Transcript MODELS OF THE SOLAR SYSTEM - Saint Paul Public Schools

MODELS OF THE
SOLAR SYSTEM
Hey, its obvious.
Everything goes around the earth
- just go outside and look up!
For hundreds of
thousands of years,
this was regarded
as fact. Why would
you think anything
else?
Aristotle (384-322 BC) – famous Greek
philosopher –said that the planets, the moon,
the sun, and the stars all revolved around the earth.
Nice job, Aristotle.
This WRONG idea
was believed for
nearly 2000 years.
One problem – sometimes some of the
planets seemed to go BACKWARDS in
their orbits around the earth!!
(“retrograde motion”)
Here’s an animation that illustrates this
mysterious phenomenon:
http://cseligman.com/text/sky/retrograde.htm
Ptolemy, another Greek –
AD 90-168 (500 years later)
kind of solved the problem
by using a complicated
model with the planets
traveling in orbits with
little circular parts called
“epicycles”.
http://csep10.phys.utk.edu/astr161/lect/retrograde/aristotle.html
However, this model did not quite match
the observed paths of the planets.
So Ptolemy made the model even more
complicated, with “epicycles inside epicycles”.
When a model of
a natural system
gets this complex,
you start to wonder
if its correct.
(Plus, it still wasn’t perfect.)
Nicolaus Copernicus, 1473 – 1543,
a Polish churchman and amateur
astronomer, proposed a new model
in the 1540’s.
He shocked everyone
by saying that the earth
was NOT at the center
of the universe!
Way to go Copernicus!!
Copernicus’ Model of the Solar System
This was
so important
that it is
often called
the “Copernican
Revolution”.
This model implied that THE EARTH
MOVED – both around the sun and
by spinning on its axis.
Most people did
not believe this.
Most importantly,
the CHURCH. The
church was VERY
powerful in Europe.
Galileo (1564-1642) - Italian
genius was the first to use a
TELESCOPE to observe planets
and the moon.
His findings helped
to prove that
Copernicus was
correct.
Nice job Galileo!!
Johannes Kepler (1571-1630)
German astronomer – figured out
that the planets’ orbits are actually
“ellipses”, rather than circles (among
other important discoveries).
Finally, the positions of
the planets could be
accurately predicted.
You rock, Johannes!
Kepler explained HOW the planets
moved. Isaac Newton (1642-1727),
English genius, showed WHY they
move as they do when he figured out
the “Laws of Gravity”.
Lebron defying the law of gravity
Isaac – one smart dude!
SO – we now know that the moon
goes around the earth, but that the
planets (including earth) go around
the sun in elliptical (slightly oval) orbits.
Inner solar system
Outer solar system