located just south of groom lake, what secret location became a bit more visible when google maps offered satellite images of the grounds? >> i don't think i can risk it here. i'm stuck between a couple. i think i'm gonna jump the question. >> okay, question's out of play. you don't have to answer it. let's see what the correct answer is. area 51. >> okay. >> is that one of the ones you were considering? >> yeah, yeah. >> okay, let's see what you jumped over here. hopefully, not too much. ouch. [audience groaning] okay, well, that's out of play but by jumping the question, you are one question closer to the million. >> that's right. >> now just 12 away. "real deal" is your next category. biting gold coins and checking for tooth imprints was an old way to verify their authenticity due to the metal's high degree of what?