And I went to see one of these experiments, and this is actually -- you can barely see it, and the reason for that is it's entirely dark in there -- this is a cavern that was left behind by the miners who left this mine in 1960.
Eu fui ver uma destas experiências, e isto mal se pode ver, porque está totalmente escuro lá dentro. É uma caverna abandonada pelos mineiros que deixaram esta mina em 1960.