Download Geocentric vs. Heliocentric

Questions
• What was the first idea of how the
universe was structured?
• What is the correct idea of how the
universe is structured?
• Define: Heliocentric
• Define: Geocentric
• What is the Copernican Revolution?
• Who was the first person to use the
telescope to study space?
Geocentric vs.
Heliocentric
A Battle for the Ages
The Beginnings of the
Geocentric Model
of the Universe
Early Greek Astronomy
• Aristotle
(384 – 322 BCE):
States that the
Universe is a
perfect sphere
with Earth at
the Center.
Objects in space
also move in
perfect circles.
Early Greek Astronomy
• Ptolomy:
Still believed that Earth
was center of Universe. Noticed that
Aristotle’s model did not explain
planetary movements. Ptolemy said
that the planets and stars moved in
EPICYCLES. In other words planets
move in CIRCLES WITHIN CIRCLES!
Ptolemaic
System
Mars
Jupiter
Ptolemy’s system provided
the intellectual framework
for all discussion of the
universe for nearly 1600
years!! So in a very true
sense,
this
idea
was
stupendously
successful
even though we now know
that it was incorrect.
Correction Added
Saturn
Earth & Moon
•Epicycles added to
epicycles
•Precision Timing for
Venus & Mercury
•Earth placed “off”
center.
Mercury
Sun
Venus
The Revolution of Ideas
The Beginnings of the
Heliocentric Model
of the Universe
Copernicus
(1473-1543)
“De Revolutionibus Orbium Coelestium”
The Copernican Revolution!
“On the Revolution of
the Heavenly Spheres”
1. Earth is not the center of “everything.”
2. All the Planets revolve around the Sun!
3. Stars are very much farther away than
the Sun
4. Any motion of the stars is a result of
the Earth’s rotation
5. Any movement of the Sun is due to Earth’s rotation
and revolution about the Sun.
6. Retrograde Motion was much easier to explain.
Changing Ideas is Not Easy.
Copernicus was no fool. He waited until his own
death before he published his new ideas.
On
March
5,
1616,
Copernicus'
work
was
banned from being taught
and discussed by the
Congregation of the Index
"until corrected." It stayed
on this list of prohibited
books and teachings until
1822!!!!
Change is Hard.
Copernicus
still
used
“perfect” circles for the
orbits.
Copernicus ended up
adding “epicycles!”
At the time his theory
was a complete disaster
at
“predicting”
the
positions of the planets
in the sky. Ptolemy’s
model “worked” much
better.
The PROOF!
• Galileo Galilei:
First to point the
TELESCOPE towards the heavens.
He studied the move and orbits of
many nearby planets in our Solar
System. Offered PROOF to
Copernicus’s Heliocentric Model of
our Universe.
Galileo Galilei
The Great
Compromise
Tycho Brahe
(1546-1601)
The Man with
the Gold Nose
Danish Nobelman
Experimentalist & Observer.
He actually made
measurements
Had his own observatory
built.
Made very careful measurements of star’s
positions
Tycho’s Observations
Tycho’s Nova! – A “new”
star appearing in the
constellation Cassiopeia.
Then dimished. (SN1572)
Heavens can Change!
A reason to doubt
Aristotle! Maybe
Ptolemy?
Tycho’s Observations
Made very precise
measurements of stellar
positions and planet
positions in the sky
Comet in 1577
is farther
away than
moon.
Still “measured” no
stellar parallax over an
entire year. Earth must
be stationary.
Tychonic Model
Tycho developed a system that
combined
the best of both worlds.
He kept the Earth in the center of
the universe, so that he could
retain Aristotelian physics and
Ptolemy’s geocentric idea.
The Moon and Sun revolved about the Earth, and
the shell of the fixed stars was centered on the
Earth.
But Mercury, Venus, Mars, Jupiter, and Saturn
revolved about the Sun.
Tychonic Model
Tycho’s Contributions
Lots of data! – Decades worth. He made the
most precise observations that had yet been
made by devising the best instruments available
before the invention of the telescope.
Decided by measurement and observation,
NOT BY DOGMA
His observations of planetary motion,
particularly that of Mars, provided the crucial
data for later astronomers
The Student
• Johannes Kepler:
Followed Tycho’s work
BUT followed the
Heliocentric Model.
Used Math to calculate
that planets moved in
ORBITS and along
ELLIPSES.
Kepler’s
Laws of Planetary Motion
Supported Newton’s Idea of
Law of Universal Graviation
Kepler’s Planetary Diagram
Today!
Questions
• What was the first idea of how the
universe was structured?
• What is the correct idea of how the
universe is structured?
• Define: Heliocentric
• Define: Geocentric
• What is the Copernican Revolution?
• Who was the first person to use the
telescope?