text version - The Moon: Phases of the Moon
Phases of the Moon
- We always see the same face of the Moon because the Moon day is
the same length as the Moon year.
- This is because the Moon's rotational period is the same as it's
orbital period.
- The phases of the Moon, or the different shapes of the Moon,
are caused by the different angles from which we see the
illuminated part of it's surface.
- Half of the Moon is always illuminated, we just cannot always
see all of the illuminated part of the Moon.
- When the Earth, Sun, and Moon are nearly in a straight line,
with the Earth in the middle, we have a
Full Moon.
- When the Earth, Sun, and Moon are nearly in a straight line,
with the Moon in the middle, we have a
New Moon.
- Just after and before a New Moon, the dark portion of the Moon is slightly illuminated by earthshine.
- Earthshine is caused by sunlight reflected from the Earth to the Moon and back to the Earth.
The Lunar Month
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