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.
Mindezt azért kell a föld alatt végezniük, mert ha a föld felszínén végeznék ugyanezeket a kísérleteket, akkor a kozmikus sugarak a radioaktív sugarak, sőt, hihetetlen, de még az emberi testek radioaktivitása is megzavarná.