Provide the theme summaries for the following conversation: 

#Person1#: There are so many people that the tickets are all sold out!
#Person2#: Luckily we got the last two.
#Person1#: Look, Danny. The Four Great Inventions!
#Person2#: Gunpowder, compass, the paper making, and the printing.
#Person1#: I really admire those who made such great inventions!
#Person2#: May, I don't see why they are great. They are just simple things.
#Person1#: They look simple today. But they were milestones in their times.
#Person2#: Milestones? May, you must be kidding.
#Person1#: Just think Bill Gates, those inventions are as important as the windows system.
#Person2#: Well, I suppose the ancient inventors made a lot of money out of them.
#Person1#: No, quite the contrary.
#Person2#: Why? Didn't you say that they were milestones?
#Person1#: Yes, but they went to the public without any patent protection.
#Person2#: Well, their inventors were not as clever as Bill Gates.

Summary: 
May and Danny got the last two tickets to an exhibition. May thinks the four great inventions are impressive while Danny disagrees.