Unit 2: Earth in Space

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Unit 2 Earth in Space

• Terminology
• Frame of Reference a fixed background which we
  can measure motions against
• P.O.V.
• Polaris the North Star directly above Earths
  North Pole/axis of rotation
• Celestial Object an object outside of Earths
  atmosphere
• Stars, our Sun, Valenti in a space suit orbiting
  earth, other planets

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• a) Angular Diameter how large a celestial
  object appears to be to an observer
• It depends on
• The objects actual size
• How far it is from the observer
• Earths Motions in Space
• Rotation Earth spins on its axis once every 24
  hours
• Earth turns 15o/hour from west to east-
• -how do we know?
• Day and night- either the sun actually rises
  and sets or Earth rotates

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• Revolution (orbit) Earth moves around the sun
  in a nearly circular orbit
• Earth orbits the sun in 365.25 days-
• -how do we know?
• Star Shift- constellations appear to change
  position each night (slightly)
• This is why we see different constellations
  during different seasons we see different views
  or snapshots at different times

Sun
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• Seasons and Earth-Sun Relationships
• The Seasons are a result of 3 factors
• Tilted axis of rotation- 23.5o
• Revolution around the sun
• Parallelism- earths axis always point to the
  same place in space
• It points at the North Star (Polaris)

Polaris
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• Season Characteristics
• September 21- Autumnal/Fall Equinox
• Direct rays of the sun hit the Equator (0o)
• Because of where we are in space, tilt is neither
  towards or away from sun
• Everywhere on Earth has 12 hours of
  daylight/night
• EQUAL on an EQUInox

0o
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• December 21- Winter Solsitice
• Direct rays of the sun hit the Tropic of
  Capricorn (23.5o S latitude)
• Because of where we are in space, Northern
  Hemisphere is tilted AWAY from the sun
• In NYS, we have 8 hours of daylight/16 hours of
  night
• Shortest day of the year
• Travel north towards the North Pole you approach
  locations of 24 hours of night (Artic Circle to
  the North Pole)

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• March 21- Vernal/Spring Equinox
• With the exception of the date and name, its the
  same as its twin the Autumnal Equinox!

0o
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• June 21- Summer Solstice
• Direct rays of the sun hit the Tropic of Cancer
  (23.5o N latitude)
• Because of where we are in space, Northern
  Hemisphere is tilted TOWARD the sun
• In NYS, we have 16 hours of daylight/8 hours of
  night
• Longest day of the year
• Travel north towards the North Pole you approach
  locations of 24 hours of daylight (Artic Circle
  to the North Pole)

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• Observing our Moon
• It takes the moon about one month (29.5 days) to
  go through a complete cycle of phases
• The moons period of rotation and revolution are
  the same
• We always see the same side of the moon facing
  the Earth
• Moon Phases- the amount of lit surface as seen
  from Earth
• Phases are caused by the moons revolution
• The angle and set up of SUN, EARTH and MOON
  determines what phase we see

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• Phases repeat every month in a cyclic manner
• Waxing/1st/New Phases- to see more of the moon
  each night
• when the light is on the right, the moon is
  getting bright
• New Moon to Full Moon
• Waning /3rd/Old Phases- to see less of the moon
  each night
• Waning Fading away
• Getting dark on the right, the moon is getting
  erased

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• Moons Affect on Earth
• The moons gravity affects our hydrosphere
• Tides are created by the pull of the moon on
  the oceans
• There are 4 changes in tides in 24 hours
• 2 high tides
• 2 low tides
• This means every 6 hours the level of the oceans
  change (from high to low OR from low to high)
• Special Tides
• Spring Tides (Severe high and low tides)
• Happens when the moon is Full or New
• Moon and Sun work together to pull on the
  oceans making height of tides more extreme

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The Moons Gravity Causes a change in our tidal
levels throughout the day
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• Eclipses
• Lunar Eclipse- Earths shadow is cast on the
  surface of a Full Moon
• Sun, Earth and moon align exactly in this order
• Happens during a FULL MOON ONLY
• Relatively common (about every 18 months)
• Safe to view
• Visible to everyone on the nighttime side of
  Earth
• Solar Eclipse- Moons shadow is cast on the
  surface of the Earth
• Sun, Moon and Earth align exactly in this order
• Happens during a NEW MOON ONLY
• Rare (about 1 every 7 to 10 years)
• Dangerous to view (burns your retinal nerve in
  your eyes (youd go blind)
• Visible to only certain locations/latitudes on
  Earth (you must be located at the right spot on
  the daytime side of Earth to experience a solar
  eclipse)

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Lunar Eclipse How do the Sun, Earth and moon
align to create this common celestial phenomenon?
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Solar Eclipse How do the Sun, Earth and Moon
align to create this more rare phenomenon?