Look at that little ball go.

 
Watching and watching.
Way back when our youngest daughter-40 was only youngest daughter-3 Sheba(aka spouse) and I took youngest daughter to the science museum in Boston.  This was back when Sheba was in grad school at Simmons College 1986. 
When you enter the main lobby of the science museum there was a large square glass case that had, for a lack of a better term, three-dimensional kinetic art inside the glass cabinet.  A square glass cabinet that stood approximately eight-feet high.  Art that with a little metal ball moves up and down and up and down and up and down again and again. Youngest daughter 3 would stand as close as she could with fingers on the glass and watch with rapt attention.  
A small steel ball about the size of a golf ball would be released at the top and start it’s convoluted descent to the bottom.  Now, I may not have this right but the ball was released on to a spiraling down track to build up momentum and then bump a buzzer switch, then drop down bouncing on to five or six metal plates.  Plates tuned like a xylophone and each plate with its own musical note.  Ping, pang, pong, and boing.  Then the little metal ball would find its way down through a descending maze of slots touching a beeping beeper each stop as it made its way down.  On and on it went until it hit bottom and rolled in to a little elevator and rose to the top and started the whole beeping, buzzing, and ponging process all over again and again and again, etc.
And yet, youngest daughter-3 stood there and stood there.  After about 30-minutes of watching the little ball descend and make it’s way to the bottom and back up, youngest daughter-3 was still mesmerized and would probably would have watched until the cows came home or the museum closed in the late afternoon.  Or whichever came first.
I will have to admit the clinking clanging moving art cabinet was fun to watch.  Almost as fun as watching the little three-year-old watcher.  Beep, Boink, ping, pang, and bonk.