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Educational application
Included as an educational resource in many schools around the world
Work done:
Idea, design and development
Technology:
Flash, AS2
Date:07 enero, 2009

Moon phases

Instructions
  • The application is divided into three parts. On the left side we have the controls. In the central part we can observe the earth, moon and sun from space, and on the right side we have the perspective from Earth.
  • Select the place from where you want to observe the moon: northern hemisphere, southern hemisphere or the equator.
  • Move the circle that marks the day of the lunar month to observe the different moon phases.
  • Move the circle that marks the hour to watch the sky at different times.

Sunlight is responsible for both day and night on Earth and for the different phases of the Moon as seen from Earth.

The time of the Moon’s rotation is the same as that of its orbit around the Earth (approximately 29 days), so we always see the same side of the moon. In the application we can see why the far side of the Moon (red in the image), can never be seen from the Earth.

Moon 1Although the sun always illuminates half of the Moon, the illuminated part will vary depending on the day, and is not always visible from Earth. As a consequence we get to see more or less of the illuminated half, and this is what we know as the phases of the Moon.

The time of day when we can see the Moon from Earth is related to the phase which the Moon is in. A first quarter Moon rises at noon, reaches its highest point at sunset and sets at midnight. When the Moon is full, we can see it from sunset until sunrise, that is overnight. A last quarter Moon, begins to be seen at midnight. It reaches its highest point at sunrise and sets at noon. The new Moon rises and sets at the same time the sun does, but we cannot see it because the sun illuminates the far side, the side which is not visible from Earth.

Moon 2When the Moon is near its new Moon phase, with its very small visible part, despite the fact that the time to rise and set are very similar to the sun, we can only see it a little before sunrise when the moon is waning and a little after sunset when the moon is waxing. That’s because, although the moon is virtually in the same direction as the sun, the sun light is too bright to see the moon during the day.

The sun and the moon rise from the east and go down on the west, more to the north in June and to the south in December. These changes in the location of both sunrise and moonrise and sunset and moonset depending on the season are more so the further we are from the Equator.

If we are in the northern hemisphere, we usually look to the south to see the sun and the moon, so east (sunrise and moonrise) is to the left, and west (sunset and moonset) on the right. So we are used to see the apparent movement of the sun and the moon from left to right throughout the hours.

On the other hand, if we are in the southern hemisphere, we usually have to look to the north to the south to see the sun and the moon. In this case, the east is on the right and west on the left, and that is why we get the impression that the sun and the moon are moving from right to left.

The side of the Moon and its phases also vary depending on our location on Earth. As the east and west are inverted in one hemisphere over another, the phases of the moon are also reflected. In the northern hemisphere the first quarter looks like a growing D, while in the southern hemisphere it looks like a C. In the northern hemisphere the last quarter looks like a C, while in the southern hemisphere looks like a D.

Moon 3And what happens at the equator? At the equator we can look in any direction to see the sun and moon. Their highest points will be vertical, neither northward nor southward. Moon rising at midnight in the fisrt quarter in the equatorIn the application I have decided to put it as the perspective of the northern hemisphere because we are more accustomed to this position, although I could have chosen the other way around. In places close to the equator the first quarter will have the shape of the letter n (inverted U) when it rises, and the shape of letter U when it sets, while the last quarter would seem like the shape of letter U when it rises and the shape of the letter n (inverted U) when it sets.

The application can be of help to understand the previously outlined concepts, but we must bear in mind that the distances and proportions are not respected due to space issues. Rising and setting times are also approximates, and vary depending on the season and the place where we are. Despite this, this application can help to broadly understand the phases of the Moon, their times, their appearances and what causes them.


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  1. Rita Fowler Responder

    This is brilliant. I have always wondered how it worked and now I sort of understand. We have a charity in Kenya

    and I had noticed that the moon was higher in the sky and now I know why. Thank you. Rita

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