Transcript From Aristotle to Newton: A Revolution in Science

From Aristotle to Newton:
A Revolution in Science
Setting the Scene: Philosophy
of the Time
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The heavens represent perfection.
The heavens are immutable.
The circle is the perfect shape.
All heavenly motions must be
circular.
• The earth is at the center of the
universe.
• These ideas originated with Aristotle.
“The astronomer
must try his utmost
to explain celestial
motions by the
simplest possible
hypothesis; but if he
fails to do so, he
must choose
whatever other
hypotheses meet the
case.”
-Ptolemy of Alexandria
(140 A.D.)
Wanderers in the Heavens
East
South
West
• Planets don’t maintain a fixed position in the sky.
• Their brightness varies depending on how far away they are
from Earth at any time.
• Planets appear to speed up and slow down in their motion.
• Planets also appear at times to move backwards, which is
known as retrograde motion (normal motion is to move west to
east across celestial sphere).
Ptolemy tried to
crate a model that
would account for
retrograde motion.
He placed the
planets in orbits
(deferents) on
orbits (epicycles)
all around the
Earth.
Epicycle
Deferent
Earth
Ptolemy’s Epicycles
Ptolemy’s Epicycles
Ptolemy’s Epicycles
Ptolemy’s Epicycles
Ptolemy’s Epicycles
Ptolemy’s Epicycles
Ptolemy’s Epicycles
Ptolemy’s Epicycles
Ptolemy’s Epicycles
Ptolemy’s Epicycles
Ptolemy’s Epicycles
Ptolemy’s Epicycles
Ptolemy’s Epicycles
Ptolemy’s Epicycles
Ptolemy’s Epicycles
Ptolemy’s Epicycles
Ptolemy’s Epicycles
Ptolemy’s Epicycles
Ptolemy’s Epicycles
Ptolemy’s Epicycles
Ptolemy’s Epicycles
Ptolemy’s Epicycles
Ptolemy’s Epicycles
Ptolemy’s Epicycles
Where is retrograde
motion occurring?
Planet’s Path
Ptolemy’s Epicycles
Where is retrograde
motion?
Planet’s Path
On the Ptolemaic system:
“A system of this sort
seemed neither sufficiently
absolute nor sufficiently
pleasing to the mind.”
--Copernicus
Why heliocentric NOW???
• Renaissance:
– art
– literature
– medicine
– exploration
Copernicus (1473 – 1543
AD) is known for :
1.
First observations of the sun
2.
First sun centered model of the solar
system or universe
3.
The world’s best naked-eye astronomical
observations in history
4.
Creating first a theoretical model to explain
planetary motions
5.
Creating first a theoretical model for
explaining gravity
Copernicus (1473 – 1543 AD) is known
for 1. First observations of the sun
2. First sun centered model of the solar
system or universe
3. The world’s best naked-eye
astronomical observations in history
4. Creating first theoretical model to
explain planetary motions
5. Creating first a theoretical model for
explaining gravity
Copernicus (1473 – 1543 AD) 1. Probably died a virgin
2. Was a priest and Lawyer
3. Had artificial wooden and silver
noses
4. Probably died of Mercury poising
5. Rumored to have died of a bladder
burst
6. Was blind at the time of his death
7. Was labeled a heretic by the church
Copernicus (1473 – 1543 AD) 1. Probably died a virgin
2. Was a priest and Lawyer
3. Had artificial wooden and silver
noses
4. Probably died of Mercury poising
5. Rumored to have died of a bladder
burst
6. Was blind at the time of his death
7. Was labeled a heretic by the church
Retrograde
motion
is
an
Copernicus devised the first
apparent
motion
caused
when
comprehensive heliocentric
one
planet
moves
from
being
cosmogony to successfully
behind
another
planet tomotion
being in
explain
retrograde
front of the other planet.
“To demonstrate that the appearances are
saved by assuming the Sun at the center and
the Earth in the heavens is not the same thing
as to demonstrate that in fact the Sun is in the
center and the Earth in the heavens. I
believe that the first demonstration may exist,
but I have grave doubts about the second.”
--Cardinal Bellarmine
(1615)
Tycho Brahe (1546-1601) 1. Probably died a virgin
2. Was a priest and Lawyer
3. Had artificial wooden and silver noses
4. Probably died of Mercury poising
5. Rumored to have died when his bladder burst
6. Was blind at the time of his death
7. Was labeled a heretic by the church
Tycho Brahe (1546-1601) 1. Probably died a virgin
2. Was a priest and Lawyer
3. Had artificial wooden and silver
noses
4. Probably died of Mercury poising
5. Rumored to have died when his
bladder burst
6. Was blind at the time of his death
7. Was labeled a heretic by the
church
Tycho Brahe (1546-1601) is known for 1. First telescope observations of the sun
2. First sun centered scientific model of
the solar system or universe
3. Being the world’s best naked-eye
astronomer
4. Creating first theoretical model to
explain planetary motions
5. Creating first a theoretical model for
explaining gravity
Tycho Brahe (1546-1601) is known for 1. First telescope observations of the sun
2. First sun centered scientific model of
the solar system or universe
3. Being the world’s best naked-eye
astronomer
4. Creating first theoretical model to
explain planetary motions
5. Creating first a theoretical model for
explaining gravity
Tycho Brahe measured distances
using parallax that disproved ancient
ideas about the heavens
• He observed a supernova in 1572 and with
this showed that the heavens were both
changing and had a dimension of distance;
this troubled scholars who previously thought
the heavens were unchanging.
• He showed that comets were objects that
occurred in the region of the planets, not in
Earth’s atmosphere.
Johannes Kepler 1571 - 1630 1. Probably died a virgin
2. Was a priest and Lawyer
3. Had artificial wooden and silver
noses
4. Probably died of Mercury poising
5. Rumored to have died when his
bladder burst
6. Was blind at the time of his death
7. Was labeled a heretic by the
church
Johannes Kepler 1571 - 1630 None of these.
He was a deeply religious man
and a family man.
He was rumored to have hated
Tycho Brahe and was in the
relationship for the data. With
that data he changed the
understanding of motion of
heavenly bodies forever.
He was also a writer, who wrote
children stories about the
heavens.
Johannes Kepler 1571 - 1630
is Known for 1. First telescope observations of the
sun
2. First sun centered scientific model
of the solar system or universe
3. Being the world’s best naked-eye
astronomer
4. Creating first theoretical model to
explain planetary motions
5. Creating first a theoretical model for
explaining gravity
Johannes Kepler 1571 - 1630 is
Known for -
1. First telescope observations of
the sun
2. First sun centered scientific
model of the solar system or
universe
3. Being the world’s best naked-eye
astronomer
4. Creating first theoretical model to
explain planetary motions
5. Creating first a theoretical model
for explaining gravity
Kepler’s First Law: The orbit of a planet about
the Sun is an ellipse with the Sun at one focus.
Eccentricity, e
•how squashed or out
of round the ellipse is
•a number ranging
from 0 for a circle to
1 for a straight line
e = 0.02
e = 0.7
e = 0.9
What is the shape of Earth’s
orbit around the Sun?
Earth, e = 0.016
Kepler’s Second Law: A line joining a
planet and the Sun sweeps out equal
areas in equal intervals of time.
Second Law Facts
• A line drawn from the planet to the Sun
sweeps out equal areas in equal times
• orbital speed is not constant for an
ellipse only for a circle
• planets move faster when near the Sun
(perihelion)
• planets move slower when they are far
from the Sun (aphelion)
Third Law
• The size of the orbit determines the
orbital period
– planets that orbit near the Sun have
shorter periods than planets that are far
from the Sun.
3
a
=
AU
2
P
years
Kepler’s Laws - Lecture Tutorials:
Kepler’s Second Law (p. 21)
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Work with a partner!
Read the instructions and questions carefully.
Discuss the concepts and your answers with one another.
Come to a consensus answer you both agree on.
If you get stuck or are not sure of your answer, ask another
group.
• If you get really stuck or don’t understand what the Lecture
Tutorial is asking, ask one for help.
According to Kepler’s second law, a
planet with an orbit like Earth’s would:
A. move faster when further from the
Sun.
B. move slower when closer to the Sun.
C. experience a dramatic change in
orbital speed from month to month.
D. experience very little change in orbital
speed over the course of the year.
E. none of the above.
Which of the following best describes what
would happen to a planet’s orbital speed if
it’s mass were doubled but it stayed at the
same orbital distance?
A. It would orbit half as fast.
B. It would orbit less that half as
fast.
C. It would orbit twice as fast.
D. It would orbit more than twice as
fast.
E. It would orbit with the same
speed.
Kepler’s second law says “a line joining a planet
and the Sun sweeps out equal areas in equal
amounts of time.” Which of the following
statements means nearly the same thing?
A.
B.
C.
D.
E.
Planets move fastest when they are moving
toward the Sun.
Planets move equal distances throughout their
orbit of the Sun.
Planets move slowest when they are moving
away from the Sun.
Planets travel farther in a given time when
they are closer to the Sun.
Planets move the same speed at all points
during their orbit of the Sun.
If a small weather satellite and the large
International Space Station are orbiting
Earth at the same altitude above Earth’s
surface, which of the following is true?
A.
The large space station has
a longer orbital period.
B. The small weather satellite
has a longer orbital period.
C. Each has the same orbital
period.
Galileo - 1564-1642 -
1.
2.
3.
4.
5.
6.
7.
Probably died a virgin
Was a priest and Lawyer
Had artificial wooden and silver noses
Probably died of Mercury poisoning
Rumored to have died when his bladder burst
Was blind at the time of his death
Was labeled a heretic by the church
Galileo - 1564-1642 -
1.
2.
3.
4.
5.
6.
7.
Probably died a virgin
Was a priest and Lawyer
Had artificial wooden and silver noses
Probably died of Mercury poisoning
Rumored to have died when his bladder burst
Was blind at the time of his death
Was labeled a heretic by the church
Galileo (1564-1642)
is known for 1. First observations of the sun
2. First sun centered scientific model of the solar
system or universe
3. Being the world’s best naked-eye astronomer
4. Creating first theoretical model to explain
planetary motions
5. Creating first theoretical model for explaining
gravity
Galileo (1564-1642)
is known for -
1. First observations of the sun
2. First sun centered scientific model of the solar
system or universe
3. Being the world’s best naked-eye astronomer
4. Creating first theoretical model to explain
planetary motions
5. Creating first theoretical model for explaining
gravity
Galileo’s Observations
Milky Way
• There are thousands (billions) more stars in
the Milky Way than are visible to the naked
eye.
• Universe is bigger than imagined.
The Bulge of Saturn
• Saturn is not a sphere.
• Circles and spheres do not dominate
the heavens.
A Being with Ears
The Moon
• The moon has craters.
• The moon is not a perfect heavenly
body.
Sunspots
• The Sun is not a perfect heavenly body.
• The Sun rotates about its own axis.
Galileo’s discoveries of the phases of Venus with
his telescope showed that Venus must orbit the
Sun and strongly supported a heliocentric model
Venus is clearly smallest when it is in the full phase and largest when it is in the
new phase. Then Venus must be very far from Earth when it is in the full
phase and quite close to Earth when in the new phase – which supports the
argument that Venus is orbiting the Sun not Earth.
Galileo’s telescope revealed phases of
Venus which could only occur IF Venus
orbits the Sun.
Galileo’s telescope
revealed that Jupiter
had moons which
orbited Jupiter
instead of Earth.
Isaac Newton (1642 – 1727) -
1.
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4.
5.
6.
7.
Probably died a virgin
Was a priest and Lawyer
Had artificial wooden and silver noses
Probably died of Mercury poisoning
Rumored to have died when his bladder burst
Was blind at the time of his death
Was labeled a heretic by the church
Isaac Newton (1642 – 1727) -
1.
2.
3.
4.
5.
6.
7.
Probably died a virgin
Was a priest and Lawyer
Had artificial wooden and silver noses
Probably died of Mercury poisoning
Rumored to have died when his bladder burst
Was blind at the time of his death
Was labeled a heretic by the church
Isaac Newton (1642 – 1727)
is known for -
1.
2.
3.
4.
5.
First observations of the sun
First sun centered scientific model of the solar
system or universe
Being the world’s best naked-eye astronomer
Creating first theoretical model to explain
planetary motions
Creating first theoretical model for explaining
gravity and …..
Isaac Newton (1642 – 1727)
is known for -
1.
2.
3.
4.
5.
First observations of the sun
First sun centered scientific model of the solar
system or universe
Being the world’s best naked-eye astronomer
Creating first a theoretical model to explain
planetary motions
Creating first theoretical model for explaining
gravity and …..
Newton’s Three Laws of
Motion
First Law - A body remains at rest or moves in a straight
line at a constant speed unless acted upon by an
outside (net) force.
Second Law - (net) Force = mass x acceleration
Third Law - Whenever one body exerts a force on a
second body, the second body exerts an equal and
opposite force on the first body.
Newton’s Law of Gravitation
• Newton’s law of gravitation states: Two
bodies attract each other with a force that
is directly proportional to the product of
their masses and is inversely proportional
to the square of the distance between
them.
Gm1m2
Fgrav 
2
d
Newton’s Laws and Kepler's
Laws
Newton’s law of gravitation and his three laws
of motion prove all of Kepler’s laws.
Gravity and Newton's Laws –
Lecture Tutorial (p. 29)
•
•
•
•
•
Work with a partner!
Read the instructions and questions carefully.
Discuss the concepts and your answers with one another.
Come to a consensus answer you both agree on.
If you get stuck or are not sure of your answer, ask another
group.
• If you get really stuck or don’t understand what the Lecture
Tutorial is asking, ask for help.
Which of the following forces
is strongest?
A. The force you exert on the earth.
B. The force the earth exerts on you.
C. This is a trick question: the force you
exert on the earth is identical in
strength to the force the earth exerts
on you.
The Circle of Scientific
Progress
• The progression from the complex
Ptolemaic model of the universe to
Newton’s laws is an example of the
scientific method in use (the model was
changed until it met the observations
and made correct predictions).