Transcript Chapter 22: Origin of Modern Astronomy

Chapter 22:
Origins of Modern Astronomy
22.1: Early Astronomy
Ancient Greeks and Astronomy
• Astronomy is the
science that studies
the universe.
• The first accurate
European
astronomers were
the ancient Greeks.
Aristotle (384 - 322
B.C.E.) concluded
that the earth was
round because it
always cast a
curved shadow
when it passes
between the sun
and the moon.
Aristotle’s belief that the Earth is round was
abandoned by the Middle Ages.
Aristotle’s Geocentric Universe
Eratosthenes (276
– 194 B.C.E.), an
ancient Greek
mathematician,
calculated that the
earth’s circumference is 39,000
kilometers - very
close to our own
modern measurement of 40,075 km.
https://youtu.be/G8cbIWMv0rI
Calculating Earth’s Circumference
The Greeks thought
that the Earth was a
sphere that stayed
motionless at the
center of the
universe. The other
planets and stars
revolved around the
Earth on their own
hollow spheres.
The Geocentric Model
• In this model, the moon, sun, and the
known planets – Mercury, Venus, Mars,
Jupiter and Saturn – orbit earth.
• Every other body in space circled this
system on their own transparent,
hollow sphere.
• This was called the celestial sphere.
A modern
version
of an
earthcentered
system.
The Heliocentric Model
• Aristarchus (312-230
B.C.E.) was the first
Greek to believe in a
sun-centered, or
heliocentric, universe.
• In the heliocentric
model, Earth and other
planets orbit the sun.
The Renaissance
and the Heliocentric
Solar System
Aristarchus was condemned by his
own religious leaders for his theory.
Modern Greece, however, honors him, and
even puts his theories on stamps…
The Ptolemaic System
• Claudius Ptolemy (c. 90 – 168 C.E.) is
our main source for what the ancient
Greeks knew about astronomy.
• He also attempted to explain retrograde
motion, or how each planet appears
sometimes to stop in the night sky,
reverse direction, and then resume
eastward motion.
Retrograde Motion
Ptolemy was wrong –
the planets do not
orbit Earth.
Yet although he used
the geocentric model,
he did try explain the
planets’ apparent
motions.
The Birth of Modern Astronomy
• The first great astronomer after the
Greeks was Nicolaus Copernicus
(1473-1543) of Poland.
• Copernicus proposed the heliocentric
model of the solar system: Earth is a
planet and all planets of the solar
system revolved around the sun at its
center.
Copernicus’ Axioms
1.
2.
3.
4.
There is no one center in the universe.
The Earth’s center is not the center of the universe.
The center of the universe is near the Sun.
The distance from the Earth to the Sun is
imperceptible compared with the distance to the
stars.
5. The rotation of the Earth accounts for the apparent
daily rotation of the stars.
6. The apparent annual cycle of movements of the Sun
is caused by the Earth revolving around it.
7. The apparent retrograde motion of the planets is
caused by the motion of the Earth from which one
observes.
Copernicus
• Since he knew that
his book
De Revoltionibus
would be considered
heresy, Copernicus
had it published by a
friend after his death.
• He also pointed out
gaps in Ptolemy’s
model .
Copernicus
• Despite the improvement
in the model of the
universe, he still believed
in the idea of perfect
circular orbits.
• This made his predictions no more accurate than
Ptolemy’s and led to doubts about his theory.
• Although the Church condemned the book, the
damage was already done and the world was
opened to new was of thinking about the world.
Heliocentric Model of the Solar System
Christopher Clavius
• 1538 to 1612
• Astronomer for Pope Leo X.
• Clavius determined that the
Julian Calendar was adding
3 days too many over a
period of 385 years.
• This caused the date of
Easter to slip against the
calendar.
• That’s a bad thing!!
Christopher Clavius
• Clavius made (2) proposals:
1. The day following
Wednesday October 4th 1582
should be called
Thursday October 15th 1582
2. Leap years occur in all years
divisible by 4 but in years
ending in “00” must be
divisible by 400 to called a
leap year.
– 1600, 2000 yes
– 1700, 1800, 1900, 2100 No
Pope Gregory X is credited for instituting the new
Calendar and today it is known as the
Gregorian Calendar.
Tycho Brahe
• 1546 to 1601
• Tycho studied medicine, law,
mathematics, astronomy,
and politics.
• A supernova seen in 1572
turned his attentions toward
astronomy permanently.
• He constructed observatories
at Hven
• After closing Hven due to the
political environment, he
became the Imperial
Mathematician to the Holy
Roman Empire in Prague.
Tycho Brahe
• Tycho was a great maker
of astronomical
instruments.
• He was able to measure
the positions of hundreds
of stars to within 4’.
• Because he found great
errors in the Alphonsine
tables he decided to create
his own Rudolphine Tables
• He measured the positions
of the planets to within 2’.
Tycho Brahe
• Tycho had devised
his own unique model
of the universe where
the moon and the sun
revolved around the
Earth but all of the
planets went around
the Sun.
• He hoped to use his
data tables to prove
his hypothesis
Tycho Brahe
• Kepler applied to work at
Tycho’s observatory.
• Tycho recognized his
talents quickly and set him
to work on the Rudolphine
tables with the purpose of
finding the laws of
planetary motion.
• Unfortunately Tycho died
less than two years later,
before Kepler worked out
his first two laws. (1601)
Giordono Bruno
• 1548 to 1600
• He was an ordained priest
by the Catholic Church.
• He believed in many
heretical ideas.
• Here are just a few:
– He believed that there was
no center to our universe
– the universe was infinite.
– He believed other stars
were suns
– He believed in atoms
Giordono Bruno
• He believed in atoms
• Because of his views, he
was persecuted by many
different churches and
peoples.
• Ultimately he went back to
face trial in the Vatican.
• The trial lasted 7 years
before he was found guilty
and sentenced
Giordono Bruno
Giordono Bruno
Giordono Bruno
• Giordano Bruno was
publicly burned at the
stake on Feb 17th, 1600.
• This was the year of the
Jubilee celebration.
• Bruno was easily 200
years ahead of his time.
Johannes Kepler
(1571-1630) was
Brahe’s assistant,
and later the first
important modern
astronomer.
Kepler applied
mathematics to
Brahe’s findings
and discovered
Three Laws of
Planetary Motion.
• First Law: The path of each planet
around the sun is an ellipse, with the
sun at one focus.
How is an ellipse different from a
circle?
• A circle is a
closed curved
shape that is flat.
In a circle, all
points on the
circle are equally
distant from the
center of the
circle.
•An ellipse is also a closed curved shape
that is flat.
•Instead of having all points the same
distance from the center (like a circle), an
ellipse has two focus points.
• Second Law: Kepler determined that a
planet travels most rapidly when it comes
closest to the Sun and moves slowest
when farthest away.
Planet Revolution
Third Law: Keppler’s third law gives the
precise relation between the distance of a
planet from the Sun and how fast it
completes an orbit, using Astronomical
Units (AU).
One AU equals
150 million km,
the average
distance of the
Earth from the
Sun.
http://www.slideshare.net/simonandi
sa/94-orbital-motion-keplers-thirdlaw
Galileo Galilei
• 1564 to 1642
• Very talented
mathematician
• Excellent
experimenter and
astronomer
• Originally trained in
medicine but never
completed the
degree
Galileo Galilei
• Strong believer in the
Copernican system.
• Understood that an object
that is dropped will fall
straight down, not left
behind because of the
Earth’s rotation!
• Used a telescope to look
at the heavens and made
improvements in quality
and magnification.
Galileo Galilei
• Galileo wrote a book
in Italian about the
new evidence for the
Copernican system.
• He ultimately faced
the Inquisition and
was force to
renounce the
Copernican system
Galileo Galilei
• He was sentenced to
house arrest for the
last ten years of his
life.
• During that time he
wrote his most
complete argument
for the Copernican
system.
• Galileo not only
provided
evidence that
proved the
heliocentric
model accurate,
but he also
invented
pendulum clocks
and the modern
thermometer.
• He also created
one of the first
telescopes,
without anything
but a written
description to
guide him. He
even ground
glass for its
lenses himself.
Galileo used his telescope to view
the universe in a new way. He
made important discoveries that
supported Copernicus’ heliocentric
model of the universe.
1. The discovery of
the largest four
moons of Jupiter.
(He also discovered
Saturn’s rings.)
2.Planets are NOT pinpoints of light.
They are actually spheres, like Earth.
3. Venus has phases,
just like the moon.
Therefore, Venus circles the Sun.
4, The moon’s
surface is not
smooth.
(Galileo
thought the
moon’s dark
areas might
be seas.)
5. The sun has sunspots,
or dark regions.
Galileo tracked the movement of these sunspots
and estimated the rotational period of the sun.
Isaac Newton
• 1643 to 1727
• Born and raised on a
farm, Newton was
relatively useless as a
farm hand.
• He showed great
promise in school and
later attended Trinity
college in London
where he graduated
with a degree in math in
1665
Isaac Newton
• The college was shut
down for two years
due to the plague so
Newton returned
home to the farm.
• Here he formulated
some of his greatest
achievements.
• These include:
Isaac Newton
• The Law of Universal
Gravitation
• Invention of Calculus
• 3 Laws of Motion
• Optical
advancements
• Nature of light and the
spectrum
Isaac Newton
•
3 Laws of Motion
1. All objects resist
changes in their
state of motion
unless acted on by
an outside net force
(law of inertia)
Isaac Newton
•
3 Laws of Motion
2. If an object is acted
on by an outside net
force, it will
accelerate according
to the following
formula
a=F/m
Isaac Newton
•
3 Laws of Motion
3. For every force there
exists an equal and
opposite force
often called
action-reaction law
Isaac Newton
• Law of Universal
Gravitation
• Newton’s great
revelation was that
the same force that
pulls an apple toward
the surface of the
Earth is the same
force that holds the
moon in orbit
Universal Gravitation
1. Every body in the universe attracts
every other body with a force
directionally proportional to their
masses.
2. Gravitational forces decrease with
distance.
3. The greater the mass of the object,
the greater its gravitational force.
Gravity’s Influence on Orbits
Isaac Newton
GM1M2
F = ----------------r2
Newton imagined a cannon
fired from high mountain.
With enough speed the
falling cannon ball would
match the curve of the earth
and remain at the same
height above the surface,
returning to the cannon from
the other side
Isaac Newton
• After returning to
Cambridge University
as a professor, He
became the Lucasian
Professor of
Mathematics. 1669
• This position is held
by Steven Hawking
today
Isaac Newton
• Newton was later hired
as the head of the
British mint.
• He was in charge of
finding and prosecuting
counterfeiters
• He often went
undercover and
ultimately convicted
more than 10 counterfeiters who were
executed
Isaac Newton
• Newton conducted hundreds of
experiments on light and
discovered the origin of the
spectrum created by prisms
• Newton also
invented the
reflecting
telescope
Isaac Newton
• Much of Newton’s life was
filled with controversy.
• He fought with many other
scientists and
mathematicians over who
was the discoverer of various
ideas.
• These included Leibnitz
(calculus) and Hooke (optics)
and several others.
Isaac Newton
• Newton is often credited as
the greatest scientist of all
time.
• He impacted more areas of
science and even invented
an entire branch of
mathematics called calculus.
• He was knighted among his
many honors and served as
president of the Royal
Society (a scientific
watchdog)
• He was ill for the last two
years of his life and was
buried in Westminster Abbey
after his death.
Isaac Newton
Famous Quotes
“If I have seen further it is by standing on the
shoulders of giants”
“I do not know what I may appear to the world, but to
myself I seem to have been only like a boy playing
on the sea-shore, and diverting myself in now and
then finding a smoother pebble or a prettier shell
than ordinary, whilst the great ocean of truth lay all
undiscovered before me”