CIESE - Tycho Brahe's Observatory

The copyright on "Tycho Brahe medal" is held by the Museum of the History of Science, Oxford, U.K.

LESSON 5: THE SUN/EARTH/MOON SYSTEM

CONCEPTS
The earth is in orbit around the sun.
Earth’s rotation on own axis produces day & night.
Earth’s axis is tilted at 23.5° relative to plane of ecliptic.
Earth’s revolution around sun, together with tilt, produces seasons.
The moon is in orbit around the earth.
Progression of moon’s phases reveals position of moon in its orbit.
The moon rises in the East and sets in the West, indicating that the Moon’s daily journey across the sky occurs because of earth’s rotation.
Day by day, the moon’s position is farther east, indicating that its revolves around the earth to the east.
We can further determine the direction of moon’s trajectory in its own orbit by observing the moon against the “fixed background” stars.
Moon’s rotation is synchronous with its revolution.
Plane of moon’s orbit is slightly inclined relative to earth’s orbit.
Moonlight is reflected sunlight.
The illuminated area we see depends on the relative positions of sun, earth and moon.
Establish generalized rising & setting times of the moon at different phases.

PERFORMANCE OBJECTIVES
Learners will be able to explain and demonstrate rotation & revolution of the earth
Learners will be able to draw upon the formal explanation to account for the moon as it appears in the sky; they will be able to anticipate phases.

MATERIALS

GLOBES
BALLS TO REPRESENT THE MOON
LAMPS

PROCEDURES
MOTIVATION
Having drawn on learners’ own observations to explore and make meaning of the phases of the moon, most are receptive to explanations for what they see. (I try to strike a balance between those learners who seek an explanations before they examine the evidence and those learners who want to figure it out for themselves. This balance becomes fodder for a discussion of differences in learning styles and implications for teaching. It challenges me to find alternative ways to present facts and concepts (i.e., readings, museum visits, mini-lectures, videos, etc.)

ACTIVITIES
I have tried, in the past, to have learners deduce the relative positions of sun, earth and moon from their observations and work with models, summarizing it all in a tidy lecture on the orbits at the end of the project. Starting anew this semester, I am planning to weave formal explanations of parts of the system into many class sessions and to ask the learners to try to visualize particular aspects of the system through the evidence they will be collecting in their journals.
I have assigned Greek letters to label the activities to indicate that the order might vary. For example, lesson d, on the planets, might be timed to coincide with a planetary event. (See Sky pointers)

ACTIVITY A. Presentation of fundamental framework and definitions.
With models, demonstrate earth’s rotation on own axis, revolution around the sun, and tilt relative to the ecliptic, to account for day and night, and seasons.
Demonstrate moon’s orbit around earth.

ACTIVITY B. Angle of the crescent.
After learners have investigated sunlight and shadow with models (Lesson 3), demonstrate it. I might present this about the time of the first quarter when the moon appears in the daytime sky.

ACTIVITY C. Presentation of succession of phases.
After students have ample empirical evidence of the phases, demonstrate the phases using a model of the sun / earth / moon system.

Demonstrate angle of plane of moon’s orbit relative to plane of the ecliptic; explain eclipses.

Provide generalized rising and setting times.

ACTIVITY D. Plotting moon’s position relative to other objects in sky.
This term I might present this in time for the students to appreciate the bright Venus at the end of February.
Earth in orbit around the sun: what portion of the sky is visible at night?
Day to day. Season to season.
The system of planets. Planets visible to the naked eye. Record the moon in proximity to plants.

ASSESSMENT / EVALUATION
OBSERVATIONS IN THE FIELD
Do learners show the ability to reconcile observed events with formal description.
Evaluation of moon journals
Precision of observation – I expect observations to improve as the details assume meaning to learners. Therefore I will look for consistency of the record with sky events.
Detail of record – What understanding do the entries reveal of relative positions of the sun – earth – moon?

Go to lesson 1, lesson 2, lesson 3, lesson 4.