2 – A saga of mankind
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2 – A saga of mankind. What do you know about the motion of the planets?. 1 – What is the shape of the Earth’s orbit around the Sun?. 2 – Do the planets orbit the Sun at constant speed?. 3 – Which planet has the largest orbital speed: Mercury or Jupiter?.

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2 – A saga of mankind

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2 a saga of mankind

2 – A saga of mankind


2 a saga of mankind

What do you know about the motion of the planets?


1 what is the shape of the earth s orbit around the sun

1 – What is the shape of the Earth’s orbit around the Sun?


2 do the planets orbit the sun at constant speed

2 – Do the planets orbit the Sun at constant speed?


3 which planet has the largest orbital speed mercury or jupiter

3 – Which planet has the largest orbital speed: Mercury or Jupiter?


2 a saga of mankind

4 – The Voyager spacecraft has now left the solar system. What force does it take to keep it moving in a straight line at constant speed?


2 a saga of mankind

5 – You bring your bathroom scale with you for a trip to the Moon. What does it display when you weigh yourself on the Moon?


6 you drop a marble and a hammer from the top of the cn tower which reaches the ground first

6 – You drop amarble and a hammer from the top of the CN tower. Which reaches the ground first?


2 1 the birth of astronomy

2-1 The birth of astronomy


First astronomical record

First astronomical record

30,000 BC:

phases of the Moon carved on a bone

Origin: Abri Blanchard,

Perigord, France


2 a saga of mankind

Picture yourself as an ancient farmer

What is the evening show?

What does your survival depend on?

Weather and seasons

One of the most important question farmers had to answer was: ‘What is today’s date?’ (When should I sow?)


2 a saga of mankind

Religious ceremonies where often linked to astronomical events

Winter solstice (shortest day of

the year): people would gather

and pray for the return of the warm season

(Christmas Eve: 24th)

Priests had to answer: “what is today’s date?” . They were often astronomers as well


Calendars

Calendars

  • Day (between two culminations of the Sun)

The natural units for calendars are:

  • Month (from one full Moon to the next one)

  • Year (from one winter solstice to the next one)

Challenges of the calendar:

between 2 full moons: 29.5 days ≠ 30

between to winter solstice: 365.24 days ≠ 365


Mesopotamia

Mesopotamia

Irak

(3000 – 100 BC)


2 a saga of mankind

Where writing was invented


2 a saga of mankind

Artist view of Babylon

Next to Baghdad

Ishtar gate


2 a saga of mankind

The hanging garden of Babylon

Babylonians believed that the planets and their motions influenced the fortune of kings and nations


2 a saga of mankind

Very precise observations but never tried to explain what they saw

Could forecast conjunctions and oppositions of planets

Babylonian astronomers knew the approximate length of the year


2 a saga of mankind

How could you measure the length of the year?

Every day at noon, record the length of the shadow of a post

June 21

March 21

~ 183 days = half a year

Dec 21


Archeological site ziggurat ur

Archeological site: Ziggurat, Ur


2 a saga of mankind

Reconstruction of the temple/observatory

Compass

points

Temples were built with specific places aligned to the heavens and based on the geometry of the land


2 a saga of mankind

Astronomical records

Letter reporting

an eclipse


2 a saga of mankind

Tablet library


British isles stonehenge

British Isles: Stonehenge

Built from 2800 to 1500 BC


2 a saga of mankind

People used stones to keep track of the motions of the Sun and Moon

N

O

D

D

N

O


Egypt

Egypt


2 a saga of mankind

3000 years ago, Egyptians adopted a calendar based on a 365-day year

Senenmut calendar


Egyptian map of the sky

Egyptian map of the sky

The ceilings of many royal tombs depict the night sky as groups of star-gods


2 a saga of mankind

Egyptians knew that five bright objects, known today as “planets”, move from night to night against the background of the stars


2 a saga of mankind

They portrayed the planets as deities sailing across the heavens in barques, and they were known as the "stars that know no rest".


2 a saga of mankind

Sirius : brightest star of the night sky

Each year, Sirius rose above horizon at dawn for ten days

Egyptians kept careful track of the rising of Sirius to forecast the flooding of the Nile river

Sirius in Canis Major


Central america

Central America


2 a saga of mankind

MAYA

Ruins of the Caracol , Chichen Itza, Yutacan, Mexico

1000 years ago


2 a saga of mankind

“Morning star”, “Evening star” = planet Venus

Maya: Sophisticated calendar based on the motions of Venus


2 a saga of mankind

You are lost on an isolated island in the Pacific ocean. How can you tell when is the shortest day of the year?


2 a saga of mankind

Sept 21

March 21

June 21

Dec 21


Aztecs

Aztecs

Aztec calendars


2 a saga of mankind

Incas

Intihuatana, Machu Pichu

Also used as a calendar


2 a saga of mankind

Solar eclipses happen only once in a lifetime


Polynesia

Polynesia

Polynesians learned to navigate by the stars over hundred of kilometers

It enabled them to colonize new islands


2 a saga of mankind

The odds came from the sky (rain, storms, haze) so people associated motions in the sky to their fate

Planets were symbols of gods that controlled human lives

Weather, diseases, accidents, were thought to be whims of the gods

Priests tried to understand what gods had in mind

Many civilizations developed their own astrology. Position of the Sun, Moon and 5 visible planets determined the fate of humans


2 a saga of mankind

Calvin’s opinion


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