the moon: earth’s only natural satellite phases and eclipses
TRANSCRIPT
Like the Earth and the other planets, the Moon is illuminated by the Sun.It has a day-side and a night-side of equal size.
North Pole
MOON (from above)
• Of course, the day-side must point toward the Sun, but it doesn’t necessarily point toward the Earth.
• We see different amounts of the illuminated side of the Moon each day, from nothing to a complete circle.
• These are the phases of the Moon (like this crescent).
• This animation compresses one month into seconds.
The Evening Sky• At sunset we see
the waxing phases of the moon.
• The farther the moon gets from the sun, the more illuminated it is.
• The light side is on the right, the “sun side.”
The Morning Sky• At sunrise we see
the waning phases of the moon.
• The farther the moon gets from the sun, the more illuminated it is.
• The light side is on the left, the “sun side.”
The Lunar Year• The time for one cycle is 29.5 days.• This means there are 12 cycles (or months) in
354 days, which is called a lunar year. • To have a lunar calendar work, you must add
a 13th month every 3-4 years.• Unfortunately, since the moon orbits the
Earth, scientists first thought every thing else did too.
The eclipse is total when the moon is in the Earth’s umbra.
Types of Solar Eclipses:
• Total Eclipse: Umbra strikes Earth’s surface
• Partial Eclipse: Penumbra strikes Earth’s surface.
• Annular Eclipse: Moon is too far away to completely block out sun. You see a ring.
Total Eclipses Show Special Features on the Sun:
The Corona.
Notice the stars in backgroundSolar flares on the sun.
The Chromosphere
Why don’t we see eclipses every month?
The full or the new moon must occur at the “X”s for complete alignment of Earth, Moon, and Sun.
WRAP-UP!• Why does the moon go through phases every
month (approximately)?• When the moon is 180° from the Sun, what
phase is it?• Why do we see the waxing phases in the
evening sky and waning in the morning sky?• Why is a half moon more correctly called the
first or last quarter?• What causes a lunar eclipse?• What causes a solar eclipse?• Why are eclipses relatively rare?