7.1 ancient astronomy - · pdf fileearly calendars organized days into a schedule of larger...
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7.1 Ancient Astronomy p. 271
Movement of objects through the night sky
rising and setting of the Sun
phases of the Moon
position of the stars changing with the seasons
Very consistent and measurable
Mayan pyramids functioned as
calendars
Used to make structure that functions as ‘calendar’
Early Calendars
Organized days into a schedule of larger units
of time (weeks, months, seasons, years)
shown as a table or chart
allowed people to predict events:
◦ seasons
◦ spring rains
◦ annual flooding of rivers and lakes
◦ location and migration of birds, insects, and
herds of animals
Early Civilizations With the invention of the calendar,
the first civilizations were born
WHY?
organized agriculture
more food
time and resources to develop
knowledge and skills in a variety of areas
Early Sky Observations
Fishers, mariners, and travellers used the fixed patterns of the stars
to help them navigate on land and water.
Early Astronomers
Our ancestors believed that the deities
(gods) ruled the skies
Changes in the heavens meant that the
gods might be getting restless.
Celestial objects: objects that exist in space (planet, star, Moon)
Celestial priests and priestesses studied these objects and learned
how to predict seasons and eclipses.
Mesopotamian Astronomers
Astronomers: scientists who study astronomy,
Astronomy: study of the night sky
The first astronomers were the Mesopotamians
kept detailed records of the sky as early as 6000 years ago
Years and Days
Revolution:
the time it takes an object to orbit another object
Year:
the number of days it takes Earth to make one
revolution around the Sun (365.25 days)
Rotation:
the turning of an object around an imaginary axis
running through it
Day:
the time it takes for Earth to make one rotation
(24 hours)
Early Clocks
Eg. sundial
tracked shadows to tell the time of day
Earth rotates
position of the Sun changes
sundial casts shadows in different directions
position of the shadow on the sundial tells
the TIME
Revolution and Rotation
Earth’s Shape
In the past, people thought the Earth was flat.
Two ancient Greek philosophers, Eratosthenes and Aristarchus
hypothesized that Earth was spherical
Based on 3 pieces of evidence
Evidence #1
The hull and then the masts of ships appeared to descend below the
horizon as ships sailed away.
Evidence #2
The appearance of the sky changed as travellers journeyed farther
north or south.
Evidence #3
During a lunar eclipse, the shadow of Earth on the moon was
curved.
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