answer: May and #Person1# are visiting the Hall of Ancient China. May tells #Person1# the glass boxes and the vacuum inside are used to protect historical relics.
documents: #Person1#: May, is this the Hall of Ancient China?
  #Person2#: Yes. Look at these historical relics here, amazing!
  #Person1#: Why are they all in glass boxes?
  #Person2#: For protection. Some relics will turn to dust if exposed to air.
  #Person1#: So there isn't air in the glass boxes?
  #Person2#: No, there isn't. There is a vacuum in every box.
  #Person1#: I wonder how old these things are. Thousands of years?
  #Person2#: Yeah, they all come from a very ancient time.
  #Person1#: Hey, look at the tripod. I've seen it on TV.
  #Person2#: It was made 4, 000 years ago. It's priceless!