by Carl J. Wenning
Physics Teacher Education Program
Illinois State University
ABSTRACT
Students rarely have a solid understanding of the nature of science. Because of the expository methods so often used to teach science at the elementary level, students come to accept scientific "facts" on the basis of faith -- faith in a teacher, faith in a textbook. This exercise exposes the failure of teaching science on the basis of authority.
OBJECTIVES
PROCEDURE
After several years of teaching physics and astronomy I have found that a great number of students, perhaps the vast majority, misunderstand the concept of scientific process. Many students accept the "facts" of science on the basis of faith and rarely know or understand the observational framework upon which rest conclusions such as the rotation of the Earth.
Almost without exception, students believe that the Earth is a spinning orb. When asked how they know this to be true, they will often reference a textbook, a teacher, or some other authority. The explanation often boils down to a belief in someone or something. The arguments in favor of the spinning earth turns out to be essentially a statement of faith. Rarely can supposedly "scientifically literate" persons cite viable proofs for the rotation of the Earth.
That the Earth rotates, or spins daily upon its axis, is counterintuitive. We see the sun rise daily in the east, move to the south by midday, and set in the west. Indeed, we speak about "sunrise" and "sunset" as though the sun itself is actually doing the moving.
This activity makes use of several discrepant events to bring students to a rapid realization that their understanding of the nature of science is at best flawed. It also shows them the limitations of their education, in that they have been aquiring beliefs and not constructing knowledge -- belief informed by reason and supported by observation. It's both fun and enlightening to make used of students' "scientific" training to both befuddle and confuse, and make them take a second look at the nature of scientific knowledge as opposed to belief. This procedure is consistent with a constructivist approach to learning.
The activity is begun by the teacher who challenges the students' belief in the rotation of the Earth. When this belief is challenged, many an enterprising student will take groping steps toward providing a scientific proof such as, "We have pictures from space." But does this constitute a proof? To drive the point home I usually respond with a question, "Haven't you seen Star Trek? Do you believe that that's real? Do you believe everything that comes out of Hollywood -- Godzilla, King Kong, Rambo?" The fact of the matter is, pictures can be faked. A picture does not a proof make!
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.
Take advantage of the students' naive Aristotelian understanding of nature to "prove" that the Earth doesn't spin. Ask the following questions and demonstrate the following "proofs."
"If the Earth is spinning, why aren't projectiles left behind? If one were to stand still and throw an object up into the air -- and eraser for instance -- it comes straight back down to the thrower. If one throws an eraser up into the air and one is moving (throw an eraser up and then walk out from underneath it), then the eraser falls behind him. 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. Therefore, the Earth must not be turning!"
"If the Earth is spinning, why don't we feel the motion? When a person rides in a car, on a horse, or in a boat, s/he feels the motion. If the Earth is spinning at 1,100 miles per hour at the equator and about 750 miles per hour at mid-latitudes, why don't we feel the motion? Evidently, it's because the Earth is not in motion!"
"If the Earth is spinning, why don't we perceive winds blowing continually from the east? When one rides a bike, in a car, or on any other form of conveyance, a wind is discernible -- coming from the direction in which one travels. If the Earth is spinning from west to east as scientists tell us, why don't we get a strong prevailing wind from the east? Evidently, it's because the Earth is not in motion!"
"If the Earth is spinning, why aren't the oceans spun off at the equator? Have you ever seen a spinning bicycle tire that has become wet? Water is cast off at the fastest moving part. Now if the Earth spins at 1,100 miles per hour at the equator -- much faster than any spinning tire -- why hasn't the Earth lost its oceans? The Earth still has oceans; therefore, the Earth must not be in motion!"
It's nice to end a lecture with this discussion. These discrepant
"proofs" often leave students all aflutter and genuinely
interested in knowing the nature of a scientific proof -- in particular,
for one that proves the Earth to spin and confirms what they "know"
to be true. Use this shocker as a motivational tool for studying
Newton's laws of motion. Once these laws are examined and explained,
the teacher can return to the above "proofs" and show
the flaws inherent in each.