Download Chapter 22 Section 1 Early Astronomers Aristotle Copernicus Kepler

Aristotle
Copernicus
Chapter 22
Section 1
Early
Astronomers
Newton
Kepler
Galilei
Let’s start at the beginning…
• Ancient Greece
– Golden Age (600 b.c. – a.d 150)
– Relied on observations
– Used geometry and trigonometry principles to measure size and
distances of sun & moon.
• Aristotle
– Earth is round—thought so b/c of Earth’s curved shadow on Moon
– Theory abandoned in Middle Ages
• Eratosthenes
– 1st successful attempt to establish size of Earth
– Used geometry to determine circumference of Earth (angles of Sun)
• Hipparchus
– Star catalog—location of ~850 stars organizes according to
brightness
– Measured length of year to within minutes of modern year (current)
Earth is #1 !
• Geocentric meaning Earth Centered was
created by Claudiaus Ptolemy. He thought the
earth was the center of everything in our Solar
system.
Oh wait… Sun is #1 !
• Heliocentric meaning Sun Centered was
created by Nick Copernicus and he thought
and proved that the sun was the center of our
solar system and every thing revolves around
the sun.
Ptolemaic System
• Cladius Ptolemy
– Ptolemaic system
• Accounted for the movements of the planets
• Retrograde motion
– Apparent movement of a planet that appears to
approach, reverse, and then continue onward
– Occurs because Earth has a faster orbital speed than
Mars (see below)
Modern Men
• Copernicus (1473-1543) Poland
– Earth as a planet, proved Earth rotates
– Heliocentric theory
• Brahe (1546-1601) Denmark
– Designed and built angle-measuring device
– Mars observations executed precisely
Modern Men: Kepler
• 1571-1630 Danish; Brahe’s assistant
• 3 laws of planetary motion
1. Planet’s orbit is an ellipse (oval) shape with sun @ one
focus.
2. The planet’s move faster when nearer the sun and
slower when farther away (equal areas in equal time).
3. Square of length of time it takes a planet to orbit the sun
(orbital period) is proportional to the cube of its mean
distance to the sun (p2=a3).
•
Defined the term astronomical unit (Au)
–
Average distance between Earth & sun (~150 million
km)
Modern Men: Galileo
• 1564-1642 Italian
• Telescopes for more precise observations
– 4 satellites (moons) orbiting Jupiter & other
moving objects
– Planets are circular disks; not just points of light.
– Venus has phases just like the moon.
– Rough, mountainous texture on moon.
– Sunspots on Sun’s surface revealed rotational
period of ~ 1 month
Modern Men: Newton
• 1642-1727 English
• Formulated law of universal gravitation
– All objects have gravity between them.
– The greater the mass of the object, the
greater the gravitational force.
• Laws of inertia and gravity
– Without gravity, planets would move in a
straight line out into space.
Contemporary Fellows
• Edwin Hubble
– 1889-1953 American
– Universe is still expanding
– Galaxies outside of our own
• Stephen Hawking
– 1942-_____ British
– Theorized existence of black holes
• Carl Sagan
– 1934-1996 American
– SETI, questioned Drake equation,
popularized science and the Cosmos TV
program
• James Webb Space Telescope
– Named after NASA administrator
– Infared
– Big bang theory and origin of universe