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?
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A Battle for the Ages
The Beginnings of the Geocentric Modelof the Universe
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.
Earth & Moon
The Beginnings of the Heliocentric Modelof the Universe
“De Revolutionibus Orbium Coelestium”
The Copernican Revolution!
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.
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!!!!
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.
Experimentalist & Observer. He actually made measurements
Had his own observatory built.
Made very careful measurements of star’s positions
Tycho’s Nova! – A “new” star appearing in the constellation Cassiopeia. Then dimished. (SN1572)
Heavens can Change!
A reason to doubt Aristotle! Maybe Ptolemy?
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.
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.
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
Supported Newton’s Idea of
Law of Universal Graviation