How the universe began
1.2 unit 1 theme 1 My wider world
Learning objectives
• What happens to the observed wave length
and frequency of a moving wave source?
• What do we mean by the ‘red shift’ in light
observed from most distant galaxies?
• What evidence do we have that the universe
is expanding and how does this support the
Big Bang theory?
Wave lengths and wave source
• Hubble used telescopes to measure the light
from stars and galaxies
• Light from stars is a blend of different colours
• Different colours of light have different blends
of colours present
• Spectroscopy - shows different colours of light
as lines on a coloured spectrum
• A line spectrum compared to a spectrum that
has been red shifted.
Doppler effect
• http://www.bbc.co.uk/schools/gcsebitesize/scien
ce/aqa/origins/redshiftrev2.shtml
• H:\My Documents\My Videos\The Doppler
Effect.flv
• http://www.bbc.co.uk/schools/gcsebitesize/scien
ce/aqa/origins/redshiftrev2.shtml
• http://www.animations.physics.unsw.edu.au/jw/
doppler.htm#example
• http://www.animations.physics.unsw.edu.au/jw/
doppler.htm#source
Doppler effect
• Imagine a train travelling past you very fast
• As it gets closer the noise it makes goes to a
higher pitch
• As it moves away the pitch falls
• This is the Doppler effect
Doppler effect
• Wave source moving towards us is squashed
• Wave source moving away from us is
stretched.
How can we tell that the stars are
moving
• When a star or galaxy moves away from us it’s
light appears redder than expected because
its wavelength is stretched.
• Hubble’s results proved that galaxies move
away from us.
• The galaxies further away have a bigger red
shift because they are moving away faster
than closer galaxies
How could Hubble tell that galaxies
further away were moving faster
than closer galaxies?
The universe is expanding
• Galaxies in all directions are moving away
from the earth
• Does this make the Earth the centre of the
universe?
• Scientists don’t think this is true
• Blow up a balloon with spots all over it – all
the spots get further away from each other
The universe was once smaller
• So small – all matter and energy squashed in
one tiny place
• Cosmic egg
• The big bang theory
• Hugh explosion 14 billion years ago
• Scientists can detect cosmic backgound
radiation coming from all directions – this is
called the ‘echo of the big bang’
Did you know?
• The researchers who
discovered the cosmic
background radiation
were investigating
something completely
different
• They thought the noise
was caused by pigeon
droppings in the
receiver of the telescope
Key points
• The universe began as a huge explosion called
the Big Bang
• The red-shift is evidence that the universe is
still expanding
• The cosmic background radiation is evidence
that the big bang took place
• The wave length and frequency of a moving
light source changes
• http://www.bbc.co.uk/science/space/universe
/questions_and_ideas/big_bang#p00fz68w
• http://www.bbc.co.uk/schools/gcsebitesize/sc
ience/add_ocr_pre_2011/wave_model/lighta
ndsoundact.shtml