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1
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2
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- Scientific Thinking is a fundamental part of human nature.
- Scientists apply the scientific method to their inquiries about the
universe.
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3
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- Central Africa: c. 6500 B.C. People use the observations of the moon to
predict the weather.
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4
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5
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- 24 hour day – the time it takes the Sun to circle our sky.
- Month – comes from the lunar cycle.
- Calendar Year – Based on the cycle of the seasons.
- Days of the week – named after the seven “naked-eye” objects that appear
to move among the constellations. (Sun, Moon and five planets)
- At night, the position and phase of the Moon give an indication of the
time.
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6
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7
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- In the daytime, ancient peoples could tell the time of day by observing
the Sun’s path through the sky.
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8
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9
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- Many cultures built structures to help them mark the seasons.
- A good example of this is Stonehenge.
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10
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11
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12
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13
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- Many ancient cultures used the lunar cycle as the basis of lunar
calendars.
- Metonic cycle:
- The ancient Greek astronomer Meton (432 B.C.) observed that the dates
of the lunar cycle repeat every 19 years.
- Other cultures based their calendars on their ability to predict
eclipses:
- Babylonian Calendar
- Mayan Calendar
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14
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- Many cultures made careful observations of the planets and the stars.
- Mayan observatories of Central America had windows placed to allow for
observations of Venus.
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15
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- In the desert regions of Peru, many large figures of animals may have
represented constellations to the Incas who lived there.
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16
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- Ancient Chinese Astronomers kept very detailed records of astronomical
observations beginning 5,000 years ago.
- They were the first to record an observation of a Supernova explosion,
which we see today as the Crab Nebula.
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17
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- In the Americas, the Mayans had developed a modern system of numbers and
mathematics, which included the invention of the concept of zero.
- It appears that virtually all cultures employed scientific thinking to
varying degrees.
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18
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- 3000 B.C. The establishment of civilization occurred in Egypt and
Mesopotamia.
- 2700-2100 B.C. Egyptians build the Great Pyramids.
- 500 B.C. Greece rises as a military power.
- 330 B.C. Alexander the Great expands the Greek empire throughout the
middle east.
- As a student of Aristotle, Alexander had a great interest in science and
education.
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19
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20
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- 300 B.C. The Library of Alexandria is established as the leading center
of knowledge, housing more than half a million books.
- ~ 415 A.D. The destruction of the library of Alexandria, along with the
loss of most of the knowledge stored there.
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21
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22
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- One of the most important scientific contributions from ancient Greece
was the idea of creating models to represent natural phenomena.
- Models are still used today to help us in understanding natural
phenomena.
- Claudius Ptolemy (100-170)A.D. developed an Earth centered (geocentric)
model of the universe that included the motions of the Sun, moon, and
planets.
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23
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- All heavenly motions proceed in perfect circles.
- To explain retrograde motion, Ptolemy maintained that each planet moved
along a small circle that, in turn, moved around a larger circle.
- This allowed for the observed
westward (retrograde) motion that some planets exhibited.
- The large circular orbit around the Earth was called the “Deferent”
- The smaller circular motion along a “deferent” was called an epicycle.
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24
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25
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- 1543 Copernicus publishes De Revolutionibus Orbium Caelestium, “Concerning
the Revolutions of the heavenly Spheres”.
- Copernicus modifies the Ptolemaic model as noticeable discrepancies
become more apparent with the improvements in observational astronomy.
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26
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- The Sun and not the Earth, is at the center of the solar system.
- The earth does move, and like the other planets, orbits the sun.
- The orbital paths follow perfect circles.
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27
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- Made detailed naked eye observations of the motions of the planets.
- Coined the term NOVA for the observation of a supernova (Nova means “New
Star”)
- Showed that comets were distant objects rather than being phenomena of
the Earth’s atmosphere, as argued by Aristotle.
- In the course of 30 years, he had amassed the best astronomical data of
the day It was accurate to within 1 arc-minute.
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28
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- A mathematician and a man of faith, who believed that understanding the
geometry of the heavens would bring him closer to God.
- Inherited Tyco Brahe’s
astronomical data.
- With his mathematical skills, Kepler spent 20 years of his life trying to
develop a consistent model to describe planetary motion.
- His efforts culminated in what is known today as Kepler’s Three Laws of
Planetary Motion.
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- The orbit of each planet about the Sun is an ellipse with the Sun at one
focus.
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30
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31
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- As a planet moves around its orbit, it sweeps out equal areas in equal
times.
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32
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- The square of a planet’s orbital period is proportional to the cube of
its semi-major axis.
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33
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- The Copernican view of the solar system and Kepler’s three laws of
planetary motion were very successful in explaining and predicting
observations.
- However, due to the degree to which the Ptolemaic model was ingrained in
the current thinking of the day, major objections were put forth with
regard to the new Copernican/Keplerian model.
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34
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- The Earth could not be moving because if it did, objects such as birds,
falling stones, and clouds would be left behind as the Earth moved along
its way.
- The idea of noncircular orbits contradicted the ancient Greek belief
that the heavens must be perfect and unchanging.
- Stellar parallax should be detectable if the Earth orbits the Sun.
(True, but difficult to detect)
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35
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36
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- Galileo performed careful experiments on the motions of moving bodies
and showed that a moving object remains in motion unless a force acts to
stop it or change its direction.
- Tycho’s observations of a comet and supernova showed that the heavens
could change.
- The lack of noticeable stellar
parallax was simply due to the fact that the stars were much farther
away than anyone had previously thought.
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37
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- Galileo observes four moons clearly orbiting Jupiter.
- This shows that objects do orbit planets other than the Earth.
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38
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39
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40
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- Galileo observes that Venus goes through phases much like the moon does.
Only a Heliocentric model of the solar system can account for all
observed phases.
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41
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- Craters, mountains and cliffs on the Moon.
- Sunspots
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Notes
