# Time

## The Geologic TimeString

#### Steven Ferris

 Target age or ability group: All ages and abilities. Class time required: The initial use of the TimeString will require about 10 minutes. Materials and equipment: About 5 meters of nylon cording (or similarly stout string). Summary of activity: This is a tool which will help students comprehend the immensity of Earth history and life's changes throughout those many millions of years. It is suggested that the teacher keep several TimeStrings handy throughout the classroom so that, when questions relating to geologic time arise, they can be readily answered. Teacher instructions The TimeString involves very simple technology--a string. The string is 4.6 meters long and, on the string, each millimeter represents one million years. I have tied three knots in the string. Knot (A) is 65 millimeters from the NOW! end; Knot (B) is 250 millimeters from the NOW! end; Knot (C) is 570 millimeters from the NOW! end. Knot (A) represents the Cretaceous/Tertiary (K/T) boundary, knot (B) represents the great Permian/Triassic (P/T) extinction, and knot (C) symbolizes the end of the Precambrian and the beginning of the Paleozoic Era.

Concepts relating to geologic time are among the most difficult for students to grasp simply because the amount of time involved is so great. The TimeString will help stu-dents understand geologic time and will also combat illiteracy with regard to all kinds of large numbers--I have even used it to communicate the size of the national debt of this country. You should use it to show geologic time's huge size--something a text-book cannot do.

My students become very familiar with the TimeString. I have overheard them talking about the string and whether a particular event would "register" on the string. As I have explained, the 65 million years of the Cenozoic are represented by 65 millimeters of cording. The students can see and feel this time and develop a real sense of the huge scale involved. In one activity, I moisten the tip of the string by touching the Cenozoic end to the tip of my tongue. I then vigorously dry off the end and tell them that the moisture that remains represents the extent of recorded history.

This simple string tool is useful to me during many parts of the school year. Of course, I use it extensively to introduce Earth history and the fossil record, but it lends itself to helping define the limits of the discussion of evolution. I suggest to my students that we confine the evolution discussion to that amount of time represented by the last 3.5 meters of string--evolution is not the beginning of the Solar System nor is it the begin-ning of the Universe. Really, evolution is not about the origin of life; rather, it is the process of change which life has undergone since its origin. Defining the parameters of the concept has helped my classes concentrate on what biological and geological sci-ence can tell us about the history of life.

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