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Ancient Astronomy

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Ancient Astronomy Astronomy the most ancient of the sciences Astronomical records back to prehistoric times – PowerPoint PPT presentation

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Title: Ancient Astronomy


1
Ancient Astronomy
  • Astronomy the most ancient of the sciences
  • Astronomical records back to prehistoric times

2
Scientific Methods Common Steps
  1. Recognize a question, a puzzle, or an unexplained
    fact.
  2. Make a hypothesis (educated guess) to resolve the
    puzzle.
  3. Predict consequences of the hypothesis.
  4. Perform experiments or make calculations to test
    the predictions.
  5. Formulate the simplest general rule that
    organizes the three main steps.

3
The Scientific Attitude
  • The scientific attitude is one of
  • inquiry.
  • experimentation.
  • willingness to admit error.

4
The Scientific Attitude
  • Scientists
  • are experts at changing their minds.
  • must accept experimental findings
  • test for erroneous beliefs
  • understand objections and positions of
    antagonists.

5
The Scientific Attitude
  • Fact is a close agreement by competent observers
    who make a series of observations about the same
    phenomenon.
  • A scientific hypothesis is an educated guess that
    is only presumed to be factual until supported by
    experiment.

6
The Scientific Attitude CHECK YOUR NEIGHBOR
  • Which of these is a scientific hypothesis?
  • The Moon is made of green cheese.
  • Atomic nuclei are the smallest particles in
    nature.
  • A magnet will pick up a copper penny.
  • Cosmic rays cannot penetrate the thickness of
    your textbook.

7
The Scientific Attitude CHECK YOUR NEIGHBOR
  • Which of these is a scientific hypothesis?
  • The Moon is made of green cheese.
  • Atomic nuclei are the smallest particles in
    nature.
  • A magnet will pick up a copper penny.
  • Cosmic rays cannot penetrate the thickness of
    your textbook.

Explanation All are scientific hypotheses!
All have tests for proving wrongness, so they
pass the test of being a scientific hypothesis.
8
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9
Oldest star chart- 32,000 years ago (Orion?)
10
Stonehenge 3100 2100 BC
11
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12
Great Pyramid at Khufu (Cheops) 2600
B.C. Aligned within 1/20 degree of true
north Possible correlations with astronomical
objects?
13
Chichen Itza Mayan observatory
14
Medicine Wheel Northern Wyoming
15
Chaco Canyon supernova of 1054?
16
Chaco canyon Anasazi sun dagger A.D.
400-1300, marks summer solstice
17
Constellations
Apparent groupings of stars relatively fixed
positions
18
Constellations the 88 semi-rectangular regions
that make up the sky
19
Star trails
20
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21
Star trails around South Celestial Pole (Gemini
Observatory, Chile)
22
Most of modern astronomy and cosmology comes from
the Greeks
23
Celestial Sphere

24
The Geocentric View
  • Aristotles View The Most Perfect Form is the
    Circle
  • The Crystalline Spheres

25
The Motion of the Earth
Correct Method - Wrong Conclusion
  • Parallax The apparent motion of an object due
    to the motion of the observer.
  • The Greeks could not detect any parallax for the
    stars (or planets).
  • Conclusion
  • The Earth is not moving.
  • OR
  • The Stars are too far away to measure parallax
    with crude instruments / eye.
  • The Greeks chose not moving.

26
Aristarchus 310 - 230 BC
  • Heliocentric model
  • Determined relative distances between
  • Sun and Moon

27
The Distance to the Sun
Aristarchus of Samos 310 - 230 BCE
  • Aristarchus measured ? to be 87 degrees
  • Sun Distance 19 Moon Distance
  • (today Sun is about 400 times further away than
    moon)

First Quarter Moon
Third Quarter Moon
28
Ptolemy (85 165 A.D) Lived in Egypt, probably
Alexandria Summarized Greek astronomy in the
Almagest Geocentric model of solar system
29
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30
Epicycles and Equants
Everything circles something else
31
Very complicated but it worked! (sort of)
http//astro.unl.edu/naap/ssm/animations/ptolemaic
.swf
http//astro.unl.edu/animationsLinks.htmlca_renai
ssance
32
Major assumptions of the Ptolemaic model
  • All motion in the heavens is uniform circular
    motion.
  • The objects in the heavens are made from perfect
    material, and cannot change their intrinsic
    properties.
  • The Earth is at the center of the Universe.

33
After the Greeks
  • Alexandria burns in 272 A.D., Roman empire
    collapses, and Europe enters Dark Ages
  • Roman Catholic Church combines Ptolemaic with
    Aristotelian thought into official church
    doctrine Earth as immovable center of cosmos
  • Much of astronomy is carried forth by Persian and
    Islamic astronomers who preserved Greek thought
    and refined it named many stars we know today

34
Breaking through the old model
35
Major problems with the Ptolemaic System It
failed to.
  • Accurately predict eclipses (off by hours, days,
    etc)
  • Predict position of planets accurate enough
  • Couldnt explain meteors, comets, supernovae

36
Nicolas Copernicus (1473-1543) proposed
heliocentric hypothesis, mostly on philosophical
grounds
37
Copernicus model
  • Gave similar predictions to Ptolemaic model, also
    used epicycles, etc
  • Proposed earth rotates on axis to cause night
    and day
  • Proposed earth and other planets travel around
    sun
  • Radical idea for time this sounded crazy to most
    people!!!

38
De Revolutionibus Orbium Coelestium, 1543 (On
the Revolutions of the Heavenly Spheres)
39
Copernicus explanation of retrograde motion
40
Galileo
1564 - 1642
  • All bodies fall at same rate!! - Tower of Pisa

41
Galileos Telescope
  • Galileos telescopic observations led him to
    firmly reject the geocentric model.

42
The Milky Way was composed of millions of stars.
He realized that wherever he looked, he saw
more and more stars
43
Saturn Galileo noticed.Saturn has ears
44
Sunspots A. The surface of the Sun was imperfect.
B. apparent motion of the spots across the
Sun's disk implied rotation.
45
  • Detailed moon drawings the moon is not a smooth
    sphere!

46
The Galilean Satellites
  • They Orbit Jupiter!
  • So Why Cannot the Planets Orbit The Sun

47
The Phases of Venus Galileo noticed that when
Venus wanes (becomes crescent), it becomes larger.
48
The Phases of Venus
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