随机实验是因果推理的黄金标准，但它们并不总是可行的。
"Randomized experiments are the gold standard for causal inference, but they are not always feasible."
艺术提供的是空间——一种精神的喘息空间。
The study of black holes has revolutionized our understanding of space and time.
The pain of parting is nothing to the joy of meeting again.