Birth of a
Solar System
Chapter 17, Section 1
1.Let’s review Gravitational Pull
QuickTime™ and a
decompressor
are needed to see this picture.
Investigate Lab: Analysis 4
Both pieces of paper should reach the
bottom at the same time when the
flat piece of paper is placed on a
book.
They should have fallen at the same
rate as the book. Gravity causes all
objects to fall at the same rate,
regardless of their mass.
Investigate Lab: Analysis 5
The crumpled piece of paper
should reached the floor first.
While gravity pulled both pieces
toward the floor, the differing
result has to do with air resistance.
2. The Hammer & the Feather
On the Moon
QuickTime™ and a
decompressor
are needed to see this picture.
3. Mythbusters : Feather & Hammer
QuickTime™ and a
decompressor
are needed to see this picture.
What is gravity?
 Gravity is a force of attraction
between two objects.
 Gravity gets stronger as objects
get bigger and closer together.
 The bigger the object, the more
gravitational pull it will have on
nearby objects.
 The Earth is so big, that it is able
to pull the pieces of paper to its
surface.
4. Moon and Gravitational Pull Explained
QuickTime™ and a
decompressor
are needed to see this picture.
How did our solar system
come to be?
 Today we are going to look at a
theory created by scientists to
explain how the solar system
ever came to be.
 We will talk about how the
planets, including Earth, were
formed.
 What is a solar system?
A solar system is composed of
the sun (a star) and the other
bodies that travel around the
sun.
It all starts with a Nebula
A what?
A nebula is a huge
interstellar cloud made up
of dust and gas.
Nebulas are so big it takes
many years to cross them.
These nebulas are cold (10
degrees above absolute
zero) and dark.
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
Gravity Pulls Matter Together
These nebulas which consist of dust and
gas have matter and therefore have
mass.
However, the matter in a nebula is very
spread out and because of this the
attraction between the gas/dust particles
is very small.
Pressure Pushes Matter Apart
As the molecules in a nebula are
pulled together by gravity, they begin
to hit each other and bounce back.
These collisions create a push, or
pressure, within the nebula.
Together, gravity & pressure reach a
balance in a nebula.
What is this lady talking about?
Ok, think of it like this.
What keeps you balanced on your chair?
Gravity pushes you down on the chair
The pressure of the chair pushes you back up.
Together, they balance each other out.
The Solar Nebula Forms
So we have this perfectly
happy & balanced nebula.
Suddenly, out of no where, a
neighboring nebula crashes
into it! Ahhhh!
When that happens stars can
explode and areas can become
so compressed that pressure
can’t react quickly enough to
balance the gravity.
The Solar Nebula Forms
Enter: the solar nebula.
When nebulas collide and the balance
is upset, a star may be formed in the
middle of the dust cloud.
This star, now called a solar nebula,
becomes the center of the new solar
system.
5. Birth of a Solar System
QuickTime™ and a
decompressor
are needed to see this picture.
The solar nebula changes
Once our solar nebula collapses, things
happen quickly (on a cosmic scale!)
The dark clouds collapsed, matter in the
clouds got closer and closer together.
The gas and dust particles moved at a
faster rate.
The center of the cloud got hotter and
hotter and hotter.
And it keeps changing…
 Before you know it…
the dust and gas
begins to rotate
slowly around the
hot center and the
solar nebula flattens
into a disk.
6. The Birth of a Solar System
QuickTime™ and a
decompressor
are needed to see this picture.
Planetesimals Form
With so many
collisions happening
in this swirling
vortex of cloud, bits
of dust start
sticking together.
This dust begins to
form the building
blocks of planets
called
planetesimals.
Planets Form
The biggest
planetesimals
collect more and
more of the dust &
gas and eventually
become a planet.
Watch it all here!
Inner & Outer Planets Form
 The gas planets (or outer planets)- Jupiter, Saturn,
Uranus and Neptune, were all able to collect a ton of
dust in the cooler, outer solar nebula.
 Once they grew large enough, their gravity was
strong enough to attract the nebula gases, hydrogen
and helium.
 The rocky planets (or inner planets) - Mercury,
Venus, Earth & Mars, couldn’t take the heat and all
of the gases burned off, leaving only the rocky
parts.
Quic kT ime™ and a
T IFF (Un compressed) d ecompressor
are need ed to s ee this pi cture.
What makes an inner planet
different from an outer
planet?
Inner Planet
Rocky
Small
Thin atmosphere
Few or no moons
Molten core in
Earth and Mars
Outer Planets
Mostly gas
Huge
Thick atmosphere
Many moons
rocky core
not dense
7. Journey to the Edge of the Universe
QuickTime™ and a
decompressor
are needed to see this picture.
Let’s Talk: Planetary Motion
We have one more
thing to talk about
today and it is…
What is planetary
motion?
It is how the planets
move.
revolution
Weird Science
When you consider the motion of
the Earth’s rotation, it’s revolution
around the sun, and the sun’s
movement around the Milky Way
galaxy, you are actually traveling
more than 900,000 km/h just
standing still!
Planetary Motion: Rotation
The Earth spins, or rotates, around its axis.
Only 1/2 of the earth faces the sun at any
given time.
As the earth rotates, different parts of the
Earth receive sunlight.
The half facing the sun is light (day), and the
half facing away from the sun is dark (night).
Planetary Motion: Rotation
Did you know we’re all a
little crooked??
The Earth’s axis is tilted
23.5˚.
The Earth also rotates
very quickly - 1000
miles per hour!
How long does it take
the Earth to complete
one rotation (or one spin
around its axis)?
1 day, or 24 hours.
Planetary Motion: Revolution
The Earth also travels around the sun in a
path called an orbit.
The motion around the sun along its orbit is
called a revolution.
The other planets ALSO revolve around the
sun on their orbits.
Planetary Motion: Revolution
How long does it take the Earth to revolve
around the sun?
The Earth revolves around the sun in 365 days or
1 year.
We call this the period of revolution.
Make sure you know the difference between
revolution & rotation!!!!
Let’s Try it!
 Whoever is the blondest person in your group is the:
 SUN - stand still & shine!
 The tallest person is the:
 EARTH rotating around its axis and revolving around the
sun - be a graceful ballerina!
 The smallest person is the:
 MOON rotating around its axis and revolving around the
Earth - be calm and serene!
 The last person:
 Make sure they’re doing it right - be a bossy dictator!
Question of the day
Why do we have seasons???
8. Harvard Graduates should know!
QuickTime™ and a
decompressor
are needed to see this picture.
9. Let’s see if these kids know better!
QuickTime™ and a
decompressor
are needed to see this picture.
Why do we have
seasons???
Does the Earth get closer to the
sun for summertime to occur????
NOOOOOOOOOOOOOOOOOOO
The placement of the Earth in orbit
has NOTHING to do with seasons
The seasons are caused by the tilt
of the Earth on its axis.
Seasons & the Earth’s Tilt
 Hey, didn’t I warn you that we’re all a little crooked?
 In the summer, the Northern Hemisphere is tilted
toward the sun.
 In the winter, the Northern Hemisphere is tilted away
from the sun.
 In fact, Earth is actually closest to the sun during the
Northern hemisphere’s winter.
Why are there seasons?
Of course, no one can explain it better
than Tim & Moby.
BrainPOP: Seasons