Transcript The Earth and Beyond

The Earth and Beyond
There are nine planets in our solar
system:
Mercury
Venus
Earth
Mars
Jupiter
Saturn
Uranus
Neptune
Pluto
We see planets and the moon because they
reflect sunlight:
The sun is different – it produces its own light.
The Earth orbits the sun every…
…year (365 1/4 days)
This orbit is actually a “slightly
squashed” circle (ellipse)
The Earth is kept in orbit by the force of…
Gravity
…and by the
fact that is is
moving at a high
velocity
Gravity also keeps the moon in orbit around
the Earth. The moon orbits the Earth every…
…month (28 days)
Gravity is ________ if the planet has more
mass:
Earth
Jupiter
How much of the moon we see
depends on where the moon is in its
orbit:
Appearance:
Appearance:
Appearance:
The Earth is divided up into the northern
hemisphere and the southern hemisphere:
Northern
hemisphere
Southern
hemisphere
Equator
The Earth is tilted on an axis
North pole
South pole
The Earth spins on its axis every ___ (__ hours)
While the Earth is spinning the side that faces
the sun is in ________
Because of this spin the sun rises in the
______ and sets in the ______
The tilt of the Earth on its axis is also
responsible for the seasons:
What date is it here?
June 21st
What date is it here?
December 21st
The sun appears lower in the _______
than it does in the ______:
Summer
Winter
Longer shadows
in winter
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)
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
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 UNIVERSE
THE MILKY WAY,
which is one of a billion
galaxies that orbit
AND move away from
the centre of…
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?
Quiz..
10)What is the name of the line that divides the two
hemispheres?
11) How long does the Earth take to rotate?
12)Where does the sun rise and set?
13)What does the tilt of the Earth’s axis cause?
14)What is the date when the northern hemisphere is
tilted towards the sun as far as possible?
15)How would you describe the shape of a comet’s orbit?
16)What is a comet made up of?
17)What point do different galaxies orbit around and move
away from?
18)What keeps these galaxies in their orbits?
Evidence about the origins of
the universe…
Source of
light
“Spectra”
If you pass the light through a gas
something different is seen…
helium
Some wavelengths of
light are absorbed by
the gas.
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).
If the light starts to move away…
Before
helium
After
The results look a little different…
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”
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.
This is the BIG BANG theory
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
The Life Cycle of a Star
Stage 1:
NEBULAE
A nebulae is a collection of dust, gas and rock.
Some examples of nebulae…
Dark nebula
Emission nebula
Planetary nebula
Reflection nebula
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
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 –
it’s in the middle of a 10 billion year life span
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.
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:
Red giant
White dwarf
Black dwarf
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
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.
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.