Transcript Astronomy

ASTRONOMY
WHAT IS ASTRONOMY?
Astronomy – the study of the universe
Astronomy? Impossible to understand
and madness to investigate.
— Sophocles, c. 420 BCE
Rotation: The turning of the Earth on its own axis
• Day and Night
• 24 hours
Revolution: The orbit of the Earth (or planets)
around the sun
• Year
• 365.25 days
•Year – the time it takes the earth to orbit
once around the sun
•Month – the time it takes the moon to orbit
once around the earth
•Day – the time it takes the earth to rotate
once around its axis
Historical figures in the Copernican
Revolution
Ptolemy – Greek Astronomer
-- 85 – 164 AD
--Proposed the Geocentric model of the
universe; that the Earth was the center of the
universe/solar system
-- Idea accepted for 1400 years
-- 1st person to use latitude and longitude to
identify places on Earth
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Historical figures in the Copernican
Revolution
Copernicus – Polish Astronomer
-- 1473 – 1543
-- Proposed the Heliocentric Model of the
universe; that the Sun was the center of the
solar system
--He thought the planets orbited the sun in
circles
Historical figures in the Copernican
Revolution
Brahe– Danish inventor, astronomer
-- 1546 – 1601
-- Invented/Improved instruments for
observing the universe
-- Kepler worked for Brahe to observe the
motion of the planets
--Modified the Geocentric Model
-- Thought the moon and sun orbited the
Earth
-- All other planets orbited the sun
Historical figures in the Copernican
Revolution
Kepler – German mathematician
--1571-1630
--Began studying the orbits of planets with
Brahe
--Discovered the orbits were not circles, but
were really ellipses (ovals)
--stated that the planets move at different
speeds around the sun
-- closer planets move faster than planets
further out
Historical figures in the Copernican
Revolution
Galileo –Italian Astronomer
-- 1564 – 1642
--1st to prove Copernicus’ Heliocentric Model with
a telescope
--Used the phases of Venus with explained that
Venus in fact revolved around the sun
--Spent the last years of his life under house
arrest
--discovered the 4 moons of Jupiter
-- invented the thermometer
-- built compasses for surveying land
Historical figures in the Copernican
Revolution
Newton – English scientist, astronomer,
mathematician
-- 1642- 1727
--1st to describe the concept of gravity
--Stated the force that holds us to the Earth is
the same thing that keeps the planets in orbit.
-- Three laws of motion
-- Law of Universal Gravitation
-- Developed Calculus
The observed solar system at the time of Newton
Sun
Mercury
Venus
Earth
Mars
Jupiter
Saturn
(all except Earth are named
after Roman gods, because
astrology was practiced in
ancient Rome)
Three outer planets discovered later…
Uranus (1781, Wm Herschel)
Neptune (1846 Adams; LeVerrier)
Pluto (1930, Tombaugh)
Historical figures in the Copernican
Revolution
Hubble – American Astronomer
--1889 -1953
--in 1929 formulated Hubble's Law, which
determined the age of the universe and that
it is expanding
--demonstrated that other galaxies besides
our own Milky Way existed
--In the same year Edwin Hubble
introduced his Hubble telescope.
-- The Hubble Space Telescope was
launched on April 25th, 1990 on the space
shuttle.
Edwin Hubble
Geocentric vs Heliocentric
Theories
Earth or Sun Centered?
•Geocentric Theory (Earth-centered) –
Ptolemy’s theory that the earth was
the center of the universe
•Heliocentric Theory (Sun-centered) –
Copernicus’ theory that the sun was
the center of the universe
Claudius Ptolemy
A geographer, mathematician, and
astronomer
Developed the theory that the Earth
was the center of the solar system
…“the natural motion of the Earth ….is
towards the center of the universe; that is
the reason it is now lying at the center.”
Aristotle, On the Heavens
The Geocentric Theory
• The earth is
located at the
center of the
universe and all
the planets
revolve around
the earth.
Nicolaus Copernicus
1473 -1543
A mathematician, and
astronomer
Developed the theory that
the sun was the center of
the solar system
To know that we know what we know, and to know that we do not know what we do not know,
that is true knowledge.
Galileo Galilei
1564 - 1642
By using the telescope, Galileo noted that
Venus had “phases” like the moon, so it
could not orbit Earth, but must orbit the
Sun….
So, these observations supported
Copernicus’ theory!
The Heliocentric Theory
• The Sun is the center of our solar system
The heliocentric model
The reasons for seasons – the Earth travels around the sun, and its
axis of rotation is tilted by 23.5 degrees to the plane of the orbit. In
July, the northern hemisphere is getting more sunlight than in January.
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Comparing and Contrasting Historical
Theories of the Solar System
Geocentric Model
Heliocentric Model
HEAVEN
HELL
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Timeline
Galileo
Newton
1564-1642
1642-1727
Brahe
Copernicus
1473-1543
1546-1601
Kepler
1571-1630
1B
The Copernican Revolution
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Nicolaus Copernicus
The Earth moves, in two ways.
• It rotates on an axis (period = 1 day).
• It revolves around the sun (period = 1
year).
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Tycho Brahe
1546 – 1601
Adjusted the Geocentric
Theory
Brahe’s precise observations
of planet movement lead him
to believe that the moon and
sun orbited the sun, and the
other planets orbited the sun
Through Brahe’s
observations with
instruments that lead to the
invention of the telescope he
developed mathematical
calculations of the orbits of
the planets, sun, and moon,
These calculations helped
Kepler determine the
equations for planetary
motion
Johannes Kepler (1571 – 1630)
Developed the laws that describe how the
planets move in the solar system
• Planets move in elliptical orbits
Mrs. Scasny’s
Galileo’s discoveries in Astronomy
Galileo did not invent the telescope, but when he heard about
the invention he figured out how to build telescopes. He had
the best telescopes of his time. He was the first person to use
telescopes to look at the heavenly bodies. He was first, so he
made the discoveries.
 Craters and mountains on the moon
 4 Moons of Jupiter
 Phases of Venus
 The Milky Way consists of innumerable stars.
 Sunspots (dark spots) move across the sun’s face.
All of these favored the Copernican (heliocentric) model.
Galileo’s sketch of the
moon as seen from his
telescope
A photograph of
the moon
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Galileo made many specific discoveries in astronomy,
through observations by telescope.
The general implications…
● The planets are objects like the Earth – masses – rather
than some kind of special heavenly objects. Or, to put it
another way, the Earth is just another planet.
● The planets, including Earth, travel around the sun.
● The Universe is a lot bigger than we can see by the
naked eye.
These ideas could be dangerous.
The Trial of Galileo
The Church decided that the heliocentric model was a heresy.
But Galileo continued to argue in favor of the theory, and published his
reasoning. The Inquisition in Rome accused him of heresy, and required
him to answer.
He was put under arrest and sentenced
to prison. But because of his fame and
age (70 years old at that time) he was
allowed to serve under house arrest in
Florence, for the remaining years of his
life.
Isaac Newton
1642 - 1727
Isaac Newton
Newton solved the premier scientific problem of his time --to explain the motion of the planets.
To explain the motion of the planets, Newton developed
three ideas:
1. The laws of motion
2. The theory of universal gravitation
1. All objects in the universe attract each other
through gravity
2. Heavy objects and those that are close together
have the strongest gravitational force
3. Calculus, a new branch of mathematics (oh what fun!!)
“If I have been able to see farther than others it is because I
stood on the shoulders of giants.”
--- Newton’s letter to Robert Hooke,
perhaps referring to Galileo and Kepler
Newton’s Theory of Universal Gravitation
Newton and the Apple
Newton asked good questions  the key to his success.
Observing Earth’s gravity
acting on an apple, and seeing
the moon, Newton asked
whether the Earth’s gravity
extends as far as the moon.
(The apple never fell on his head,
but sometimes a stupid person
will say that, trying to be funny.)
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Warm Up
•How much time passes when…
1. …..the moon goes around the earth
3 times?
2. …..the earth goes around the sun 50
times?
3. …..the Earth rotates 360 degrees?
4. …..there are 12 full moons?
5. …..the Earth rotates halfway
around?
Warm Up
1. What causes the Earth’s seasons?
2. Draw the diagram below and label which season
we would be having:
Warm Up
1. What causes the Earth’s seasons?
2. Draw the diagram below and label which season
we would be having:
SUN