Heliocentric models
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Transcript Heliocentric models
Lesson 5
Astronomy
in the
Renaissance
Lesson 5:
Astronomy in the Renaissance
(1400 to 1650)
Motivation
Introduction
What did Copernicus believe?
How did Tycho Brahe contribute to our understanding
of space?
What are Kepler’s three laws?
How did Galileo Galilei help us understand the solar
system?
What did Copernicus believe?
Nicolaus Copernicus
(14731543)
Had trouble with
Ptolemy’s geocentric
(Earth-centered) model.
Believed in
Aristarchus’s
heliocentric model
What is retrograde
motion?
Heliocentric models
explain retrograde
motion as a natural
result of two planets
passing each other.
To better understand,
look at the diagram
and following
QuickTime
animations.
Movie
Retrograde Motion (revisited)
http://www.jimloy.com/astro/retro.htm
http://www.wlym.com/~animations/part1/1/index.html
What is the heliocentric model?
Heliocentric view – the sun is the center
of the solar system
This view plus the geometry yields the
distances of the planets from the sun
Problems: religious issues and accuracy
But theory was simpler – and it was
correct
Copernicus Arrested?
What did Tycho Brahe do?
(1546−1601)
Observed planetary
motion with accurate
instruments
Accurately measured
planets’ locations
Observed things that
suggested heavens
were changeable and
complex
Proposed different, but
still incorrect,
geocentric model
Who was
Johannes
Kepler?
(15711630)
Young
assistant to
Tycho Brahe
Used
Brahe’s data
Developed
three key
laws of
planetary
motion
Monument of Tycho Brahe and Johannes Kepler in Prague, Czechia
What are Kepler’s three laws?
Kepler's First Law: The Law of Ellipses
-- How planets move around the sun
Kepler's Second Law: The Equal-Areas Law
-- How planets move when nearer to the Sun
Kepler's Third Law: The Harmonic Law
-- How planets move when farther from the Sun
Kepler's First Law: The Law of Ellipses
-- How planets move around the sun
The orbits
of the
planets are
ellipses
with the
Sun at one
of the foci.
Kepler's Second Law: The Equal-Areas Law
-- How planets move when nearer to the Sun
The line that
connects the
planet to the Sun
sweeps out equal
areas in equal
times.
A planet's speed changes with its distance from the sun
http://www.astro.uiuc.edu/projects/data/KeplersLaws/
.
Kepler's Second Law: The Equal-Areas Law
-- How planets move when nearer to the Sun
Planet’s speed
also depends on
position in its
orbit around the
Sun
Kepler's Third Law: The Harmonic Law
-- How planets move when farther from the Sun
The squares of the orbital
periods of the planets
around the sun are
proportional to the cubes of
the orbital semimajor axes.
P2=a3
What Kepler's third law entails is that the
larger the orbit of a planet, the slower the
planet will travel in its orbit, and conversely,
the smaller the orbit of a planet, the faster it
will travel.
A3
P2
Galileo Galilei
(15641642)
First person to use a
telescope to study the
heavens
Saw key features:
•
What the Moon is made of
•
Sun spots and appearance
•
Jupiter’s moons
•
Milky Way’s size and content
Galileo Galilei, 2000 Itialian Lire (1973)
Were Galileo’s ideas accepted?
No: house
arrest for
rest of his
life.
Why?
Trial by Inquisition
Summary
Which key people changed the way we
understand the Earth, Sun, and planets?
Copernicus, Brahe, Kepler, and Galileo
What idea did Copernicus develop and promote?
Believed in Sun-centered (heliocentric) solar system
Measured relative distances of planets from the Sun
Summary (cont’d)
What is a heliocentric model?
Sun at center of solar system and planets revolving
How did Tycho Brahe contribute to our
understanding of space?
Observed and recorded planets’ locations
Still supported geocentric theory
Summary (cont’d)
What are Kepler’s three laws?
1.
The Law of Ellipses (planets’ movement around sun)
2.
The Equal-Areas Law (closer to Sun = faster)
3.
The Harmonic Law (farther from Sun = longer)
How did Galileo Galilei help us understand
the solar system?
Observed moon, sun, three planets
Developed theories to support heliocentric solar
system