Download on his death bed. Retrograde Motion The heliocentric

The Copernican Revolution
1540 - 1690
started by
Nicolaus Copernicus
1473 -1543
Astronomy in the Renaissance
• However, problems
remained:
– Could not predict
planet positions any
more accurately than
the model of Ptolemy
– Could not explain lack
of parallax motion of
stars
– Conflicted with
Aristotelian “common
sense”
Copernican System
Copernicus concluded that the
sun, not the Earth, was the center of
the solar system.
This is known as heliocentric - sun
centered.
This was a radical departure from
Aristotle's view.
Although Copernicus was a
priest, his position was troubling to
the Church.
His idea was published in 1543 in
De Revolutionibus - on his death bed.
Retrograde Motion
The heliocentric idea was able to
explain observations of the planets.
The idea of retrograde motion
could be explained without the use
of epicycles.
Copernicus' idea of uniform
circular motion did have its
problems.
There were observed variations in
the movement of the planets.
The uniform circular motion
which Copernicus assumed, was not
correct so he kept epicycles.
Tycho Brahe 1546 - 1601
Funded by the king of Denmark
built the first modern observatory
Uraniborg (Sky Castle)
Tycho Brahe made the most
accurate visual observations of the
planets.
His observations allowed for
precise position predictions.
His discovery of a 'new star' was
more proof against Aristotle's
perfect and unchanging starry
sphere.
However, he did believe the Earth
was stationary because he could not
measure parallax of the stars.
Tychonic Universe
Not detecting parallax, Brahe developed a complex scheme.
He made the Earth fixed, around which the sun and moon circled.
The planets then rotated around the sun.
His goal was to publish an improved Alfonsine Tables based on his
Tychonic Universe idea.
Brahe's Model
Tycho's idea is
represented in this
figure.
The revised
Alfonsine Tables
would be called the
Rudolphine Tables.
This was to honor
his new patron
Emperor Rudolph
II.
Kepler 1571 - 1630
Kepler was appointed to succeed Brahe as imperial
mathematician by Rudolph II and was able to transfer Brahe's
extremely accurate observations into the planetary laws of motion
which bear his name.
Kepler was an extremely religious man and deeply troubled in
his personal life but this did not stop him from his great
discoveries of planetary motion.
Kepler's Model
Kepler was trying to
know the mind of God.
He was convinced that
geometry was the mind
of God, which held the
answer to the motion of
the planets.
He placed the sun at
the center and invoked
the regular solids using
one for each planet's
orbit.
His model did
not work.
Elliptical Orbits
Ultimately, Kepler had to
abandon his belief in geometry
and use the data from Brahe to
determined his three laws of
planetary motion.
(1) All planets orbit the sun in
an elliptical orbit.
(2) A planet will sweep out
equal areas in equal time.
(3) The Harmonic Law states
that the period squared of a
planet's orbit is equal to its
distance from the sun cubed.
rd
3
law
T2 / r 3 = k
T is the period in years
“r” is the radius in Astronomical Units (AU)
T2a / r3a = T2b / r3b
Kepler's Orbits
*Kepler's laws described planetary motion but did not explain what caused it.
*He finally completed the Rudolphine Tables which allowed for accurate
prediction of planetary position.
*Kepler's accuracy was from 10 to 100 times better than previous tables.
Retrograde Motion
http://projects.astro.illinois.edu/data/Retrograde/index.html
Galileo 1564 - 1642
Galileo Galilei was the
first scientist to write
directly to the people.
It was common practice
for scholars to write in
Latin but Galileo also
wrote popular books in
Italian.
Galileo invented the
astronomical telescope
(bringing images 30 x
closer), although a
lensmaker in Holland
made the first telescope.
Galileo's Telescope
Galileo observed Jupiter in 1610.
His telescopic observations revealed an imperfect moon, the
Milky Way was made of stars, and Jupiter had four objects orbiting
it and these observations ended Aristotle's incorrect views on
astronomy.
These views also got Galileo in trouble with the church.
Evidence for the Heliocentric Model
• Venus undergoes full phase cycle  Venus must
circle Sun
Galileo
To challenge Aristotle was to
challenge the authority of the
Church.
The Church could not afford
anymore attacks on its authority.
Galileo was placed under
house arrest until he died.
His trial caused many
questions through the years and
in 1992 an indication of
innocence was implied by the
Church.
Isaac Newton 1642-1727
• Isaac Newton was born the year Galileo died.
• He made major advances in mathematics, physics,
and astronomy.
• He pioneered the modern studies of motion, optics,
and gravity and discovered the mathematical
methods of calculus.
• It was not until the 20th century that Newton’s
laws of motion and gravity were modified by the
theories of relativity.
Birth of Modern Astronomy
Here we see the time line showing the transition from the ancient
astronomy of Ptolemy to the birth of modern astronomy.