发现恒星围绕银河系中心的超大质量黑洞运行是天体物理学的一个转折点。
The greatest thing you'll ever learn is just to love and be loved in return.
In the end, survival is not about how much you have, but how well you can use what you have.
解释:货卖完了才知道不足,是由于不懂得计量;事情结束了才知道有余,是由于不懂得调节。