Transcript Reading Guide/Note sheet – Ancient Astronomers

Ancient Astronomy
Simple markers
Circles
Temples or tombs
Stonehenge
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Southern England
One of about 900 megalithic circles
2800 BC – 1075 BC
Used to observe Sun & Moon
Largest stone weigh 50 tons and
came from miles away
Newgrange (Ireland)
• 3000 BC
• Underground chamber
(tomb)
• Window allows light on
winter solstice, precisely
measures solar
movement for 15 min.
• Sun shines on
• certain carvings
• on specific days
Big Horn Medicine Wheel
• 90 ft. diameter, 28 spoke
wheel
• Oldest 2500BC (age of
Egyptian pyramids)
• Most recent 1500-1700
AD
• indicator of solstices
• Also mythological
cemetery(door between
good and evil
• in no way related to the
20th century native Am.
Mayan Astronomy
• Yucatan peninsula,
Mexico
• 1000AD
• Mayan culture built
temples as
• observatories
• Solstice and equinox
alignments, some
• stars and Venus
• Most based on Zenial
Passages
• Religious based
nabta
• West of Nile River in
south Egypt
• 48,000 Yr. old, predates
stonehenge
• Spokes on a wheel,
following 3 stars (one pt.
to the stars in belt of
Orion
Namoratunga
• Sub-Saharan Africa
• 25 stone alignments w/7
position in the sky
• Built by an unknown
people 300 BC
• Observatory using a
detailed understanding of
the motions of the stars &
Moon
• Very accurate lunar
calendar
Aztec Ruins
• temples in eastern
Mexico
• Used for marking
significant events in
nature that were
important to society
• Highly religious to the
people
Incan Astronomy
• Temples built for worship
and for sacrifices
• Religious gods based on
observations of the sky
• Universe made of 3
worlds: Cosmos, Earth’s
surface, and the Earth’s
interior.
Egyptian Astronomy
• Temple at Karnak has
alignments to solstices
• 2600 BC
• Pyramid of Khufu has
opening aligned w/Polaris
and Orion’s belt
• Perfectly aligned N-S, EW
• Debated if tombs or
astronomical
sophisticated temples
Chinese Astronomy
• Tower built in 1270 marking
solstices and precise
movements of Sun
• During the Dark Ages in
Europe China achieved major
advance in science,
technology, medicine, and
math
• Recorded “guest stars”(comets)
• Tracked stars more than
planets. Advanced more slowly
than Babylonians
• Searched for balance in life.
Planetary phenomena meant
life out of balance
• Precise record’g of eclipses
Early Greek Astronomy
• Used philosophical arguments to explain
natural phenomena
• Used some observational data
• A. phases of the moon
They understood that the
Curve of the moon phase
Was really the edge of the
Earth creating a shadow on
The Moon
• B. ships disappear
from sight at the
horizon from bottom
to top. Due to fact
they are traveling on
a curved surface
If you are at the N. Pole, Polaris is
Directly above you, if you travel south
Polaris appears to drop towards the
Horizon. This is because you are
Traveling on a curved surface
The Greeks held a “Geocentric
view of the Earth”
• A. “Geocentric” view –
Earth is a motionless
sphere at the center of
the universe
• Celestial sphere” – a
transparent hollow
sphere on which the
stars traveled daily
around the earth
The Greeks recognized
the seven heavenly
bodies they called
“planetai”– they move
across the sky compared
to the relatively
“fixed stars”: the Sun,
Moon, Mercury, Venus,
Mars, Jupiter, Saturn.
Hipparchus (2nd century B.C)
• Created a star catalog
of 850 stars divided into
groups according to
their brightness.
• He measured the length
of a year to within a
minute of its modern
value and accurately
predicted time of lunar
eclipses.
• Identified precession
• Division of circle into
360o, devised early
trigonometry
Aristarchus (312 – 230 B.C)
• First Greek to profess a
sun-centered universe
(helio-centric)
• 1st to propose that Earth
rotated on an axis
• Calculated distances
between Sun, Earth &
Moon
Aristotle
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384 -322 BC
Earth is a sphere
Geocentric model
Great philosopher
Eratosthenes
• 276-195 BC
• Measured circumference
of Earth (less then 5%
error)
Ptolemy (83-161 A.D)
• Believes in the geo-centric
model
• Wrote a 13 volume book
called “The Almagest”
about mathematics and
astronomy
• develops a method to
explain retrograde motion
of the planets
Retrograde Motion – the apparent backward movement of a planet
Ptolemaic System
• Retrograde motion – the apparent
movement of a planet reversing
its motion due to the passing of
another planet with faster speed.
i.e. – a race car passing on a
circular track.
• To explain retrograde motion,
Ptolemy used 2 motions for
plants:
• 1. Large orbital circles, called
deferents
• 2. Small circles, called epicycles
• Even Though Ptolemy used the wrong
model, he was able to account for the
planets motion
Birth of Modern Astronomy
• A.) Nicolaus Copernicus
(1473-1542)
• 1. Sun is the center
“heliocentric” constructed a
model and taught this idea
• 2. earth is simply a planet
• 3. writes a controversial book
called The Revolutions, later
banned by the church and
burned
• ridiculed by many for his
writings
Tycho Brahe (1546-1601)
• Built the predecessor to
the telescope
• recorded very precise
locations of stars and
planets
• located many stars and
the known planets
positions on given day
and hour.
• designed and built
“pointers” instruments
used to systematically
measure the locations or
stars or planets
Johannes Kepler(1571-1630)
• 1) a teacher,
mathematician, devout
catholic
• 2. spent lifetime
mathematically proving
the helio-centric model
was correct. He used
Brache’s data to do this
• 3. Developed the three
Laws of Planetary
Motion
1st Law - Orbits are
ellipitical
2nd Law – ellipitical
Orbits of planets
Cover equal areas in
Equal amt.s of time
3 Laws of Planetary Motion
• A) Orbits of planets are elliptical, not
circular
• B) the orbital speed of planets varies,
covering equal areas, equal times
• C) orbital periods and distances to sun are
proportional
P2 = d3 orbital periods(squared) = distances
to Sun(cubed)
What is an astronomical unit?
• The average distance from earth-sun
• 1.5x108 Km (150,000,000 km)
• 93 million miles
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See page 618 chart
Galileo Galilei
(1564-1642)
• Supported & taught
Copernican theory
• Used experimental data to
prove his theories
• Constructed the
First astronomical
telescope. Using
the telescope
Using the telescope he
discovers:
4 moons (satellites) of
Jupiter
planets appear as discs
(not spherical balls)
saw phases of Venus
Galileo’s discoveries cont.
• Saw features on the moon’s
surface (Mt.s and seas (maria)
before it was thought to be a glass
sphere reflecting sunlight.
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Saw sunspots on the Sun
and determined they were
on the surface, not floating above the sun.
Galileo was tried and
convicted by the Inquision.
He recanted to save his life
and died while still under
“house arrest”
Sir Isaac Newton (1643-1727).
• Explains the forces
involved in planetary
motion
Formulates and tests
the Law of Universal
Gravitation
Perfects Kepler’s 3
Laws of Planetary
Motion by adding
mass to the
calculations
Isaac Newton Laws of Motion cont.
• 1. Law of Inertia – object in motion will remain in motion
until acted upon by an outside force
• 2. F=ma - all objects accelerate at the same rate
(9.8m/sec2). The difference in mass determines when
each object will reach terminal velocity.
• 3. For every action there is an equal and opposite
reaction
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stretching a rubber band
rocket ship
pushing on a wall
20th centruy Astronomers
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Edmund halley
Sir William Herschel
Albert Einstein
William deSitte
Georges-Henri Lamaitie
Edwin P. Hubble
Dr. Carl Sagen
Dr. Stephen Hawking
• Halley 1656 – 1742 english study of comets, star maps
• Herschel – 1738-1822 German, discovered planet Uranus, moons
of Saturn & uranus. (composer)
• Einstein 1879 – 1955 German born, father of modern physics,
theory of relativity
• De Sitte – 1872 1934 Dutch, wk’ed w/Einstein, dark matter
• Lemaitre – 1894 – 1966 Belgian Big Bang theory
• Hubble – 1889 – 1953 American, redshift, Hubble’s law, expanding
universe
• Sagen – 1934 – 1996 American, astrophysicist, communicator
,exobiologist SETI
• Hawking – 1932 English quantum gravity(blk holes) A Brief History
of Time