ORIGIN OF MODERN ASTRONOMY
Chapter 22 Page 612
A. EARLY ASTRONOMY
1. Introduction
a. Earth is one of 8 planets
b. We are found in the Milky Way galaxy which contains
100 billion stars
c. There are billions of galaxies
d. Astronomy – Study of the universe
2. Ancient Greeks
a. Made many discoveries
1) Aristotle – earth is round b/c of the curved shadow
on the moon
2) Eratosthenes
a) Calculated circumference of earth
b) Measured 39,400 km (Actual = 40,075)
3) Hipparchus
a) Star catalog of almost 850 stars
b) Measured length of the yr. w/in minutes of modern yr.
c) Could predict lunar eclipses to within hours
b. Geocentric Model
1) Earth was the center of our galaxy
2) Planets, moon, and sun orbit earth
c. Heliocentric Model
1) Sun is the center of our galaxy
2) Planets and moons orbit the sun
d. Ptolemaic System
1) Named after Claudius Ptolemy
2) Accounts for the movements of the planets
3) Used a geocentric model
4) Had to account for retrograde motion
5) He used wrong model & still made correct predictions
RETROGRADE
MOTION
Not a problem with the
heliocentric theory
3. Birth of Modern Astronomy
a. Nicolaus Copernicus
1) Said earth is a planet
2) Proposed the heliocentric theory
3) Used circle orbits
a) Considered the perfect geometric shape
b) Caused planets to stray from predicted patterns
b. Tycho Brahe
1) Made very close calculations of planets
2) Kepler was his assistant
c. Johannes Kepler
1) Planets orbit in an ellipse w/sun at one focus
2) Orbits speed up by sun and slow down away from sun
KEPLER’S 2ND AND 3RD
LAW OF PLANETARY
MOTION
Heliocentric model is being used
Elliptical orbits
Planets “sling-shot” around sun
d. Galileo Galilei
1) First to use telescope
2) Found 4 moons of Jupiter – proved heliocentric theory
3) Venus has phases – proved heliocentric theory
4) Moon’s surface not smooth
5) Sun has sun spots
6) Proposed theory of inertia
SUN SPOTS
Sun spots – cooler spots on the sun
PHASES OF VENUS
Using the heliocentric model simplified how
it worked
e. Sir Isaac Newton
1) First to formulate and test law of universal gravitation
2) Universal Gravitation
a) Every thing gravity
b) Gravity is proportional to mass
c) Gravity is inversely proportional
to distance
d) Earth and Moon
e) Weight vs. mass
B. THE EARTH-MOON-SUN SYSTEM
1. Motions of Earth
a. Rotation
1) Turning or spinning on axis
2) Cause day and night
3) About 24 hours
4) Days get longer/shorter by 2-3
minutes every day
5) Axis 23.5°
b. Revolution
1) Orbit
2) Elliptical orbit
3) Perihelion
a) Earth is closest to
sun
b) About January 3 (91.3 million miles)
4) Aphelion
a) Earth farthest from sun
b) About July 4 (94.4 million miles)
c. Precession
1) Movement along axis
2) 26,000 years
3) 14,000 years Vega will be
the North Star
4) Minor effect on seasons
d. Earth-sun Motion
1) Sun spins around galaxy
2) Galaxy is moving as well
2. Motions of the Earth-Moon System
a. Elliptical orbit
1) Perigee – moon is closest to earth
2) Apogee – moon is farthest from earth
b. Moon is only natural satellite
c. Phases of the Moon
1) How the moon appears to be lit
2) Takes about 1 month
3) Happens b/c light from sun being reflected
4) Stages
a) New moon – can’t see it
b) Waxing crescent – growing with a thin sliver
c) First quarter – growing, ½ showing
d) Waxing gibbous – growing, ¾ showing
e) Full
f) Waning gibbous – shrinking, ¾
g) Third quarter – ½ showing
h) Waning crescent – shrinking,
only a sliver
i) New moon
d. Lunar Motions
1) Takes 29.5 days
2) Rotation and revolution
a) Same speed
b) Always see the same side of the moon
c) Daylight and darkness last for about 2 weeks
i. Daylight temp = 260°F
ii. Night temp
i) -280°F
ii) No atmosphere
3. Eclipses
a. Usually 4/yr – 2 solar, 2 lunar
b. Solar Eclipse
1) Moon blocks sunlight
2) Happens during the new moon
3) Umbra – dark shadow (total eclipse)
4) Penumbra – light shadow (partial eclipse)
5) Sun, earth, and moon have to be in direct line
6) Temperature drops, stars possibly visible
7) Can last up to 7 minutes
8) Can see the sun’s corona
DIAMOND RING
BAILY’S BEADS
PARTIAL SOLAR ECLIPSE
HULL, IA JUNE 1, 2012
TAKEN BY: MARK STEIGER
How it works
–
https://www.youtube.com/watch?v=IZza3Ijpixo
–
https://www.youtube.com/watch?v=DVqew5gJU2o
BBC 2015 Solar Eclipse
–
https://www.youtube.com/watch?v=iG9GdfL_ToU
c. Lunar eclipse
1) Earth blocks sunlight
2) Causes the moon to turn red
3) Can last up to 4 hours
4) Seen by anyone on that side of earth
How it works
https://www.youtube.com/watch?v=wuhNZejHeBg
Lunar Eclipse Time Lapse
https://www.youtube.com/watch?v=lcRp1jKJmJU
C. EARTH’S MOON
1. Introduction
a. Unusually large compared to earth’s size
1) 2,159 miles in circumference
2) ¼ of earth’s circumference
b. Apollo missions gathered information
c. Density 3.3x that of water (Earth is 5.5x)
d. Gravity is 1/6 that of earth
- 150lb person weighs 25lbs on moon
WHICH IS BIGGER?
The Moon
Elephant
2. Lunar Surface
a. Doesn’t have weathering and erosion
b. No more volcanic eruptions
c. Craters
1) Round depression in surface
2) Created by meteors
3) Atmosphere doesn’t burn up meteors
4) Similar to a splash
5) Rays – splash marks that radiate outward
d. Highlands
1) Form mountain ranges
2) A lot on the back side of the moon
3) Lighter color
e. Maria
1) Dark, smooth areas of the moon
2) Formation
a) Meteors hit cooled surface of moon
b) Broke through and let magma seep out
3) Rilles – long channels like valleys or trenches
https://www.youtube.com/watch?v=2msFzwil5HM
FEATURES OF THE
MOON
Rays
Highlands
Maria
“Splash” mark
3. Lunar History
a. Many different theories
b. Formation
1) When Earth was forming meteor the size of Mars hit
it
2) Liquefied Earth’s surface
3) Sent large amounts of crustal and mantle rock from
earth
4) Ejected material entered orbit around Earth
5) Eventually combined into the moon
MOON FORMATION
https://www.youtube.com/watch?v=Sp4IEAO_ngU
c. Supporting evidence
1) Ejected material wouldn’t have much iron –
accounts for lack of large iron core on moon
2) Ejected material would have lost water – accounts
for lack of water on moon