Transcript Copernican Revolution

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Objectives – Same as Last Lecture
Describe the geocentric and the heliocentric models of the solar system.
The word planet derives from the Greek "planetes" which means wanderer. Why were the planets called wanderers?
Explain Aristotle’s main argument against the heliocentric model.
What was Aristotle’s other (and weaker) argument against the heliocentric model?
Who gave the first evidence in favor of the heliocentric model? What was the evidence?
Who added the mathematical calculations to the geocentric model?
When a planet undergoes retrograde motion, how does it look?
How did the geocentric model explain retrograde motion?
How did the heliocentric model explain retrograde motion?
What did Brahe contribute to the heliocentric vs. geocentric debate?
Define perihelion and aphelion.
Considering Kepler's three laws of planetary motion (you do not have to memorize them):
What shape orbit does a planet have?
When a satellite orbits the Earth, does it move faster at perigee or at apogee? When a comet orbits the Sun, does it
orbit faster at perihelion or at aphelion?
What is meant by the period of a planet? In our solar system, what planet has the longest period? The shortest? Which
planet orbits with the highest speed? Slowest?
What did Galileo notice about the Moon, the Sun, Jupiter, and Venus? What did he conclude from these observations?
How did the church/state react?
Why does Venus exhibit phases but Mars does not? (Hint: Draw the Sun as well as Venus, Earth and Mars in their
orbits. Shade in Venus and Mars. What do they look like from Earth’s view?)
State Newton's Universal Law of Gravity. If the mass of one of two objects increases, what happens to the
gravitational force between the objects? If the distance between the two increases, what happens to the force?
How can you tell if a process is science? (See earlier lecture on the hallmarks of science.)
When science uses the term “theory” such as the “Theory of Evolution”, is that a weak or a strong statement? What
backs up any theory in science?
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~1500 to ~1700
People Who Contributed*
Copernicus (~1500)
Brahe
(~1570)
Kepler
(~1600)
Galileo
(~1600)
Newton
(~1670)
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Copernicus (~1500)
Resurrected heliocentric model*
First suggested by Aristarchus*
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Is solar system geocentric or heliocentric?*
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Both models have:
Circular orbits (heavenly perfection)
Uniform motion (heavens cannot change)
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Both models explain observations…
Sun, Moon, Planets
Rise in east, Set in west
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Both models explain observations…
Retrograde motion
of planets
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Retrograde motion – Geocentric
Planets ride on epicycles
Sometimes appear
to move backwards
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Retrograde motion – Heliocentric
One planet overtakes
another planet.
Slower planet appears to
move backwards.
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Copernicus (~1500)
Brahe
(~1570)
Kepler
(~1600)
Galileo
(~1600)
Newton
(~1670)
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Brahe (~1570)
Built excellent instruments.*
Collected 20+ years of data from
observations.*
Measured position of Mars very accurately.*
Stayed with geocentric model.*
Saw a supernova! (the sky changed)
Copernican Revolution
Copernicus (~1500)
Brahe
(~1570)
Kepler
(~1600)
Galileo
(~1600)
Newton
(~1670)
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Kepler (~1600)
Derived (from Brahe’s data)
Three mathematical laws
of planetary motion.
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Kepler’s First Law
1. Planets have elliptical orbits around the Sun*
<
aphelion
perihelion
>
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Kepler’s Second Law
2. The radius vector sweeps out equal areas in equal times.
<
>
Thirty
days
Thirty
days
Radius
vector
>
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Kepler’s Second Law means that…
A planet changes speed*;
faster at perihelion, slower at aphelion
Perihelion
(faster)
Aphelion
(slower)
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Definition needed for
Kepler’s Third Law
Period = Time to complete one cycle
Ex: Earth’s period of rotation =?
Ex: Earth’s period of revolution = ?
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Kepler’s Third Law
3. Period2 is proportional to (Radius of orbit)3
• Sometimes written as P2 α r3
• Bigger orbit radius means longer to revolve
• More distant planet takes more time to revolve.*
• More distant planet moves slower.*
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Kepler’s 3 Laws
1.
2.
Planets have elliptical orbits around the Sun*
The radius vector sweeps out equal areas in
equal times.
•
3.
A planet changes speed*
Period2 is proportional to (Radius of orbit)3
•
More distant planet takes more time to revolve.*
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Kepler’s Laws
Also applies to objects in orbit around a central mass
•Satellites around Earth
•Star around a black hole
•Planets around other stars
•Two stars orbiting each other
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Copernicus (~1500)
Brahe
(~1570)
Kepler
(~1600)
Galileo
(~1600)
Newton
(~1670)
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Meanwhile…
Out in the streets…
Galileo (~1600)
Developed and used the telescope
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Galileo observed…
1. Moon craters*
Heavens are not perfect*
!!!Heavens are Earth-like!!!*
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Cigoli – 1622
El Greco < 1600
Painted
imperfect
cratered Moon
Painted imperfect heavens
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Art and ideas flourished*
Frontpiece of G.B.
Riccioli's
Almagestum
Novum, 1651.
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Important astronomy
reference book
Image includes
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Models (Copernicus,
Riccioli, Ptolemy)
Riccioli’s model has
Jupiter and Saturn
centered on Earth
Solar scope.
Top of the Riccioli’s famous image
(from previous slide)
•
Planets around the Sun
Galileo observes…
1. Moon Craters*
Heaven is
not perfect!!*
2. Sunspots*  Sun Rotates
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3. Galileo observes…
4 Moons
of Jupiter*
Earth is
not the
ONLY
center of
motion in
the
heavens
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3. Galileo observes…
4 Moons
of Jupiter*
AND
Take that, Aristotle!
Hey, Aristotle.
Earth can move
and pull the
Moon along.
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4. Galileo Observes Phases of Venus*
• Geocentric model predicts:
• Crescent phase only and little size change
• Heliocentric predicts:
• All phases AND
• Gibbous is small, while crescent is large
Play Venus phases video
http://galileoandeinstein.physics.virginia.edu/more_stuff/flashlets/PhasesofVenus.htm
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4. Galileo Observes Phases of Venus*
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http://astronomy.nmsu.edu/geas/lectures/lecture11/slide02.html
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Galileo Observed*
1. Imperfect heavens, like Earth*
•
Moon craters*
2. Sunspots*
3. Jupiter’s moons*
4. Phases of Venus*
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Copernicus (~1500)
Brahe
(~1570)
Kepler
(~1600)
Galileo
(~1600)
Newton
(~1670)
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Newton (~1700)
HOW planets orbit
(and objects move)
Same laws apply to terrestrial (Earth) objects
and celestial objects*
o called the Newtonian synthesis
o Means Earth and heavens are alike*
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Newton (~1700)
HOW planets orbit
(and objects move)
Newton’s Cannon Demo
http://spaceplace.nasa.gov/how-orbits-work/en/
• Objects in orbit are continuously falling*
• Floating in space is really falling (not due to zero gravity)
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Newton (~1700)
Three Laws of Motion
(Read but not on test)
And
The Universal Law of Gravity*
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Newton - Universal Gravity*
Every mass exerts a force on every other mass.
Note the UNIVERSAL statement.
F
m1
F
m2
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Newton - Universal Gravity
F
m1
F
m2
Gravity always attracts*
Bigger mass means bigger force*
Bigger separation means smaller force*
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Newton - Universal Gravity
F
m
F
D
M
mM
FG 2
D
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Newton - Universal Gravity
Side comments:
Predictability, Mechanistic universe
F
m1
F
D
mM
FG 2
D
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m2
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Newton - Universal Gravity
Side comments:
Predictability, Mechanistic universe
Chaos theory
F
Why gravity?
m1
F
D
mM
FG 2
D
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m2
Copernican Revolution - Summary
Geocentric Vs. Heliocentric
Five people, contributions, significance
Copernicus
Brahe
Kepler
Galileo
Newton
(~1500)
(~1570)
(~1600)
(~1600)
(~1670)
Process of science
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Science
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Science - A process of knowing that
uncovers the laws and processes of the
universe*
Differs from theology or philosophy
 Way to get past the conflicts in various belief
systems (by looking at evidence)
 Sagan: “It doesn’t matter if it makes you feel
good. What matters is, is it true?”
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Process of Science*
(scientific method)
1.
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3.
4.
5.
6.
Observe
Question
Model (hypothesize)
Predict
Test
Revise
You use much of this process all the time
in daily life
 Examples: Car stops….
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Flashlight doesn’t work…
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Cooking…
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Three Hallmarks of Science*
Natural explanations (not supernatural)
 Models that make testable predictions
 Simplest explanation; K.I.S.S. (Occam’s
Razor)
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Theory vs. Law
Vote: Which is stronger? Or more
powerful?
 Theory !!!!!!
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“Oh it’s just a theory.”
 It is not just a theory. It is more powerful
than a law.
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Law
Explains what happens*
 Predicts what will happen in specific cases
 Ex - Universal Law of Gravity
If you drop a rock, it will fall down (and
what force is exerted on it)
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Theory
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Explains why things happen*
Includes laws
Allows predictions of new tests of itself
Ex - General Theory of Relativity
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Explains WHY gravity works
Includes the Law of Gravity AND more
Explains the precession of Mercury’s perihelion
Predicts the existence of Black Holes
Theory
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Explains why things happen*
Includes laws
Allows predictions of new tests of itself
Supported by many scientists
Supported by many testable predictions
Can never can be proven but has not been
disproven
Can always be modified, based on new
data/information*
Exercise
Can you investigate this using science?
 If so, does science support the idea?
 If not, why not? (what hallmarks?)
Ex –
People get nuttier during a full Moon.
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Exercise
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Can you investigate these using science?
If so, does science support the idea?
If not, why not?
1.
2.
3.
4.
5.
A car can skid on ice.
Your personality is determined by the position of the
Sun, Moon, and Planets when you were born.
The universe and its contents evolve.
God exists.
Intelligent Design is science.
Homework
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Grades are updated on class website.
D2L 4 quizzes available to practice for test
Test update – 50-60 multiple choice Tuesday, Feb. 7
• Bring pencil (required) & simple calculator (optional, not
necessary for simple division/multiplication, some available in
class)
• Best test prep: 1. objectives (updated on web),
2. D2L quizzes, 3. lectures/notes, 4. textbook
Observations
• Sunset Part 1 Due Feb. 14
• Moon Phases Due Mar. 2
• Star Gazing, Telescopes & Moon Craters – Show options on
calendar
Keep up with objectives and reading the textbook
Lab Students – No lab today