An essential element in learning any subject is relatively of the subject matter to the learner. By comparing two ideas, on concrete and one abstract, the learner can easily create logical deductions about the information presented. In science education many times students are confronted with extremely large measurements and values. How much more is 500 billion that 500 million?, what is the relationship between the distance between the Sun and the Earth as opposed to between Earth and the edge of our solar system. These are just two examples that can confuse a student who is attempting to reasonably deduce an answer to a real world problem. By relating abstract values to known similar values, we as teachers provide the student with a concrete mental image in which they can use to ‘measure’ other problems.
One of the most common subjects in an Earth-Space Science classroom is the age of the Earth, or the Geologic Timeline. This representation has several methods. It has been done by rolling out a roll of toilet paper, adding machine tape, or similar tool. The problem that I see with this method is that the length of the tape is arbitrary to the student. Yes, I agree that this method visually represents the time periods as compared to each other but it does not represent those spaces in relation to a real-world scale.
Secondary students tend to have a limited view of time. One of the most tangible timescales to a youth is that of their own existence. They can readily relate their own experience in segments of baby, toddler, preschool, etc. By essentially placing these scales side by side, this exercise provides the ‘reason-ability’ tool that they can use when assessing other problems.
"If I were the same age as the Earth, how old would I have been when...." Students are shocked to find out how recent our human history has occurred when put in this perspective.