Trivia: When Scotty orders the blackout on the planet, the camera looks at Chekov's hands. It is a re-used shot of his hands from Season 2 Episode 4 "Mirror, Mirror."
Trivia: The caves where the Children of the Son hide out are located right below the famous Hollywood sign.
Answer: Kirk was getting his physical and Dr. McCoy probably turned off communications, because if he hadn't, Kirk would have left and headed straight for the bridge, leaving McCoy irritated.