RENE DESCARTE1596-1650

• BORN IN LA HAYE, FRANCE• LIVED AT THE SAME TIME AS GALILEO• KNOWN AS THE “FATHER OF PHILOSOPHY”

– HE “DISMISSED” ARISTOTILEAN IDEAS AS “INCOMPREHENSIBLE” AND HE RARELY MENTIONED HIM.

• MATHEMATICIAN– HE REASONED THAT “THE SPACE OF THE

GEOMETERS WAS THE SPACE OF THE REAL WORLD”– HE MAINTAINED THAT THE UNIVERSE WAS INFINITE

AND UNIFORMLY DENSE. HE CALLED IT THE CARTESIAN UNIVERSE.

– THE CARTESIAN COORDINATE SYSTEM IS NAMED IN HONOR OF HIS CARTESIAN UNIVERSE.

– HE DEVELOPED ANALYTICAL GEOMETRY• PHYSICIST

– HE ARGUED THAT SPACE AND MATTER WERE IDENTICAL AND THE IDEA OF VACUUM WAS ABSURD.

– MOTION IS WHAT DIFFERENTIATED OBJECTS.– THE SUN WAS JUST ANOTHER STAR– THE PLANETS WERE KEPT IN THEIR ORBITS BY

FORCES CAUSED BY THEIR INTERACTION WITH SPACE

DESCARTE• “THE DIFFICULTY WITH THE WIDER APPLICATION OF THE METHOD

OF THE GEOMETER WAS THAT GEOMETRICAL REASONING BEGAN FROM ESTABLISHED TRUTHS, WHEREAS, IN EVERY DAY LIFE, PEOPLE TOOK FOR TRUE WHAT MAY IN FACT HAVE BEEN MISTAKEN ASSUMPTIONS THAT THEY HAD ADOPTED IN CHILDHOOD AND HAD UNTHINKINGLY ACCEPTED EVER SINCE.”

• DESCARTE’S SOLUTION TO DETERMINING WHAT WAS FACTUAL WAS TO DOUBT EVERYTHING, REASONING THAT TRUE FACTS COULD STAND THE SCRUTINY.

• HE EVEN DOUBTED HIS OWN EXISTANCE UNTIL HE REASONED THAT, IF HE DIDN’T EXIST HE WOULDN’T BE ABLE TO THINK. HENCE HIS STATEMENT, “I THINK, THEREFORE I AM”. HE ALSO REASONED THAT GOD EXISTED.

SIR FRANCIS BACON1561-1626

• BORN IN LONDON• 1ST VICOUNT OF ST.

ALBAN• PHILOSOPHER• STATESMAN• LAWYER• JURIST• AUTHOR• KNIGHTED IN 1603

FRANCIS BACON

• PRIMARILY REMEMBERED AS THE DEVELOPER OF THE SCIENTIFIC METHOD

• FOUNDED THE “NEW ATLANTIS” FOUNDATION OF SCIENCE

• KNOWN FOR HIS PRACTICAL APPLICATION OF SCIENCE

SCIENTIFIC SOCIETIES• ACCADEMIA DEI LINCEI (ITALY)

– Founded in 1603 by Federico Cesi– NAMED AFTER THE LYNX BECAUSE IT HAD SHARP VISION– GALILEO WAS A MEMBER

• ACCADEMIA DEL CIMENTO (ITALY)– FOUNDED IN 1657 BY STUDENTS OF GALILEO– FUNDED BY GRAND DUKE FERDINANDO II DE’ MEDICI– EXPERIMENTALISTS– CREATED STANDARDS OF MEASUREMENT

• ROYAL SOCIETY (ENGLAND)– FOUNDED IN 1660– CHARTERED BY CHARLES II– CALLED THE “INVISIBLE COLLEGE”– MET IN HOMES AND AT GRESHAM COLLEGE– ALONG WITH THE CURRENT U.S. “NATIONAL ACADEMY OF SCIENCE”, THE MOST

PRESTIGIOUS SCIENTIFIC SOCIETY IN THE WORLD• ACADEMIE DES SCIENCES (FRANCE)

– ESTABLISHED IN 1666– FOUNDED BY LOUIS XIV AT THE SUGGESTION OF JEAN BATISTE COLBERT

WILLIAM GILBERT1544-1603

• PROFESSIONALLY HE WAS A PHYSICIAN

• IN ON THE MAGNET HE ARGUED THAT THE EARTH IS A MAGNET

• HE ARGUED, CORRECTLY, THAT THE CENTER OF THE EARTH WAS IRON

• HE MAINTAINED THAT THE MAGNETIC FORCE OF THE SUN ON THE PLANETS KEPT THEM IN MOTION

• THE “GILBERT”, A UNIT OF MAGNETISM, IS NAMED FOR HIM

• HE ORIGINATED THE TERM “ELECTRICITY”

• HE WAS A STAUNCH COPERNICAN

ROBERT HOOKE1635-1703

• A RENAISSANCE MAN – CAPABLE IN PHYSICS, MATH, ASTRONOMY AND PHILOSPHY

• PROFESSIONALLY – AN ARCHITECT– HE COLLABORATED WITH CHRISTOPHER WREN IN

REBUILDING LONDON AFTER THE GREAT FIRE OF 1666

• A ROYALIST AND CHURCHMAN WHO MAINTAINED THAT SCIENCE AND THE BIBLE SHOULD AGREE IF BOTH WERE INTERPRETED CORRECTLY. HE FOUGHT WITH CHURCHMEN WHO CLAIMED THAT THE BIBLE TAUGHT A STATIONARY EARTH. BACON HAD INTRODUCED THE SCIENTIFIC METHOD NEARLY A CENTURY EARLIER.

• PROFESSOR OF ASTRONOMY AT GRESHAM COLLEGE, THEN OXFORD

• CURATOR OF EXPERIMENTS FOR THE ROYAL SOCIETY• PROFESSOR OF GEOMETRY AT GRESHAM• HIS SQUABBLES WITH NEWTON ARE SAID TO HAVE LED

TO NEWTON’S FAILING TO PRESERVE ANY PORTRAITS OF HIM. THE ONE ON THE RIGHT IS A MODERN RENDITION (2004)

• HE WAS AN EARLY MEMBER OF THE ROYAL SOCIETY

HOOKE’S ACCOMPLISHMENTS

• HOOKE’S LAW OF ELASTICITY – F = -kx, , If you pull on an elastic member with a force F it will stretch an amount x where k is the “spring constant”.

• THE ESCAPEMENT MECHANISM FOR A WATCH – HE HAD A BITTER DISPUTE WITH CHRISTIAAN HUYGENS OVER THE RIGHTS TO IT.

• ASSISTED ROBERT BOYLE (OF BOYLE’S LAW, PV=K) , IN FACT HE MAY HAVE DEVELOPED THE MATHEMATICS FOR BOYLE’S LAW

• DEVELOPED AN AIR PUMP FOR BOYLE’S EXPERIMENTS• THE EFFECT OF CAPILLARY ACTION

HOOKE’S CONTRIBUTIONS TO PHYSICS AND ASTRONOMY

• ALL CELESTIAL BODIES ATTRACT THEMSELVES AND OTHER CELESTIAL BODIES

• THIS FORCE WAS EITHER INVERSE OR INVERSE SQUARE – HE WAS PARTIAL TO THE INVERSE SQUARE AS LIGHT INTENSITY VARIES WITH THE INVERSE SQUARE OF THE DISTANCE.

• ALL BODIES IN MOTION WILL CONTINUE IN MOTION UNLESS A DEFLECTING FORCE IS APPLIED

HOOKE’S STATEMENTS ON GRAVITY

• "I will explain," says Hooke, in a communication to the Royal Society in 1666, "a system of the world very different from any yet received. It is founded on the following positions. 1. That all the heavenly bodies have not only a gravitation of their parts to their own proper centre, but that they also mutually attract each other within their spheres of action. 2. That all bodies having a simple motion, will continue to move in a straight line, unless continually deflected from it by some extraneous force, causing them to describe a circle, an ellipse, or some other curve. 3. That this attraction is so much the greater as the bodies are nearer. As to the proportion in which those forces diminish by an increase of distance, I own I have not discovered it...."

MORE ON THE HOOKE/NEWTON CONTROVERSY

• "One must not think that this idea ... of Hooke diminishes Newton's glory", Clairaut wrote; "The example of Hooke" serves "to show what a distance there is between a truth that is glimpsed and a truth that is demonstrated".

HOOKE’S ASTRONOMICAL OBSERVATIONS

• IN 1669 HE CLAIMED (ERRONEOUSLY) TO HAVE DETERMINED THE STELLAR PARALLAX OF GAMMA DRACONIS. FLAMSTEED ALSO THOUGHT HE MEASURED IT.

• ABOUT 65 YEARS LATER WILLIAM BRADLEY DISCOVERED THE “ABERRATION OF STARLIGHT” BY STUDYING THE SAME STAR.

• HE DISCOVERED ONE OF THE FIRST DOUBLE STAR SYSTEMS, GAMMA ARIETIS, IN 1664

CHRISTIAAN HUYGENS1629-1695

• BORN IN THE HAGUE• EXPERTISE– Mathematician– Astronomer– Physicist– Horologist– Writer of early science

fiction

HUYGENS• MEMBER OF BOTH THE FRENCH ACADEMY OF SCIENCES AND THE

ROYAL SOCIETY• INDIVIDUAL ACCOMPLISHMENTS

– INTRODUCED THE WAVE THEORY OF LIGHT– DESCRIBED THE QUALITIES OF CRYSTALS CALLED BI-REFRINGENCE

(DOUBLE REFRACTION) AND SHOWED HOW IT DESCRIBED POLARIZED LIGHT

– INVENTED THE PENDULUM CLOCK• DEVELOPED THE EXPRESSION, T = 2∏(L/g)1/2, GIVING THE PERIOD OF A

PENDULUM – INVENTED AN ESCAPEMENT MECHANISM FOR A WATCH (CHRONOMETER)

(DISPUTED WITH HOOKE OVER WHOSE INTELLECTUAL PROPERTY IT WAS)– DESIGNED AN INTERNAL COMBUSTION ENGINE RUN BY GUN POWDER:

HOWEVER, HE NEVER ACTUALLY BUILT ONE.

HUYGENS

• HUYGENS DESCRIPTION OF CENTRIPETAL FORCE: F = mv2/r• ACCORDING TO KEPLER’S 3RD LAW, P2=a3. IF ONE HAS A

CIRCULAR ORBIT P = circ/v = 2∏r/v.• SO P2 = (const x r2/v2) = r3

• This implies v2 = const/r• Therefore F = m x const /r2

• This implies that the force obeys the inverse square law

HUYGEN’S TELESCOPE

• TUBELESS – ONLY STRINGS– NEEDED VERY LONG

FOCAL LENGTH AS LENSES WERE NOT VERY RELIABLE AT THERE EDGES SO THEY USED ONLY THE PARAXIAL RAYS

– PROBLEM WAS THAT AMBIENT LIGHT INTERFERED WITH THE OBSERVATIONS

HUYGENS TELESCOPIC DISCOVERIES

• SATURN’S RING IN 1655– "a thin, flat ring, nowhere

touching, and inclined to the ecliptic."

• SATURN’S MOON TITAN IN 1659– USING A 50 POWER TELESCOPE

• THE ORION NEBULA• IN 1661 HE OBSERVED A

TRANSIT OF MERCURY ACROSS THE FACE OF THE SUN.

ORION NEBULA

HUYGENS

• IN 1695, JUST BEFORE HE DIED HE PROPOSED THE EXISTENCE OF EXTRA-TERRESTRIAL LIFE

• HE POSTULATED THAT WATER WOULD HAVE DIFFERENT CHARACTERISTICS ON DIFFERENT PLANETS

• HE CLAIMED THAT HE SAW DARK AND BRIGHT SPOTS ON MARS AND JUPITER SUGGESTING THAT WATER EXISTED THERE.

JOHANNES HEVELIUS1611-1687

• BOHEMIAN/GERMAN – LIVED IN DANZIG

• A BEER BREWER , HE BREWED THE FAMOUS “JOPENBIER”

• A COUNCILMAN IN DANZIG

• CHIEF INTEREST WAS ASTRONOMY

HEVELIUS TELESCOPE• IN 1641 HE BUILT AN

OBSERVATORY ON THE ROOFS OF HIS THREE CONNECTED HOUSES

• HE BUILT A LARGE 45 METER FOCAL LENGTH KEPLERIAN TELESCOPE WITH A WOOD AND WIRE TUBE.

• FIRST GERMAN MEMBER OF THE ROYAL SOCIETY

• CHARTED THE LUNAR SURFACE• DISCOVERED THE MOON’S

LIBRATION IN LONGITUDE

HEVELIUS ACCOMPLISHMENTS• CHARTED THE LUNAR SURFACE• DISCOVERED THE MOON’S LIBRATION IN

LONGITUDE• DISCOVERED FOUR COMETS• PROPOSED THAT COMETS ORBIT THE SUN

IN PARABOLIC ORBITS• DESCRIBED 10 NEW CONSTELLATIONS,

SEVEN OF WHICH ARE STILL RECOGNIZED• LAST ASTRONOMER TO OBSERVED

WITHOUT A TELESCOPE• HOOKE HAD SENT HALLEY TO CONVINCE

HEVELIUS TO USE HIS A TELESCOPE TO DO HIS OBSERVATIONS

• HEVELIUS DECLINED SAYING THAT NAKED-EYE OBSERVATIONS WERE SUFFICIENT – LEADING TO A CONTROVERSY WITH HOOKE.

HIS LUNAR MAP

JOHANNES HEVELIUS

• HIS OBSERVATORY AND BOOKS WERE DESTROYED BY ARSON IN 1679

• HE REBUILT THE DAMAGE AND NAMED THE CONSTELLATION “SEXTANS” IN MEMORY OF HIS LOST INSTRUMENTS.

• IN 1683 KING JOHN III SOBIESKI’S FORCES WON THE BATTLE OF VIENNA. HE NAMED THE CONSTELLATION “SCUTUM SOBIESCIANUM” (SOBIESKI’S SHIELD)

• IT’S CALLED SCUTUM NOW.

GIOVANNI DOMENICO CASSINI1625-1712

• ITALIAN/FRENCH ASTRONOMER, BORN IN THE REPUBLIC OF GENOA

• PROFESSOR AT THE UNIVERSITY OF BOLOGNA

• DIRECTOR OF THE PARIS OBSERVATORY UNDER LOUIS XIV

• SERVED AS ASTROLOGER TO LOUIS XIV

CASSINI’S CONTRIBUTIONS TO ASTRONOMY

• FIRST TO OBSERVE FOUR OF SATURN’S MOONS INCLUDING IAPETUS WHICH SHOWS VARIATIONS IN BRIGHTNESS HE CORRECTLY ASCRIBED TO DARK MATERIAL IN ONE HEMISPHERE

• HE DISCOVERED THE GAP IN SATURN’S RINGS WHICH WE CALL “CASSINI’S DIVISION” TODAY.

• SHARES CREDIT WITH HOOKE FOR DISCOVERING JUPITER’S GREAT RED SPOT

• SUCCESSFULLY MEASURED MARS’ PARALLAX (WITH ASSOCIATE JEAN RICHER) – FIRST DIRECT MEASUREMENT OF THE TRUE DIMENSIONS OF THE SOLAR SYSTEM

• FIRST TO USE JUPITER’S MOONS AS A CLOCK IN CALCULATING LONGITUDE ON THE EARTH

• HIS MEASUREMENT OF LONGITUDE ALLOWED HIM TO DETERMINE THE TRUE SIZE OF FRANCE FOR THE FIRST TIME.

THE CASSINI DIVISION ON SATURN