Transcript 01_planetary motion and copernican revolution

Lecture Outline
Chapter 1
The Copernican
Revolution
Copyright © 2010 Pearson Education, Inc.
Copyright © 2010 Pearson Education, Inc. and R. Fisher
In the news
• http://www.space.com/27016-galaxysupercluster-laniakea-milky-wayhome.html
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12 sept: Chapter 1
The Copernican Revolution
Copyright © 2010 Pearson Education, Inc. and R. Fisher
Units of Chapter 1
Preview the chapter….
The Motions of the Planets
The Birth of Modern Astronomy
The Laws of Planetary Motion
Newton’s Laws
Summary of Chapter 1
Copyright © 2010 Pearson Education, Inc. and R. Fisher
1.1 The Motions of the Planets
The Sun, Moon, and stars all have simple
movements in the sky, consistent with an
Earth-centered system.
But the Planets:
(Show on Stellarium)
•Move with respect to
fixed stars
• Change in brightness
• Change speed
• Have retrograde motion
• Are difficult to describe
in earth-centered system
Copyright © 2010 Pearson Education, Inc. and R. Fisher
1.1 The Motions of the Planets
A basic geocentric model, showing an
epicycle (used to explain planetary motions)
Copyright © 2010 Pearson Education, Inc. and R. Fisher
1.1 The Motions of the Planets
Lots of epicycles
were needed to
accurately track
planetary motions,
especially retrograde
motions. This is
Ptolemy's model.
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1.1 The Motions of the Planets
A heliocentric (Sun-centered) model of the solar
system easily describes the observed motions
of the planets, without excess complication.
So, what is
the primary
advantage
of the
heliocentric
model?..
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*13 sept; 1.2 The Birth of Modern Astronomy
Observations of Galileo:
• The Moon has mountains, valleys, and craters.
• The Sun has imperfections, and it rotates.
• Jupiter has moons.
• Venus has phases.
All these were in contradiction to the general
belief that the heavens were constant, perfect,
and immutable.
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1.2 The Birth of Modern Astronomy
The phases of
Venus are
impossible to
explain in the
Earth-centered
model of the
solar system.
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The birth of modern
astronomy
• https://www.youtube.com/watch?v=zHU
WP9zu4W8
• Watch until 10:45.
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1.3 The Laws of Planetary Motion
Kepler’s laws:
1. Planetary orbits are ellipses, Sun at one focus.
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**1.3 The Laws of Planetary Motion
Kepler’s laws:
2. Imaginary line connecting Sun and planet
sweeps out equal areas in equal times.
When an orbiting planet or comet
is near the sun, it goes fast, and
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© 2010it’s
Pearson
Education,
Inc. and R.it
Fisher
when
far
away,
goes slowly.
1.3 The Laws of Planetary Motion
Kepler’s laws:
3. Square of period of planet’s orbital motion
is proportional to cube of semimajor axis.
The period of a planet goes up as the radius of
the planet increases
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Compare
this to
Kepler’s
second
law.
Who was Kepler?
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The greatest astronomer.
Born 1571.
Worked for Tycho Brahe (“teesho”)
Analyzed motion of the planets, worked
out laws of planetary motion
• a good and interesting 20 min video of this history
• http://www.youtube.com/watch?v=IBvMhpx8Q0Q plus
http://www.youtube.com/watch?v=ShQXRBDBfaA
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From this video, know
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Aritotle
Ptolomy
Renaissance
Copernicus
Tycho brahe
Kepler
Galileo
Newton
Copyright © 2010 Pearson Education, Inc. and R. Fisher
1.3 The Laws of Planetary Motion
The Dimensions of the solar system
• The distance
from Earth to the
Sun is called an
astronomical unit.
Its actual length
may be measured
by bouncing a
radar signal off
Venus and
measuring the
transit time.
Copyright © 2010 Pearson Education, Inc. and R. Fisher
1.4 Newton’s Laws
Newton’s laws of motion explain how objects
interact with the world and with each other.
Copyright © 2010 Pearson Education, Inc. and R. Fisher
1.4 Newton’s Laws
Newton’s third law: know this one!!!!
When object A exerts a force on object B, object
B exerts an equal and opposite force on object A.
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1.4 Newton’s Laws
Gravity
On Earth’s surface,
the acceleration
due to gravity is
approximately
constant, and
directed toward the
center of Earth.
Copyright © 2010 Pearson Education, Inc. and R. Fisher
1.4 Newton’s Laws
Gravity
For two massive objects,
the gravitational force is
proportional to the
product of their masses
divided by the square of
the distance between
them.
The closer they are, or the
bigger (more massive) they
are, the harder they pull on
each other.
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1.4 Newton’s Laws
Gravity
The gravitational pull
of the Sun keeps the
planets moving in
their orbits.
Compare to a
spinning ball on
string….
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1.4 Newton’s Laws
Two or more Massive objects orbit around
each other.
look at http://phet.colorado.edu/sims/my-solarsystem/my-solar-system_en.html and see binary
star or double double to see various types of
orbit.
Or look at
http://phet.colorado.edu/en/simulation/gravityand-orbits to see earth wobble the sun.
Copyright © 2010 Pearson Education, Inc. and R. Fisher
1.4 Newton’s Laws
Kepler’s laws are a
consequence of
Newton’s laws.
Copyright © 2010 Pearson Education, Inc. and R. Fisher
18 sept. Quiz on chapter 2
1.
2.
The shape of every orbit is
a. Circle b. square c. parabola
d. ellipse
Which was NOTan observation of Galileo?
a. The Moon has mountains, valleys, and craters. B. The Sun has
imperfections, and it rotates. C. Jupiter has moons. D. Venus has moons
3. Which of these people was NOT part of the Copernican
revolution
a. Copernicus
b. Aristotle
c. Kepler
d. Newton
4. What is the force that holds all planets, moons, comets,
asteroids, galaxies, and stars in their orbits?
a. Gravity
b. Magnetism
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c. Jedi
d. Mass
18 Sept 2015
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Quiz on Stelarium
Find your object
Any moons? Their period
Magnitude, phases
Look at variation with time
Why change size
Moon on sept 27, 9:40pm
Turn on equatorial grid
Find your zodiac constellation
Where was the moon when you were born?
Copyright © 2010 Pearson Education, Inc. and R. Fisher
Summary of Chapter 1
• First models of solar system were
geocentric, but couldn't easily explain
retrograde motion.
• Heliocentric model does.
• Galileo's observations supported
heliocentric model.
• Kepler found three empirical laws of
planetary motion from observations.
Copyright © 2010 Pearson Education, Inc. and R. Fisher
The varieties of orbital motion
• http://phet.colorado.edu/sims/my-solarsystem/my-solar-system_en.html
• Look at the range of possibilities
• Check: why are only stable orbits
present in our solar system & galaxy?
• Are all orbits stable? Examples….
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Summary of Chapter 1, cont.
• Laws of Newtonian mechanics explained
Kepler’s observations.
• Gravitational force between two masses is
proportional to the product of the masses,
divided by the square of the distance
between them.
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Update on New Horizons
http://pluto.jhuapl.edu/
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Show this tool in google earth
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• NY
Times
yesterd
ay
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Practice for exam 1
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1) In an annular eclipse,
A) the Moon is totally blocked by the Earth.
B) the Sun is partially blocked by the Earth.
C) the Moon appears as a thin, bright ring.
D) the Sun appears as a thin, bright ring.
E) the Sun is totally blocked by the Moon.
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2) The interval from new Moon to first quarter is about a(n)
A) month.
B) day.
C) hour.
D) year.
E) week.
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3) Put these important scientists in proper order of when they lived and worked
a. Galileo, b. Copernicus, c. Newton, d. Ptolomy, e. Kepler
Copyright © 2010 Pearson Education, Inc. and R. Fisher