translation.en: And the reason why they have to go underground is that, if you did this experiment on the surface of the Earth, the same experiment would be swamped by signals that could be created by things like cosmic rays, ambient radio activity, even our own bodies. You might not believe it, but even our own bodies are radioactive enough to disturb this experiment.
translation.zh: 之所以要到地下需找的原因是 如果在地球表面做同样的实验， 会被其他的信号干扰 比如宇宙射线 以及周围的无线电干扰， 甚至是人类的身体。你可能不相信， 但是我们的身体具有的放射性也足够去影响这项实验了