Modeling Day and Night

View from space shows the terminator on the Earth and moon.
Courtesy of NASA.
- Grades:
- Length: 60 Minutes
Overview
Earth rotates completely on its axis about every 24 hours. This rotation, in combination with Earth’s position relative to the sun, produces the cycles of day and night. In this lesson, students make a “mini-globe” to investigate the causes of day and night on our planet.
This activity is from The Science of Sleep and Daily Rhythms Teacher's Guide, and was designed for students in grades 6–8. Lessons from the guide may be used with other grade levels as deemed appropriate.
- Teacher
Background - Objectives and Standards
- Materials and
Setup - Procedure and
Extensions - Handouts and
Downloads
Teacher Background
Our lives, and those of other organisms on Earth, are shaped in countless ways by the cycle of day and night. This repeating sequence of light and darkness is caused by the spinning of our planet and its position relative to the sun.
Earth, like other planets in our solar system, revolves around the sun in a slightly elliptical orbit. It takes about 365 days—one year—for Earth to go around the sun. Other planets require more or less time to complete their orbits, and their years are correspondingly longer or shorter than Earth’s. In any case, a year is defined as the amount of time it takes a planet to make one complete revolution around the sun.
As Earth orbits the sun, it also rotates, or spins, on its axis. It takes about 24 hours—one day—for Earth to complete a single rotation. As students will discover through the activities in this unit, the functions of living organisms on Earth are linked to this 24-hour cycle.
During each 24-hour period, most locations on Earth will experience several hours of sunlight (day) followed by a period of darkness (night). Solar noon is the moment at which the sun reaches its highest point in the sky in a given location. It rarely coincides with the “noon hour” on a clock. Many factors—location (longitude) on Earth, time of year, time zone, and whether daylight savings time is in effect—influence what “clock time” it will be when solar noon occurs. Midnight occurs 12 hours before and after noon.
As viewed from the North Pole, Earth spins counterclockwise. This is why the sun appears to rise in the east and set in the west. In reality, of course, the sun remains relatively stationary, while Earth rotates in its orbit. The following activity uses a simple model to help students visualize Earth’s rotation about its axis, the slight tilt in Earth’s axis, and the cycle that produces day and night.
Related Content
-
Earth Moon Cycles
Presentation
How does Earth move within the Solar System? What causes the phases of the Moon? Brenda Lary, MS, covers basics about the relative motion and positions of Earth, the Sun and the Moon.
-
Phases of the Moon
Presentation
Dr. Greg Vogt explains how to create and use models to teach students about the phases of the moon.
-
Sleep and Daily Rhythms
Teacher Guide
Students explore the day/night cycle and seasonal cycles on Earth; create and use sundials; and investigate circadian rhythms, sleep patterns and factors affecting the quality of sleep. (8 activities)
Funding
National Space Biomedical Research Institute

This work was supported by National Space Biomedical Research Institute through NASA cooperative agreement NCC 9-58.