The Earth and Beyond

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The Earth and Beyond
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There are nine planets in our solar system
Mercury
Venus
Earth
Mars
Jupiter
Saturn
Uranus
Neptune
Pluto
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We see planets and the moon because they reflect
sunlight
The sun is different it produces its own light.
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The Earth orbits the sun every
year (365 1/4 days)
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This orbit is actually a slightly squashed
circle (ellipse)
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The Earth is kept in orbit by the force of
Gravity
and by the fact that is is moving at a high
velocity
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Gravity also keeps the moon in orbit around the
Earth. The moon orbits the Earth every
month (28 days)
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Gravity is ________ if the planet has more mass
Jupiter
Earth
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How much of the moon we see depends on where the
moon is in its orbit
Appearance
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Appearance
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Appearance
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The Earth is divided up into the northern
hemisphere and the southern hemisphere
Northern hemisphere
Southern hemisphere
Equator
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The Earth is tilted on an axis
North pole
South pole
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The Earth spins on its axis every ___ (__ hours)
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While the Earth is spinning the side that faces
the sun is in ________
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Because of this spin the sun rises in the ______
and sets in the ______
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The tilt of the Earth on its axis is also
responsible for the seasons
June 21st
December 21st
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The sun appears lower in the _______ than it does
in the ______
Summer
Winter
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Two things happen because of this tilt

1. The days are longer during the summer
2. The weather is warmer during the summer (due to
   the hemisphere being closer to the Sun)

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Comets
Comets are balls of dust and frozen gas. They
have very elliptical orbits
As the comet approaches the sun gases evaporate
from it, forming a tail. This tail always
faces AWAY from the sun
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Solar systems, galaxies and the Universe
(Basically, everything in the universe orbits
around something else)
OUR SUN is one of millions of stars that orbit
the centre of
THE MILKY WAY, which is one of a billion galaxies
that orbit AND move away from the centre of
THE UNIVERSE
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Quiz..

1. What is the sixth planet in the solar system?
2. What is the biggest planet in the solar system?
3. Name 2 differences between stars and planets
4. How long does the Earth take to orbit the sun?
5. What force keeps the Earth from flying away from
   the sun?
6. Where does this force point towards when it acts
   on the Earth?
7. How long does the moon take to orbit the Earth?
8. Would the acceleration due to gravity on Mars be
   bigger or smaller than on the Earth?
9. Which hemisphere is Britain in?

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Quiz..

1. What is the name of the line that divides the two
   hemispheres?
2. How long does the Earth take to rotate?
3. Where does the sun rise and set?
4. What does the tilt of the Earths axis cause?
5. What is the date when the northern hemisphere is
   tilted towards the sun as far as possible?
6. How would you describe the shape of a comets
   orbit?
7. What is a comet made up of?
8. What point do different galaxies orbit around and
   move away from?
9. What keeps these galaxies in their orbits?

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Evidence about the origins of the universe
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Source of light
Spectra
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If you pass the light through a gas something
different is seen
Some wavelengths of light are absorbed by the gas.
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These patterns are called absorption spectra
because they show which wavelengths of light are
absorbed by the gas (this is how we know the sun
is made of helium).
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If the light starts to move away
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Before
helium
After
The results look a little different
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The absorption lines have all been shifted
towards the longer wavelength end (red end)
This is called red shift. The faster the light
source moves the further its light will be
shifted
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Light from different stars and from the edge of
the universe also shows this red-shift. This
suggests that everything in the universe is
moving away from a single point.
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Red shift summary
White light is made up of the colours of the
visible _______. Each colour has a different
__________. When this light is passed through a
gas certain wavelengths are _________ - the
patterns produced are called _________
________ If the light source is moving ___
from us we would find that the absorption lines
are all _______ towards the ___ end of the
spectrum (the longer wavelength end). The
________ the light source is moving the further
its pattern is shifted. Light from the edge of
the ______ also shows this pattern, so we assume
that the edges of the universe are all moving
away from a single point. This is called the ___
_____ theory.
Words to use shifted, red, spectrum, Big Bang,
absorbed, wavelength, absorption spectra, away,
universe, faster
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The Life Cycle of a Star
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Stage 1 NEBULAE
A nebulae is a collection of dust, gas and
rock. Some examples of nebulae
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Dark nebula
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Emission nebula
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Planetary nebula
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Reflection nebula
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Stage 2 PROTOSTAR
Gravity will slowly pull these particles together
As they move inwards their gravitational
potential energy is converted into heat and a
PROTOSTAR is formed
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Stage 3 MAIN SEQUENCE STAR
In a main sequence star the forces of attraction
pulling the particles inwards are BALANCED by
forces acting outwards due to the huge
temperatures inside the star.
Stars are basically nuclear reactors that use
hydrogen as a fuel. During its main sequence a
star will release energy by converting hydrogen
and helium (light elements) into heavier elements.
Our sun is an example of a main sequence star
its in the middle of a 10 billion year life span
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Stage 4 RED GIANT
Eventually the hydrogen and helium will run out.
When this happens the star will become colder and
redder and start to swell, forming a RED GIANT.
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Stage 5 THE DEATH
What happens at this point depends on the size of
the star 1) For SMALL stars the red giant will
collapse under its own gravity and form a very
dense white dwarf
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2) If the red giant is VERY BIG it will shrink
and then EXPLODE, releasing massive amounts of
energy, dust and gas.
Before
After
This explosion is called a SUPERNOVA
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The dust and gas on the outside of the supernova
are thrown away by the explosion and the
remaining core turns into a NEUTRON STAR. If
the star is big enough it could become a BLACK
HOLE.
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Stage 6 Second generation stars
The dust and gas thrown out by a supernova can be
used to form a new star
Our sun is believed to be a second generation
star this is because it contains some heavier
elements along with hydrogen and helium. These
heavier elements would have been the products of
a previous star that have been thrown out by a
supernova. These heavier elements are also found
on planets, indicating that they might have been
made from remains of previous stars as well.