GALILEO GALILEI (1564-1642)
• ITALIAN
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PHYSICIST
MATHEMATICIAN
ASTRONOMER
PHILOSOPHER
• KNOWN AS THE FATHER
OF:
– MODERN OBSERVATIONAL
ASTRONOMY
– SCIENCE
– MODERN PHYSICS
– MODERN SCIENCE
GALILEO
• "GALILEO, PERHAPS MORE THAN ANY OTHER
SINGLE PERSON, WAS RESPONSIBLE FOR THE
BIRTH OF MODERN SCIENCE.“ STEPHEN
HAWKING
GALILEO
EARLY LIFE
• BORN IN PISA
• FATHER WAS A MUSICIAN (HE BECAME INVOLVED
WITH A NEW FORM OF MUSIC, OPERA)
• HE WAS EDUCATED IN THE CHURCH
• HE STARTED WORK ON A MEDICAL DEGREE BUT DID
NOT FINISH AND, INSTEAD, TURNED TO MATHEMATICS
• WHEN HE WAS 25 HE WAS APPOINTED CHAIR OF
MATHEMATICS AT THE UNIVERSITY OF PISA.
• HE BECAME INTERESTED IN ASTRONOMY AND, AS
MOST ASTRONOMERS OF HIS DAY, HE ALSO STUDIED
ASTROLOGY.
GALILEO
HIS SCIENCE AND MATH
• DYNAMICS OF MOVING SYSTEMS – BODIES FALLING
UNDER THE INFLUENCE OF GRAVITY ACCELERATE AT
THE SAME RATE REGARDLESS OF THEIR MASS
• HARMONIC RELATION IN MUSIC – THE PITCH OF A
STRETCHED STRING VARIES AS THE SQUARE ROOT OF
THE TENSION
• HE UNDERSTOOD MATHEMATICS BOTH AS GEOMETRY
AND AS ALGEBRA– I.E. HE RECOGNIZED THAT A
PARABOLA WAS NOT ONLY A CONIC SECTION BUT THAT
IT HAD A MATHEMATICAL EXPRESSION: Y = X2.
• HE DID NOT ACCEPT KEPLER’S ELLIPTICAL ORBITS
ARGUING THAT THE CIRCLE WAS THE PERFECT SHAPE.
GAILIEO
HIS STUDY OF THE TIDES
• IN 1615 HE WAS CHALLENGED BY CARDINAL
BELLARMINE TO PROVE THAT THE EARTH ACTUALLY
MOVED.
• HE PROPOSED THAT THE ACTION OF THE TIDES
PROVED IT, CITING THE VARIATION OF THE HEIGHT OF
THE TIDES IN OCEAN BASINS AND IN DIFFERENT PARTS
OF THE ADRIATIC.
• HIS OPPONENTS ARGUED THAT HIS THEORY IS
INCORRECT AS THERE ARE TWO TIDES PER DAY, NOT
ONE.
• HE MAINTAINED THAT ONLY THE SUN CAUSED THE
TIDES, NOT THE MOON. I’LL DISCUSS TIDES LATER.
GALILEO’S TECHNOLOGY
• IN 1604 HE MADE A MILITARY COMPASS
• HE MADE AN AIR-EXPANSION THERMOMETER
• HE MADE A REFRACTING TELESCOPE AND
USED IT TO OBSERVE THE STARS
• HE INVENTED THE COMPOUND MICROSCOPE
• HE PROPOSED USING THE MOONS OF JUPITER
AS AN INFALLIBLE CLOCK IN ORDER TO
ACCURATELY DETERMINE ONE’S LONGITUDE.
EARLY LENSES AND TELESCOPES
• CRUDE VERSIONS OF LENSES AROSE AS EARLY AS
1350
• SPECTACLES BECAME STATUS SYMBOLS OF
LEARNING
• IN 1608 HANS LIPPERHEY AND JACOB METIUS
APPLIED FOR A PATENT ON A CONCAVE/CONVEX
LENS THREE POWER TELESCOPE – THE PATENT
WAS NOT AWARDED AS THE PATENTING
COMMITTEE THOUGHT THE IDEA TOO SIMPLE TO
COPY.
GALILEO’S TELESCOPES
• PLANO-CONVEX OBJECTIVE AND PLANO-CONCAVE EYEPIECE (OCULAR) –
THE GLASS WAS GREENISH IN COLOR AND HAD BUBBLES IN IT – THE
SHAPES OF THE LENSES WERE PRETTY GOOD NEAR THE CENTER BUT NOT
AT THE EDGES.
• IN JUNE 1609 HE BUILT HIS FIRST ONE – 3 POWER
• TWO MONTHS LATER HE BUILT ONE WITH 8 POWER
• TWO MONTHS LATER HE OBSERVED THE MOON AND JUPITER WITH AN ~
20 POWER TELESCOPE. OBJECTIVE FOCAL LENGTH ~30-40 INCHES:
OCULAR FOCAL LENGTH ~2 INCHES.
• EVEN THOUGH HE WAS OFFERED A BIG INCREASE IN SALARY AT THE
UNIVERSITY OF PADUA THE GRAND DUKE OF TUSCANY(COSIMO II DE’
MEDICI) TOPPED THE OFFER
• GALILEO WAS GIVEN A LIFETIME APPOINTMENT TO THE DUKE’S STAFF IN
1610
• NO ONE COULD VERIFY HIS FINDINGS AS YOU NEEDED A TELESCOPE TO
DO SO.
GALILEAN TELESCOPE
• VIRTUAL ERECT IMAGE
• CURRENT DAY OPERA
GLASSES
• GALILEO OBTAINED HIS
PRIMARY FUNDING
FROM THE MILITARY
• THEREFORE HIS
TELESCOPE
(BINOCULARS) HAD TO
GIVE ERECT IMAGES
GALILEO’S TELESCOPIC DISCOVERIES
1. THE MILKY WAY IS “STARLIKE”, I.E., WHEN YOU
MAGNIFY THE MILKY WAY IT BECOMES MILLIONS OF
DISCRETE OBJECTS, NOT A CLOUD
2. THE PLANETS HAVE VISIBLE DISKS BUT THE STARS
DON’T
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WHEN YOU MAGNIFY A PLANET IT GETS LARGER AS YOU
INCREASE THE MAGNIFICATION WHEREAS STARS REMAIN
POINTS REGARDLESS OF HOW MUCH YOU MAGNIFY
THEM
THIS WAS GRATIFYING TO COPERNICANS AS IT PUT THE
STARS AT GREAT DISTANCES, THUS EXPLAINING TYCHO’S
INABILITY TO SEE STELLAR PARALLAX
GALILEO’S TELESCOPIC DISCOVERIES
3. JUPITER HAS FOUR MOONS
(ACTUALLY THE NUMBER THAT WE
KNOW OF TODAY IS 49 WITH 14
MORE UNDER CONSIDERATION.)
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THE DISCOVERY OF THESE MOONS
ENCOURAGED GALILEO TO SUPPORT
COPERNICUS’ HELIOCENTRIC THEORY
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THE GALILEAN MOONS ARE NAMED
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OBVIOUSLY THE EARTH WAS NOT THE
ONLY CENTER OF REVOLUTION IN
THE SOLAR SYSTEM
THE EARTH WAS NOT THE ONLY
PLANET WITH A MOON
IO (CLOSEST) (ABOUT THE SIZE OF
THE EARTH’S MOON)
EUROPA
GANYMEDE (LARGEST MOON IN THE
SOLAR SYSTEM)
CALLISTO (FARTHEST)
BAD NEWS FOR TYCHONISTS
GALILEO’S TELESCOPIC DISCOVERIES
4. FEATURES ON THE
MOON – HE NAMED
MANY OF THEM
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SEAS (MARIA)
MOUNTAINS
CRATERS
RILLES (VALLEYS)
GALILEO’S “STARRY MESSENGER”
• AFTER HE HAD MADE THESE DISCOVERIES HE
PUBLISHED A SMALL BOOK CALLED THE
“STARRY MESSENGER” TO REPORT HIS
OBSERVATIONS. HE DEVOTED ABOUT HALF
OF IT TO REPORTING JUPITER’S MOONS.
GALILEO’S TELESCOPIC DISCOVERIES
5. SUNSPOTS – IN 1610
• TO THE RIGHT SEE AN EARLY
GALILEO DRAWING SHOWING
SUNSPOTS
– OTHERS HAD OBSERVED THEM
EARLIER, SOME AS EARLY AS THE
4TH CENTURY BC.
– IN 1611 DAVID AND JOHANN
FABRICIUS OBSERVED SUNSPOTS
AND REPORTED THAT THEY WERE
ON THE SUN’S SURFACE AND THAT
THE SUN ROTATED
– IN 1612 GALILEO PUBLISHED
“LETTER ON SUNSPOTS” WHICH
ALSO REPORTED THAT THE SUN
WAS ROTATING BUT WENT A STEP
FARTHER IN SAYING THAT THE AXIS
OF THE SUN IS INCLINED ABOUT 7
½ DEGREES TO THE ECLIPTIC POLE.
GALILEO’S TELESCOPIC DISCOVERIES
6. “RINGS OF SATURN”
• ACTUALLY HE SAW THE
DRAWINGS ON THE RIGHT
WHICH SHOWED THAT SATURN
WAS NOT ROUND
• IN 1659 CHRISTIAAN HUYGENS, A
DUCTCH ASTRONOMER, WAS THE
FIRST TO CONCLUDE THAT
SATURN’S APPENDAGES REALLY
WERE RINGS. THEY WERE
INCLINED TO THE ECLIPTIC PLANE.
IF WE LOOK AT THEM EDGE-ON
THEY ARE TOO THIN TO BE SEEN.
• THEY ARE ACTUALLY ICY ROCKS
ORBITING SATURN
SATURNS RINGS
SATURN’S RINGS OVER A 26 YEAR PERIOD
MAXIMUM TILT = ~27 DEGREES
VOYAGER PHOTO OF SATURN’S
RINGS
GALILEO’S TELESCOPIC DISCOVERIES
7. PHASES OF VENUS
• ON THE LEFT, PTOLEMY’S
THEORY (GEOCENTRIC)
SHOWS THAT VENUS WILL
ALWAYS BE IN A CRESCENT
PHASE
• ON THE RIGHT, COPERNICUS’
THEORY (HELIOCENTRIC)
SHOWS THAT VENUS WILL GO
THROUGH A COMPLETE SET
OF PHASES. NOTE THAT THE
SIZE OF VENUS CHANGES BY A
FACTOR OF SIX FROM NEW
PHASE TO FULL PHASE, FULL
VENUS BEING SMALLER.
GALILEO’S DRAWING SHOWING VENUS’ PHASES
ACCORDING TO PTOLEMAIC THEORY AND
COPERNICAN THEORY.
GALILEO AND THE CHURCH
• HIS IDEAS IN HIS FIRST TWO BOOKS, THE STARRY MESSANGER AND
LETTERS ON SUSPOTS, HAD BEEN MUTED AND HAD NOT RAISED
MUCH ATTENTION.
• HE HAD CALLED THE MOONS OF JUPITER “MEDICEAN STARS”.
• HE WAS AN AVID COPERNICANIST
• HIS ENEMIES ANGLED TO USE THESE VIEWS AGAINST HIM
• ULTIMATELY CARDINAL ROBERT BELLARMINE FORBADE HIM TO
HOLD HELIOCENTRIC IDEAS UNTIL THEY WERE FIRMLY
ESTABLISHED. HE ARGUED THAT, IN THE LIGHT OF THE
“RECANTING” FORWARD TO DE REVOLUTIONIBUS, THAT EVEN THE
AUTHOR DIDN’T BELIEVE IT.
• IN 1616 CARDINAL BELLARMINE THEN PUT DE REVOLUTIONIBUS
ON THE BANNED READING LIST.
DIALOGUE ON THE TWO GREAT
WORLD SYSTEMS
• IN 1623 GALILEO’S FRIEND MAFFEO BARBERINI BECAME
POPE (URBAN VIII)
• THE TITLE IMPLIED THAT THE DISCUSSION IN THE BOOK
WAS BETWEEN PTOLEMAIC COSMOLOGY AND
COPERNICAN COSMOLOGY.
• HOWEVER, PTOLEMAIC COSMOLOGY WAS DEAD. MOST
NON-COPERNICANS WERE TYCHONISTS
• IN THE BOOK THREE MEN, SALVIATI (GALILEO), SAGREDO (A
THOUGHTFUL PERSON) AND SIMPLICIO (A HARD-HEADED
ARISTOTILEAN), DISCUSS TIDES, MOTIONS OF ACCELERATED
OBJECTS AND GALILEO’S OBSERVATIONS.
• UNFORTUNATELY GALILEO PUT THE POPE’S WORDS IN THE
MOUTH OF SIMPLICIO.
GALILEO’S LAST DAYS
• GALILEO WAS FORCED TO RECANT HIS COPERNICAN
BELIEFS (LORE HAS IT THAT, AT HIS TRIAL BEFORE THE
INQUISITION, HE MUTTERED UNDER HIS BREATH THAT
THE SUN IS STILL AT THE CENTER OF THE SOLAR
SYSTEM.)
• GALILEO WAS SENTENCED TO HOUSE ARREST
• BY NOW HE WAS IN HIS 70’S AND WAS ALMOST BLIND
• MUCH OF GALILEO’S WORK ON ACCELERATION WAS
REFERRED TO BY NEWTON
• GALILEO DIED ONE YEAR BEFORE NEWTON WAS BORN