JOHANNES KEPLER
1571-1630
• BORN IN WEIL DER STADT
NEAR PRESENT DAY
STUTTGART
• HE WAS BORN PREMATURELY
AND WAS PHYSICALLY WEAK.
• HIS FAMILY WAS POOR
– HIS FATHER WAS A MERCENARY
WHO IS BELIEVED TO HAVE
DIED IN THE EIGHTY YEARS
WAR IN THE NETHERLANDS
– HIS MOTHER WAS A
HEALER/HERBALIST WHO WAS
LATER TRIED FOR WITCHCRAFT
JOHANNES KEPLER
• HE BECAME INTRIGUED BY ASTRONOMY AT AN EARLY AGE WHEN
HE OBSERVED THE GREAT COMET OF 1577 (IT WAS ALSO
OBSERVED BY TYCHO) AND THE TOTAL LUNAR ECLIPSE OF 1580
• AT AGE 18 HE ATTENDED THE UNIVERSITY OF TUBINGEN WHERE HE
STUDIED PHILOSOPHY AND THEOLOGY
• AT AGE 19 HE BECAME CHANCELLOR AT THE UNIVERSITY OF
TUBINGEN IN 1590 (?)
• HE BECAME AN ACCOMPLISHED MATHEMATICIAN AND ALSO
PRACTICED ASTROLOGY.
• HE BELIEVED IN COOPERNICUS’ HELIOCENTRISM AND DEFENDED IT
IN DEBATES.
• AT AGE 23 HE JOINED THE MATHEMATICS AND ASTRONOMY
FACULTY AT THE UNIVERSITY OF GRAZ, AUSTRIA.
JOHANNES KEPLER
• HE, LIKE PYTHAGORAS MANY YEARS EARLIER,
BELIEVED THAT THERE WAS A HARMONY IN
NATURE THAT COULD BE EXPRESSED IN
SIMPLE MATHEMATICAL RATIOS AND COULD,
IN FACT, BE DETECTED AS MUSIC.
• HIS MATHEMATICAL SPECIALTY WAS
GEOMETRY.
JOHANNES KEPLER
• HE WONDERED WHY THERE WERE SIX PLANETS, NOT FIVE, REASONING
THAT GOD MUST HAVE HAD A REASON.
• HE WAS INSPIRED BY THE 1595 CONJUNCTION OF JUPITER AND SATURN
TO EUCLID’S POLYGONS.
• HE THEN REALIZED THAT THERE WERE FIVE REGULAR SOLIDS (PYRAMID
(4), CUBE (6), OCTAHEDRON (8), DODECAHEDRON (12) AND
ICOSAHEDRON (20)).
• HE ORGANIZED THEM: OCTAHEDRON, ICOSAHEDRON, DODEDAHEDRON,
TETRAHEDRON AND CUBE, RESPECTIVELY STARTING WITH MERCURY AND
WORKING OUT TO SATURN.
• IF THEY WERE SUCCESSIVELY INSCRIBED AND CIRCUMSCRIBED BY SPHERES
THESE SPHERES COULD REPRESENT THE ORBITS OF SIX PLANETS.
• HE MAINTAINED THAT THE PLANETS WOULD STOP UNLESS THERE WAS A
FORCE CAUSING THEM TO MOVE. THE SUN WAS THAT SOURCE AND THE
PLANETS NEARER THE SUN WOULD MOVE FASTER AS THEY WERE CLOSER.
• HE ARGUED THAT, AS PROPOSED BY WILLIAM GILBERT (1544-1603), AN
ENGLISHMAN, MAGNETISM WAS THE SOURCE MECHANISM.
• HE REASONED THAT, SINCE THE SUN WAS OBVIOUSLY BIGGER THAN THE
EARTH, IT OUGHT TO BE AT THE CENTER OF THE SOLAR SYSTEM.
KEPLER’S NESTED SPHERES
OUTER PORTION
INNER PORTION
KEPLER MEETS TYCHO
• HIS FIRST MAJOR ASTRONOMICAL WORK, MYSTERIUM
COSMOGRAPHICUM (THE COSMIC MYSTERY), PUBLISHED IN 1595,
DESCRIBED HIS INSCRIBED POLYHEDRONS.
• HE COMMUNICATED WITH TYCHO AND WITH REIMARUS URSUS (A
COPERNICAN AND BITTER RIVAL OF TYCHO), IMPERIAL MATHEMATICIAN
TO RUDOLPH II, SOLICITING THEIR OPINIONS ABOUT “COSMIC MYSTERY”.
(TYCHO REPLACED URSUS A FEW YEARS LATER.)
• HE ALSO STUDIED THE “HARMONY” OF THE RELATIONSHIPS AMONG
MUSIC, MATH AND THE PHYSICAL WORLD, WITH SPECIAL EMPHASIS ON
ASTROLOGY.
• HOWEVER, TO CHECK ALL OF HIS THEORIES, HE BADLY NEEDED TYCHO’S
DATA.
• TYCHO WAS NOW IN PRAGUE. KEPLER NEEDED TYCHO’S SUPPORT, BOTH
FINANCIAL AND PROFESSIONAL. AND, KEPLER WAS IN TROUBLE WITH THE
CHURCH AS HE WAS BEING PRESSURED INTO CONVERTING TO
CATHOLICISM.
• KEPLER TRAVELED TO PRAGUE TO MEET TYCHO.
HOW DID KEPLER GET HIS HANDS ON
TYCHO’S DATA?
• TYCHO KNEW THAT KEPLER WANTED ACCESS TO HIS DATA
BUT REFUSED TO LET HIM COPY THEM.
• KEPLER ANGRILY LEFT PRAGUE TWO MONTHS LATER BUT
RETURNED AND RECONCILED TWO MONTHS AFTER THAT.
• KEPLER MOVED TO PRAGUE PERMANENTLY AFTER HAVING
BEEN BANNED FROM GRAZ FOR REFUSING TO CONVERT TO
CATHOLICISM.
• IN 1601 TYCHO TASKED KEPLER WITH WRITING A TRACT
AGAINST URSUS, TYCHO’S NOW DECEASED FOE.
• AFTER TYCHO’S DEATH KEPLER SNATCHED HIS DATA.
• EVENTUALLY HIS HEIRS REGAINED THE VALUABLE DATA BUT
NOT BEFORE KEPLER HAD COPIED ALL THAT HE WANTED.
JOHANNES KEPLER
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AFTER TYCHO’S DEATH KEPLER REPLACED HIM AS THE IMPERIAL MATHEMATICIAN.
MARS WAS OF SPECIAL INTEREST
– IT (OTHER THAN MERCURY) HAS THE MOST ECCENTRIC ORBIT OF ANY PLANET
– TYCHO HAD MADE COPIUS OBSERVATIONS OF IT
USING ABOUT HALF OF TYCHO’S DATA HE GENERATED A SYSTEM PREDICTING
MARS’ ORBIT AS SEEN FROM THE EARTH WHEN MARS WAS AT OPPOSITION
HE THEN USED THE OTHER HALF OF TYCHO’S DATA TO REVERSE THE PROCESS TO
PREDICT THE POSITION OF THE EARTH AS SEEN FROM MARS.
HE HAD ADOPTED THE IDEA THAT PLANETARY ORBITS WERE ELLIPTICAL.
REMEMBER, APPOLONIUS HAD DEFINED THE SHAPE OF AN ELLIPSE ABOUT 1500
YEARS EARLIER.
TYCHO’S DATA FORCED HIM TO ABANDON THE IDEA THAT THE SUN WAS AT THE
CENTER OF THE ELLIPSE AND PUT IT A FOCUS. HIS “SUN-CENTERED ELLIPSE”
THEORY DISAGREED WITH TYCHO’S DATA BY ABOUT 8 ARC MINUTES. HE FELT
TYCHO’S DATA WERE MORE ACCURATE THAT THAT AND ABANDONED HIS THEORY.
KEPLERS’ SUPERNOVA (1604)
SN-1604
• THOUGHT BY ASTROLOGERS
TO BE THE ANNOUNCEMENT
OF A NEW ERA. THEY HAD
THOUGHT THERE WAS AN 800
YEAR PERIOD IN THE STARS.
1600 YEARS EARLIER WAS THE
TIME OF CHRIST. 800 YEARS
AFTER THAT WAS THE
BEGINNING OF THE REIGN OF
CHARLEMAIGN.
• HE OBSERVED, AS DID TYCHO,
THAT SUCH OBJECTS DO NOT
HAVE ANY MEASURABLE
PARALLAX THEREFORE THEY
ARE OUTSIDE THE EARTH’S
ATMOSPHERE.
KEPLERS’ SUPERNOVA (1604)
SN-1604
• SUPERNOVA IS
LOCATED AT THE FOOT
OF OPHIUCHUS (THE
SNAKE HOLDER) ONE
OF THE
CONSTELLATIONS
NAMED BY PTOLEMY
JOHANNES KEPLER
• IN 1610 GALILEO OBSERVED THE MOONS OF
JUPITER AND SOUGHT KEPLER’S THOUGHTS
• KEPLER RESPONDED ENTHUSIASTICALLY AND
PROCEEDED TO PUBLISH ANALYSES OF BOTH
GALILEO’S AND HIS OWN TELESCOPES
• IT APPEARS BOTH THOUGHT THAT JUPITER
WAS SOMETHING VERY SPECIAL, PROVING
THAT THE EARTH WAS NOT THE CENTER OF
ALL REVOLUTIONS
GALILEAN TELESCOPE
VIRTUAL ERECT IMAGE – CURRENT DAY OPERA GLASSES
KEPLER’S TELESCOPE
INVERTED IMAGE
KEPLER’S HARMONICES MUNDI,
(HARMONY OF THE WORLDS)
• PUBLISHED IN 1619
• MOST OF IT DEALT WITH
ASTROLOGY
• HE ATTEMPTED TO
CORRELATE MUSICAL
TONES WITH PLANETARY
SPEED.
• NOTE: BACH’S WELL
TEMPERED CLAVIER WAS
STILL A CENTURY AWAY.
• WE GET HIS THIRD LAW
FROM IT.
KEPLER’S Epitome astronomia Copernicanae
(Epitome of Copernican Astronomy)
• PUBLISHED IN FOUR VOLUMES FROM 16151621
• HE WROTE MUCH OF IT DURING HIS
MOTHER’S WITCHCRAFT TRIAL
• HIS MOST INFLUENTIAL WORK
• CONTAINED ALL OF HIS THREE LAWS
KEPLER’S LAWS
• PLANETS MOVE IN ELLIPTICAL ORBITS, THE
SUN AT A FOCUS.
• THE RADIUS VECTOR OF A PLANETARY ORBIT
SWEEPS OUT EQUAL AREAS IN EQUAL TIMES.
• P2 = a3, WHERE P IS THE SIDEREAL PERIOD OF
A PLANET IN EARTH YEARS AND A IS THE
SEMI-MAJOR AXIS IN ASTRONOMICAL UNITS.
JOHANNES KEPLER
• IN 1627, 26 YEARS AFTER THEY HAD BEEN
COMMISSIONED (HE HAD TROUBLE WITH TYCHO’S
HEIRS AND THE PUBLISHING REQUIREMENTS OF THE
EMPEROR), HE FINISHED THE RUDOLPHINE TABLES.
• IN 1631, ONE YEAR AFTER HIS DEATH, PIERRE
GASSENDI, A FRENCH ASTRONOMER, MADE THE FIRST
OBSERVATION OF MERCURY’S SOLAR TRANSIT.
• KEPLER’S TABLES WERE ACCURATE TO 1/6TH OF A
DEGREE, THIRTY TIMES MORE ACCURATE THAN THE
OLD COPERNICAN (PRUTENIC) TABLES.
JOHANNES KEPLER
• IN 1625 HE RAN AFOUL OF THE CATHOLIC CHURCH ONCE AGAIN
• AGENTS OF THE CATHOLIC “COUNTER-REFORMATION” SEALED HIS
LIBRARY.
• HE MOVED TO ULM IN 1626 WHERE HE PRINTED HIS TABLES AT HIS
OWN EXPENSE.
• MILITARY TENSION EASED IN 1628 AND, EVEN THOUGH THE
EMPEROR (FERDINAND) WAS A STAUNCH CATHOLIC, HE WAS
NAMED AN OFFICIAL ADVISOR TO GENERAL WALLENSTEIN,
FERDINAND’S HIGHEST RANKING GENERAL.
• HIS PRIMARY DUTIES TO THE GENERAL WERE TO SUPPLY SUPERIOR
DATA TO THE GENERAL’S ASTROLOGERS.
• AFTER A BRIEF ILLNESS HE DIED IN REGENSBURG IN 1630.
• HIS GRAVE SITE WAS DESTROYED WHEN THE SWEDISH ARMY
DESTROYED THE CHURCH YARD AND ITS LOCATION IS UNKNOWN.