2.1 Time of Day Tutorial

Introduction | Tutorials: 1) Time of Day ; 2) Time of Month ; 3) Direction | TOOL AND QUIZ | Beyond the Basics | Credits | For Teachers

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We begin our discussion of the lunar phases diagram with the positions of the Earth and Sun. We view the Earth, which is fixed in the center of the diagram, from above the North pole. You can spin the Earth on its axis by clicking on one of the two rotation buttons (one for clockwise motion, one for counterclockwise). Try this! A red stick figure is standing on North America, and a red line marks the horizon viewed by this figure. This defines the directions up (above the head) and down (below the feet) for the diagram. Note that these directions are not fixed, but rotate along with the Earth.

The Sun is fixed at a position far to the right of the diagram. It is marked by the parallel rays of sunlight coming from that direction.

We can now label the time of day, which is determined by the direction to the Sun as observed by the stick figure. For example, move the Earth until the word "Noon" is above the figure. Note the sunlight is coming from directly overhead. Now move the Earth counterclockwise until the figure is by the word "6 PM". Notice the sunlight is coming in parallel to the horizon. That is, the Sun is now setting. We can now define the directions East and West by recalling that the Sun rises in the East and sets in the West. The end of the horizon pointing towards the setting Sun is labelled "W", while the opposite end is labeled "E".

As a final check that you understand the connection between time of day and the orientation of the Earth, select a time of day from the menu on the right. The stick figure will jump to the orientation for that time.

Lunar phases web tool site map

  1. Introduction
  2. Tutorial
    1. Time of Day
    2. Time of Month
    3. Apparent Direction of Moon
  3. Lunar Phases Tool and Quiz
  4. Going Beyond the Basics
  5. Credits and Feedback
  6. Note for Teachers