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Units of Chapter 2
2.1 Ancient Astronomy
2.2 The Geocentric Universe
2.3 The Heliocentric Model of the Solar System
The Foundations of the Copernican Revolution
2.4 The Birth of Modern Astronomy
© 2011 Pearson Education, Inc.
Units of Chapter 2, continued
2.5 The Laws of Planetary Motion
Some Properties of Planetary Orbits
2.6 The Dimensions of the Solar System
2.7 Newton’s Laws
2.8 Newtonian Mechanics
Weighing the Sun
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White Board Question
• What are some ancient structures that people used
the sun and stars to help keep track of time and
seasons?
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2.1 Ancient Astronomy
• Ancient civilizations observed the skies
• Many built structures to mark astronomical
events
Summer solstice
sunrise at
_____________:
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2.1 Ancient Astronomy
Spokes of the _________________________in
Wyoming are aligned with the rising and
setting of the Sun and other stars
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2.1 Ancient Astronomy
This temple at
_______________,
in Mexico, has many
windows that are
aligned with
astronomical events
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2.2 The Geocentric Universe
Earth based
Ancient astronomers
observed:
Five planets:
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2.2 The Geocentric Universe
Sun, Moon, and stars all have simple
movements in the sky
Planets:
• Move with respect to
fixed stars
• Change in brightness
• Change speed
• Undergo retrograde
motion
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Golden Age
600 BC-AD 150
Aristotle
• _______
philosopher (384-322 BC)
• Earth is _____________
• Casts a curved shadow when
passes between _________ and ______
His belief was abandoned during the Middle
Ages
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_________________
276-194 BC
• First successful attempt to figure out the
size of the earth
____________________
2nd Century BC
• Divided stars into six groups according
to brightness
• Method for predicting lunar eclipses
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________centric model
• _______________________
orbit the earth
• _________________(stars)
orbits the earth
• Incorrect
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2.2 The Geocentric Universe
Earliest models had ____________________ at
center of solar system
Needed lots of
complications to
accurately track
planetary motions
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Carl Sagan on epicycles
http://www.dailymotion.com/vide
o/xerwsh_carl-sagan-videosepicycles-of-ptol_tech
Take notes:
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_____________centric Model
• First heliocentric astronomer-Aristarchus (Greek 312-230 BC)
• Earth and other planets orbit the sun
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Heliocentric vs. Geocentric Model
Model
Location of
Earth
Center of
__________ the universe
Heliocentric
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_________
Location of
Sun
Orbits
_______
________ of
the universe
Who
supports
White board question
• On your white board make a Venn Diagram
comparing Heliocentric and Geocentric views of the
universe.
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Ptolemaic System
• Claudius ______________ wrote a 13
volume work on Greek astronomy
• ___________centric, used ___________
to explain the varying brightness of planets
and planet retrograde motions
• Used mathematical terms to
explain the heavenly bodies
2.3 The _____________________
Model of the Solar System
_______________ is at center of solar system.
Only Moon orbits around Earth; planets orbit
around Sun.
This figure
shows
retrograde
motion of
Mars.
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Understanding retrograde
motion
• http://astro.unl.edu/classaction/animations/re
naissance/retrograde.html
• Interactive
– http://highered.mcgrawhill.com/olcweb/cgi/pluginpop.cgi?it=swf::800::600:
:/sites/dl/free/0072482621/78780/Retro_Nav.swf::
Retrograde%20Motion
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White board
• Explain retrograde motion to your
neighbor, see if you can write it out
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Discovery 2-1: The Foundations of
the Copernican Revolution
1. ____________ is not at the center of everything.
2. Center of Earth is the center of _________ orbit.
3. All _________________revolve around the Sun.
4. The ________________ are very much farther
away than the Sun.
5. The apparent movement of the stars around the
Earth is due to the Earth’s __________________.
6. The apparent movement of the Sun around the
Earth is due to the Earth’s __________________.
7. ______________________motion of planets is
due to Earth’s motion around the Sun.
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2.4 The Birth of Modern Astronomy
_________________________
invented around 1600
___________________ built
his own, made observations:
• Moon has mountains and
valleys
• Sun has ___________, and
rotates
• ______________has moons
Venus has ________________
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Galileo and Venus
• How did Venus retrograde motion
definitely prove that the sun is at the
center of the solar system?
• Turn to your table group and see if you
can figure it out
2.4 The Birth of Modern Astronomy
_______________
cannot be
explained by
geocentric model
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_______________
1546-1601
Denmark
• Developed instruments to measure
the locations of heavenly bodies
• Collected a vast amount of data that
Keplar was able to use
to build his laws of
planetary motion
2.5 The Laws of Planetary Motion
___________________
were derived using
observations made by
Tycho Brahe
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Johannes Kepler
1571-1630
• Three laws of planetary motion
–Kepler observed:
• Mars orbit was elliptical
• As Mars approaches the sun it
speeds up and slows down as
it goes away from the sun
Three laws of planetary motion
1.
The path of each planet around the sun is an ellipse
with the sun at one focus.
2.
Each planet revolves around the sun so that it sweeps
over equal areas in equal amounts of time causing it to
travel more rapidly in areas closer to the sun.
The square of the orbital period is proportional to the
cube of its distance from the sun.
3.
2.5 The Laws of Planetary Motion
Law 1. Planetary orbits are ________________,
Sun at on a
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Time to try it on your own
• An ellipse can be drawn with the aid of
a string, a pencil, and two thumbtacks.
The wider the separation of the foci, the
more elongated, or eccentric, is the
ellipse. In the special case where the
two foci are at the same place, the
curve drawn is a circle.
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2.5 The Laws of Planetary Motion
Law 2. Imaginary line connecting Sun and
planet sweeps out _________________________
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Keplar’s 2nd law
http://www.youtube.com/watch?v=5a2mcEtzKE
2.5 The Laws of Planetary Motion
Law 3. Square of ____________ of planet’s
orbital motion is proportional to cube of
_______________________________________
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More Precisely 2-1: Some
Properties of Planetary Orbits
____________________: closest approach to
Sun
__________________: farthest
distance from Sun
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Another way to say them
• The path of the planets about the sun is elliptical in shape,
with the center of the sun being located at one focus. (The
Law of _________________________)
• An imaginary line drawn from the center of the sun to the
center of the planet will sweep out equal areas in equal
intervals of time. (The Law of ___________________)
http://www.physicsclassroom.com/mmedia/circmot/ksl.cfm
• The ratio of the squares of the periods of any two planets is
equal to the ratio of the cubes of their average distances
from the sun. (The Law of ________________________)
Easy math
If planet A is 4 units from the sun then what
is its orbital period. (a3 = p 2)
Keplar’s laws
http://www.youtube.com/watch?v=5a2mcEtzKE
http://www.youtube.com/watch?v=GcKiGCuvtA
Let’s watch different planets in
action
• http://astro.unl.edu/classaction/animations/
renaissance/kepler.html
__________________
• Mathematician
• Invented calculus to solve the gravity
2.7 Newton’s Laws
____________________
____________________
____________________
explain how objects
interact with the world
and with each other.
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Newton: Three laws of motion
Law 1:
An object at rest will remain at rest
unless acted on by an unbalanced
force. An object in motion continues in
motion with the same speed and in the
same direction unless acted upon by
an unbalanced force. This law is often
called “________________________".
http://teachertech.rice.edu/Participants/lo
uviere/Newton/law1.html
White board question
• If everything in an airplane is traveling at
the same speed when do you feel the
motion?
Law 2
• Acceleration is produced when a force
acts on a mass. The greater the mass
(of the object being accelerated) the
greater the amount of force needed (to
accelerate the object).
• http://teachertech.rice.edu/Participants/lou
viere/Newton/law2.html
• Force=____________________________
• Forceg=mass x gravitational acceleration
Definitions
• ___________________ is an intrinsic
property of an object and remains the
same independent of where it is in the
universe
• _________________is the downward
force experienced by an object as a result
of gravitational interaction
A little math
• If Marvin the Martian is 100 lbs on Earth
how much would he weigh on the moon if
the surface gravity is 17% of that on
Earth?
Weight=mass x gravitational acceleration
Or weight = weight on earth x specific
gravity
Now see if you can figure it out
W= 100 lbs x .17=17 lbs.
Law 3
• For every action there is an
_____________and _______________
re-action.
• http://teachertech.rice.edu/Participants/lou
viere/Newton/law3.html
Sir Isaac Newton
1642-1727
Newton in a nutshell
Without the influence of
____________, planets would move
in a straight line out into space.
The tendency of planets to remain in
a straight line and the force of
________________ result in
elliptical patterns
Using Newton’s gravity
Basically
Force is proportional to the product of the
mass of two objects/distance between
them squared so:
If the mass doubles the force ____________
but if the distance doubles then you have
________ the force.
So you can figure weight of an object if you
know the distance from earth
2.7 Newton’s Laws
Gravity
On the Earth’s
surface,
__________________
_________________
is approximately
constant, and
directed toward the
center of Earth
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2.7 Newton’s Laws
Gravity
The constant G is called the
______________________________________;
it is measured experimentally and found to be
G = 6.67 x 10-11 N m2/kg2
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But let’s look at an easier way
Fgm1m2/d2
The force of gravity
is proportional to
the product of the mass of the
two objects divided by the
distance squared
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White board problem
If Marvin is 36 lbs how much is his weight if
he is at 2r (distance from Earth)
Weight = 36/22 36/4=9lbs
So if this is true and
astronauts at the space
station are still within the
earth’s gravity, why do they
experience
weightlessness???
http://www.youtube.com/watch?v
=2V9h42yspbo
2.8 Newtonian Mechanics
_________________:
the speed necessary
for a projectile to
completely escape a
planet’s
_________________
________________.
With a lesser speed,
the projectile either
returns to the planet
or stays in orbit.
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So what did Einstein have to say about gravity?
But what is gravity, what is it that attracts to objects to one
another? http://www.youtube.com/watch?v=O-p8yZYxNGc
http://www.youtube.com/watch?v=DbhuRcmSkMg&feature=rel
ated
Gravity as Curved Space
Curved space
• Einstein noticed ___________________.
A beam of light follows the curvature of
space
• Planets follow the _________________
so if gravity has curvature then anything with
mass will curve the space around it