Transcript Early Astronomers

Early
Astronomers
Aristarchus and Eratosthenes
 From
Greece, 4 and 3 BC
 Based on observations believed in
Heliocentric model
 Able to calculate the diameter of the
earth, believing it was round.
 List observations they could have made
to support their hypothesis
 Aristarchus
Eratosthenes
Ptolemy
 Earth
centric model,
 Believed the portions of the universe
visible at the time were much smaller in
scale and closer than Aristarchus who’s
scale was a bit more realistic
 What observations would have lead to
believing in an earth centered system?
 Ptolemy's model
Geocentric Modeling
 Please
experiment with how a system
would have worked based on the
geocentric model. Use the sun, earth,
mars, venus.


Draw it in your lab journal first – then we will
use the actual globes and lights to attempt
to demonstrate.
In your lab journal – write down three things
that do not work with this model when you
try to put it together physically.
Copernicus and Galileo
 Heliocentric
model, with mathematical
proof
 Used telescopes to view moons of Jupiterwhich was evidence of _____________?
 Our moon has craters and phases
 Venus went through phases similar to our
moon
 Evidence which supports the ____________
model.
Heliocentric modeling
 In
your lab journal – sketch a heliocentric
model – include Sun, Earth, Venus, Mars


Consider Galileo’s observations, give three
more reasons why this model works better
to explain movements in our solar system
What motion in the planets helps resolve
other observation problems?
 Mars
in retrograde, Venus phases,
 Retrograde motion
Tycho Brahe
 Known
for his “naked eye” observations,
both being accurate and huge in
quantity
 Offered a “geo-heliocentric” model to
accommodate a number of observations
 Used “stellar parallax” to calculate
distance to stars he observed.
 Tycho Brahe
Geo-Helio Model by Tycho
Brahe
Kepler
 Kepler
used mathematics to prove
and solve problems with other
astronomers observations
 Kepler's laws are:
 1. The orbit of every planet is an ellipse,
with the Sun at one of the two foci.
 2. A line joining a planet and the Sun
sweeps out equal areas during equal
intervals of time.
 3. The square of the orbital period of a
planet is proportional to the cube of
the semi-major axis of its orbit.
(2) The two shaded sectors A1 and A2 have the same surface area and the time for
planet 1 to cover segment A1 is equal to the time to cover segment A2.
(3) The total orbit times for planet 1 and planet 2 have a ratio a13/2 : a23/2.
How do ellipses work?
 How
is an ellipse different than a circle?
 How does this solve some problems of
observation in the solar system?
 Mars in retrograde?
 Rate of speed of planets as they travel
around the sun?
The flaws in previous thinking?
 Planetary
orbits were perfect circles
 Size and speed of planets, orbits, etc
 Affects on each other en-route- hmm,
Moon Mapping
 We
are going to track the moon for a
month. This is a long term assignment,
which will create a lot of data and
questions. 
 1st – put your name on the back of the
paper and label according to my notes
on the board.
 2nd – lightly, draw lines at the levels noted
on the board.
 3rd – add a horizon line
Moon mapping
requirements
 All
moon’s must have date and time next
to it, and be properly shaded based on
your observation.
 Special notes will go on the back of the
moon map as per class discussion
 Hypothesis ideas will also
Isaac Newton and gravity
 Contributions:
laws of motion and gravity
 These laws could be applied to all things
in the field of science – not just astronomy
 Worked with light and color, and built a
reflecting telescope.
 Apple idea – why did the apple fall to the
ground, why do the moons orbit larger
planets, and why do planets orbit the
sun?
 Gravity!
Universal Law of Gravitation
"All bodies attract each other with a force
proportional to the product of their
masses, and inversely proportionate to
the square of the distance between
them.
Okey – so what does that really mean?
http://ed.ted.com/lessons/jon-bergmannhow-to-think-about-gravity
 Practically,
this law says that large, heavy
objects pull each other harder than small,
light ones. And the pull is greater between
objects near each other than objects that
are far apart.
 Put that in context to the sun, the moon,
the earth, and other planets.

http://www.richeast.org/htwm/NEWTON/Newton.htm
Question If
you drop a feather and a hammer
which will land first?
 Why? Defend your answer with facts.
http://www.youtube.com/watch?v=4mTsrR
ZEMwA
The formula ,
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
And so, lets talk about those variables.
What if?
What if?
 If
you climbed to the top of Mt Everest
would you feel less gravity?
 Why do you experience less gravity on the
Moon?
 Which variable is at play in each of these
problems?
Moon Map modeling
 Using
your information from the moon
mapping activity – please practice and show
me what actions happen between the sun,
moon and earth for the phases to appear as
we observed them.
 On the back of your moon map draw the
moon, sun and earth in the correct positions to
show a full moon, and new moon.
 Show both your model and diagram to me to
get checked off before proceeding.
Moon Map summary

On the back of your moon map, after completing the
modeling, and diagram, you need to write a summary
that follows the format:
 The lunar period from full moon to full moon, both its
orbital period, and rotational period.
 We only ever see one side of the moon, explain why
that is the case. Refer to video
 Explain why we the moon rise/ set later and later each
day.
 Include a statement about the lunar orbit and its
rotation on its own axis.
 End your summary with two new things you learned
from this observation period and modeling practice