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The Expanding Universe
You have looked at two important pieces of evidence which support the theory
that the universe is expanding.
1)
the red shift of light from stars and galaxies
2)
the cosmic microwave background (CMB) radiation.
When we look at stars and galaxies, some of the light looks different. It looks a
little bit more red than it should. The further away a star is, the more red it
looks. This means the wavelength of the light wave is getting longer – the wave
is being stretched.
We know that sounds increase in pitch (it will sound higher) when an object
moves towards us, and decrease in pitch when it moves away. This is called the
Doppler Effect. This is what makes an ambulance sound suddenly lower when it
goes past us.
Light is another type of wave, so the Doppler Effect applies to light as well.
When a star’s light is red shifted, the star must be moving away from us. To us,
almost every star looks red shifted, which means they are all moving away. This
is only possible if the Universe is expanding.
The second piece of evidence is called the cosmic microwave background. When
the Universe began, there was a huge expansion and lots of energy produced.
This created a lot of gamma rays (or gamma radiation) which bounced around
without being absorbed.
When we look out with our telescopes, we don’t see lots of gamma rays, but lots
of microwaves. These microwaves appear to be coming from every direction.
Microwave wavelengths are a lot longer than gamma rays. The only way this
radiation could exist was if they gamma rays from the Big Bang have stretched
out as the universe expanded.
Cosmic – because ______________________________________________
Microwave – because ___________________________________________
Background – because___________________________________________
The Expanding Universe
You have looked at two important pieces of __________ which support the
theory that the universe is __________.
1) the ____ ______of light from stars and galaxies
2) the cosmic microwave __________ (CMB) radiation.
When we look at stars and galaxies, some of the _______ looks different. It
looks a little bit more _____ than it should. The further away a star is, the
more _____ it looks. This means the __________ of the light wave is getting
longer – the wave is being stretched.
We know that sounds increase in pitch (it will sound __________ ) when an
object moves _________ us, and _________ in pitch when it moves ______.
This is called the __________ Effect. This is what makes an ambulance sound
suddenly lower when it goes past us.
Light is another type of _______, so the Doppler Effect applies to light as
well. When a star’s light is red shifted, the star must be moving away from us.
To us, almost _______ star looks red shifted, which means they are all moving
away. This is only possible if the Universe is ________.
The second piece of evidence is called the ________ microwave background.
When the Universe began, there was a huge expansion and lots of ________
produced. This created a lot of _______ rays (or _______ radiation) which
bounced around without being _________ .
When we look out with our telescopes, we don’t see lots of gamma rays, but lots
of microwaves. These microwaves appear to be coming from _______ direction.
Microwave wavelengths are a lot ________ than gamma rays. The only way this
radiation could exist was if they gamma rays from the ___ _______ have
stretched out as the universe expanded.
Cosmic – because ______________________________________________
Microwave – because ___________________________________________
Background – because___________________________________________
wavelength
gamma
longer
every
red shift
towards
absorbed
Big Bang
evidence
red
expanding
away
light
decrease
every
background
energy
expanding
gamma
red
higher
cosmic
wavelength
gamma
longer
every
red shift
towards
absorbed
Big Bang
evidence
red
expanding
away
light
decrease
every
background
energy
expanding
gamma
red
higher
cosmic
wavelength
gamma
longer
every
red shift
towards
absorbed
Big Bang
evidence
red
expanding
away
light
decrease
every
background
energy
expanding
gamma
red
higher
cosmic
wavelength
gamma
longer
every
red shift
towards
absorbed
Big Bang
evidence
red
expanding
away
light
decrease
every
background
energy
expanding
gamma
red
higher
cosmic
wavelength
gamma
longer
every
red shift
towards
absorbed
Big Bang
evidence
red
expanding
away
light
decrease
every
background
energy
expanding
gamma
red
higher
cosmic