomers can infer the cluster's mass.通过测量星系在一个星系团内的运动,天文学家们可以推定这个星系团的质量。They turned their telescopes towards other nearby galaxies...他们把望远镜转向附近其他星系。Space fli...