Here we are to visit Dr. Pepper, oops Mr.
Kepler. "Hello Kepler, can I ask you some questions about your ideas
of planetary motion?
"Of course you can."
"Well what is your philosophy of the
motion of the planets, as well as the positioning of Earth?"
"Well those are some far out questions.
Well you see I was looking over my late teachers work (Tycho Brahe). I
noticed a certain relationship between a planet's rotation and the radius
from the center of the universe to the planet. I found out that the radius
cubed was directly proportional to the period squared. When I calculated a
constant value for this, I found that the values for each planetary system
was pretty close for each moon. There was about a 5% discrepancy for these
values. I then looked back at my values and found that if the orbits of
the planets were ellipses, then the values worked out quite well. I then
followed this concept up and found that the planets do orbit in ovals, or
ellipses, with the Sun at one of the foci of the ellipse. After
experimenting with some beer keg barrels I found that if you joined a line
from the sun to a planet, it would sweep out equal areas in equal times.
Thus, the planet sometimes moves faster, and sometimes closer, depending on
your proximity to the sun."
"A very interesting concept Kepler. I
would then assume that you believe the universe is heliocentric - the sun
at the center"
"Yes I do, and you have a very nice hat"
"Thank you for your time, and yes I do
have a nice hat."
Kepler's ideas were revolutionary. He had developed three laws for
the planets which are as follows:
planets travel in an elliptical or oval shape
area swept out by a line joining the sun and a planet was equal in equal
average radius of an object to its center cubed is directly proportional to
its period of rotation squared. Kepler changed the way we looked at
heavenly motion because he showed that motion in the heavens was not
circular like Aristotle had said. It was elliptical, and the sun was at the
center of the universe.
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