To explain this, they hypothesise that galaxies must contain a great deal of missing matter which cannot be detected. 为了解释这一点，他们假定各星系一定包含了大量无法探测到的不明物质。
Bilingual Time: Why do you think buskers are so popular in Europe?《双语时代》: 你认为,街头艺人在欧洲非常受欢迎的原因是 什么 ?Many buskers choose subway tunnels because of the interesting sound effects.许多街头艺人选择地铁通道是因为那里有趣的声音效果.Also respect the spa...