
This book was created and published on StoryJumper™
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Claudius Ptolemy lived in Alexandria, Egypt from
100CE-170CE. He was a famous astronomer. His
life goal was to build upon the theories of the
philosopher Plato in order to explain the movement
of the planets in the Universe.



Plato's model showed the Earth at the center,
with each planet moving in its own perfectly
circular orbit.


Everything was studied without a telescope. Ptolemy
used math based on the positions of the planets that he
observed with his eyes to create his models.

embarking upon his creation, I should have recommended
something simpler."

Ptolemy had a geocentric model of the universe. That
means that everything revolved around the Earth,
while the Earth stayed in the same place. He had
three ideas that helped explain this.


First, he concluded that the Earth was not
exactly in the center of the circle the planets
made around Earth. This means that the
system was eccentric.


Ptolemy used an equant. An equant is a mathematical
point that Ptolemy created to explain the speeds of the
planets. The planets went different speeds at different
parts of their orbit. The equant helped explain why this
happened.


Lastly, he thought that the planets moved in
epicycles in their orbit. This means that they
moved in small circles as they moved around
Earth.

Epicycles explained retrograde motion. If the planets
went faster in the epicycles then they did on the rest of
their orbit, this would explain why sometimes the
planets looked like they were moving backwards.

Despite the fact that Ptolemy was able to predict the
position of the planets, none of his theories were
correct. Ptolemy's model of the solar system was
accepted for over 1300 years. How could people have
believed him for so long if his model wasn't correct?
Well, there were many factors that made Ptolemy's
geocentric model so convincing.
+


People believed Ptolemy because when they looked
at the sky at night, the planets appeared to change
positions, and the earth didn't feel like it was
moving, so it made sense that the earth was the
center of the universe and didn't move.
Ptolemy's model could also predict the positions of
the sun, moon, and planets with math, which gave
him credibility.
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This book was created and published on StoryJumper™
©2015 StoryJumper, Inc. All rights reserved.
Publish your own children's book:
www.storyjumper.com




Claudius Ptolemy lived in Alexandria, Egypt from
100CE-170CE. He was a famous astronomer. His
life goal was to build upon the theories of the
philosopher Plato in order to explain the movement
of the planets in the Universe.



Plato's model showed the Earth at the center,
with each planet moving in its own perfectly
circular orbit.
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