[Rocky]

It's a good thing the aliens have divided their circles into the same size arcs as we have (60x360). That number must have universal significance. Without it, we would have never decoded their intentions. It's also a good thing we invented tin foil in time for this. If the aliens had come two hundred years ago, we'd be their slaves for sure.

[SwinneySwitch]

Lead foils them as well as or better than aluminium or tin!