1. JOHANNES KEPLER FATİH ZENGİN TALHA SALKAYA
ÇAĞRI TÜRKMENER Senior Assist. Faruk Berat Akçeşme
ENES ÖZKAN
FARUK İLBAY

2. The birth of modern astronomy
Johannes Kepler
The birth of modern astronomy
“I measured the skies, now the shadows I measure.
Sky-bound was the mind, earth-bound the body rests.”

3. Johannes Kepler German astronomer Birth: December 27, 1571
Death: November 15, 1630
Place of Birth Weil der Stadt, Württemberg
Known for:
Discovering the three laws of planetary motion, now known as Kepler's laws.
A very good mathematician.

4. Johannes Kepler The Three Laws of Planetary Motion
Kepler was a very religious person.
He believed that the creator made an orderly universe.
In 1619, Kepler published his third law in “The Harmony of the Worlds”.

5. Johannes Kepler Career: 1594: Became professor of mathematics at Graz
1600: Assisted Danish astronomer Tycho Brahe with his astronomical research in Prague
1601: Took over as imperial mathematician and court astronomer to Emperor Rudolf II in Prague upon Brahe's death
1609: Published Astronomia Nova (New Astronomy), which included the first and second laws of planetary motion
1612: Accepted a position as mathematician to the states of Upper Austria at Linz
1619: Published Harmonice Mundi (Harmony of the World) which contained the third law of planetary motion

6. Johannes Kepler
In addition to astronomy, Kepler studied astrology, which proposes that astronomical bodies influence the course of earthly events.
A Lutheran, Kepler was forced to move and change jobs several times during his life to escape religious persecution.

7. Johannes Kepler’s Portrait in 1610 by an unknown artist

8. Kepler’s Law
The first two laws resulted from his inability to fit Tycho’s observation of Mars to a circular orbit.
This led him to discover that orbit of Mars is not a perfect circle but is elliptical.
He also realized at about the same time that Mars orbital speed varies in a predictable way.
In 1609, after almost a decade of work, Kepler proposed his first two laws of planetary motion.

9. Johannes Kepler
The Three Laws of Planetary Motion as proposed by Kepler:
1. The path of each planet around the
Sun is an ellipse.
> The Sun is located at one focus.
> The other focus is symmetrically located at the opposite end of the ellipse.

10. The First Law
I - The planets move in elliptical orbits with the sun at a focus. Kepler found from trying to calculate the position of the Earth in its orbit that as it sweeps out an area defined by the Sun and the orbital path of the Earth.

11. The radius vector describes equal areas in equal times
The radius vector describes equal areas in equal times. (The Second Law)
II - In their orbits around the sun, the planets sweep out equal areas in equal times.
For a circle the motion is uniform but in order for an object along an elliptical orbit to sweep out the area at a uniform rate, the object moves quickly when the radius vector is short and the object moves slowly when the radius vector is long.

12. Johannes Kepler The Three Laws of Planetary Motion
2. The planet revolves so that an imaginary line connecting it to the Sun sweeps over equal areas in equal intervals of time.
> Expresses geometrically the variation in orbital speeds of the planet.

13. The Third Law
The squares of the times to complete one orbit are proportional to the cubes of the average distances from the sun.
This law he published in 1619 in his Harmonices Mundi . It was this law, not an apple, that led Newton to his law of gravitation. Kepler can truly be called the founder of celestial mechanics.

14. PARTS OF AN ELLIPSE Major axis – the maximum diameter of the ellipse.
Semimajor axis – the distance from the center of the ellipse to one point.
Eccentricity – ratio of the distance between the foci to the major axis.

15. DRAWING AN ELLIPSE WITH TWO PINS, A PEN AND A STRING.

16. A group of ellipses with the same major axis but various eccentricities

17. Ellipses with the same eccentricity but various major axes

18. Diagram of the geocentric trajectory of Mars through several periods of apparent retrograde motion.

19. KEPLER’S LAW OF EQUAL AREAS

20. Johannes Kepler
3. The orbital speeds of the planets and their distances to the Sun are proportional.

21. Johannes Kepler
The solar distances of the planets can be calculated when their periods of revolution are known.

22. Johannes Kepler
Kepler attempted to associate numerical relations to the Solar System with music.
The Earth plays the note mi, fa, mi.
Kepler’s laws assert that the planets revolve around the Sun and therefore support the Copernican theory.
Kepler fell short on determining the forces that act to produce the planetary motion he had described.

23. Sources : http://kepler.nasa.gov/ Oxford journals
wikipedia.org/wiki/Johannes_Kepler