Transcript Origins of the Universe

Origins of the Universe
What we know
• We know that stars are not
fixed in place in the universe
• They are moving rapidly apart.
• This means the universe is
expanding
• If something is expanding it
must have come from
somewhere.
• That somewhere is the Big
Bang
But how can we tell how fast
stars move?
• When something that
emits waves moves the
waves in front of the
object get compressed and
the waves behind get
spread out
• You notice this when a car
or train passes you. The
sound has a higher pitch
before it gets to you and a
lower after it passes.
• This is called the Doppler
effect
Ok but these are stars not cars?
• For light the colour of light depends on the length
of the waves
• Red light has a long wavelength
• Blue light has a short wavelength
And?...
• If a star is moving
away from us its
waves are stretched
and it appears more
RED (RED SHIFT)
• If a star is moving
towards us its waves
are squished and it
appears more BLUE
(BLUE SHIFT)
And Finally the Point
• When we look into the sky
all the stars we can see are
red shifted.
• The farther a star is from
us the more it is red
shifted
• The only explanation for
that is if everything is
moving away from us.
• This means the universe is
expanding
But where does it come from
• Since the universe
seems to be expanding
outwards it is logical
to assume that it
started at a point
• The Big Bang theory
states that the universe
began in a giant
explosion 14 billion
years ago
But the galaxies didn’t pop out
like that right?
Steps after the big bang
1) Energy cooled to form
matter
2) First stars formed
3) Galaxies formed
We are a second or third
generation star
Proof of the big bang theory
• Expansion
– We know from red
shift the universe is
expanding
• Leftover heat
– Looking out at the sky
we can still see that
there is some heat left
over from the giant
explosion
Where next?
• Honestly we don’t know
• We could stop expanding
and collapse back (big
crunch)
• We could keep expanding
till everything is so far
away that there is no heat
left (big chill)
• Or we could be eaten by a
giant space duck…