What are the speakers talking about?

M: I have a question. I’m never quite sure where to sit during a business meeting.
W: The ancient Chinese art " Feng Shui" teaches that you should never sit with the door behind you—and actually there’s a scientific reason for that. When a person’s back is placed towards an open space he becomes stressed: his blood pressure increases and his heart beats faster.
M: That makes sense! People subconsciously worry about getting attacked if they don’t know what’s going on behind them.

W: Many famous people discovered important things when they were just sitting silently by themselves... you know the story about Isaac Newton, right?
M: Yes, He came up with the theory of gravity while sitting in a field and seeing an apple fall from a tree.
W: He probably wouldn’t have had time to think about gravity if he was talking on his cell phone. Anyway, I really hope they don’t allow cell phones on planes. We need a few last places without cell phones’.