GRE Reading Comprehension: ETS-GRE阅读ETS - NMMYB7DV148466758

It would be wonderful to observe a singularity (an infinitely dense concentration of matter) and obtain direct evidence of the undoubtedly bizarre phenomena that occur near one. Unfortunately, in most cases a distant observer cannot see the singularity; outgoing light rays are dragged back by gravity so forcefully that even if they could start out within a few kilometers of the singularity, they would end up in the singularity itself.