7. Stretch your arm out straight in front of you and hold your thumb straight up. Close one eye and look at a distant object.
Without moving your arm (or thumb), switch eyes. What
appears to happen? Measure the distance between your eyes
and the distance between one eye and your thumb. Explain
how, with one other piece of information, you can now use
similar triangles to estimate the distance to the distant object.
What else do you need to know?