Kepler improved the Copernican theory by changing the circular orbits of the planets into elliptical ones.

1. © ABCC Australia 2015 new-physics.com
THE ELLIPTICAL ORBITS OF
JOHANNES KEPLER
Cosmic Adventure 3.06

2. © ABCC Australia 2015 new-physics.com
Tyco Brahe
Although Copernicus
was already dead, there
were a growing number
of opponents, among
whom Tyco Brahe
(1546-1601) was the
strongest one since he
himself was also an
established astronomer.

3. © ABCC Australia 2015 new-physics.com
Johannes Kepler
Brahe had gathered a lot of
astronomical data in order to
prove Copernicus wrong, never
knowing that these data would
help Copernicus instead.
It was because these data were
later used by Brahe’s student
Johannes Kepler (1571-1630)
with whom Brahe was not
getting along well.

4. © ABCC Australia 2015 new-physics.com
Problematic Job
In order to keep Kepler away
from his major work, Brahe
assigned Kepler a
problematic job of the
planet Mars so that he
himself could concentrate on
forming his theory of the
solar system.

5. © ABCC Australia 2015 new-physics.com
Elliptical orbit round the sun
After a long struggle,
Kepler finally realized that
the orbits of the planets
were not the circles
prescribed by Aristotle but
assumed implicitly by
Copernicus. They were
instead "flattened circles"
that geometers call ellipses.
Planet’s elliptical orbit

6. © ABCC Australia 2015 new-physics.com
Heliocentre
What is more, Kepler further
found that the model would
match the observed
planetary positions better if
the Sun is placed at one
focus of elliptical planetary
obits. This would provide
significantly increased
accuracy in predicting the
position of the planet.
Sun

7. © ABCC Australia 2015 new-physics.com
Earth Removed from Centre Position
As a student Kepler had been a
believer in Copernicus’
heliocentric theory. It is not hard
for him trying to project the
image of Mars to that of the
Earth and did likewise
calculations. In such a situation,
the earth will be moving and is
dislodged from its position as
the centre of the universe. Heliocentre
Geocentre

8. © ABCC Australia 2015 new-physics.com
Kepler’s first 2 laws of
planetary motion
In Epitome Astronomiae
Copernicanae published in
1909, Kepler presented a
heliocentric model of the
solar system in which all the
planets have elliptical orbits.
This was also the first Kepler’s
law of planetary motion.

9. © ABCC Australia 2015 new-physics.com
Kepler’s Second Law
The second law was
published along with the
first one. It stated that
planets farther away from
the sun will move slower,
and vice versa when
closer. The planet will
sweep over equal areas in
equal amount of time.
One
month
One
month
Equal
areas

10. © ABCC Australia 2015 new-physics.com
Kepler’s 3rd Law
In 1619, 10 years after the
appearance of his first two laws,
Kepler published his third law of
planetary motion. It stated that the
square of the orbital period (time
for one orbit) varies in proportion
to the cube of the orbit’s size.
Kepler's work enabled the
heliocentric solar system model of
Copernicus to accurately match and
predict planetary positions on the
zodiac for many centuries.
𝑃= Period in years
𝑎 = semi-major axis

11. © ABCC Australia 2015 new-physics.com
Too Far a Step Forward
Pre-Copernican thinkers definitely could not conceive of an earth in
motion and its disappearance from the centre of the universe. What
Kepler had thought of was so bold an imagination that they would have
never dreamed of.
However Kepler's ideas were
not immediately accepted.
Galileo, for example,
completely ignored Kepler's
work.

12. © ABCC Australia 2015 new-physics.com
Kepler’s Book Prohibited
The church also placed Kepler’s work on the
index of prohibited books despite Kepler being
a Protestant.

13. © ABCC Australia 2015 new-physics.com
The Establishment of Heliocentrism
Although prohibited at the time,
the superiority of Kepler’s
discovery marked a great advance
in the history of astronomy, making
a great step forward in the way of
understanding of the Universe.
When the heliocentric model was
later established, astronomers
were able to accurately match and
predict planetary positions on the
zodiac for many centuries.
The cosmologies of Aristotle and
Ptolemy were finally abandoned.

14. © ABCC Australia 2015 new-physics.com
GALILEO’S TELESCOPIC ASTRONOMY
To be continued in Cosmic Adventure 3.07