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Earth/Moon as seen from Mars
Bit of Administration ….
• Homeworks
– Bless, pp. 105-139
– BNSV, pp. 70-83
• Observing Lab
– Nice Work on Lab 1 !
– Start Lab 2 on Saturday
• Timing Matters!
• 10 minutes every clear night for two weeks
M
V
S
J
E
M
S
Not to scale!
The Transition to A Heliocentric Cosmology
• Copernicus
–
–
–
–
–
–
–
1500 AD
Daily Motion due to Earth Rotation
Solar Motion due to Earth Revolution
Prograde Motion of Moon and Planets due to their Orbital Motion
Retrograde Motion
Maximum Elongations of Mercury and Venus
Stars Very Far Away - No Parallax
Geometric Distances to the Planets
Planet
Mercury
Venus
Earth
Mars
Jupiter
Saturn
Copernicus
0.38
0.72
1.00
1.52
5.22
9.07
Modern
0.39
0.72
1.00
1.52
5.07
9.54
Distances Measured in Astronomical Units
M
V
S
J
E
M
S
Not to scale!
The Transition to A Heliocentric Cosmology
• Copernicus
1500 AD
– Daily Motion due to Earth Rotation
– Solar Motion due to Earth Revolution
– Prograde Motion of Moon and Planets due to their Orbital
Motion
– Retrograde Motion
– Maximum Elongations of Mercury and Venus
– Stars Very Far Away - No Parallax
– Geometric Distances to the Planets
– Non-Uniform Motion of Sun, Moon and Planets
• Retained Uniform Circular Motion, thus required Hipparchus’ epicyles!
Hipparchus
Summer
Winter
Copernicus
Summer
Winter
The Transition to A Heliocentric Cosmology
• Copernicus
–
–
–
–
–
–
–
1500 AD
Daily Motion due to Earth Rotation
Solar Motion due to Earth Revolution
Prograde Motion of Moon and Planets due to their Orbital Motion
Retrograde Motion
Maximum Elongations of Mercury and Venus
Geometric Distances to the Planets (example for Venus)
Star Very Far Away
• No observed parallax
– Non-Uniform Motion of Sun, Moon and Planets
In the 1500’s, the Copernican system did not predict positions
better than the highly refined Ptolemaic system
The Copernicans had no proof arguments were aesthetic and philosophical
The Triumph of Heliocentric Cosmology
• Galileo
– Siderius Nuncius
(Star Messenger)
1600 AD
1610
The Triumph of Heliocentric Cosmology
• Galileo
– Siderius Nuncius
(Star Messenger)
1600 AD
1610
– Application of the Telescope
• Revolutionary impact of new technology
The Triumph of Heliocentric Cosmology
• Galileo
1600 AD
– Siderius Nuncius
(Star Messenger)
1610
– Moon
• Craters, mountains, valleys
– Earth-like, not perfect or celestial
The Triumph of Heliocentric Cosmology
• Galileo
1600 AD
– Siderius Nuncius
(Star Messenger)
1610
– Moon
• Craters, mountains, valleys
– Earth-like, not perfect or celestial
– Sun
• Sunspots
• Rotation
QuickTime™ and a YUV4 20 code c d eco mpre ssor are n eede d to see thi s pi ctu re.
The Triumph of Heliocentric Cosmology
• Galileo
1600 AD
– Siderius Nuncius
(Star Messenger)
1610
– Moon
• Craters, mountains, valleys
– Earth-like, not perfect or celestial
– Sun
• Sunspots
• Rotation
– Saturn
• Not spherical
•
I discovered another very strange wonder, which I should like to
make known to their Highnesses . . . , keeping it secret, however,
until the time when my work is published . . . . the star of Saturn is
not a single star, but is a composite of three, which almost touch
each other, never change or move relative to each other, and are
arranged in a row along the zodiac, the middle one being three
times larger than the lateral ones, and they are situated in this
form: oOo
The Triumph of Heliocentric Cosmology
• Galileo
1600 AD
– Siderius Nuncius
(Star Messenger)
1610
– Moon
• Craters, mountains, valleys
– Earth-like, not perfect or celestial
– Sun
• Sunspots
• Rotation
– Saturn
• Not spherical
– Milky Way
• Knowledge unknown to ancients or naked eye
The Triumph of Heliocentric Cosmology
• Galileo
1600 AD
– Siderius Nuncius
(Star Messenger)
1610
– Moon
• Craters, mountains, valleys
– Earth-like, not perfect or celestial
– Sun
• Sunspots
• Rotation
– Saturn
• Not spherical
– Milky Way
• Knowledge unknown to ancients or naked eye
– Jupiter’s Moons
• Microcosm of Copernican Solar System
The Triumph of Heliocentric Cosmology
• Galileo
1600 AD
– Siderius Nuncius
(Star Messenger)
1610
– Moon
• Craters, mountains, valleys
– Earth-like, not perfect or celestial
– Sun
• Sunspots
• Rotation
– Milky Way
• Knowledge unknown to ancients or naked eye
– Jupiter’s Moons
• Microcosm of Copernican Solar System
The Triumph of Heliocentric Cosmology
• Galileo
1600 AD
– Siderius Nuncius
(Star Messenger)
1610
– Moon
• Craters, mountains, valleys
– Earth-like, not perfect or celestial
– Sun
• Sunspots
• Rotation
– Saturn
• Not spherical
– Milky Way
• Knowledge unknown to ancients or naked eye
– Jupiter’s Moons
• Microcosm of Copernican Solar System
– Phases of Venus
• Unexplainable in Ptolemaic System
Venus
Phases
Copernicus
Ptolemy
ConcepTest!
The Earth would be seen to have phases from a life form on
A) Mercury
B) Mars
C) The Sun
D) No planet in the Solar System
Earth/Moon as seen from Mars
The Triumph of Heliocentric Cosmology
• Galileo
1600 AD
– Siderius Nuncius
(Star Messenger)
1610
Galileo too did not abandon Uniform Circular Motion,
and did not embrace his contemporary Kepler
Galileo’s Problems with the Church were Self-Generated
A Dialog Concerning the Two Chief Worlds
The Triumph of Heliocentric Cosmology
•
Tycho Brahe
1575 AD
– Finest observer since Hipparchus
•
Discovered Nova Stella (“new star”)
– Changes in the heavens
•
Showed Comet to be 6x further than Moon
– Not atmospheric
– “Shattered the crystalline spheres”
•
Couldn’t Detect Stellar Parallax
– Rejected Copernicus!
•
Made Extensive Precise Measurements
of Planetary Positions
The Triumph of Heliocentric Cosmology
•
Tycho Brahe
1575 AD
– Finest observer since Hipparchus
•
Discovered Nova Stella (“new star”)
– Changes in the heavens
•
Showed Comet to be 6x further than Moon
– Not atmospheric
– “Shattered the crystalline spheres”
•
Couldn’t Detect Stellar Parallax
– Rejected Copernicus!
•
Made Extensive Precise Measurements
of Planetary Positions
•
Did not abandon Uniform Circular Motion
The Triumph of Heliocentric Cosmology
• Kepler
1600 AD
– Primacy of (Tycho Brahe’s) observations
– Physical machine that mimics the skies precisely
Kepler’s Three Laws of Planetary
Motion
1. The Orbits of the Planets are Ellipses with the
Sun at One Focus
ConcepTest!
Which of the following orbits has the smallest eccentricity?
A)
B)
D) All have the same eccentricity.
C)
ConcepTest!
Which of the following orbits has the smallest semi-major axis?
A)
B)
D) All have the same semi-major axis.
C)
The Orbits of the Planets are Ellipses with the
Sun at One Focus
Kepler’s Three Laws of Planetary
Motion
2. The Line Joining The Sun and A Planet
Sweeps Out Equal Areas in Equal Times
30 days
30 days
The Line Joining The Sun and A Planet
Sweeps Out Equal Areas in Equal Times
Kepler’s Three Laws of Planetary
Motion
3. The Square of a Planet’s Period (P in Years)
Equals the Cube of the Semi-Major Axis of its
Orbit (A in AU)
P2 = A3
P2=A3
A
1