Download Earliest Astronomers

Earliest Astronomers
Earliest
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10,000 years ago – Africa & Europe
Symbols carved in bones
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Counting attempts
Moon Phases
From 5000 years ago
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Stonehenge- British countryside,
Salisbury
Solstice/equinox carvings, drawings,
peckings (petroglyphs)
Plantings & harvesting
Moon phases computer
Early Astronomy
Ancient Greeks
 Geocentric Model = Ptolemy Greek Astronomer
• In the ancient Greeks’ geocentric model, the
moon, sun, and the known planets—Mercury,
Venus, Mars, and Jupiter—orbit Earth.
 Heliocentric Model = Nicolaus Copernicus
• In the heliocentric model, Earth and the other
planets orbit the sun.
Ptolemy
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Geocentric Theory of Earth
thought planets moved in epicycles as
they orbited, helped explain retrograde
motion
was the first to develop circular charts
to explain planetary motion
Aistotle
Copernicus
Copernicus concluded that Earth is a
planet. He proposed a model of the
solar system with the sun at the center.
Heliocentric Model
This model explained the retrograde
motion of planets better than the
geocentric model.
Early Astronomy
Ancient Greeks
 Ptolemaic System
• Ptolemy created a model of the universe that
accounted for the movement of the planets.
• Retrograde motion is the apparent westward
motion of the planets with respect to the stars.
March
Feb.
Jan.
Dec.
April
Sept.
May
Aug.
East
June
July
Retrograde
motion of Mars
West
Retrograde Motion
Tycho Brahe (1546-1601)
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Tycho Brahe designed and built instruments
to measure the locations of the heavenly
bodies. Brahe’s observations, especially of
Mars, were far more precise than any made
previously.
With the use of his inventions he was the
first to accurately record positions of stars
and planets
Early Astronomy
The Birth of Modern Astronomy
German astronomer
Johannes Kepler
(1571-1630) helped establish the era
of modern astronomy by deriving
three laws of planetary motion.
Kepler provided mathematical evidence
that explained the positions and motions
of planets
Johannes Kepler (1571-1630)
Kepler discovered three laws of planetary
motion:
1. Orbits of the planets are elliptical.
2. Planets revolve around the sun at
varying speed.
3. There is a proportional relationship
between a planet’s orbital period and
its distance to the sun.
Early Astronomy
Johannes Kepler used Tycho Brahe’s data to develop
three laws that explained the motions of the planets.
Earth’s orbit
June 15th
Equal areas
(30 days)
July 15th
January 15th
(30 days)
Sun
December 15th
KEPLER’S EQUAL AREA LAW states that a line connecting Earth to the sun will pass
over equal areas of space in equal times. Because Earth’s orbit is elliptical, Earth moves
faster when it is nearer to the sun.
Early Astronomy
Equal areas law
Faster
Slower
KEPLER’S EQUAL
AREA LAW states that
a line connecting
Earth to the sun will
pass over equal areas
of space in equal
times. Because
Earth’s orbit is
elliptical, Earth moves
faster when it is
nearer to the sun.
Early Astronomy
 Galileo Galilei
Italian scientist
Galileo Galilei (1564—1642) used a new
invention, the telescope, to observe the
Sun, Moon, and planets in more detail than
ever before.
Galileo
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Called the ―Father of Science‖
Galileo’s most important contributions
were his descriptions of the behavior of
moving objects
Lived Under House arrest because he
would not recant his views of a suncentered moving Solar System
Early Astronomy
The Birth of Modern Astronomy
 Galileo Galilei
• Galileo’s most important contributions were his
descriptions of the behavior of moving objects.
• He developed his own telescope and made
important discoveries:
1. Four satellites, or moons, orbit Jupiter.
2. Planets are circular disks, not just points of light.
3. Venus has phases just like the moon.
4. The moon’s surface is not smooth.
5. The sun has sunspots, or dark regions.
Newton
English scientist
Sir Isaac Newton (1642—1727) explained
gravity as the force that holds planets
in orbit around the Sun.
Early Astronomy
The Birth of Modern Astronomy
 Sir Isaac Newton
• Although others had theorized the existence of
gravitational force, Newton was the first to formulate and
test the law of universal gravitation. The universal law of
gravitation, helped explain the motions of planets in the
solar system.
 Universal Gravitation
• Gravitational force decreases with distance.
• The greater the mass of an object, the greater is
its gravitational force.
Gravity’s Influence on Orbits
Newton’s Laws of Motion
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1st Law
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2nd Law
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A body at rest, or in uniform motion, will
remain so unless acted upon by an
unbalanced force.
The change in motion (acceleration) is
proportional to the unbalanced force
3rd Law
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For every action there is an equal and
opposite reaction
Summary
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Kepler’s and Galileo’s Laws provided Newton
with important clues that helped him
formulate his laws of motion
Newton arrived at 3 laws that govern the
motion of objects
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The law of inertia
The law of force
The law of action and reaction
Newton also arrived at a law of gravity
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But it seemed to require action at a distance!