3/11/2013
Doppler shift review
1. What is the Doppler shift? How does it affect light?
2. How do astronomers measure the speeds of galaxies
moving away from us?
3. What is Hubble's Law?
4. If you could travel backward in time, what would
you notice about the motion of galaxies (how would
galaxies appear)?
Doppler Shift of Light
Measuring Galaxy Speed
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3/11/2013
Hubble’s Law
Big Bang Video
• What scientists think happened.
Listen carefully – You do not need to take
notes…yet
The Early Universe
• Fill in your table about what happened in the
video.
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3/11/2013
The Kelvin Temperature Scale
Some baseline temperatures in the three
temperature scales:
temperature
kelvin
degree
Celsius
degree
Fahrenheit
symbol
K
°C
°F
boiling point
of water
373.15
100.
212.
melting
point of ice
273.15
0.
32.
absolute zero
0.
-273.15
-459.67
The Big Bang Theory
• Approximately 13.7 billion years ago,
everything in the universe was packed into an
almost unimaginably small, unimaginably
dense, unimaginably hot point that violently
exploded.
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3/11/2013
Timeline of
Matter in the
Universe
The Big Bang
Time
Temperature
What Was Happening
0 Unimaginably Everything in the universe
hot!
was packed into an
unimaginably small, dense,
hot point that violently
100 trillion,
exploded.
trillion,
trillion Kelvin
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3/11/2013
10-35 seconds after
Time
Temperature
10-35
sec
100 billion The universe inflated from the size
of an atom to the size of the Earth.
billion
At first, energy dominated the
billion K
What Was Happening
universe. Then the universe
consisted of a dense “soup” of
energy and fundamental particles.
When inflation ended, the universe
continued to expand at a slower
rate.
10-4 seconds after
Time
Temperature
What Was Happening
10-4 1 trillion
degrees K
Protons and neutrons
formed from
fundamental particles.
1 second after
Time
Temperature
1
sec
10 billion Neutrons and protons fused
K
together to form the nuclei of
what later became hydrogen
and helium (and trace amounts
of lithium) atoms. The universe
was still a dense “soup”
of energy and particles.
What Was Happening
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3/11/2013
3 minutes after
Time
Temperature
What Was Happening
3 min 1 billion K
Fusion of neutrons and
protons into hydrogen,
helium, and lithium nuclei
stopped.
300,000 years
Time
Temperature
What Was Happening
300, 3000 K Stable atoms of hydrogen and helium
(and trace amounts of lithium) formed
000
when nuclei captured free-moving
years
electrons. Photons of energy could now
move freely through the universe. The
universe was no longer a dense “soup,”
and you could now
“see” to very great distances in the
universe.
Read Article
• “Scientific Evidence for the Big Bang”
• Answer the 4 questions
• When complete summarize what we have
learned about the Big Bang by answering the
4 questions and put your worksheet in YOUR
BINDER.
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3/11/2013
The Big Bang
• The THEORY proposes that between 13-15 billion
years ago everything in the universe was crowded
into an infinitely small, hot, dense point that
violently exploded. The universe has been expanding
ever since.
Evidence for the Big Bang
• The redshifts of the lines in the spectra of galaxies
indicate that they are all moving away from one
another, evidence in favor of the expansion of the
universe.
Temperature
• The temperature of the universe has
decreased over time. Heat left over from the
Big Bang has been detected.
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3/11/2013
Evidence for the Big Bang
• The Cosmic Microwave
Background Radiation
can only be explained
by the Big Bang theory.
First Stars & Galaxies
• It took over 1 billion years for gravity to condense the
Hydrogen, Helium, and Lithium created moments
after the Big Bang into the first stars and galaxies.
Evidence for the Big Bang
• The amounts of
hydrogen, helium, and
lithium observed in gas
from the early universe
(a few billion years after
the Big Bang) match
those predicted by the
theory.
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