Download The Solar System

The Solar System:
Historical Perspective
Objectives
• After this lesson, students will be able to:
– Define the concept of Astronomy
– Describe the geocentric model of the solar
system.
– Recognize how scientists such as Copernicus,
Kepler, and Galileo contributed to acceptance of
the heliocentric model of the solar system.
What do you know about the solar
system?
______
________
Solar
System
________
_______
What is Astronomy?
• It is the study of outer
space and all the
objects on it.
Why do we study Astronomy?
• Natural disasters
• Recreation and esthetics
• Scientific inquiry and
curiosity
• Education of an informed
society (you !)
• Our place in the Universe
• Origin and fate of the
Universe (Cosmology)
• True Science versus
science fiction
Astrology is NOT a Science
• Seeks to discover “hidden knowledge” by
the interpretation of omens (like reading
tea leaves).
• Results are not repeatable.
• Predictions are vague and not testable.
• Does not incorporate sciences like
chemistry and physics.
The Roots of Astronomy
• Already in the stone and bronze ages, human
cultures realized the cyclic nature of motions
in the sky.
• Monuments dating back to ~ 3000 B.C. show
alignments with astronomical significance.
• Those monuments were probably used as
calendars or even to predict eclipses.
Stonehenge
• Constructed 3000 – 1800
B.C. in Great Britain
• Alignments with locations of
sunset, sunrise, moonset and
moonrise at summer and
winter solstices
• Probably used as calendar.
Other Examples around the World
Caracol (Mexico); Maya culture, approx. A.D. 1000
Passage of astronomical knowledge
Ancient
Babylon
Ancient
Egypt
Ancient Roman Empire
Ancient
Greece
Ancient Times
Greeks
• Many believed
Earth was inside
rotating spheres
nested inside each
other, that
contained the stars
and planets
Chinese
• Believed
Earth was under
a dome of stars.
Mayans
• Other civilizations such as
mayans, egyptians, etc.
Egyptians
Saw patterns in the Sun,
moon, and Venus
Called the sun “Ra” (Sun
god) – rode in his boat
across the sky daily
Developed 365 day year
solar calendar
Hipparchus surrounded by
his astronomy equipment
(drawn centuries later).
A Greek astrolabe discovered
in the Mediterranean
Geocentric Model
Ptolemy
• Greek astronomer
• A.D. 140
• Developed the Geocentric Model
 Earth was the center, and the
other planets and stars revolve
around it.
 It was accepted for nearly 1,500 years because of
it’s accuracy at explaining the motions
overserved in the sky.
 Geo = Earth
Centric = center
 Thought planets moved in perfect circles.
Geocentric Model
Heliocentric Model
Aristarchus
• Greek scientist, father of
astronomy
• Developed the Heliocentric
Model
 Helios = sun
Centric = center
 It was not well received
in ancient times because
people could not accept
that Earth was the
center of the universe.
Ancient Rome
The Romans most important contribution
to the field of astronomy is the
enforcement of a systematic calendar
that would account for fact that the year
is about ¼ of a day more 365 days. The
astronomers of Julius Caesar
convinced him to create the
Julian Calendar which adds
one day to the calendar every
4 years to account for the time
we had skipped. This is
known as a “leap year”.
Heliocentric Model
Nicolaus Copernicus (1473-1543)
• Developed the Heliocentric
Model in detail
• Described the arrangement
of the known planets of the
time and how they moved
around the sun.
• Published it in 1543
• At first, people were
skeptical, but then his
theory revolutionized the
science of astronomy
•
Thought planets
moved in perfect
circles.
Heliocentric Model
Geocentric or Heliocentric?
• Of the early philosophers, only
Hipparchus favored the heliocentric
model
• Most philosophers thought that the
evidence supported the Geo model more
than the Helio model
• What was the evidence? Let’s Look….
Geocentric Evidence
• Everything appears to revolve around the
Earth each day (diurnal motion).
• There is no observable parallax of the stars,
planets, Moon, or Sun.
• The motions of the stars and heavens are
perfect circles.
• The heavens were unchanging but the Earth
was not.
Problems With the Geocentric Model
• The planets appear to change brightness, implying a
change of distance.
• The planets undergo retrograde motion (they move
backwards compared to the direction the Sun
moves).
• The Sun, Moon, and Planets do not move at the same
speed all the time.
• Mercury and Venus are never seen at opposition
(they always appear close to the Sun.
Evidence of the Heliocentric Model
• The changing brightness of the planets is explained by
the Earth getting closer and farther from the planets
during our orbit of the Sun.
• Our passing planets explain the retrograde motion of
the outer planets.
• Mercury and Venus are not seen at opposition because
they orbit the sun, just as we do.
Problems with the Heliocentric Model
• The changing speeds of the Sun, Moon, and planets
is not explained by simply placing the Sun at the
center of the universe.
• We do not feel the Earth moving or the
atmosphere being pulled away as we fly around the
Sun.
• If the Earth were spinning, wouldn’t we be thrown
off into space?
• Why is there no parallax due to our spin or our
orbit?
Heliocentric Model
Tycho Brahe and Johannes Kepler
• Worked together
• Brahe was a Dutch
astronomer that made more
accurate observations of the
movement of the planets
• Kepler was his assistant and
used Brahe’s observations to
figure out the shape of
planet’s orbit.
• Kepler described the orbit of
each planet as an ellipse.
•
Ellipse= oval shape
Kepler
After Tycho’s death, Tycho’s family sued to
recover instruments and books of
observations
Why?
Kepler was a Copernican, and they knew he
wouldn’t follow the Tychonic system
Kepler kept the books! Began to study motion
of Mars …
Kepler’s First Law
of Planetary Motion
 Orbits are elliptical (oval shaped),
sun is at the focus
Kepler’s Second Law
of Planetary Motion
A line from a planet to the sun sweeps over
equal areas in equal times
Planets travel at different speeds – due to pull
of gravity
Closer to Sun,
moves faster…
Why?
Same time,
moves slower
Kepler’s Model (the elliptical orbit)
Heliocentric Model
Galileo Galilei
• Italian scientist
• 1500’s- 1600’s
some people
still believed in
the geocentric
model.
• Collected enough evidence to
convince others of the
heliocentric model.
• 1610, used a telescope to
discover four moons around
Jupiter.
•
•
The
movement of
those moons
around Jupiter
proved that
not everything
revolves
around Earth.
In conclusion,
the geocentric
model must
be incorrect.
Isaac Newton (1643 - 1727)
• Adding physics interpretations to
the mathematical descriptions of
astronomy by Copernicus, Galileo
and Kepler
• Major Achievements:
– Invented Calculus as a necessary
tool to solve mathematical problems
related to motion
– Discovered the three laws of motion
– Discovered the universal law of
mutual gravitation
Hipparchus
Claudius
Ptolemy
Nicolas
Copernicus
85 – 165 AD
1473 – 1543
Sir Isaac
Newton
Edmund
Halley
Sir William
Herschel
Caroline
Herschel
Albert
Einstein
Edwin
Hubble
1642 – 1727
1656 – 1742
1738 – 1822
1750 – 1848
1879 – 1955
1889 – 1953
190 – 120 BC
Tycho Brahe
1546 – 1601
Johannes
Kepler
1571 – 1630
Galileo
Galilei
1564 – 1642
References
Earth Science, Interactive Science. (2013). Saddle
River, New Jersey: Pearson Education, Inc.