Science Starter
Answer the following in your notebook:
1. When is the Earth closest to the Sun?
2. Does the speed of the Earth’s revolution change?
3. How can we tell if we are moving faster?
Today’s Agenda
• Science Starter
• History of Astronomy
• Lab Simulation
• Vocabulary Review Activity
• Haley’s Comet Summarizer
Lesson Essential Question
How do planets move through space?
Historical Models of our Solar System
and
Kepler’s Laws of Planetary Motion
Geocentric Model
• Earth is center of our Solar
System
• Aristotle- Over 2000 years ago
• Unexplained on how planets
appear to move backwards
• Ptolemy- Planets move in small
circles or epicycles
Heliocentric Model
• Sun is center of our Solar System
• Copernicus- Over 450 years ago
(1543 ad)
• First to suggest heliocentric
theory and vaguely mapped out
the planets orbiting the sun in a
circular orbit.
Galileo
• Supporter of Copernicus’s
Heliocentric theory
• House arrest
• Observed moons orbiting
Jupiter and theorized
objects can revolve
around other planets not
just Earth
Solar System precisely measured
• Tycho Brahe- studied Solar
System and made very
accurate recordings of his
observations
• Tycho’s assistant, Kepler, used
information for the details of
orbits
Kepler’s Laws of Planetary Motion
1st Law - Law of Ellipses
Each planet orbits the Sun in a path called an ellipse or elongated circle
Ellipse is a closed curve whose path is determined by 2 points or foci
within the ellipse
Focus 1 is the Sun and Focus 2 is an imaginary point
Eccentricity
• Degree of elongation or
shape of planet’s orbit
• Ratio between the foci
and length of major axis
• Circular =0
• Very elongated =1
2nd Law – Law of Equal Areas
• An imaginary line between the Sun and a planet sweeps out
equal areas in equal times as the planet travels around the
ellipse.
Keplers’
nd
2
Law- Law of Equal Areas
• This also means that as the planet comes closer
to the Sun in its orbit, it travels faster.
• So, the planets speed is slowest when it is the
farthest from the Sun
Challenge Question
What time of the year is Earth moving
faster in its orbit?
Challenge Question
What time of the year is Earth moving
faster in its orbit?
Winter (closer to the sun)
3rd Law – Law of Periods
• Mathematical relationship
• P 2 = a3
• a= semi-major axis (planets average
distance from Sun measured in AU’s)
• p= planet’s orbital period (time)
• Simply means that the farther a
planet is from the Sun, the longer
it takes to orbit around the Sun
Einstein (1879-1955)
• Changed Newton’s
gravitational theory based on
findings of Mercury’s orbit.
• Developed Theory of
Relativity. It completely
changed the way we study
gravity and even changed our
understanding of the
universe.
Kepler’s Lab Simulation
• Each group will sign out a laptop (1 per group)
• Each person at the group will have a lab sheet to fill out
• Work together in your group to answer the questions and
make sure everyone understands!
• DO NOT VISIT OTHER SITES BEYOND THE SIMULATION!!
(LOSS OF LAPTOP)
• If you finish early: show Mr. Houtz your work, return your
laptop, and grab a vocabulary activity from the front
Kepler’s Lab Simulation
• Suggested that you break up the work like so:
1. Computer Manager (signs out laptop)
2. Question Answerer (makes sure all group understands)
3. Task Manager (makes sure group is working at ALL times &
follows the procedures)
4. Researcher (Keeps notes out to answer analysis questions,
ask Mr. Houtz for help)
Vocabulary Activity
• Grab a vocabulary activity from the front of the classroom
• The sheet has 4 activities for you to complete
• You can use your notes or the book to answer (Ch.22-24)
• Should be completed by the end of class
Haley’s Comet
Haley’s Comet follows the orbit path above, cycling once every 80 years.
1. When is Haley’s comet moving fastest & how do you know? (close or
far from the sun)
2. Why does Haley’s comet not orbit the Sun in a circle?
3. How is Haley’s orbit similar to the Earth’s revolution?