History of Astronomy

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History of Astronomy

• From Prehistoric Times to the Present Day

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Periods of Astronomical Discovery

• Our picture of the universe has been assembled
  from ________________ of discoveries made by
  scientists from all part of the world.
• Prehistoric Period (Before 500 B.C.)
• Classical Period (500 B.C. 1400 A.D.)
• Renaissance (1400 1650)
• Modern Period (1650 to Present)

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Prehistoric Astronomy

• Astronomical observations are a part of every
  __________________
• Observations of the rising and setting _____, the
  changing patterns of the ____________, eclipses
• These observations uncovered a ___________
  pattern __________________________________
• These patterns could serve as timekeepers because
  they are _____________________
• Could help foretell future events

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Stonehenge
What is its purpose
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Prehistoric Astronomy

• The early astronomers had to rely on
  ____________________ observation
• The most direct link to our ancient ancestors
  come from studying the _____________________

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The Celestial Sphere

• Impossible to get a sense of the 3-dimensional
  shape of the universe
• We can treat the stars as if they were all the
  same distance from Earth and that they lie on the
  inside of gigantic dome surrounding the Earth
  called the __________________ with the Earth at
  the very center
• This serves as a model even though it has no
  ___________________ reality
• This served as the first model of the heavens

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Constellations

• An arrangement of the stars on the celestial
  sphere that seemed to resemble something from
  their everyday lives (mostly animals)
• Many have shapes that bear _____________
  resemblance to their namesake
• The stars in a constellation have no
  ____________________ relationship to each other
  except their direction in the night sky

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The Constellations

• Astronomers recognize _______ constellations
• These are a collection of stars that appear to
  form a pattern

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The constellations

• Help divide the sky up into __________
• Stars are labeled within the constellation based
  upon their ______________________ magnitude
• a alpha is the ________________
• ß beta is the next brightest

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Orion The Hunter
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Ursa Major The Great Bear
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Cassiopeia The Queen
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Constellations

• All stars move, but their positions as seen from
  Earth change so ____________ that it takes tens
  of thousands of years to notice any shift at all
• Ancient people used the rising sun and what
  ____________________ was present in that portion
  of the sky to predict _____________ and to
  __________________

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Constellations

• If the sun rose in the constellations Pisces and
  Aquarius ______ travel was dangerous because they
  appear in the eastern sky when the stormy winter
  season is upon us.
• Harvest time is when the sun appears in the
  constellation __________

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Motions of the Sun and Stars

• ________________ or Diurnal motion
• Stars rise in the __________ and set in the
  _____________ just like the Sun
• Could be explained by the rotation of the
  celestial sphere around us
• Was easier for the ancient people to believe this
  than that the earth wasnt moving

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Motions of the Sun and Stars

• If we look at the spinning celestial sphere there
  are two points that dont move, the
  ____________________
• The north celestial pole marks the direction of
  _____________ north
• Helps to locate stars in the sky just like N S
  on regular maps
• Celestial _____________ lies directly above
  Earths equator, another useful reference pt.

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Motions of the Sun and Stars

• Earths orbit around the sun also changes the
  motion of the Sun and stars across the sky
• This motion is ____________________ and harder to
  observe so records need to be kept of these
  observations
• These motions repeat on an annual basis and are
  called __________________ motions
• The stars move in a tilted line with respect to
  the horizon which is 90 minus your latitude

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Motions of the Sun and Stars

• Annual Motion
• New constellations appear in the eastern sky and
  other disappear in the west
• Allowed for a means to measure the passage of
  time and the coming and going of seasons
• Caused by the Earths motion about the sun
• The stars that we cant see are still there, we
  just cant see them through the _________________
• A given star rises ________________________
  earlier each night If we add that up over a
  full year we get just about 24 hours.

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The Ecliptic

• The path that the sun traces out on the celestial
  sphere and it is merely an extension of the
  Earths orbit
• This path is tilted with respect to the Earths
  axis by _______________
• The name comes from eclipse because when a new or
  full moon would cross this line an eclipse takes
  place

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The Ecliptic

• In reality it is the Earths axis that is tilted
  and gives us the seasons we experience

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Solstices and Equinoxes

• For half of the year the sun rises _________ of
  due east and for the other half of the year it
  rises _______________ of due east (and likewise
  sets the same way in the west)
• In the Northern Hemisphere in the summer the sun
  rises in the northeast and sets in the northwest.
  What happens in the winter?

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Solstices and Equinoxes

• Spring and Fall begin when the sun crosses the
  ______________________ this is the
  ___________________ where day and night are of
  equal length
• Spring or vernal equinox is about _____________
• Fall or autumnal equinox is about _____________
• At this point the sun will rise due east and set
  due west
• Summer and winter begin when the sun stops its
  northern or southern trek and reverses direction
• These are called the _______________________
• Summer solstice is around ____________ and the
  winter solstice is around ____________________

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Solstices and Equinoxes

• Buildings were also aligned to coincide with
  astronomical events
• Mayan pyramids allowed them to devise a very
  precise and complex calendar based on the
  movements of the planet _____________

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The Planets and the Zodiac

• Greeks gave the name planets to those heavenly
  bodies that didnt move in the same way that the
  other stars did
• The planets appear to move because of Earths
  orbiting of the Sun and their own orbits around
  the Sun
• Planets moved within a very narrow band on the
  celestial sphere called the ___________
• ___ constellations are within this narrow band

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Signs of the Zodiac
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The Planets and the Zodiac

• Planets appear to move ________________ against
  the stars
• However, they rise in the east and set in the
  west. Why the difference in apparent motion?
• Sometimes the pattern is interrupted and the
  planets move in the opposite direction of that
  expected.
• This is called ___________________ motion

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Retrograde Motion
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The Moon

• Rises in the __________ and sets in the
  _______________
• Lunar phases take place over a months time
• Origin of the ___________________
• What causes the phases?

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Eclipses

• ___________ when one planetary body passes
  through the shadow of another
• ___________ part of the shadow where sunlight is
  completely blocked
• ___________ part of the shadow where sunlight is
  only partially blocked

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Solar Eclipses

• When the ____________ is between the sun and the
  earth
• Shadow of the __________ falls on the earth
• If within the umbra we see a total solar eclipse
  never lasts more than _____ minutes
• Outside the umbra we see a ________ solar eclipse
• ____________ solar eclipse when the shadow
  doesnt reach earth moon is near apogee
  (furthest from Earth) thin ring of sunlight
  visible around the outer edge of the moon

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Lunar Eclipses

• ____________ is between the moon and the sun
• Total lunar eclipse moon passes into earths
  umbra
• Partial lunar eclipse moon passes through only
  part of the umbra
• Penumbral eclipse when the moon passes only
  through the earths penumbra moon darkens only
  slightly
• Must be a _____________ moon

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Eclipse Frequency

• Lunar eclipses are seen by more people visible
  anywhere on the dark side of the earth
• Solar eclipses seen only by those people where
  the small shadow of the moon is cast
• Occur almost ______________ as often

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Eclipse Frequency

• Orbit of the moon tilted 5º to plane of the earth
  and the sun moon is usually above or below the
  plane of the earths orbit
• 2X each year the moon crosses the plane of the
  earths orbit
• Usually no eclipse happens when the moon crosses
  the plane of the earths orbit. Why?