Traditional Agroforestry System in India- Shifting Cultivation, Taungya, Home...
Early Observers Astronomers.ppt
1. How is the amount
of daylight we are
receiving changed
over the last two
weeks?
2. What can you tell
me about how the
stars move in the
sky during an
evening?
3. What is the current
phase of the moon?
How has this
changed over the
last three weeks?
4. What can you tell
me about how the
stars move in the
sky over the period
of a year?
5. Ancient cultures studied the sky and
developed calendars based upon the
patterns they saw
Motion of the sun
Motion of the moon
Motion of the stars
Ancient culture based their calendars on repeating cycles they observed
in the sky.
6. What is a day?
What they saw:
The time it takes the sun to cross the sky and return to
the same point
What we know:
Time required for the Earth to rotate once on its axis
7. What is a month?
What they saw:
The amount of time required for the moon to move
through a complete set of phases
What we know:
The amount of time it takes the moon to revolve around
the Earth
8. What is a year?
What they saw
The time it takes for a group of stars (constellation) to
return to the same part of the sky at a certain time of
day
What we know:
Time required for the Earth to revolve around the sun.
9. Early Observers
The Beginnings of
Astronomy
Scientists have found evidence for ancient
astronomical activities from all over the world.
11. Nabta
Southern Egypt – Some stones are positioned such that
they would have lined up with the sun during the
summer solstice 6,000 years ago.
The summer solstice occurs on the longest day of the
year. (Day with most amount of sunlight)
12.
13. Stonehenge
Another ancient site that was probably used to make
observations of the sky.
Stones are arranged primarily in circles which are
aligned with the sunrise during the summer and winter
solstices.
Built over a period of 1,500 years.
Built for ceremony and ritual.
14.
15. Babylonians
Ancient empire located in present-day Iraq
700 B.C. to A.D. 50, Babylonians precisely tracked the
positions of the planets and moon.
Skilled at forecasting the movements of these celestial
bodies, which enabled them to make an accurate
calendar.
16.
17. Ancient Chinese
1,000 B.C. could predict eclipses.
The Chinese named 800 stars by 350 B.C.
The Chinese skillfully tracked and predicted the same
motions in the sky as the civilizations that influenced
Western astronomy.
18. Ancient Greeks
Learned to observe the sky to keep track
of time.
Helped make astronomy a true science.
Greek philosophers had tried to
understand the place of Earth and humans
in the universe (Logic & Geometry)
Aristotle (Greek philosopher) successfully
explained the phases of the moon
Correctly stated that Earth was a sphere
(an idea that was not popular at the time)
19. Native Americans
Skilled in observing the sky
Maya – 1,000 years ago in the Yucatan
Had complex systems of mathematics and astronomy.
Many buildings were aligned with celestial bodies during
certain astronomical events
20. Ancient Arabs
Followed Greeks, Romans, early
Christians. Used Greeks’ knowledge of
astronomy to develop astronomy into a
science while Europe fell into the
“Dark Ages”
Many stars have Arabic names because
of this period.
Invented Astrolabe, algebra, modern
number system.
21. Earliest Astronomers
Summary
The ancient people had no history to
learn from.
Almost everything they knew about
the universe came from what they
could discover with their own eyes and
minds.
They thought that the universe was
made up of the sun, moon, planets
with all the stars somewhere towards
the edge of the universe.
23. Pythagoreans (500
B.C.)
Believed the stars, planets,
sun, and moon were
attached to crystalline
spheres which rotated
around the earth.
(geocentric)
24. Aristotle (350 B.C.)
Believed the Earth is
motionless at the center of
the universe and all the
stars and planets rotated
around it.
Stars and planets moved in
circular paths.
(geocentric)
25. Ptolemy (140 A.D.)
Expanded Aristotle’s theories to try to
account for “retrograde motion” of
the planets (Ptolemaic Theory)
Planets traveled in smaller circular
paths as they traveled around the
Earth
(epicycles and deferents)
Popular model of universe for 1,500
years.
26. Copernicus (1543)
Sun at center of universe and the planets orbit the
sun
(Heliocentric)
Solved the problem of “retrograde motion”
Theory did not immediately replace Ptolemy’s theory.
27. Tycho Brahe (1600)
Favored an Earth-centered universe different from
Ptolemy’s theory
Thought that other planets revolved around the sun,
and that the sun and moon revolved around the
Earth.
Theory incorrect, but made many precise observations
of planets and stars.
28. Johannes Kepler (1609)
Mathematician
Tycho’s assistant
Used Tycho’s observational data to
develop laws of planetary motion
Kepler’s 3 Laws of Planetary Motion
Law of Ellipses
Law of Equal Areas
Law of Periods
29. Galileo Galilei (1609)
First person to use telescope for astronomical observations
Discoveries
* Galilean Satellites (Jupiter’s moons)
* Craters on the moon
* Sunspots on the Sun
* Phases of Venus
Favored Copernicus’s theory over Ptolemy’s
30. Isaac Newton
1687
Explained why planets orbit the Sun, and why moons
orbit planets
Newton’s Law of Motion
Newton’s Law of Gravitation
Completed the work of Copernicus, Tycho, Kepler, and
Galileo
