GALILEO GALILEI (1564-1642)

1. GALILEO GALILEI (1564-1642) • ITALIAN • PHYSICIST • MATHEMATICIAN • ASTRONOMER • PHILOSOPHER • KNOWN AS THE FATHER OF: • MODERN OBSERVATIONAL ASTRONOMY • SCIENCE • MODERN PHYSICS • MODERN SCIENCE

2. GALILEO • "Galileo, perhaps more than any other single person, was responsible for the birth of modern science.“ STEPHEN HAWKING

3. GALILEOEARLY 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.

4. GALILEOHIS 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.

5. GAILIEOHIS 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.

6. 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.

7. EARLY LENSES AND TELESCOPES • CRUDE VERSIONS OF LENSES AROSE AS EARLY AS 1350 • SPECTACLES BECAME STATUS SYMBOLS OF LEARNING • IN 1608 HANS LIPPERSHEY 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.

8. 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.

9. 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

10. 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 • 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

11. GALILEO’S TELESCOPIC DISCOVERIES 3. JUPITER HAS FOUR MOONS (ACTUALLY THE NUMBER THAT WE KNOW OF TODAY IS 49 WITH 14 MORE UNDER CONSIDERATION.) • THE DISCOVERY OF THESE MOONS ENCOURAGED GALILEO TO SUPPORT COPERNICUS’ HELIOCENTRIC THEORY • OBVIOUSLY THE EARTH WAS NOT THE ONLY CENTER OF REVOLUTION IN THE SOLAR SYSTEM • THE EARTH WAS NOT THE ONLY PLANET WITH A MOON • THE GALILEAN MOONS ARE NAMED • IO (CLOSEST) (ABOUT THE SIZE OF THE EARTH’S MOON) • EUROPA • GANYMEDE (LARGEST MOON IN THE SOLAR SYSTEM) • CALLISTO (FARTHEST) • BAD NEWS FOR TYCHONISTS

12. GALILEO’S TELESCOPIC DISCOVERIES 4. FEATURES ON THE MOON – HE NAMED MANY OF THEM • SEAS (MARIA) • MOUNTAINS • CRATERS • RILLES (VALLEYS)

13. 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.

14. 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.

15. 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

16. SATURNS RINGS SATURN’S RINGS OVER A 26 YEAR PERIOD MAXIMUM TILT = ~27 DEGREES VOYAGER PHOTO OF SATURN’S RINGS

17. GALILEO’S TELESCOPIC DISCOVERIES 7. PHASES OF VENUS GALILEO’S DRAWING SHOWING VENUS’ PHASES ACCORDING TO PTOLEMAIC THEORY AND COPERNICAN THEORY. • 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.

18. GALILEO AND THE CHURCH • HIS IDEAS IN HIS FIRST TWO BOOKS, THE STARRY MESSENGERAND 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.

19. 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.

20. 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