PHASES OF THE MOON Moon Phases Diagram QUIZ: PHASES OF THE MOON.
1 Phases of the Moon The Phases of the Moon are the variations in the Moon’s appearance as the...
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Transcript of 1 Phases of the Moon The Phases of the Moon are the variations in the Moon’s appearance as the...
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Phases of the Moon• The Phases of the Moon
are the variations in the Moon’s appearance as the Moon orbits the Earth.
• They are due to the changing Sun-Earth-Moon angle through each month.
• The following is the cycle of lunar phases: new, crescent, first quarter, gibbous, full, gibbous, third quarter, crescent, new
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Moon Phases• The Moon orbits
the Earth in about one month (29.5 days)
• Over one orbit the appearance and rise and set times change with the cycle of Lunar Phases.
• The figure is not to scale
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Light & Dark• We only see the Moon because
sunlight reflects off its surface.
• At any one time, half the Moon is always lit and half is in darkness.
• The amount of the illuminated half we see from Earth depends on the position of the Moon in its orbit
• The time of day the Moon is visible also depends on its phase. How the Earth and Moon would
look high above Earth’s North Pole.The figure is not to scale.
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Example: Observing the Moon• Between January 23-25, 2004,
at dusk, the Moon was visible in its waxing crescent phase.
• The first night it appeared close to the Sun. Subsequent nights it appeared higher in the sky (farther from the Sun) and the lit portion appeared to be growing larger.
• What do you think you would see the next night? How about a week later?
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Lunar Phase Terms
We can only see the half of theMoon above and to the right of thediagonal line drawn on the Moonin the figure above.
• The cycle of Lunar Phases starts at the New Moon.
• At New Moon the Moon is not visible to us on Earth.
• From New Moon to Full Moon the illuminated fraction of the Moon we see from Earth grows. It is said to be waxing.
• After Full Moon the fraction of the illuminated Moon visible from Earth shrinks. It is said to be waning.
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The Cycle of Lunar Phases• The Lunar cycle is
split into quarters– New Moon
– 1st Quarter
– Full Moon
– 3rd (or Last) Quarter
• Since the whole cycle lasts about a month each quarter lasts about a week.
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As you view the moon from different directions (relative to the Sun) its appearance changes.
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crosses meridianat sundown
crosses meridianat about 9:00 pm
crossesmeridianat midnight
crossesmeridianat about 3:00 am
crosses meridianat dawn
crosses meridianat about 9:00 am
crossesmeridian at noon
crosses meridianat about 3:00 pm
sunlight
sunlight
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The Lunar Phases Web Tool• This is an interactive tool
that helps illustrate how – the time of day, – the phase of the Moon
and, – the position of the Moon
in its orbit are all related to one another.
• The time that is used in this tool is only an average 6 PM represents sunset, 6 AM represents sunrise, etc.
“Lunar Phases Web Tool” located at
http://www.calvin.edu/~lmolnar/moon/index.html