Download “Geocentric vs. Heliocentric Theory”

“Geocentric vs. Heliocentric
Theory”
Claims and Evidence from the
Ancient Astronomers
Cornell Notes pg. 53
Astronomy
• The study of celestial
objects such as moons,
planets, stars, and
galaxies.
• One of the oldest
branches of science.
Moving Back • Think back to over 2000
years ago. No high tech
in time…
equipment for studying
the far reaches of
space… no idea of the
law of gravity…
scientists were stilling
trying to develop basic
explanations for the
world.
Geocentric • CLAIM: Earth is the center
of the universe
Theory
– Sun, planets, and stars all
rotate around the earth.
• EVIDENCE: things appear
to move around Earth;
Earth doesn’t feel like its
moving…
Basic
Assumptions
about the
Universe…
• Everything outside of
Earth is perfect
– Planet shapes are
perfect spheres
– Orbits of Planets are
perfect spheres
– Stars are fixed to an
outer sphere
Aristotle
• CLAIM: 5 elements each
have
a
natural
place
in
384-322 BC
the universe- Earth at
center (geocentric).
• EVIDENCE: earth sinks
in water…gas bubbles
rise, fire rises above
air… etc.
– Scientific teachings were
taught for over 1000
years, but never tested!
A Problem
with the
Geocentric
Model…
• Retrograde Motionplanets temporarily
appear to move
backwards
Ptolemy
90-168 AD
• CLAIM: Celestial bodies
revolve around the Earth
(geocentric).
• EVIDENCE: created a
model of space that
could be used to predict
future positions of
planets AND explained
retrograde motion
http://www.polaris.iastate.edu/Eve
ningStar/Unit2/unit2_sub1.htm
Heliocentric
Theory
• CLAIM: The sun is at the
center with planets
revolving around the
sun.
• EVIDENCE: failure of
Ptolemy’s model over
time; retrograde motion
can be explained simply
if earth is moving, too.
http://www.polaris.iastate.edu/Evenin
gStar/Unit2/unit2_sub2.htm
Copernicus
• Given credit as
developing the
1473-1543 AD
Heliocentric Theory.
• Created a simpler, more
accurate model that
could be used to predict
future locations of
planets.
– Other Claims: earth is
spinning on axis and
revolving around the sun.
Brahe
• CLAIM: Moon’s orbit
isn’t a perfect circle, it’s
1546-1601 AD
an ellipse.
• EVIDENCE: careful
observations with
diligent records.
– (Brahe actually supported
the Geocentric Theory)
Kepler
• CLAIM: Planets do not
orbit in perfect circles
1571-1630 AD
but instead orbit in
ellipses.
• EVIDENCE: used
records collected by
Brahe
• This discovery was the
last piece needed to
perfect Copernicus’s
model. (Still not widely
accepted).
Galileo
• CLAIM: our moon has
craters and the sun has
1564-1642 AD
spots (they’re not
perfect!); and Jupiter has
it’s own moons- they
don’t orbit the earth!
• EVIDENCE:
observations made
through his carefully
crafted telescope
Sir Isaac
Newton
1642-1727 AD
• Defined the Laws of
Motion and the Law of
Gravity.
• Now our solar system
makes sense!