1 - Northwest ISD Moodle
Transcript 1 - Northwest ISD Moodle
Students will be able to:
• Describe Ptolemaic model of the universe
• Discuss contributions made by Aristotle,
Aristarchus, Galileo, and Hubble
• Understand Copernicus’ contributions to the
heliocentric solar system
• Describe Kepler’s three laws of planetary
• Understand how Newton’s Laws helped Kepler
develop his laws of planetary motion.
Early Greeks believed that the Notice, there were seven
bodies orbiting the Earth
Earth lay at the center of the
in the Ptolemaic Model
universe. This is known as the • The Sun
• The Moon
This model was proposed by a
philosopher and mathematician
• and Saturn
named Claudius Ptolemy, who
All other bodies in
lived from AD90-AD168
space appeared to be
The area beyond the orbiting bodies was known as the firmament, or
the area of space that was infinite with fixed stars, aka “heaven”.
To the ancient Greeks, the stars traveled daily around the Earth on a
transparent, hollow sphere called the celestial sphere.
It was Aristarchus (312-230 BC) who first proposed the heliocentric
model, that placed the Sun in the middle of everything. This was
centuries BEFORE the accepted Ptolemaic model, which was geocentric.
Aristarchus came to this
conclusion after very
cleverly observing something
called “retrograde motion”.
Planets exhibit an
apparent westward drift.
In this photo series of
motion, you can see
how it appears to
double back on itself.
Aristotle was a Greek who studied under
Plato, and knew that the Earth was a
sphere, and that the light we see from the
moon, is actually sunlight.
Known as the father of science because
of his many observations, both accurate
Aristotle believed in a geocentric model of
the universe, and did not have knowledge
of forces such as gravity or inertia, so
Earth was static (unmoving).
1. Another name for an Earth-centered universe
is______________ and the ____________ believed
this because of improper observations.
2. In Ptolemy’s model of the universe, what was
3. What model correctly placed the Sun at the
4. Who was it who first proposed a helio-centric
5. Whose model did Aristotle’s observations
These years were known as
the time of the birth of
modern astronomy. The big 4
• Nicolaus Copernicus
• Galileo Galilei
• Sir Isaac Newton
I’m sure you’ve heard most of
their names before, but here
is a brief synopsis of what
each one contributed to the
field of space science…
Copernicus was the first
• Conclude that Earth
was a planet.
• Prove Aristarchus’
thought that the Sun was
at the center of things.
• Usher in the new age of
Copernicus continued to
believe…in error…that the
planets traveled around
the sun in circular paths.
Of course, we know today,
that the planets orbit the
Sun in “elliptical” paths.
The Earth’s path in this diagram is greatly exaggerated, however, it also
shows how the Earth’s gravitational field could influence the Sun’s
motion. When the Earth is closest to the Sun in its orbit (a point called
Perihelion), as small as we are, we do influence the Sun slightly, pulling it
6. What were Copernicus’ contributions
7. What were Copernicus’
misconceptions about astronomy?
8. What shape is the actual path of the
planets around the Sun?
9. At what point is the Earth closest to
the Sun, during its annual journey?
•Proved that planets revolve
around the Sun
• Founded the three laws of
Orbits of the planets are
Planets revolve around the
Sun at varying speeds
There is a proportional
relationship between a
planet’s orbital period and its
distance to the Sun (as
measured in AUs)
If it takes the Earth the same
amount of time to travel from
A-B, as it does for it to travel
from C-D, then it is obvious
that the Earth will travel
faster when it is closest to the
Sun (at perihelion)
Kepler's third law of motion states the
obvious. The relationship between the
orbital period of a planet and its distance
from the Sun is direct. This relationship is
mathematical and can be summarized in the
P2 = d3 0r p2 = a3
In the equation, "p" stands for the orbital period of the
planet measured in years and "a", for the average distance
of the planet from the Sun measured in astronomical units.
The significance of Kepler's third law is that given the
period of revolution of any body, be it a planet or a moon,
one can calculate the size of its orbit.
If it takes a planet 8 years to
revolve around our sun, what is the
size of its orbit (how many AUs?)
p2 = d3 or p2 = a3
8 2 = a3
64 = a3
a = 4 p2 =d3 or p2 = a3
You can also do this in reverse. If a
p2 = 53
planet has an orbital distance of 5 AUs,
p2 = 125
how long does it take the planet to
a = 11.18 years
revolve around the Sun?
• found evidence to
• Used experimental
• Constructed an
telescope in 1609
features on the
Sir Isaac Newton set forth:
• The law of universal
• that the force of
gravity, combined with
the tendency of a planet
to remain in straight-line
motion (inertia), resulted
in the elliptical orbits
discovered by Kepler.
10. What were Kepler’s contributions to the
science of astronomy?
11. What are the 3 Laws of Planetary Motion?
12. Write and describe Kepler’s equation that
summarizes his 3rd Law.
13. What were Galileo’s main contributions to
14. What were Isaac Newton’s contributions to
In 1919, the prevailing view of the cosmos was that the
universe consisted entirely of the Milky Way Galaxy.
Using the Hooker Telescope at Mt. Wilson, Hubble
identified Cepheid variables (a kind of star) in several
spiral nebulae, including the Andromeda Nebula and
Long after his death, the launching of the Hubble Space
on the Space
to be part
the Milky Wayobservations.
and were, in fact, entire galaxies outside
Hubble’s ultra deep field image reveals over 10,000 galaxies!
Hubble also devised the most commonly used system for
An AU, or Astronomical
Unit, is defined as the
average distance from the
Earth to the Sun. This
distance is: 149,500,000
Jupiter is 779,000,000 km from the
Sun. How many AUs is Jupiter from
15. Venus is 108,208,930
km from the Sun. How
many AUs is Venus from
16. What were Hubble’s
biggest contributions to
the understanding of
108,208,930 = 149,500,000X
779,000,000 = 149,500,000X
.7238 = X 149,500,000
or .7238 AUs
779,000,000 = X
5.21 = X
so Jupiter is 5.21 AUs from
In your journals, construct a “Trace”
Map (combination Tree, and Brace) of
the contributing scientists,
mathematicians, and philosophers to
the science of astronomy.
Begin with a tree map of contributors (how
Construct a brace at the end of each branch
with their contributions.