Topic 4 Motions of Earth, Moon, and Sun

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Topic 4 Motions of Earth, Moon, and Sun
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Apparent Motion of Celestial Objects

• Why do the Stars in the Sky Move?

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1. Daily Movement of Celestial Objects

• Stars and the Sun Rise in the East and Set in the
  West
• Stars move 150 / Hour in the Sky.
• Due to Earths Rotation

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2. Apparent Motion of Celestial Objects over
months

• Celestial Objects Change Positions as Earth
  Revolves around the Sun!
• Example Constellations Your Sign
• Example Moon Rise Changes by 50 minuets each
  night!

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3. Apparent motion of Sun

• How does the sun change over the year here?

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Apparent Motion of Sun

• Days are longer in the summer and shorter in the
  winter
• The altitude of the Sun is higher in the summer
  and lower in the winter
• THE SUN IS NEVER DIRECTLY OVERHEAD IN NY

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Spring March 21
Seasons
Summer June 21
Winter Dec 21
Fall Sept. 23
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Lets make a chart of the 4 key dates and what
they each mean.

Date
Name
Key points
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Summer Solstice

• June 21
• N. Pole is tilted towards the sun
• Sun is highest in the sky in NY
• Longest day, shortest night
• Sun is directly over the Tropic of Cancer 23.5 N.

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Fall (autumnal) Equinox

• September 23
• Equal day and night
• Sun is directly over the equator

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Winter Solstice

• December 21
• N. Pole is tilted away from the sun
• Shortest day, longest night
• Sun is directly over the Tropic of Capricorn

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Spring (vernal) Equinox

• March 21
• Sun is directly over the Equator
• Equal day and night

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Zenith
Summer Solstice June 21
Equinoxen March 21/Sept 23
Winter Solstice Dec 21
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4. Geocentric vs. Heliocentric

• Geocentric

• Heliocentric

• Earth Centered Solarsystem

• Sun Centered Solarsystem

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5. Earth Motion Rotation

• Earth rotates on its axis
• Axis- imaginary line though the planet from the
  North Pole to the South Pole
• Axis of Earth tilted 23.50
• Earth Rotates Counterclockwise
• Tilt causes seasons

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6. Earth Motion Proof of Rotation

• Foucault Pendulum
• Coriolis Effect

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Foucault Pendulum

• Foucault Pendulum The first good evidence of the
  Earth's rotation was provided by a swinging
  pendulum. The pendulum would continue to swing in
  the same direction while the Earth rotated
  beneath it. A more recent source of evidence of
  rotation is the swirling pattern of weather
  systems seen by satellites.

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Coriolis Effect

• The Coriolis Effect makes the Foucault Pendulum
  work. The rotation of the Earth puts a "spin" on
  the air movement which causes a curve in the
  travel direction. In the Northern Hemisphere the
  turn is towards the objects right.

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7. Earth Motion Revolution

• Earth Revolves around the sun once every 365 days
• Evidence Changing background stars

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8. Earths Moon

• Revolves around Earth once every 27.3 days but it
  takes 29.5 days from 1 full moon to the next
• Revolves in an elliptical orbit that is tilted 50
• Rotates once every 27.3 Days (thus we only see
  one side of the moon)

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9. Moon Phases

• When the side lit up by the sun is visible to
  Earth we see the moon
• The revolution and changing amount of light
  visible on Earth causes phases
• The phases are cyclic

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Phases of the moon handout
Sun way the heck to the left
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Last Half/ Last Quarter
Waning Crescent
Waning Gibbous
New
Full
Waxing Crescent
Waxing Gibbous
First Half/ First Quarter
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Tides

• Cyclic rising and falling of water due to the
  gravitational pull of the Moon and Sun on Earth
• The tides are mostly caused by the Moon because
  it is closer than the sun (More Gravitational
  Force)

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Tides

• The strength of gravity depends on how close two
  objects are and their masses.

m1 and m2 are masses of the objects d is the
distance
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High Tide

• Located on Earth directly under the moons
  position and on the opposite side of the earth
  because the solid Earth is closer to the
  Earth-moon center of gravitation than the ocean
  water

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Low Tide

• At a Right angle to the high tides where the pull
  from the moon is the smallest

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Cycle of High and Low Tide

• Since Earth rotates and the moon revolves around
  Earth there are 12 hours and 25 minutes between
  two high tides
• A complete cycle of 2 high tides and 2 low tides
  takes 24 hours and 50 minutes!

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Lets draw a diagram of how the moon causes
tides! Lets draw a diagram of what the tides
look like.
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Spring Tide vs. Neap Tides

• A Spring Tide is caused by a full moon and a new
  moon. The water springs from its highest level
  to its lowest for the month.
• A Neap Tide is caused by the half moon phases.
  The high tide is not so high and the low is not
  so low.

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Spring Tide Diagram
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Neap Tide Diagram
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Eclipses

• Eclipse-when a celestial object partly or
  completely comes into the shadow of another
  object
• What are the names of the two types of eclipses

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Eclipses

• A lunar eclipse occurs when the Earth blocks out
  the Moon's sunlight. The moon goes into the
  Earth's shadow.
• Lunar eclipses happen during a Full Moon.

penumbra
Earth
umbra
moon
sun
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• A solar eclipse is when the moon blocks sunlight
  from reaching the Earth.
• Solar Eclipses happen during a New Moon.
• Eclipses do not occur every time there is a full
  or new moon because the moon's orbit around the
  Earth is inclined.

moon
sun
penumbra
umbra
Earth
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A view of a Solar Eclipse as Seen from Space

• http//www.stormcenter.com/media/060331/