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RENE DESCARTE
1596-1650
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BORN IN LA HAYE, FRANCE
LIVED AT THE SAME TIME AS GALILEO
KNOWN AS THE “FATHER OF PHILOSOPHY”
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MATHEMATICIAN
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HE “DISMISSED” ARISTOTILEAN IDEAS AS
“INCOMPREHENSIBLE” AND HE RARELY MENTIONED
HIM.
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
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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 BACON
1561-1626
• 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)
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FOUNDED IN 1657 BY STUDENTS OF GALILEO
FUNDED BY GRAND DUKE FERDINANDO II DE’ MEDICI
EXPERIMENTALISTS
CREATED STANDARDS OF MEASUREMENT
• ROYAL SOCIETY (ENGLAND)
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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 GILBERT
1544-1603
• 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 HOOKE
1635-1703
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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 HUYGENS
1629-1695
• BORN IN THE HAGUE
• EXPERTISE
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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 HEVELIUS
1611-1687
• 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
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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 NAKEDEYE 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 CASSINI
1625-1712
• 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