Strange Attractors
Purpose: The purpose of this lab was to investigate whether
the points created by choosing purely random numbers, generated by rolling
a die, would lead to any specific pattern.
Procedure: On the first day of the lab, each student pair received
an overhead transparency with an equilateral triangle drawn on it, an overhead
marker, a ruler, and a six-sided die. The vertices (A, B, and C) of
the triangle were numbered as follows: A = 1 or 2, B = 3 or 4, C =
5 or 6. We chose a random starting point within the triangle and made
a dot with the marker on the transparency. Then we took turns rolling
the die. I rolled first and rolled a three. Then I took the ruler
and found the halfway point between the original point and vertex B and marked
a new point. Next my partner rolled the die and rolled a five. He
took the ruler and found the halfway point between my last point and vertex
C and made a new point. Next it was my turn again. I rolled a
two and used the ruler to mark the halfway point between my partner's last
point and vertex A. We took turns repeating this activity until we
had each had 15 turns. The transparency just looked like a mess of
randomly placed dots. When we looked at the work of the other partners
in our class, their work was also just a random mess. Our teacher put
a blank transparency with just the original triangle on the overhead and
had each pair place their transparency on top, being careful to match up
vertices A, B, and C. We ran out of time the first day, so when we
came to class the next day each group was asked to realign their transparency.
When all eleven groups had placed their transparencies on the overhead,
the teacher turned it on and asked us if we saw any pattern. After
each person recorded their impressions of the pattern, we linked graphing
calculators to download the "Chaos" program from the computer. When
everyone had a copy of the program on their calculator, we ran the programs,
chosing a random starting number. Within a few minutes, everyone started
to see the same pattern on their calculator, except that the patterns on
the calculators were much more clear than the transparencies had been. The
teacher had each pair of partners chose and post five differnent starting
numbers on the board and then run the program with their starting numbers.
Although the class used over 100 different starting numbers, the ending
pattern was always the same. Weird, huh?
Data: Data generated on day one was turned in to the teacher
on our transparency. On day two, my partner and I used the starting
numbers of 5, 27, 43, 119, and 523. All of these numbers generated
the Sierpinski triangle on the graphing calculator.
Results: It was kind of hard to tell on from the hand drawn
data on day one, but when all of the transparencies were placed on top of
one another and lined up, definite clear (empty) and dark spaces appeared
with in the triangle. Most of the empty spaces were sort of triangle
shaped and they varied in size. It was fuzzy but it sort of looked
like the Sierpinski triangle fractal we learned to draw at the beginning
of this unit. The "Chaos" program always generated the same result
no matter what starting number you used or how many iterations you told it
to repeat. Every time it made the Sierpinski triangle.
Discussion: If the layered transparencies with the whole classes
hand-drawn data had not shown results similar to the Chaos program on the
graphing calculator I probably would have thought the program was rigged.
After all, I don't know anything about programming a calculator or
what the program makes the calculator do. But since the hand drawn
data of everyone put together and the program (no matter what starting number
anyone chose to use) made Serpinski triangles, I have to conclude that completely
random data can produce an ordered pattern and strange attractors really
do happen.
Conclusion: Regardless of the starting position chosen, with
enough repetitions finding and marking the midpoints of the random data results
in a drawing of the Sierpinski triangle, so random data can form a non-random
pattern.