# Mile-Long Xylophone

Well, we’re not sure it’s a full mile, but it could be the world’s longest xylophone. In this video (which is actually an ad for a cellphone), we see and hear a ball roll down a really long row of wooden steps. The steps are actually bars of all different lengths, so as the ball hits each one, it makes a cute plinking musical note, just like a mallet hitting a xylophone. So the ball plays a whole song, a famous grown-up piece called “Jesu, Joy of Man’s Desiring”. Think of all the work to cut hundreds of pieces of wood the right length, line them up in order, and then nail them to the ramp. It takes homemade musical instruments to a whole new level.

Wee ones: Shorter bars play higher notes than longer bars. Which one plays a higher note, a 6-inch bar or an 8-inch bar?

Little kids: The ball knocks other balls down tunnels of smaller bars to play faster notes. If a tunnel has 2 sets of 10 wooden bars, how many bars is that? Bonus: If all the tunnels have 20 bars and 3 balls each do this trick, how many notes do those 3 balls play altogether?

Big kids: The ball plays about 3 notes each second. How many does it play in 1 minute? (Reminder: A minute has 60 seconds.) Bonus: How many notes does it play over the 2 minutes and 2 seconds, assuming all the same quick notes?

The sky’s the limit: If each regular step brings the ball 6 inches forward and takes 1/3 of a second, how far does the ball travel in a 2-minute song?