1. Exploration
EQ: How has mankind’s need to
explore led to our current view
of the solar system?

2. Our First Views of the Universe
• Egyptians – need a way to predict the
annual flooding of the Nile River
• Studied the star Sirius and noticed it
was in the morning sky every spring
shortly before the flooding began

3. Our First Views of the Universe
• Mayans – developed a calendar that
was centuries before their time
• Observed the solstices

4. Our First Views of the Universe
• Stonehenge
–Built in several stages
–We don’t know who built it or exactly
why
–It does have connections to the
summer and winter solstices

5. Our First Views of the Solar
System: Reflect
Choose one of the reflections below to answer.
•M: Restate the reason why Egyptians' exploration of
the night sky was important.
•I: Which of the three ancient societies would you
have preferred to explore the sky with? Why?
•U: What are the similarities in the explorations of the
people who built Stonehenge and the Mayans?
•S: Imagine you are looking up at the stars in 3,000
B.C. How can you explore them?

6. Beginning to Make Sense of the
Universe
• Greeks observed the planets.
–Called them wandering stars
–Were aware of 5 planets – Mercury,
Venus, Mars, Jupiter, and Saturn

7. Beginning to Make Sense of the
Universe
• Aristotle
–Placed the earth at the center of the
solar system surrounded by 55
crystalline spheres – GEOCENTRISM
–Earth did not move at all
–Everything revolved around the Earth

8. Beginning to Make Sense of the
Universe
• Ptolemy
–Refined geocentric model of the solar
system
–Epicycles – smaller circles around large
circles to help explain planetary
motion
–Messy way to explain the movement
of planets

9. Epicycles
• Used to explain retrograde rotation –
the apparent backward movement of
planets

10. Beginning to Make Sense of the
Universe: Reflect
Choose one of the reflections below to answer.
•M: Summarize the contributions of Aristotle and
Ptolemy to our understanding of the solar
system.
•I: How would you feel if I told you the Earth
really is the center of the solar system?
•U: Contrast Aristotle and Ptolemy’s discoveries
about the solar system.
•S: Design a NASA mission patch dedicated to
studying geocentrism.

11. The Revolution Begins
• Copernicus
–Published Revolutionibus Orbium
Coelestium (On the Revolution of the
Celestial Orbs) the year he died
–Math based
–Introduced the heliocentrism – the sun
is the center of the solar system

12. Copernican Solar System

13. The Revolution Begins
• Brahe – recorded many detailed
astronomical observations – one of the
first to make such detailed records
• Kepler – used Brahe’s data to develop
his laws of planetary motion – planets
orbit in ellipses

14. The Revolution Begins
• Galileo
– first person to use a telescope to explore the
night sky; he became an expert at building
refracting telescopes
– Evidence for heliocentrism
• Jupiter – four moons that revolved around
it – not Earth
• Venus – goes through phases like the
moon
• Sun – has spots and rotates

15. The Revolution Begins
• Newton
– Developed a new kind of telescope to explore
with – reflector
– Wrote the Three Laws of Motion to explain
the movements of the planets
– Planets are kept in orbit around the sun by
• Inertia – objects in motion stay in motion
• Gravity – force of attraction between
objects

16. The Revolution Begins: Reflect
Choose one of the reflections below to answer.
•M: What do you think were the two most important
discoveries made by these astronomers?
•I: Galileo’s findings were rejected the Catholic Church.
How would you feel if you were Galileo?
•U: If everyone around you believes in a geocentric
universe, hypothesize what their reactions would be
when you explain heliocentrism to them.
•S: What would it be like to live on Jupiter and watch
four moons orbit around your planet? What
explorations would you conduct?

17. Our Growing Solar System
• Our continued need to explore has
helped us learn more about the solar
system and our views have changed
over time because of that

18. Our Growing Solar System
• Uranus – discovered in 1781 by William
Herschel using a telescope
• Ceres – discovered in 1801; initially
called a planet; started a big debate that
led to the creation of the asteroid
category
• Neptune – discovered in 1846 using a
telescope

19. Our Growing Solar System
• Pluto – discovered in 1930 by Clyde Tombaugh
• Kuiper Belt – discovered in 1992
– It’s the region beyond Neptune where Pluto is
– Many other dwarf planets (Plutoids) are located
here
• As our tools become more advanced, we continue
to explore and learn about our solar system
– The Oort Cloud is a region beyond the Kuiper Belt
– We’ve discovered a lot more about the moons of
other planets

20. Our Growing Solar System:
Reflection
Choose one of the reflections below to answer.
•M: What explorations led to Ceres no longer being
considered a planet?
•I: If you were in charge of deciding where our next
unmanned space probe will go in the solar system, where
would you send it?
•U: Draw parallels between Ceres’ demotion from planet to
asteroid and Pluto’s demotion from planet to dwarf planet.
•S: Imagine your patient observations night after night lead
to the discovery of a new planet. How would you announce
your discovery to the world?

21. Organize the Exploration!
• Create an illustrated timeline to
organize the explorations that led to our
current understanding of the solar
system.