# Moon Phases and Eclipses

In Texas, teachers are expected to teach the phases of the Moon, both as an example of an observable pattern of change in the sky (2nd through 4th grades), and as a part of understanding the nature and orbit of the Earth-Moon system (5th grade and up).

This can be a difficult subject to teach; if teachers attempt to teach the causes of the changing phases too early, students who are unable to conceptualize a three-dimensional model of the Earth-Moon-Sun system will create their own preconceptions.  Also, many adults have mistaken notions of the causes of the phases of the Moon, and have confused eclipses with some phases.

2.7 D: The student is expected to observe, measure, and record changes in weather, the night sky, and seasons.
4.6 A: The student is expected to identify patterns of change such as in weather, metamorphosis, and objects in the sky.
5.6 A: The student is expected to identify events and describe changes that occur on a regular basis such as in daily, weekly, lunar, and seasonal cycles.
7.13 B: The student is expected to relate the Earth's movement and the moon's orbit to the observed cyclical phases of the moon.
8.12 A: The student is expected to analyze and predict the sequence of events in the lunar and rock cycles.

Note that while none of these includes the term “eclipses,” there have been TAKS tests incorporating eclipse models to test the students’ understanding of the nature of science.

Preliminary Concepts
Before students can learn the names of the phases of the Moon, they will need to understand the term “crescent” which is not used as often today as in the past.
In order to understand the reason for lunar phases, the students need to understand that the Moon orbits (revolves) around the Earth, and takes about a month (27.3 days) to make a complete orbit. The students also need to understand that half of the Moon’s surface is lit at any time by the Sun.
In order to understand why eclipses do not happen every month, the students first need to understand that the Moon orbits the Earth at an angle to the ecliptic. Students should also model out the size and distance of the Earth and Moon before covering eclipses; there are a few good activities to do this: http://ares.jsc.nasa.gov/Education/activities/ExpMoon/DistanceMoon.pdf and How Far Is the Moon

Misconceptions and Educational Research