The activity is begun by the teacher who challenges the students' belief in the rotation of the Earth. The fact of the matter is, pictures can be faked. Challenging students' ignorance of science can prove to be a powerful motivational tool, especially when dealing with long-held beliefs. The ultimate goal is to exhibit the nature of a scientific proof and to demonstrate that we cannot depend merely upon faith in authority figures to determine whether or not something is true. Clearly, when a person stands upon the Earth and throws an eraser up into the air, it comes back to the person who threw it.
Water is cast off at the fastest moving part.
It's nice to end a lecture with this discussion. Use this shocker as a motivational tool for studying Newton's laws of motion.