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Section 7.3
THE EXPANDING UNIVERSE
Hubble’s Ideas...
 ____________________________(1889-1953)
 An American astronomer
 One of the first to study _______________
 Two of his major findings changed astronomy (1918-1929)
1. Confirmed many other galaxies existed beyond the
_________________________
2. Found that almost all galaxies are _________________
from each other

This meant that the universe is _____________________!!
(this was stated by a man named _________________)
But how?
 How did Hubble do this?
 Measured the distance from Earth of _____________
 Measured the _____________of their movement
 Collected light from the galaxies and examined their
__________________________ (spectra)
 ____________________________________: the rainbow
band of colours into which white light separates when it
passes through a prism
 Hubble’s work and ideas remain the foundation
of modern understanding of the nature and
origin of the universe
The REAL Big Bang Theory
 What is it?
 One of the most remarkable theories of the 20th
century
 _____________________________________________
_____________________________________________
_____________________________________________
_____________________________________________
_____________________________________________
 NO _______________________________!!
 All matter and energy today was created during the
early minutes of the hot, rapid expansion
 Credited to George Gamow and Ralph Alpher
Evidence for the BBT
 Commonly accepted that universe formed
________________________ years ago
 ______________of universe and SPACE and TIME!!
 What Hubble saw:
 Looking at light spectra, figured out each galaxy’s
speed moving away from ours
 He saw that the _______________________ the
galaxy was, the ____________it was moving away
 Loads of “light” elements (H and He)
The Wave Nature of Light
 _____________________________: energy that
travels in waves of varying lengths
 E.g.: light, radio waves, microwaves, ultraviolet
radiation, X-rays
 __________________is E.R. we can see with our eyes
 When it is split into a rainbow of colours, it’s called the
_______________________________________
Electromagnetic Spectrum
Full range of E.R. organized by wavelength from very
long to very short
The Wave Nature of Light
 Wavelength of _________ light is longer than the
wavelength for ___________light
 Spectroscope
 This is an optical instrument that separates
_____________ into its spectral colours
 Helps astronomers analyse star light
The Wave Nature of Light
•Spectral
Lines
• Look like a
UPC/bar code
• Created when
each gas that
makes up a
star absorbs
some of the
light energy
• Each gas does
this differently,
creating different
lines
•We can see the spectral
lines of H in the spectra
of almost all celestial
objects, meaning H is
present throughout the
universe
Red-Shifted Spectral Lines
 ___________________________
 The change in position of spectral lines to the left
or right of where they normally are in the
spectrum of a light source that is not moving
 Astronomers noticed that in all galaxies Hubble was
studying, spectral lines were shifted to the ________
 This meant that the light source and observer are
________________________ from each other at a high
speed!!
Picture the Waves...
a) In this picture, the
duck sits still, creating
even ripples on the
water
b) As the ducks starts
swimming, ripples
behind stretch out
(wavelength is longer)
c) This is how Hubble
knew galaxies were
moving away from
earth (expanding); he
measured light
wavelengths emitted
from a galaxy to see if
and where it was
moving
Seeing Shorter VS Longer
Wavelengths
Red-Shifted Spectral Lines
 Hubble saw this _________________ pattern
in many galaxies
 Gave support to theory that space was
_____________________________!
 _____________________ telescope in Hawaii
repeated Hubble’s work with 60 000 galaxies
instead of 46
 Added to Hubble’s work
Learning Checkpoint
1. What is a spectrum?
2. What is the name given to the generally
accepted scientific theory that describes the
origin and evolution of the universe?
3. How is it possible to know that the element
hydrogen exists throughout the universe?
4. How does the idea that space itself is
expanding relate to the observation that the
spectra from distant galaxies are red-shifted?
Using Microwaves to Map
Cosmic Background Radiation
 Critical question related to BBT:
 __________________________________________
_________________________________________?
 First bit of universe was HOT with short waves
 Then universe cooled and waves lengthened 
where did the extra energy go?
 All space should have evidence of this
__________________________
More Evidence for BBT
 ____ Arno Penzias and Robert Wilson made
the big discovery (_________________________)
 _________________________________________
 Energy left over from the massive split-sec expansion
 ______________________ Radiation Maps
 Maps of cosmic background radiation collected from
most distant parts of visible universe
 CBR found fits with predictions consistent with BBT