Transcript Post Galilean Astronomy

Post Galilean Astronomy
Kicking and Screaming into the
Modern Age
This logo denotes A102 appropriate
Old ideas die hard
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Giambattista Riccioli
(1598-1671) in 1651
publishes Almagestum
Novum (The New
Almagest)
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Mercury, Venus, Mars orbit
the Sun
Sun, Jupiter, Saturn orbit
Earth
20 arguments for, 77
against heliocentism
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Geocentric
Tychonean
Heliocentric
Copernicanism prompts questions:
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If Earth is not the center, then
what?
How can natural motion be
explained?
If the Earth is a celestial body,
is there really a difference
between terrestrial motion and
celestial Physics?
What is really true?
By 1700, the old scholasticism
gives way to more modern
epistemologies, and away
from southern to northern
Europe
Astronomy begins to look familiar
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Galileo’s telescope
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Kepler’s Laws
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Seeing things as they
really are
Seeing more than ever
imagined
Application of
protocalculus
Slow abandonment of
old ideas
The known planets in the 17th
Century
And What Is This?
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Giovanni Battista
Hodierna
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1654
Noted in his “De
Admirandis Coeli
Characteribus”
His sketch
The evidence of the new technologies leads to
CHANGES IN THINKING FROM
1600-1700
Aristotelian Scholastism
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A mixture of ancient Greek and medieval
scholasticism, dominant in 1600
universities
Four components of causality
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Material cause: stuff has to exist in the first
place
Formal cause: what the stuff becomes
Efficient cause: somebody/something has to
do the forming
Final cause: the reason for the action
Aristotelian physics:
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Distinction between terrestrial and celestial physics
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Every body has a rightful place and must move naturally
(up or down) toward it
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This has now changed to coupling Earth and sky
Newton finally buries this concept
Material composition determines where that rightful
place is
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Earth -- center of universe
Water -- above earth; below air
Air -- above water; below fire
Fire -- boundary of terrestrial and celestial realm
Quintessence -- natural motion is at a constant speed in perfect
circles
The Disputatio
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A hierarchy of belief or acceptance of
ideas;
Authority: supernatural (God) first, then
natural, usually ancient Greek
 Reason: Aristotelian causality
 Experience
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These are the intellectual descendants of
medieval scholasticism and the influence
of Thomas Aquinas
Francis Bacon
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Contemporary of Galileo, Kepler
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Sets the tone for 17th C inquiry in his New
Organon (new way to organize thinking)
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Not an astronomer
Knowledge is human power
Science is separate from theology
Science should always be tested through
experimentation
Science is an ongoing, cumulative activity
Galileo echoed this sentiment in this quote:
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“The Bible tells how to go to Heaven, not how
the heavens go”
The Royal Society
Founded 1660 in London
 A reaction to the continued Aristotelian
curriculum at Oxford and Cambridge
 Initially very much influenced by William
Gilbert’s ‘magnetic philosophy’, that
celestial motion is caused by magnetism
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No theories of gravity are extant
 “When
all you have is a hammer, everything looks
like a nail”
Rene Descartes 1596-1650
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French
Mathematician/Philosoph
er
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Afraid in Catholic France
to embrace
Copernicanism publicly
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Cartesean coordinates
Cogito ergo sum
Believed like Averroes that
God (the Great
Clockmaker) created the
Universe and then just let it
run without daily
adjustments
Remembered Bruno’s fate
Couched his ideas in a
hypothetical distant
planet
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Heliocentric
The cosmos was filled
with unseen matter that
flowed like a river,
carrying the stars and
planets along
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Emptiness is impossible
– “nature abhors a
vacuum”
Motion occurs due to
physical contact
Orbits were vortices of
this celestial fluid, the
luminiferous aether
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Stars at the center of
the ‘whirlpools’
Planets carried
around
Comets swoop
through, unbound to
any particular star
Not Gilbert’s
magnetic forces;
fluids!
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“When all you have is
a hammer, everything
looks like a nail”
Even earthly motion fits the vortex
model, according to Descartes
Isaac Newton
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Born in England the
year Galileo dies in
Woolsthorpe-byColsterworth
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300 years before Steven
Hawking is born: 1642
Father dies before he is
born
A sickly child, given up
by his mother
(remarried) to her
parents at age 2
Early Years*
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Newton began his schooling in the village schools
and later was sent to Grantham Grammar School
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Naturally he was the top student!
At Grantham he lodged with the local apothecary,
William Clarke
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He became engaged to the apothecary's
stepdaughter, Anne Storey, before he went off to
Cambridge University at the age of 19
As Newton became engrossed in his studies, the
romance cooled and Miss Storey married someone
else.
It is said he kept a warm memory of this love, but
Newton had no other recorded 'sweethearts' and
never married.
*Men of Mathematics E.T. Bell (1937,
Simon and Schuster)
Schooling
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Entered Trinity College (Cambridge) in
1661
Still taught Aristotelian physics
 Students discussed Galileo and Kepler, but
not in class
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Brilliant (geeky) student
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Devoted to the Cartesian model of the
universe
1665 school closes because of the plague
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Newton invents calculus (!) to solve a problem
Professorship
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School reopens 1667
Newton elected
fellow, then in 1669
becomes a professor
of mathematics
Studies Descartes’
theory of light as
motion in a medium
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Shows white light is
made of all colors
Motion
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Newton's (Cartesian) ideas on falling bodies (ca. 1664):
 ...so may the gravitating attraction of the Earth be
caused by the continuall condensation of some ...
aethereall Spirit, not of the main body of flegmatic
aether, but of something very thinly and subtily
diffused through it ..
1679: Debate in the Royal Society on the elliptical
motion of planets
 Newton was still working with vortices
Robert Hooke:
 “...of compounding the celestiall motions of the
planetts of a direct motion by the tangent (inertial
motion) and an attractive motion towards the centrall
body ... my supposition is that the Attraction always is
in a duplicate proportion to the Distance from the
Center Reciprocall...
Newton to the Rescue
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1684: Edmund Halley goes to Newton, asks
what orbital shape would an inverse square
force yield?
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Newton has already done the problem
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An ellipse!
The reason he invented calculus during his forced
vacation in 1665
Newton sends papers off to Halley who
finances the project
He goes into seclusion for 18 months and
writes the Principia Mathematica (1687)
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THE book on Physics, even now
Three Laws of Motion
1.
2.
3.
An object moves in constant motion in a
straight line unless acted upon by an
external force (inertia)
The acceleration of an object depends
directly on the applied force and
inversely upon its mass
For every action there is an equal and
opposite reaction
And the answer is:
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The solution to the ellipse question combines
Kepler’s third law, calculus, and Newton’s laws of
motion
The Law of Universal Gravitation: every mass in
the universe attracts every other mass with a
force equal to the product of their masses and
inversely proportional to the square of the
distance between them
Newton had to abandon a matter-filled universe
for one of forces across empty space
Consequences
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How gravity makes
orbits
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The apple myth
Newton offered no
explanation as to why
gravity worked this
way
100 years later
Coulomb would use
Newton’s ideas for
electric force
Illustration of Newton’s Laws
War with Leibniz over calculus
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Newton’s infinite series
(not far from Kepler’s
swept areas)
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Fluxions
Developed before but
published after Leibniz
Wilhelm Leibniz
differentials
Bitter dispute
Delayed acceptance of
Newtonian Physics into
continental Europe
Newton’s later life
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Studies alchemy extensively
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Pursues the corpuscular
theory of light
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Hawking’s position today
Warden of the Mint 1699
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Optics published in 1704
Lucasian Chair in
Mathematics at Cambridge
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Looks for scientific revelations in
scripture
Leibniz beat him up over this
Ceases to do much science
Concentrates on finding
counterfeiters
Dies in 1727
1726 engraving
Edmund Halley (1656-1742)
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HALL ee, not Hail ee!
English Astronomer
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Proposed using transits of
Mercury and Venus to
determine the distance of the
Sun and therefore the scale of
the solar system using
Kepler's third law
Suggested that Kepler’s 3rd
Law implied an inverse square
relation
Predicted the return of the
1705 comet
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1305, 1380, 1456,1531, 1607,
1682
Period?
Bill Haley and the Comets
Christian Huygens (1629 - 1695)
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Dutch Physicist
Proponent of wave
theory of light
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Discoverer of Titan
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Argued with Newton
over this
Lander named after
him
Correctly identified
Saturn’s ‘ears’ as
rings
Comparison of
observations of
Saturn by Galileo,
Scheiner,
Hevelius and others
from 1616-1655,
from Huygens'
Saturnian System
(1659)
Giovanni Cassini (1625 - 1712)
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Mathematician and
Astronomer
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Viewed a ‘gap’ in Saturn’s
ring system
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Astronomer at the Panzano
Observatory
Director of the Paris
Observatory
correctly proposed that the
rings were composed of
large numbers of tiny
satellites each orbiting the
planet.
But he was a geocentrist!
Other Accomplishments
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1664: measured the period of rotation of
Jupiter on its axis, discovered the bands and
spots on the planet, and saw that the planet
was flattened at its poles
1666: measured the period of rotation of Mars
on its axis, getting a value within three minutes
of the correct one, and observed surface
features
He was the first to observe four of Saturn's
moons: Iapetus (1671), Rhea (1672), Tethys
(1684), and Dione (1684)
Made successful measurements of longitude
by the method suggested by Galileo
The Longitude Problem
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Age of discovery: needed for navigation
Latitude easy
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North Star
Equal spacing
Longitude more difficult
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The lines of longitude fan out from one pole to a maximum at the equator then
reconverge
A clock is needed
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1530 Gemma Frisius of Antwerp proposed use
of portable mechanical clock
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1636 Galileo proposes using mechanical clock
and moons of Jupiter to determine longitude
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Won’t work on a rocking ship
Off world clock versus local time
1676 Greenwich Observatory founded
1714 Queen Anne establishes the longitude
prize -- £20,000!!
And the winner is:
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John Harrison 1693-1776
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working class carpenter
Build dual spring
pendulum H1
H2 and H3
H4 1765
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Accurate to 40
seconds/day, 3X better
than the prize required
Prize committee baulked
at £20,000, offered
£10,000 for H1-H4
Both sides stubborn but
Harrison finally agreed
Actually got £8750 in
1773 for H1-H5
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Prime Meridian
established through
Greenwich
Observatory
GMT
As important to
Astronomy as to
navigation
118W, 34N: home!
Time Zones
Coincidence???
Capt. James Cook
Used the H4 chronometer
on his 2nd and 3rd voyages
of discovery
Capt. James Kirk
Boldly voyaged where
no-one had gone before
Eventual Acceptance: Laplace
1796
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Astronomy considered in its entirety is the
finest monument of the human mind, the
noblest essay of its intelligence. Seduced by
the illusions of the senses and of self-pride,
for a long time man considered himself as the
centre of the movement of the stars; his
vainglory has been punished by the terrors
which its own ideas have inspired. At last the
efforts of several centuries brushed aside the
veil which concealed the system of the
world…
continued
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…We discover ourselves upon a planet,
itself almost imperceptible in the vast
extent of our solar system, which in turn is
only an insensible point in the immensity
of space. The sublime results to which this
discovery has led should suffice to console
us for our extreme littleness, and the rank
which it assigns to the earth.
Eventual Acceptance: Goethe 1810
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“But among all the discoveries and new convictions nothing
may have produced greater effect on the human spirit than
the doctrine of Copernicus. The world had scarcely been
recognized as round and complete in itself when it was
expected to relinquish the enormous privilege of being the
center of the universe. A greater demand may never have
been addressed to mankind. For think of all the things that
went up in smoke as a result of accepting this: a second
Paradise, a world of innocence, poetry and piety, the
testimony of the senses, the conviction of a poetic-religious
faith: it is no wonder that people did not want to give up all of
this, and that they opposed such a doctrine in every way--a
doctrine that justified those who accepted it in, and
summoned them to a previously unknown, indeed unimagined
freedom of thought and largeness of views”