Download The Earth in Space

Topic: Models of the Universe
Key Terms:
Geocentric Theory
Heliocentric Theory
Geocentric Theory
Ancient Greece
Geocentric Model
• ___
• ___
Motion of the other planets
Mars Retrograde
Motion
Geocentric Model: Ptolemy (87-150 AD)
Used epicycles to explain planetary movements
Retrograde Motion
Ptolemy’s system provided the first
framework for all discussion of the
universe for nearly 1500 years!!
But… there was a problem…
Problems with Geocentric Theory
1. This model does explain apparent
motions of celestial (space) objects
2. Cannot explain Foucault’s Pendulum or
the Coriolis Effect
Heliocentric Theory
Heliocentric Model
• ___
• ___
Copernicus (1473-1543)
• Suggests a model that the
Sun was the center of the
universe.
• Argued that the motion of
the Sun & planets could be
equally described by a Sun
centered (heliocentric)
system.
Retrograde Motion
Planet's
apparent path
around sky.
6
6
5
5
4
3
Sun
3
2
2
1
Earth
Outer
Planet
4
1
Earth overtakes slow outer planet so the outer
planet appears to slow down, move in reverse, and
then move forward again with respect to the fixed
stars.
http://faculty.salisbury.edu/~jwhoward/astro108/html/GeoHelio.ppt#274,10,Slide 10
Fixed Stars
Tycho Brahe (1546-1601): the
greatest of the pre-telescope
observers in Europe.
20+ years measuring the positions
of the Sun, Moon and planets with
great accuracy.
Johannes Kepler (1609)
• Johannes Kepler was an assistant to
Tycho Brahe. He used Brahe’s
observations to study the orbit of Mars
• Discovered three laws of planetary
motion: predict with accuracy the
motions of the planets
• Galileo (1564-1642) first scientist to
use a telescope to observe the sky. He
observed the phases of Venus and the
moons of Jupiter. Both observations
supported the heliocentric model.
Modern Universe
Is the Sun the center of the Universe?
Final Question
• Final Question