

Time that Period! 
Objectives
 Students will recognize a periodicity within a set of data.
 Students will learn how to complete and apply the method of Folding to
finding the period of the periodicity.
 Students will apply the method of Folding to determine the periodicity of
pendulums, sample data, and orbits of binary star systems.
 Students will learn an appreciation for basic astronomy and astrophysics
through the exposure of such topics embedded in this lesson.
Grade Level
7th through 12th grades
Summary
This has been developed as a multiday lesson plan. Each lesson
day has been designed to take approximately an hour to complete. The lesson
is broken down as follows:
Prerequisites  Students review the concepts such as "Our
Universe" or "Stars"
Day 1  Students complete a handson lab involving a pendulum and
recognition of periodic behavior.
Day 2  Students apply the method of Folding to determine a period in
sample data and from actual satellite data.
Enrichment  Students learn and apply the chisquare test to determine the period in a set of data.
Prerequisites
Students should know how to graph/plot data and determine the mean from a
set of data. Students should have also been exposed to a variety of
astronomy and astrophysical concepts, such as those discussed in the
"Imagine the Science!" section of this Web site. Information in the
Introduction section of this lesson's Day 2 can also be used.
References
 Kaufmann, William J. III, Universe, Freeman and Company, 1994,
pgs. 336435
 Kerrod, Robin, Encyclopedia of Science: The Heavens Stars, Galaxies,
and the Solar System, Macmillan Publishing Company, 1991
 Kondo, Herbert, The New Book of Popular Science Vol. 1,
Grolier Incorporated, 1982, pgs. 174205
 Sanford, Peter W. and Salton, Jane and Laskarides, Paul,
Galactic Xray Sources, John Wiley and Sons, 1982
pgs. 161162
 Seward, Frederick D. and Charles, Philip A., Exploring the Xray
Universe, Cambridge University Press, 1995
The graphics and other information found within this lesson
can also be found on Imagine the Universe! which is
located on the World Wide Web. The URL for this site is
http://imagine.gsfc.nasa.gov/.
Some of the data was retrieved within The HEASARC Data Archive using
W3Browse which is located on the World Wide Web. The URL for this site is
http://heasarc.gsfc.nasa.gov/.
