Chapter 10.2, Problem 1aT

Close one eye and lean down so that your open eye is at table level. Have your partner drop very small piece of paper (about 2mm square) onto the table.

Hold one figure above the table and then move your finger until you think it is directly above the piece of paper. Move your finger straight down to the table and check whether your finger is, in fact, directly above the paper.

Try this exercise several times, with your partner dropping the piece of paper at different locations. Keep your open eye at the table level. After several tries, exchange roles with your partner.

How can you account for the fact that when your finger misses the piece of paper, your finger is always either in front of the paper or behind it, but never to the left or right of the paper?